Grouted lining systems for the renovation of old steel pipelines and the design of new pipelines

Grouted lining systems for the renovation of old steel pipelines and the design of new pipelines

Report to the Water Research Commission by SJ van Vuuren University of Pretoria

WRC Report No. 1448/1/12 ISBN 978-1-4312-0317-8 SEPTEMBER 2012

This report is available on the WRC website only – www.wrc.org.za

DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Š WATER RESEARCH COMMISSION

Grouted linings for renovating steel pipelines

ii

Executive Summary This report reflects a summary of the findings for the research which was sponsored

by Water Research Commission (WRC) and Rand Water (RW) with the objective to review alternative liner systems that can be used for the renovation of steel water pipelines.

The issues associated with liner system selection, design and installations refer to the following issues: •

Material performance in the environment of installation;

•

Uncertainty of the earth and live design loads on the liner systems (especially when the host pipeline has been eroded);

•

Buckling of the liner under hydrostatic external load and during installation (grouting of the annulus); and

•

New developments in the process of implementation.

During the initial planning of this research project it was envisaged that after an appropriate liner had been identified and tested, it would also be installed in pipelines that would be renovated by Rand Water. The renovation priorities shifted, excluding the intended field tests from this project, which would now be undertaken in a followup study (Section 9).

The aspects that are covered in this Summary Report are: •

Discussion of alternative lining systems;

•

Research findings on the two liners which were investigated;

•

Results obtained from the assessment of an HDPE liner (AKS);

•

Development of a field installation system;

•

Development of initial selection criteria for liners;

•

Proposal for the development of a test facility for liners; and

•

Reflection of further research to be conducted.

Grouted linings for renovating steel pipelines

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At the time of this research the HDPE (AKS) liner system used in low pressure pipelines (sewers) was identified as a possible candidate liner to be used for the renovation of old steel pipelines.

The capacity of the HDPE liner which was tested (2 mm hick) to breach holes and to be functional at high pressures (up to 300 m heads) indicated the potential of this system.

The annulus grouting of the liner did not result in any difficulty and it is anticipated that field conditions could be resolved.

The development of the field joint (Figure i) proved to be practical and that a water tight joint could be created.

Figure i: Field joint system developed

Grouted linings for renovating steel pipelines

iv

It is suggested that the following steps need to be considered when a liner is selected: •

Description of the current status of the pipeline;

•

Establish the current and future operation of the pipeline;

•

Determine the strategic importance of the pipeline;

•

Review the access to conduct the required renovation;

•

Identify suitable and available liners and their respective installation requirements;

•

Obtain a description of the required skills to install the liners;

•

Determine the availability of the liners and knowledge available on potential problem areas;

•

Review all the functional and physical limitations of the liner material;

•

Select alternative liners which could probably be implemented;

•

Conduct the required economic analyses to reflect the costs and benefits;

•

Select the appropriate liner system and undertake the required design review of all aspects;

•

Derive an installation criteria which will have to define the different quality assurance tests;

•

Establish the pre- and post-installation assessment;

•

Produce Tender documentation for the provision and installation of the liner;

•

Appoint an experienced contractor and contract an experienced person for site supervision;

•

Ensure water tightness prior to grouting of the annulus space; and

•

Develop a performance appraisal system for the liner as well as a management reporting system.

Uncertainty to install stiff liners around bends is unresolved and it is proposed that a test facility be developed to test different liners (Figure ii).

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v

Figure ii: Proposed layout for a test facility

Grouted linings for renovating steel pipelines

vi

Acknowledgements The research presented in this Summary Report emanated from a study funded by the Water Research Commission (WRC) and Rand Water (RW), whose support is acknowledge with gratitude.

The Reference group made important contributions and provides direction and support to the Project team for this project.

The patience, support and guidance of the Chairman and Manager of this study, Mr Jay Bhagwan, as well as the supporting staff of the WRC and RW are greatly appreciated.

The Reference Group and Project Team responsible for this study consisted of the following persons: Mr JN Bhagwan Mr B Mokgonyana Mr DDP Tebicki Mr Edwin Varkevisser Mr AK Copley Mr S Efrat Mr A Goyns Mr AR Kockott Prof GGS Pegram Mr MJ Shand Dr MC Webb Prof S J van Vuuren Prof E Kearsley Mr I Venter Mr D Roy

: : : : : : : : : : : : : : :

Water Research Commission – Chairman Water Research Commission – Coordinator Rand Water – Project Leader Rand Water eThekwini Water Services Trenchless Technologies Pipes CC Umgeni Water University of KwaZulu-Natal Ninham Shand Consulting Engineers SSIS Consulting Engineers University of Pretoria – Main researcher University of Pretoria – Researcher Petzetakis Africa Engineered Linings

The contribution by a number of staff and students from the University of Pretoria are appreciated, who assisted in the compiling of research findings. They are: Mr H Booysen, Mr D Mostert and Mr DJJ van der Merwe.

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Table of contents EXECUTIVE SUMMARY

iii

ACKNOWLEDGEMENTS 1.

INTRODUCTION

vii 1-1

2.

OBJECTIVES OF THE RESEARCH

2-1

3.

METHODOLOGY

3-1

4.

LINER SYSTEMS

4-1

4.1 Introduction

4-1

4.2 Criteria for liners

4-1

4.3 Planning considerations

4-4

4.4 Alternative lining options

4-17

4.5 Design aspects and procedures

4-17

4.6 Installation procedure and installation control

4-26

4.6.1 Installation procedure

4-26

4.6.1.1 Installation of Slip linings

4-26

4.6.1.2 Installation of Cement mortar linings (CML)

4-29

4.6.1.3 Pipe coated linings

4-30

4.6.1.4 Cured in place linings

4-32

4.6.1.5 CemPipe

4-33

4.6.2

Annulus grouting

4-36

4.6.3

Welded steel liner

4-37

4.6.4

Case study of the implementation of CIPP

4-37

4.6.4.1 4.6.4.2

Introduction

4-37

Installation of CIPP

4.7 New developments 4.7.1

4-38 4-39

Alternative protection methods

4-39

5.

FIELD INVESTIGATIONS

5-1

6.

EXPERIMENTAL INVESTIGATIONS

6-1

6.1

Objectives of the experimental work

6-1

6.2

Identification of possible liners

6-1

6.3

Initial comparative test of the selected two liner materials

6-2

6.3.1

Purpose of the experiment for determining the tensile strength

6-2

6.3.2

Experimental set-up for the tensile test

6-3

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6.3.3

Results obtained for the comparative tensile tests

6-3

6.3.4

Conclusions and recommendations from the comparative

6-9

tensile test 6.4

6.5

Flat Plate test (Bondage between grout and steel pipe material)

6-9

6.4.1 Purpose of the flat plate experiment

6-9

6.4.2

Experimental set-up for the flat plate test

6-9

6.4.3

Results obtained from the flat plate tests

6-10

6.4.4

Conclusions and recommendations

6-11

Performance of AKS under internal pressure in areas without grout

6-11

(circular sections) 6.5.1

Purpose of the experiment

6-11

6.5.2

Experimental set-up

6-11

6.5.3

Results obtained from the review of an un-grouted AKS liner

6-14

experiencing high pressures 6.5.4

Recommendations

6-14

6.5.5

Review of the deformation of a larger unsupported AKS liner

6-14

disc 6.6

Installation of the liner

6-15

6.7

Primary grouting of the first pipe segment

6-16

6.8

6.7.1

Purpose of the experiment

6-16

6.7.2

Experimental set-up

6-16

6.7.3

Results from the grouting of the first pipe section

6-18

Installation and grouting procedures

6-20

6.8.1 Grouting procedure

6-20

6.8.2

6-24

Conclusions and recommendations

6.9 Preparation of the experimental setup for secondary grouting

6-24

6.9.1

Purpose of the experiment

6-24

6.9.2

Experimental set-up

6-25

6.9.2.1

Positioning and welding of HDPE flanges onto the

6-25

liner 6.9.2.2

Welding of steel flanges

6-25

6.9.2.3

Positioning and flogging of steel flanges

6-27

6.9.2.4

Positioning of end domes

6-27

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6.10

Testing of different seal arrangements at the couplings

6-27

6.10.1 Different seals

6-27

6.10.2 Experimental setup to evaluate different seal arrangements

6-27

6.10.3 Recommendation pertaining the field arrangements for a watertight coupling 6.11 Determination of the pressure strain relationship of the pipeline

6-28 6-29

with the liner 6.11.1 Testing procedures

6-29

6.11.2 Pressure tests which were conducted

6-31

6.11.3 Strain calculations and results

6-32

6.11.4 Conclusions and recommendations based on the results from

6-40

the strain assessment of the experimental set-up 7.

SELECTION OF AN APPROPRIATE LINER SYSTEM

7-1

8.

FIELD JOINTS

8-1

9.

FUTURE RESEARCH

9-1

9.1 Introduction

9-1

9.2 Setting up a facility

9-1

9.3 Field work

9-3

10. REFERENCE

Grouted linings for renovating steel pipelines

10-1

x

LIST OF FIGURES Figure 4.1: Different rehabilitation options applicable for the rehabilitation of pressure pipelines Figure 4.2: Framework for exploring rehabilitation needs and strategies (Saegrov et al. (1999) Figure 4.2 (b): Reduction factors on two-lobe buckling pressure due to symmetrical gap imperfection expressed as a function of gap/thickness ratio Figure 4.3: Typical form of new design chart for CIPP incorporating a characteristic gap imperfection Figure 4.4: Polyethylene slip lining (Wood, 2003) Figure 4.5: Folded PE slip lining ((Wood, 2003) Figure 4.6: Cement mortar lining and drag trowel (Wood, 2003) Figure 4.7: Resin spray machine (Wood, 2003) Figure 4.8: CIPP process Figure 4.9: CemPipe (Wood, 2003) Figure 4.10: Anchor knob sheets from Engineering Linings (Pty) Ltd Figure 4.11: Anchor stud sheets from Steuler SA (Pty) Ltd Figure 4.12: Repairing processes of underground pipes with RTM: (a) preprocessing; (b) placing of the reinforcing element; (c) attaching of the covers and sealing; (d) removal of wrinkles and twists of the reinforcing element; (e) injection of polyester resin; (f) wetting of resin into the fiber preform and removing voids and excessive resin within the perform (Chin and Lee, 2004).

Figure 4.13: Schematic diagram of the repairing-reinforcing experiment with glass fiber fabric and unsaturated polyester resin using RTM and dielectrometry.

Figure 4.14: Configuration of the reinforcing element.

Figure 4.15: Model for resin flow in the fiber preform used for resin wetting analysis Figure 4.16: Principle working of the dielectrometry procedure Figure 6.1: AKS liner system Figure 6.2: Cemlam liner system Figure 6.3: Test setup for tensile testing (Cemlam) Figure 6.4: Load deformation comparison Figure 6.5: Deformation of AKS Figure 6.6: Stress strain behavior of AKS

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Figure 6.7: Stress strain behavior of Cemlam Figure 6.8: Stress strain behavior of second AKS sample Figure 6.9: Extent of deformation of the AKS system (HDPE) prior to failure Figure 6.10: Flat plate test to determine the bonding of the grout and the pipe Figure 6.11: Mortar stuck to the liner Figure 6.12: Experimental components to verify the response of the liner without grouting support Figure 6.13: Deformation of the liner without backing (no grout) and a pressure of 100 m Figure 6.14: Deformation of the liner under a pressure of 300 m Figure 6.15: The burst disc that was pressurized to about 100 m Figure 6.16: Setup for the deformation measurement of the disc Figure 6.17: The liner installed in a 3 m long steel section Figure 6.18: Configuration of the setup during the primary (initial) grouting Figure 6.19: Compressive strength of the grout Figure 6.20: Bulging of the tube that was used to seal the liner Figure 6.21: Bulging of the liner due to the loss of internal pressure during grouting Figure 6.22: Inside view of the HDPE flange with the 35 mm recess for the liner Figure 6.23: Positions where the liner has been damaged by the welding of the steel flange Figure 6.24: The arc weld plasma shining through the liner Figure 6.25: Schematic layout of the couplings which were tested Figure 6.26: Sealing arrangement at the field joints Figure 6.26(a): Installation of the strain gauge Figure 6.27: Installed strain gauge and LVDT mounting Figure 6.28: Wiring of the instrumentation to conduct the measuring Figure 6.29: Reference positions along the pipeline stain gauges were installed Figure 6.30: Reference positions where the stain gauges were positioned Figure 6.31: Pressure variation – Test 1 – Lined and grouted – 22 November 2007 Figure 6.32: Pressure-circumferential expansion – Test 1 – Lined and grouted – 22 November 2007 Figure 6.33: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 1 – Lined and grouted – 22 November 2007

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Figure 6.34: Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 1 – Lined and grouted – 22 November 2007 Figure 6.35: Pressure variation – Test 1 – Unlined – 22 February 2008 Figure 6.36: Pressure-circumferential expansion – Test 1 – Unlined – 22 February 2008 Figure 6.37: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 1 – Unlined – 22 February 2008 Figure 6.38: Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 1 – Unlined – 22 February 2008 Figure 6.39: Pressure variation – Test 2 – Unlined – 26 February 2008 Figure 6.40: Pressure-circumferential expansion – Test 2 – Unlined – 26 February 2008 Figure 6.41: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 2 – Unlined – 26 February 2008 Figure 6.41(a): Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 2 – Unlined – 26 February 2008 Figure 8.1: Proposed field joint arrangement Figure 9.1: Side view of the proposed experimental setup at the University of Pretoria Figure 9.2: Plan view of the proposed experimental setup at the University of Pretoria Figure 9.3: Isometric view of the proposed experimental setup at the University of Pretoria

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LIST OF TABLES Table 1.1: Overview of the World’s Water Network Infrastructure Table 4.1: Durability of the lining systems (Youseff Diab and Morand, 2001) Table 4.2: Different rehabilitation options (Abraham et al., 1999) Table 4.2 (continued): Different rehabilitation options (Abraham et al., 1999) Table 4.3: Analyses matrix for the different rehabilitation techniques (Abraham et al., 1999) Table 4.4: Performance properties of typical elastomeric polyurethane, elastomeric polyures and polyurethane coatings used for pipeline applications (Guan, 2003) Table 4.5: Key consideration attributes in Pipe Coating Selection (Guan, 2003) Table 4.6: Comparison between several common pipe coatings with 100% Solid Rigid Polyurethane (Guan, 2003) Table 5.1: Pipelines targeted for investigation by Rand Water Table 6.1: Details of the tests that were conducted on the AKS disc Table 6.2: Proposed steps for the installation of the AKS liner system Table 6.3: Grout mix composition Table 6.4: Initial suggested installation and grouting procedure Table 6.5: Details of the setup at the coupling Table 6.6: Overview of the water tightness of the couplings Table 6.7: Pressure transducers installed to capture the internal pressure Table 6.8: Details of the test phases that were conducted on the 900 mm pipe Table 6.9: Details of the pressure tests which were performed on the lined and unlined pipeline Table 6.10: Notation used to reflect the positions where the strains were measured Table 7.1: Grouping of the liners based on the characteristics of the pipeline Table 8.1: Description of the components of the field joint

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1.

INTRODUCTION

During the International Conference recently held in San Diego, the extent of the water network infrastructure of the world was provided. Table 1.1 reflects the estimated lengths of the current networks and provide an estimated cost for (NoDig Conference, San Diego, April 2007).

Table 1.1: Overview of the World’s Water Network Infrastructure

Waste Water Region

Population 6

(10 )

Network Length (km)

United Kingdom Western Europe Europe EC Accessions Eastern Europe North America

Capex 6

(10 Euro) #

Water Network Length (km)

Capex (106 Euro) #

60

354 000

36 000

334 413

31 500

391

1 598 000

195 800

2 887 754

123 912

236

143 525

20 060

318 050

8 869

318

236 296

3345

772 181

4 175

300

1 287 450

102 000

1 440 000

92 000

Note: #

estimated capital requirement for the period 2005 to 2016

It is generally understood by water utilities that the aging of the infrastructure will require the replacement, repair or renovation of certain components. The normative allocation for maintenance is set to be about 2% of the infrastructure, which is rarely adhered to.

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1- 1

In South Africa steel pipes have been installed as late back as 1930. Steel pipes amongst other need to be protected against corrosion. This is normally achieved by the provision of an internal lining and external coating. Some of the liner systems that have been used in the past have to be replaced and in the case of Rand Water the largest water utility, consideration is given to install grouted viscous-elastic liners in a number of their pipelines to extend their useful life. Practical challenges exist to install liners at joints, bends, pipe transitions, fittings, branches and at valves.

In selecting a liner, one of the major aspects to consider is whether the pipeline still has sufficient structural capacity for the intended use. The structural contribution of the different layers in the composite pipe influences the buckling characteristics of the pipeline.

The funding of this project by the WRC and the invaluable contribution of Rand Water created the opportunity to investigate alternative lining systems applicable for South African conditions.

In the following chapter the objectives of the study and the results that were obtained are reflected. The initial intention was also to undertake some field installations, which were however not attended to and which will probably be conducted under a separate assessment.

The report layout will address the following aspects: •

Objectives of the research (Section 2);

•

Methodology that is used in this research (Section 3);

•

Review of different liner systems (Section 4);

•

Field work (Section 5);

•

Experimental work conducted on selected liner systems (Section 6);

•

Selection of an appropriate liner (Section 7);

•

Field joint system (Section 8); followed by

•

Future research (Section9).

Grouted linings for renovating steel pipelines

1- 2

2.

OBJECTIVES OF THE RESEARCH

The objectives of the research are: •

Investigate alternative end sections (field joints) for grouted viscous-elastic type linings to be used in steel pipelines;

•

Investigate the integrity of the mechanical bond between different external profiles of the lining and the surrounding cement mortar grout;

•

Determine the integrity of the lining under varying internal pressures;

•

Determine the integrity of the lining during installation and grouting and under external loading conditions on the pipeline;

•

Develop design relationships that reflect the structural contribution of the different layers in a composite pipe and the effect of shape imperfections; and

•

Develop installation criteria for grouted viscous-elastic linings in steel pipelines.

Grouted linings for renovating steel pipelines

2- 1

3.

METHODOLOGY

To achieve the objectives set out above, the following main focus areas of this research were identified: •

LITERATURE STUDY – A literature survey of available lining systems and field installation experiences available;

•

LABORATORY TESTS – Experimental tests to determine the mechanical bonding of different external profiles of extruded HDPE linings and other liners. Review of the effectiveness of the liner installation at fittings such as end sections, small diameter branch pipes and field joints. Establish the performance of the liners under different loadings (internal pressure fluctuations and external loads) and determine the de-bonding of the liner from the steel pipe. Establish a relationship of any shape imperfections of the liner and the host steel pipe on the buckling capacity of the lined system.

•

FIELD INVESTIGATION – Rand Water has identified two pipelines that will be installed with different liners to establish any complication of the lining systems and how they perform. The pipes that were identified will be scheduled for renovation and will be prioritized on the schedule of Rand Waters 5 year strategic renovation plan.

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3- 1

4.

LINER SYSTEMS

4.1

Introduction

The objective of the literature review is to obtain as much material as possible that is applicable to the field of study and to restate the trends and procedures currently used from which the research focus will be narrowed.

The following aspects have been addressed:

4.2

•

Criteria for liners

•

Planning considerations

•

Alternative lining options

•

Design aspects and procedures

•

Installation procedure and installation control and

•

New Developments

Criteria for liners

A first compilation of the criteria (preliminary) for grouted linings for renovating steel pipelines for water transport, have been compiled and should adhere to the following: •

Good hydraulic properties – low friction factor, low decay value of friction factor and capable to operate under high velocities

•

Must be stable in all the operating conditions, Must not react with disinfectant chemicals and contaminate drinking water

•

Should resist microbial growth or slime (gel layer) build up

•

Prevent corrosion of steel pipe wall by either: o passivate the steel surface – protected adherent scale in right pH and potential environment, or

Grouted linings for renovating steel pipelines

4-1

o provide a complete watertight barrier between water and steel pipe (internal and external water sources – holes in old steel pipes) •

Low cost – initial and life cycle

•

Durable with long life expectancy. Change of properties with time to be included in design

•

Easy to install and repair – surface preparation, application and curing environment not too onerous or costly to provide

•

Quick to install and return to service under shutdown conditions

•

Proven cost effective methods of lining connections to valves, bends, branches, tapers etc.

•

Structurally stable under all expected loading and service conditions: o be able to support external water pressure and internal pipe vacuum simultaneously o be able to span and seal holes in the old steel pipe o must not delaminate, crack and spall off the pipe wall under expected low internal pressures, high water table conditions outside the pipe or distortional loading causing acceptable ring deflections o be able to withstand impact loading due to handling, transportation or water hammer pressures. o have a high abrasion resistance.

Lining systems for pressurized and low-pressure systems (partially full flow) are extremely different.

Lining systems for pressurized pipes have to be grouped into those that are:

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4-2

•

Appropriate for man entry applications (diameters more than 900 mm) and

•

Lining systems for small bore pipelines

These criteria will be extended and quantitative standards will be defined to evaluate different lining systems.

Figure 4.1 reflects the different rehabilitation options applicable for the rehabilitation of pressure pipelines.

Figure 4.1: Different rehabilitation options applicable for the rehabilitation of pressure pipelines

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4.3

Planning considerations

When considering enhancing the life of a steel pipeline by the installation of a liner for internal protection, it is important to establish the structural integrity of the pipeline. Marshall (2001) describes the different tests that could be considered to determine the current condition of a pipeline, which includes the following aspects: •

Structural Integrity

•

External Coating condition and the

•

Effectiveness of cathodic protection system

Youseff Diab and Morand (2001) reflect that about 200 000 km of small sewers in Europe needs urgent rehabilitation in the following 5 years, while the situation in North America is worse. It is postulated that a global methodology for the inspection, diagnosis, maintenance and rehabilitation is required.

The procedure to select the most applicable rehabilitation method is a two-phased process. In the first phase, the pipe and surrounding conditions and impact are related to the rehabilitation options, from which certain alternative rehabilitation options will be discarded. During the second phase a multi criteria assessment is undertaken, identifying the dominant solutions.

The rehabilitation techniques are divided into the following two groups: •

Cut trench application and

•

No-dig techniques.

The selection criteria that are proposed consist of the following aspects: •

Diagnosis results

•

Hydraulic performance

•

Abrasion strength

•

Pipeline nature

•

Implementation difficulties

•

Financial cost and social cost

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4-4

•

Mechanical performance

•

The fluid nature and

•

The durability of the selected rehabilitation option.

Some of the aspects, like the durability of the selected rehabilitation option, are evaluated in a quantitative manner.

Table 4.1 reflects the durability of the lining systems.

Table 4.1: Durability of the lining systems (Youseff Diab and Morand, 2001) Material

Mechanical

Installation factors

Durability

properties Tensile

The

The

The

Abrasive

Resistance

Joints

strength

stiffness

installation

shock

strength

to

state

speed

strength

chemical attacks

Cement

X

XXX

X

X

XX

XXX

XX

Ductile

XXX

XXX

X

XXX

XXX

X*

XX

Asbestos

XX

XXX

X

XX

X

X*

XX

Concrete

XX

XXX

X

X

X

X*

XX

GRP

XX*

XX

XX

XX

XX

XX*

XX*

PRC

XX*

XXX

X

X

XX*

XXX

XX

PVC

XX

X*

N/A

N/A

XX*

XX*

N/A

PEHD

X*

X

XXX

XX*

XXX

XXX

XXX

PP

X*

XX

XXX

XX*

XX*

XX

XXX

iron cast

Note: X: low, XX: medium, XXX: high, *: indicates that available data is insufficient to distinguish a value between the two proposed (the lowest value will be considered)

Derr (2003) reflects his experience and indicates the best “Trenchless Technology Systems” that can be used for pipeline renovation. Trenchless Technology dates back to the 1970 when the Japanese developed a micro-tunnelling machine, which was followed by the Germans and English.

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4-5

Patents for the different methods limited the expansion and improvement of initial systems.

The options available for water main rehabilitation are: •

Cement Mortar Lining

•

Epoxy spray

•

Sliplining

•

Cured in Place Pipe (CIPP)

•

Fold and form systems

The two most important factors for the selection of the liner type are: •

Initial cost and life cycle cost

•

Durability

•

Influence on hydraulic capacity

•

Knowledge and experience to install the system.

The author reflects that although CML’s initial cost is low, the life cycle cost of epoxy systems are competitive and are currently regularly specified as the appropriate and preferred procedure for renovation in the UK. The CIPP systems have far less influence on the hydraulic capacity and accommodate the insertion of laterals.

Trypus, Darrow and Mattigly (2003) reported that a 42-inch inceptor sewer was rehabilitated with CIPP at the same cost as sliplining, but due to the much shorter construction time CIPP was more advantageous.

The introduction of fast cure epoxies (2-3 hours) expands the scope of applying this method for rehabilitation.

The current status of steel mains has to be defined by undertaking a corrosion investigation, which is carried out in two phases: “Phase 1: Line pipe characterization and assessment of internal corrosion on six cut out pipe sections and three VJ couplings. Line pipe characterization is done by means

Grouted linings for renovating steel pipelines

4-6

of mechanical tests on a section of pipeline, chemically analyzing the content of steel and non-destructive testing on the coating, lining and wall thickness and measuring corrosion pit depths. The results are used to predict remaining service life of the pipeline based on environment and operating pressures.

Phase 2: A DC voltage gradient (DCVG) survey and visual inspection of defects to assess the external corrosion conditions. A DCVG survey is an overland technique used to pinpoint coating defects from the soil surface with a high degree of accuracy.

This is done by measuring the voltage gradient that is established in the ground by applying direct current to the pipeline via an external source. The cathodic protection system on the pipeline is used to supply the current. In addition, the technique allows for the ranking of defects in terms of severity, as well as an approximate indication of the corrosion status (anodic or cathodic), both with the cathodic protection turned on and off�.

Financial assessment of alternative solutions over the lifetime of the project will assist to prioritise the potential solutions.

Saegrov, Baptista, Conroy, Herz, LeGauffre, Moss, Oddevald, Rajani and Schiatti, (1999) indicated that the number of pipe failures remains an important parameter to reflect the status of a water distribution system and could be used to prioritize areas for rehabilitation. Figure 4.2 reflects the framework for rehabilitation needs and strategies.

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Statistics of failures and rehabilitation Breaks, leakage, rehabilitation rate

Current stock Network mileage by year of construction and types of pipes

Definition of types of pipes

Lifetime estimates Of types of pipes

Calibration of ageing functions

Cohort survival model Forecasting stock deterioration and calculating annual mileage of types of pipes for rehabilitation

Options of rehabilitation -

Decision criteria for rehabilitation strategy

fully vs. partly in time vs. delayed replacement vs. renovation

Economic input data -

annual rehabilitation rates by types of pipes network age - network residual lifetimes - annual failure rates - annual leakage rates - savings from reduced leakage and repair costs break-even-year - internal rate of return

-

past network investments for extensions and rehabilitation specific costs of rehabilitation technology fixed and variable costs of water production water price inflation rates budget restraints

Choice of best rehabilitation strategy

Figure 4.2: Framework for exploring rehabilitation needs and strategies (Saegrov et al. (1999) Saegrov et al. (1999) discuss the knowledge gaps and suggested that the following aspects should be acknowledged when rehabilitation is considered.

Grouted linings for renovating steel pipelines

4-8

Traditional renewal methods will be too expensive and often inappropriate for many of the future upgrade requirements of water mains systems and that trenchless technologies will often be more cost effective.

Saegrov et al. (1999) suggests that the current research needs should include: •

Establish easily used methods to share previous objective and independently verified research and developments (e.g. via internet) relating to rehabilitation methods, selection, specifications, durability testing, prioritization, etc.

•

Establish framework and methods whereby newer rehabilitation methods are encouraged but without compromising the need for objective and independent verification of key parameters, e.g. regarding durability and specification.

•

Additional issues regarding decision support systems for establishing viable rehabilitation options (e.g. existing pipeline condition influence, structural contribution of existing pipeline)

•

Technology Transfer projects to ``pump prime'' new markets for newer rehabilitation methods such that the expensive lessons learnt elsewhere are not relearned. Many manufacturers and contractors are willing to subsidize such projects, and this route has been successfully used before.

The team involved will need to organize suitable adoption of the technology, organizing relevant approvals (e.g. regarding new materials in contact with potable water), etc.

Marshall, Thomas and Pearson (1990) reflect the experience of North West Water, UK in the use of Epoxy Mortar Linings and Polyethylene slip linings. These methods are compared with replacement and cement mortar linings and the benefits favor the first two procedures.

Installation of slip linings requires that the draw-down ratio be determined with care to ensure sufficient space between the liner and the host pipe but with acceptable resizing time.

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4-9

Field and experimental tests have been conducted to allow for the prediction of: •

Running reductions;

•

Permanent deformation;

•

Length increases;

•

Dimensional recovery rates and

•

Pulling forces.

Ahammed (1997) derived a relationship that can be used for corroded pipes to determine the allowable pressures. The author reflects that most of the current methods (Kiefner and Vieth (1990), O’Grady II, Hisey, and Kiefner (1991) and O’Grady II, Hisey, and Kiefner (1992)) can only determine the allowable pressure in the pipeline but cannot be used to calculate future maximum allowed pressures. The advantage of the new relationship is: •

Need for continuous monitoring

•

Frequency of the evaluation of remaining strength and

•

Prevent the unnecessary early replacement or renovation of sections

The proposed relationship is as follows:

p a = 2 (s y + 68,95)

t 1 − (d 0 + R c (T − T0 ))/t DF 1 − (d 0 + R c (T − T0 ))/ (tM )

where: pa

=

Maximum allowable fluid pressure (MPa)

sy

=

Material yield stress (MPa)

T

=

Time when the second measurement was taken (annum)

T0

=

Time when the initial measurement was taken (annum)

D

=

Internal diameter (mm)

F

=

Factor of safety

d0

=

Initial measurement value, (mm)

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∆d (mm/a) ∆T

Rc

=

Steady state rate of corrosion,

M

=

Folias factor that can be estimated as shown below

t

=

Wall thickness of the pipe

L

=

Length of the pipeline projected on the longitudinal axes (mm)

 L2 L4 M = 1 + 0,6275 − 0,003375 2 2 Dt D t 

 L2  for ≤ 50 Dt 

  L2 L2 > 50 M =  0,032 + 3,3  for Dt Dt   A recent survey (USEPA, 2003) indicates that water authorities need to invest $83.2 billion by 2018 to improve the nation’s drinking water distribution infrastructure, which accounts for over 55% of the total water infrastructure investment needs nationwide. At least $65.6 billion is needed immediately to rehabilitate or replace pipes for adequate protection of public health (Barber, Bakeer, Sever and Boyd, 2004). One option is the reline the pipelines, leading to the need to quantify the influence of rehabilitation on the hydraulic capacity of the infrastructure.

Barber et al. (2004) investigated the influence of the hydraulic capacity of a 152,4 mm diameter steel pipe before and after it was sliplined with a 6,35 mm HDPE liner. It was found that for the same head loss, the reduction in flow was about 16% for the reduction in diameter of 8,3%. The wall friction factors were almost the same.

Abraham and Gillani (1999) describe the materials that can be used for sewer rehabilitation and provide a comparison of the rehabilitation options that were adapted from Schrock (1994). Table 4.2 reflects the different rehabilitation options and Table 4.3 is an analyses matrix for the different rehabilitation techniques.

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Table 4.2: Different rehabilitation options (Abraham et al., 1999)

Rehabilitation

Principal

Principal

Potential

option

advantages

disadvantages

application

Removes all problems on

Expensive, particularly if

length

deep

Traditional design

Disruptive

Removes all problems on

Usually more

Approximate cost

CONVENTIONAL REPLACEMENT Open cut

Tunneling

length Traditional design

expensive than

Any size

Greater than 90 cm

$165 to $300/m for a 36 cm line

open cut May need expensive

Reduces disruption

ancillary work

Flexibility on line/elevation

GROUTING Internal grouting (acrylamide, acrylate, acrylic, urethane foam, urethane gel)

Seals leaking joints and minor cracks Prevents soil loss

Infiltration may find other

Any size

routes of entry Existing sewer must be structurally sound

Low cost and causes

$120 to $175/m for a 30

minimal disruption

cm line

Can reduce infiltration Can include root inhibitor External grouting

Improves soil conditions

Difficult to assess

surrounding the conduit

effectiveness

Can reduce infiltration

May be costly

Any size

and soil loss

PIPE LININGS SLIP LININGS Continuous pipe (fusion-

Quick insertion

welded PE/PB)

Circular cross-section only

Large radius bends

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10-160 cm

$160 to $250/m for a 30 cm line

accommodated

Insertion trench disruptive High loss of area in smaller Less cost effective

Short pipes (PE, PB,

High strength to weight

where deep

PVC, FRP, DI)

ratio

Some material easily

Variety of cross section

damaged during

can be manufactured

installation

10-360 cm

Larger pipes may require Minimal disruption

temporary support during grouting

CURED-IN-PLACE

Rapid installation

May involve labor

PIPE (CIPP) (thermoset

intensive jointing

resins:

Full bypass pumping

polyester, epoxy or

necessary

vinylester)

No excavation

10-275 cm

Accommodates bends and

Sole source often

minor deformations

necessary

Maximizes capacity No excavation

High set-up costs on small

Grouting not required

projects

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Table 4.2 (continued): Different rehabilitation options (Abraham et al., 1999)

Rehabilitation

Principal

Principal

Potential

option

advantages

disadvantages

application

Approximate cost

DEFORMED PIPES Formed pipes (high

Rapid installation

Lateral relocation may be

6-60 cm

difficult

density PE, PVC) Continuous pipes

$215 to $280/m for a 30 cm line

Relies on existing pipe for support

Maximizes capacity No excavation Grouting not required SWAGELINING/

Rapid installation

ROLLDOWN (high

Lateral relocation may be

6-60 cm

difficult

density PE, mediumdensity PE)-

Maximizes capacity

$160 to $250/m for a 30

Relies on existing pipe for

cm line

support Minimal excavation Grouting not required SEGMENTAL

$200 to $245/m for a

LININGS (FRC, FRP, RPM, PE

High strength-to- weight

Some material easily

PVC, PRC, gunite

ratio

damaged during

90 cm and larger

160 cm line

installation

COATINGS (gunite/shotcrete resin)

Connection easily

Difficult to supervise

accommodated

larger

Zero/minimal excavation

May be labor Intensive

Variety of cross sections

Control of infiltration

possible

required

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120 cm and

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$65 to $215/m square meter

Table 4.3: Analyses matrix for the different rehabilitation techniques (Abraham et al., 1999) Social issuesTechnology

Structural

Hydraulic

Ease of

Consideration

Consideration

installation

Efficiency

Availability

Durability

Social issues-

Social issues-

commerce

Social issues-

and life

traffic

environment

and

citizens

industry *Strength

*Ability to

*Length

*Maint.

reduce/prevent

options

Frequency

*Effect on traffic

Health and

safety

safety

issues

issues

Health and safety issues

*Cutting of

*Reduced

*Person

*Sewer in

*Toxicity of

roots/trees

access to

entry vs.

operation of

materials if any

businesses

remote

not

options

*Disruption

Health and

operation

inflow/infiltration (I/I) *Availability to

*Size

*Maint.

*Presence of open

*Air

*Hindrances

withstand

options

Ease

trenches/openings

pollution

due to

vibrations and

equipment

shock *Maint.

*Variation in

Cost

groundwater

*Injuries

level Excavation

Restores

and

structural

replacement

strength

Prevents I/I

Any size

Variable

Easily

50-100

available

years

Very disruptive

Maximum

Maximum

Maximum

Adherence

Sewer not

effect

effect

effect

to safety

in operation

N/A

standards required

Sewer in

Minimum

Person

operation

effect

entry

materials are

structural

required for

toxic

strength

large

Chemical

Not able to

grouting

improve

Excellent

N/A

Depends on

Easily

Data not

material

available

available

Minimum effect

N/A

sewers

Depends on

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N/A

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Some sewer

Some grouting

Fiberglass

Pipe lining

Excellent

Excellent ability to

Can be

Sliplining

ability to

prevent I/I

installed in

CIPP

improve

diameters of

structural

4 to 144 in.

strength

material

Intermediate

50-70

Some effect on

Minimum

Minimum

Minimum

Person

flow

reinforcement

years

traffic because of

effect

effect

effect

entry not

facilitates

may be

required

installation

hazardous

Sewer can

Care should be

the access pit Variable

4 ft. and Deformed

May improve

May improve

larger

Easily

10-50

pipe

structural

hydraulic

diameters

available

years

Segmental

strength

characteristics

only

Minimum effect

N/A

N/A

Minimum

Person

be in

taken against

effect

entry

operation

inhaling

required

coating

lining

materials

Coatings

Variable N/A

Robotic

N/A

Prevents I/I

rehabilitation

Grouted linings for renovating steel pipelines

Sewer not Limited

Data not

Minimum effect

available

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N/A

N/A

N/A

Remote operation

in operation

N/A

4.4

Alternative lining options

There are about 80 sorts of trenchless technologies so far developed all over the world and largely classified into four kinds (Chin, Kwon and Lee, 2002): •

Slip-lining,

•

Cured-in-place pipes (CIPP) lining (Insituform)

•

Close-fit lining (Fold and Form), and

•

Spirally wound pipes lining.

These technologies are described in more details in the other sections of this report.

4.5

Design aspects and procedures

Loadings on pipes that are assumed to be fully deteriorated (the host pipe will in the course of time loose its structural ability to restrain any load), are described in ASTM F 1216 Specification in which a modified buckling relationship and an ovality factor has been included. The design specification for GRP pipes (AWWA C 950) are supposed to be used but do not incorporate the ovality factor. McAlpine (2003) reflected the shortcomings and inconsistencies in the approach.

The geometrical configuration assumes four pipe quadrants hinged and the loads on the liner are experienced at the crown and invert. McAlpine (2003) suggests that a uniform radial pressure around the pipe should be used in the design and indicated that none of the tests results supports the use of the Lusher buckling equation and the design procedure of AWWA C 950.

In the case of Cured In Place Plastic (CIPP) liners McAlpine (2003) reports results that suggest that the bonding between the liner and the host pipe contributes to structural stiffness. It is also shown that for Grout in Place liners (GIP), the liners and grout resists the initial load and starts to deflect when the grout has cracked. The rate of deflection per vertical load increase showed that the vertical deflection is 1,725 times more for the GIP system in comparison to the CIPP system.

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McAlpine (2003) indicates that a “safe” design should be based on the assumption that there is no soil support and that the ground load should be assumed to be a prism load.

Gumbel (2001) considered the external loads on the pipeline and indicated that the following two loading conditions, in accordance with Appendix X1 of ASTM F1216 (1998) external load conditions, apply in the design of liner pipes: •

Sustained hydrostatic groundwater pressure and

•

Earth and traffic load (Installation and live loads)

Gumbel (2001) reflects that only the United Kingdom design procedures (WRc/WAA, 1994) accepts that the earth and traffic loads will only happen in exceptional cases, making the inclusion of this load condition grossly “over-conservative”. The discrepancy with the North American industry’s approach led to the formation of a new “Rehabilitation Design Task Group” of ASCE Pipeline Infrastructure Committee (PINS) in 1999.

After reviewing the shortcomings of the ASTM relationship for hydrostatic buckling and describing the mechanisms of restraining the buckling, a design relationship is proposed which can be expressed in the dimensionless form as:

Pcr  D  = c  E*  t 

m

where: Pcr = Critical buckling pressure, (kPa) D = Diameter of the pipe (mm) E* = Plain Strain Modulus = E/(1-µ2), (kPa) µ = Poissons ratio t

= Thickness of the pipe wall (mm)

c (ovality factor) and m are functions of the imperfections in system.

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For zero imperfections, m = -2,2 and c = 1,003 for one-lobe (gap occurs only at one location on the peripheral) buckling and c = 1,323 for two-lobe (gap occurs at two opposite locations on the peripheral) buckling. As the mean gap ratio (Gap/Radius) (W02/R) increases both m and c increase and for large gaps, reach a respective value of –3 and 2 for m and c. A graphical presentation of the reduction factor of the buckling pressure for different values of D/t is reflected in Figure 4.2(b).

Figure 4.2(b):

Reduction factors on two-lobe buckling pressure due to

symmetrical gap imperfection expressed as a function of gap/thickness ratio The imperfections are however not limited to the gap and ovality but should also include the longitudinal dimensional variation or wavy imperfections.

Gumbel (2001) indicated that for each renovation technique and host pipe that have to be lined, the combined effect of the buckling pressure and all the imperfections should be considered. The German design standard (ATV, 2000) proposes a reduction factor for each of the imperfections and is unduly conservative.

In comparing the proposed new design procedure, Gumbel (2001) compared the required D/t ratio for a 1200 mm pipeline with a 5 % ovality and a 6 m sustained hydrostatic pressure. According to ASTM F1216 method a D/t of 50 is required, while the new procedure reflected in Figure 4.3, requires a D/t ratio of only 60.

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Figure 4.3: Typical form of new design chart for CIPP incorporating a characteristic gap imperfection Gumbel (2001) concluded that: “Decide on suitable groupings of renovation techniques for which common design tools can be developed. Ideally the classification of renovation technique families in the process of being adopted as a European standard (CEN, 2001) should be followed.

Establish minimum testing requirements for each technique family and liner material, and/or assign appropriately conservative default values to all relevant design characteristics, including characteristic imperfections, for which test data are not yet available.

Publish fully detailed design procedures for beta-testing by both user and producer sides of the industry, which should also provide a consistent and balanced framework for validation testing of all individual products covered�.

Zhao and Daigle (2001) provide a theoretical analyses procedure for slip lined water mains in which the load sharing is defined mathematically and a procedure for the

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estimation of the service live of a slip lined system in which a lightweight grout has been used is provided.

A document entitled: “Pipeline Rehabilitation by sliplining with Polyethelene pipe” written by the Plastic Pipe Institute (1993) reflects the five steps in the design of a slip lining project: •

Select liner diameter (Hydraulically 75 to 100 % of design flow and the clearance should be less than 10% of the diameter).

•

Determine the liner wall thickness (The liner should be able to withstand the hydrostatic external load with an accepted safety factor against buckling).

•

Analyse the flow capacity (Diameters and friction parameter of the pipe material will reflect the difference in flow capacity of the host pipe and the slip lined pipe).

•

Design necessary accesses such as terminal manholes, headwall services and transition connections (Design of the launch areas and headwalls).

•

Compile a contract document (describe the procedure which will include: initial inspection, cleaning and preparation of the pipe, join the polyethylene pipe sections, access the line and position the liner, provide lateral and service connections, provide terminal connections and provide an indication of the maximum pulling force).

The tests that were conducted on cracked pipes by Utah State University reflected that a fully deteriorated pipe still has significant residual load bearing capacity and that the current design pressures can therefore not be used to determine the load conditions on the liners. The procedures proposed by ASTM F1216 are not applicable (McAlpine, 2003).

Lienberger (2003) reflected the need for procedures and a universal design approach to enhance the design of liners for pipelines, ensuring that infiltration into the ground through leaks or backflow into the pipeline due to high pressure differential during the

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operation, be addressed in the design and to compare the structural capacities of available products.

The descriptive data that is required to compare the materials are: •

Material characteristics (flexural modulus, flexural strength, tensile strength, compressive modulus, coefficient relative flexibility and relative stiffness).

•

Creep curve reflecting the decrease in structural strength with time.

•

Physical material stability – degradation of the modulus of the material.

•

Thermal curve reflecting the influence of temperature on the material characteristics.

•

Construction auditing.

Lienberger (2003) indicated that the thicker the liner the less forgiving it would be to cater for construction irregularities.

Nassar and Yousef (2002) reflected that there is a need for analytical or empirical models that predict the time until failure or buckling of a pipe liner system under a hydrostatic pressure load and developed such a prediction model that give a probabilistic distribution function for the failure to occur after a number of years. The author indicated a regression line based on censored data provides a very conservative estimate of the pressures that can be sustained over 50 years. The main reason for this is that censored observations (non-failure) are assumed to be failed observations.

Nasser and Yousef (2002) proposed that for censored observations, the following relationships should be used: T = T0 e bx

Here T0 denotes a random variable representing the 0 baseline distribution of time until failure, b is a constant, and x is a covariate that affects time until failure. For the pipe liner data, let x be the hydrostatic pressure in psi. For each baseline distribution,

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4 - 22

the log-likelihood function can be established based on the observations of time until failure. Given n observations, r of which are uncensored and n - r censored (time until failure exceeded 10 000 h), the log-likelihood function is: r

L = ∑ log f (t i ) + i =1

n

∑ (1 − F (t ))

i = r +1

i

where: f(t)

= The probability density function of accelerated time until failure;

F(t) = Cumulative distribution function of accelerated time until failure.

Estimates of the parameters in the model can be obtained by maximizing the loglikelihood function using the Newton-Raphson technique.

Boot and Toropova (1999) summarized the factors affecting structural performance of thin-walled linings, such as loading, host pipe characterization and installation techniques. The authors consider the ability of the lining to span small gaps and voids, which they perceive as a major design issue. The performance of linings installed using the two most popular pipe grade polyethylenes (PE80 and PE100) were evaluated for both short-term and creep loading conditions. The results are based on laboratory testing and two- and three-dimensional finite element modeling which reflected a high correlation. It was however established that two-dimensional analyses for the prediction of creep lives, provides conservative results and should not be used.

The possible effects of longitudinal notches induced by the installation processes on spanning capacity are included in the investigation. The authors obtained explicit design recommendations for the criteria considered.

El-Sawy and Elshafei (2003) developed a neural network to predict the buckling pressure of loosely fitted liners for rigid pipe rehabilitation. The authors compared the results with previous parametric study using the Finite Element Method (FEM) and the Jacobsen solution, and found that the neural network provides a good estimate for the critical pressure of an elasto-plastic loosely fitted liner. The parameters that the author included are the liner’s thickness-to-radius, gap-to-radius, and the equivalent Grouted linings for renovating steel pipelines

4 - 23

yield stress-to-Young’s modulus ratios. This network provides a new tool that can be used in the structural design of loosely fitted liners.

Zhu and Hall (2001) also evaluated the contact conditions and stresses, which a thin liner will experience under uniform external pressures. The authors determined the influence and relationship of the host pipes ovality, gap, longitudinal imperfections and pressure on the creep behavior of the liner.

According to U.K. water industry statistics, there are over 295,000 km of water mains in England and Wales, the majority of which were laid as unlined cast iron at least 50 years ago; about 35% of the total network; is estimated to be subject to corrosioninduced bursts and leakages and is therefore in need of remedial attention. In this respect there are considerable advantages in renovation over renewal (Boot, Guna and Toropova, 1996).

Boot et al. (1996) reflect that if it is assumed that the host pipe will have some structural ability, one of the major concerns are the ability of the liner to span discontinuities or holes in the host pipe.

Gokhale and Hastak (2000) describe a model that can be used to evaluate different alternative solutions for the selection of the most appropriate solution for rehabilitation. The authors suggest that the following 5 criteria have to be reviewed: •

Need based criteria – Labour intensity, high skill requirement, diversity and precision specification, repetitiveness, tedious and boring, critical to production, unpleasant and dirty.

•

Technological criteria – Material handling, precision work, quality requirements, production rate requirements.

•

Economic criteria – Productivity improvement, quality improvement, savings in labour, initial investment, operating cost and overall savings in project cost.

•

Safety and Risk criteria – Investment risk, operating hazards, equipment reliability, performance reliability and hazard to health.

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•

Project specification criteria – Site constraints, social constraints, schedule constraints and constructability constraints

Jeyapalan (2001) indicated that the design of pipe renovation normally meets some minimum consensus standards and due to the lack of standardized design methods that allow direct comparisons between available materials, or provide final designs on an equal performance basis, a unified design procedure for “no-dig” rehabilitation is proposed. The author describes the design philosophy and provides relationships for: •

Pipe stiffness calculations

•

Soil properties

•

Soil load on liner

•

Live load on liner for the different directions of travel

The design calculations for buckling include different configurations of the support from the host pipe.

Thèpot (2000) developed a design method for non-circular sewer linings for the French National Project of Research. The author divided the linings into two groups.

The first group is referred to as critical linings, which are liable to buckle but whose deflection lobe remains localized. The second group is referred to as sub-critical linings that do not buckle but whose deflection lobe may extend to the entire lining.

In the case of a critical liner the design method gives formulas for the buckling pressure, the bending moment and the axial force. The design method gives safety factors with respect to buckling and material breakdown.

For linings, which are sub critical, non-linear finite element analysis with appropriate formulation of the boundary condition may be used.

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4.6

Installation procedure and installation control

4.6.1 Installation procedure The installation procedures for the most common liner systems are discussed below.

4.6.1.1 Installation of Slip linings

Definition of a slip lining A pipe rehabilitation technology whereby the existing pipe is lined with a loose or tight fitting liner made of a plastic material such as polyethylene or PVC. Installation Procedure of slip linings According to PPI (1993) the procedure followed in slip lining is normally a seven-step process: 1. Inspect the existing pipe.

2. Clean and clear the line.

3. Join lengths of polyethylene pipe.

4. Access the original line.

5. Position the liner.

6. Make service and lateral connections.

7. Make terminal connections and stabilize annular space.

There are several ways in which the slip lining process is performed: •

The VIP-liner process uses segments of polyethylene pipe, which are jacked, into position from existing manholes. Joints are flush with “Oring� gaskets. It can be grouted if required.

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Figure 4.4: Polyethylene slip lining (Wood, 2003) •

The Danby process utilizes profiled PVC strips, which are spirally wound through existing manholes to form a liner. It requires grouting.

•

Expandit, PIM and Expand-a-line is where a pipe bursting machine destroys the existing pipeline and pushes the debris into the surrounding backfill material. Polyethylene pipe is inserted into the resulting cavity.

The new pipeline may be larger than the one, which was destroyed.

Renovation of buried water mains by insertion of a polyethylene (PE) lining (Figure 4.4) which achieves either a close-fit (small gap) or tight-fit (no gap) with the host pipe is now standard industrial practice. According to Boot & Toropova (1999) this work is mainly undertaken using one of three installation techniques, all of which involve a temporary reduction of the lining cross sectional area to enable the lining to be winched into the host pipe. The lining pipe is first formed by welding together lengths of factory produced PE pipe.

Grouted linings for renovating steel pipelines

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•

In the Rolldown process the welded pipe string is pushed through rollers to reduce its diameter plastically. A close fit between lining and host pipe is then achieved by applying an appropriate internal water pressure to expand the liner.

•

Swagelining involves drawing the lining pipe through a diameter-reducing die. In this case the deformations induced are largely visco-elastic, so that release of the die-drawing force results in a natural reversion of the lining towards its original dimensions; a close or tight fit can often be designed by appropriate selection of liner diameter.

•

The Subline technique achieves a significantly greater cross-sectional reduction by folding the pipe into a "U" shape (see Figure 4.5). During insertion, the pipe is maintained in this configuration using steel bands, following which internal water pressure is used to break the steel bands and revert the lining to achieve a close fit with the host pipe.

Figure 4.5: Folded PE slip lining ((Wood, 2003) Initially linings were invariably installed as full-thickness pressure pipe; however, it is now appreciated that in many cases the host pipe will only be subject to local damage during the lifetime of the renovated system. This realization has led to the concept of a polyethylene thin-walled lining (PETWL) as one capable of spanning only small (local) gaps and voids in the host pipe. In this manner hydraulic integrity is restored at significantly reduced cost and with optimum flow characteristics.

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4.6.1.2 Installation of Cement mortar linings (CML)

Description of CML The application of a cement mortar lining is a common and relatively inexpensive method of water main renovation. The cement mortar serves two main functions – the alkalinity of the cement inhibits corrosion of iron pipe, and the relatively smooth internal surface reduces hydraulic roughness and improves flow characteristics. It should be noted that cement mortar lining is also applied to many new cast iron and ductile iron pipes, also to inhibit corrosion.

The lining can fulfill a structural function other than to reduce the rate at which the host pipe will deteriorate. CML should not be used to resist internal pressure where corrosion has reduced the wall thickness significantly. The technique is not appropriate for pipes, which are leaking and complicate the installation of the liner due to groundwater ingress.

Installation Procedure for CML Application is generally carried out by a spraying machine which is either fed through hoses from the surface, or, particularly in larger pipes, may have its own hopper containing pre-mixed mortar. Forward speed control of the machine is important to produce a consistent thickness of mortar. Trowelling follows spray application (Figure 4.6). This may be carried out by rotating spatulas fitted to the spraying machine, or sometimes by a simple tubular shield of the required internal diameter, which is pulled through behind the machine. Whatever system is used, it is essential to centralise the equipment within the host pipe so that the coating is of constant thickness around the whole perimeter.

Historically this has been the most frequently used technique, it involves the scraping or high pressure water jetting of the deposits from the inside of the main and then applying a centrifugally sprayed cement mortar lining. •

Minimal excavation (approx. every 100 metres).

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•

Low cost – approx. 25 to 40% cost of replacement.

•

Minimum reduction to the available pipe bore.

•

There are sensibly no limitations on the size of pipe refurbished.

Figure 4.6: Cement mortar lining and drag trowel (Wood, 2003)

4.6.1.3 Pipe coated linings

Description of pipe coated linings A pipe rehabilitation technology whereby the pipe interior is coated with epoxy, resin, wax, polymer, rapid-setting polymeric or other material.

The use of non-structural lining for the passive protection of pipelines against internal corrosion has increased continuously since the early 1900’s when cement mortar was first used for in-situ lining. The perceived shortcomings of cement mortar lining with regard to carrying capacity, durability and restrictions on its use in contact with soft water supplies led to the development of similar lining systems using epoxy resin materials.

Epoxy lining may be seen as an alternative to cement mortar lining, and its function is similar – to provide corrosion protection and a smooth bore. The objective is for the resin to bond with the prepared internal surface of the pipe, forming a coating, which

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prevents water penetration and corrosion. Epoxy coatings are generally much thinner than cement mortar linings, and therefore do not cause significant bore reduction.

They also cure more quickly than cement-based materials. However, any defect in the epoxy coating may allow corrosion to start and, unlike cement mortar, there is then no alkalinity to inhibit deterioration chemically. Epoxy resins are also relatively expensive compared with cementitious materials.

Installation Procedure for coated liners Whilst initially used unsuccessfully some ten years ago, the technique has since been improved and is being used. The method is the same as for cement mortar lining but with the application of an epoxy resin (Figure 4.7). It has the advantages of: •

Minimal excavation required for rehabilitation.

•

Low Cost – although more expensive than cement mortar.

•

Minimal reduction in available bore – less reduction than cement mortar.

•

Smooth finish – gives improved hydraulic capacity c.f. cement mortar lining.

but the disadvantages of: •

No structural integrity – this limits its use to structurally sound pipelines.

•

Does not stop leaks (does not cover or seal joints).

•

Limited life expectancy – unknown at present but possibly less than 50 years.

•

Need for high degree of quality control – linings are very thin (less than 2 mm).

•

Cannot cope with displaced joints – insufficient thickness to "seal over"

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Figure 4.7: Resin spray machine (Wood, 2003)

4.6.1.4 Cured in place linings

Description of cured in place linings CIPP process is a widely used trenchless method for restoring structural integrity to and removing infiltration from sewers. It has been proven in pipes with a wide range of shapes and in large diameters.

Installation Procedure for cured in place linings In the CIPP process, a resin-impregnated tube is installed into a damaged sewer (see Figure 4.8). This process results in a seamless, jointless "pipe-within-a-pipe" with a smooth, continuous inner surface, which usually increases flow capacity. The steps are typically: •

Polyester felt tube is coated with a permanently bonded, continuous polyethylene layer;

•

The tube is filled with resin using a serial vacuum impregnation process.

This technique ensures the tubes are completely filled with resin, not air;

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•

The resin-filled tube is inverted (turned inside out) into a deteriorated pipe;

•

Water pressure propels the inverting tube through the pipe;

•

After the tube is fully inverted, hot water is circulated through it, curing the thermosetting resin and forming a new pipe; and

•

Service laterals are restored internally using robotically controlled cutting devices. The rehabilitated pipe is then inspected.

Figure 4.8: CIPP process

4.6.1.5 CemPipe CemPipe is a patented procedure, which employs a thermoplastic outside ribbed liner, and an annulus grouted procedure to construct the liner system.

Description of CemPipe CemPipe uses a cement mortar and PE with integral grout key hooks on one face (Figure 4.9). Thickness control is achieved by the depths of the grout key hooks.

Mortar slump is contained by the concentration of the hooks.

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Installation Procedure for CemPipe Quite simply, a CemPipe polyethylene tube, of the correct dimensions is winched along the length of pipe to be lined and a slug of cement grout fed into the void between the folded PE tube and the host pipe. The length of the lining and the requirement to completely fill the gap between the expanded PE tube and the pipe wall determines the quantity of mortar.

The PE tube is restrained at either end or a calibration hose cuffed into position at the start end of the lining. Using water and/or air, the calibration hose is then everted along the interior of the PE tube, progressively rounding the tube and distributing the cement mortar.

Once the entire length has been lined, pressure is maintained in the calibration hose until hydration takes place, after which the calibration hose is withdrawn and the ends trimmed.

Figure 4.9: CemPipe (Wood, 2003) The following manufacturers of other lining systems in South Africa were identified and information with regard to their systems were obtained:

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•

Petzetakis – Thermo plastic pipe manufacturer;

•

Engineering Lining (Pty) Ltd – Current international supplier of the Anchor Knob Sheets (Figure 4.10 refers); and

•

Steuler SA – German based company who specialize in floor and wall protection layers (Figure 4.11 refers).

Figure 4.10: Anchor knob sheets from Engineering Linings (Pty) Ltd

Figure 4.11: Anchor stud sheets from Steuler SA (Pty) Ltd

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4.6.2 Annulus grouting Schrock (2001) reflects some of the material limitations and required specification for annulus grouting for thermoplastic and thermosetting resin slip liners. Reference is made to the South Californian’s Standard Specification for Public Works Constructions, which has been quoted, in Imperial units According to the specification the following design considerations should be reviewed: •

Buoyancy stability and loading conditions on the slip liner;

•

Grout collapse pressure for the slip liner;

•

Grout Mix characteristics; and

•

Grouting installation procedures.

The upper value for the grout density can be determined by evaluating the vertical forces on the liner.

During the grouting care should be taken to prevent the annulus pressure to exceed the allowable or critical grouting pressure that can be determined as follow:

Pcgr =

24 EI C 2 3 (1 − µ ) Dm N

(Imperial units)

where: Pcgr

=

Allowable/critical grouting pressure

µ

=

Poisson Ratio – short term

I

=

Moment of Inertia (lb/ft)

I

=

t3/12 , solid wall pipe

C

=

Ovality Factor

N

=

Safety factor

D

=

Mean Diameter (inches)

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The author suggests that the sand and aggregate material should have a particle size less than the cement used for the mix and that fly ash additives should not be considered. Specifications for the density have been provided and the grout setting time should be in excess of 2 hours.

During installation the upstream and downstream pressures should be obtained through the use of pressure gauges with a saddle-type diaphragm seal to prevent clogging, and should be calibrated for accuracy. The range on the gauge should not be more than 100% greater than the design grout pressure 4.6.3

Welded steel liner

Suydam, Woods, Stewart, Shift (Unknown date) report on the installation of a welded steel liner 9,5 mm thick that was installed in 1,75 m diameter pre-stressed concrete cylinder pipe (PCCP). The specification required that the external diameter of the liner had to be 38 mm less than the internal diameter of the PCCP and that the annulus have to be grouted with concrete.

4.6.4 Case study of the implementation of CIPP

4.6.4.1

Introduction

Water quality complaints led the city of Ottawa to refurbish some of the water infrastructure, which dates back to the 1870’s. Since 1998 different non-structural and structural cured in place lining projects were completed. A common problem to the different installations was the disposing of the residual debris from the water used for the cleaning process.

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4.6.4.2 Installation of CIPP It is reported that the epoxy lining process requires quality control on the material and the application process.

The ensuing list presents some of the quality control elements that are required: •

A weight check on the material before application in the pipe;

•

Hard copy printout from the lining rig indicating the time elapsed, the

length lined, the thickness applied, the mix ratio, the application pressure of the components; •

A tab card to monitor the color and hardness of the mixed material;

•

A pre-lining and a post lining CCTV survey.

The structural linings were either epoxy resin lined or a polyester woven fabric, with an internal polyurethane lining.

The structural liner was then impregnated with a

two-part epoxy resin. This new product, known as Aqua-Pipe, is classified as a cured in place pipe (CIPP).

The aspects that were included in the quality assurance were: •

Pre-Lining CCTV inspection,

•

Number of service connections on section being lined,

•

Batch numbers of resin used,

•

Time of impregnation (start and finish),

•

Time of installation of impregnated tubing (start and finish),

•

Time of curing (start and finish),

•

Pressure gauge readings (during curing),

•

Water temperature (during curing),

•

Pressure testing before reinstatement of service connections (date and results),

•

Reinstatement of service connections (date and time),

•

Post-Lining CCTV inspection (date),

•

Third party testing results,

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•

Date the section was accepted by the Engineer.

The success of the projects has been due to the appropriate pre-construction planning and communication, coupled with the proper site supervision for the different technologies.

4.7

New developments

4.7.1 Alternative protection methods Guan (2003) reflected the historic development and current status of 100 % solids Polyurethane coatings for which numerous standards have been developed and which is one of two preferred protection methods in the coating choices in water and wastewater industry. (AWWA C222 – 100% solids Polyurethane coatings for interior and exterior protection of steel water pipes and fittings).

The characteristics of 100% solids Polyurethane coatings are that it contains no solvents, comprising only of liquid, poly-isocyanate and polyol-cured urethane.

Table 4.4 reflects the performance properties of typical elastometric polyurethane, polyurea and rigid polyurethane coatings while Table 4.5 reflects the key considerations for pipe coating selection and Table 4.6 compares 100% solids Polyurethane coatings with other common pipe coatings.

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Table 4.4: Performance properties of typical elastomeric polyurethane, elastomeric polyures and polyurethane coatings used for pipeline applications (Guan, 2003) Variable Typical application thickness

Elastomeric polyurethane

100% Rigid

Elastomeric polyurea

polyurethane

1 mm to 1,5 mm

1 mm to 1,5 mm

0,38 mm to 0,75 mm

1,5 mm to 3,8 mm

1,5 mm to 3,8 mm

1 mm to 2 mm (40 to 80

for steel Typical application thickness for concrete Adhesion to steel (SP1 0,2 mil

mils) 700-2 200 psi

500-2 000 psi

1 000-4000 psi

Cathodic disbondment (ATM

10mm to 35 mm disbonding

25 mm to 38 mm disbonding

3 mm to 1 5 mm disbonding

G95,3%NaCl,-1.5 volts, 30

radius

radius

radius

20% NaOH

Pass

Pass

Pass

10%H2SO4

Pass

Pass

Pass

25% H2SO4

Fail

Fail

Pass

3% NaCl

Pass

Pass

Pass

Gasoline

Fail

Fail

Pass

Toluene

Fail

Fail

Pass

Dielectric strength ASTM G149

5-20 V/um

5-20 V/um

10-30 V/um

Elongation, %

50-1 500%

20-1 000%

3 -5 0%

Impact resistance, fully cured, 1

80-200 in.lbs

60-200 in.lbs

30-125 in.lbs or 45-160

profile)

days, 23째C) Chemical resistance (ASTMD7 16, 1,000 hours immersion)

mm (40 mils) DFT

in.lbs* * ceramic modified

Shore Hardness

A20 to D65

A20 to D65

D50-D90

Taber abrasion resistance (CS

2-4Q mg weight loss

6-70 mg weight loss

30-60 or 10-30* mg

17, 1 Kg, 1000 cycles), fully

weight loss * ceramic

cured

modified

Tensile strength

1 000-2 000 psi

1 1 00-4 000 psi

3 500-7 000 psi

Water absorption (ASTM

5-15%

5-16%

1-2%

D570, 48 hours at 50째C/122째F)

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Table 4.5: Key consideration attributes in Pipe Coating Selection (Guan, 2003) Attribute

Main Considerations Format, mixing ratio, solids content, compliance with OSHA, EPA, and FDA

Handling and safety

environmental and health standards such as VOC and industrial or standard

characteristics

requirements such as NSF 61 for water safety, flammability, application methods; Containing of any hazardous ingredients such as coal tar, amines, solvents, etc.

Shop/field application and repair attributes

Quality and inspection; Technical support of the coating's manufacturer; Ease of application

and

repair;

Environmental

conditions

(e.g.

humidity,

ambient

temperatures, dew point, etc.).

Surface preparation

There should be no short cut here; Blasting profiles; Surface containment levels;

requirements

Surface preparation for field coating.

Properties such as adhesion; permeability; impact, penetration, and abrasion

Physical performance

resistance; cathodic disbondment resistance; flexibility; chemical resistance, as results

requirements

of considering the type of soil and back fill; the use of cathodic protection; pipe installation methods and location; corrosive environmental conditions.

Case histories

Performance and capability of shop/field technical support, particularly while selecting and launching new pipe coating systems.

The true coating cost is the sum of materials cost + application cost + maintenance

Cost analysis

cost +hidden cost Coats to be applied; Hidden costs such as project timing; flow efficiency of the lining; installation and repairs; and operation cost.

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Table 4.6: Comparison between several common pipe coatings with 100% Solid Rigid Polyurethane (Guan, 2003) Coating System

Advantages Easy to apply; Minimal surface preparation

Bituminous enamels

required; Long track record; Permeable to cathodic protection; Very Economic

Limitations

Application

Subject to oxidation and cracking; Soil stress has been an issue; Limitations at low application temperatures; Environmental and exposure concerns; Associated with

Exterior; Usage has been diminished

corrosion and stress crack corrosion failures Poor shear stress resistance; Many documented failures; Easy damage;

Tape coating

Simple application

Adhesives subject to biodegradation; Exterior only;

Exterior; Water & wastewater pipe

Shield effect to CD possible 2LPE

FEE

Excellent track record; Good handling Excellent corrosion resistance

Limited temperature range; Poor shear stress resistance; Limited pipe size (<24); Field application Low impact resistance; limited to pipe size (< 43 inch); Field application

Mostly oil & gas pipe; Maui line Mostly oil & gas pipe; Main line

Economical; long Solvent or 100% solids epoxy

history; Most uses

Slow curing; Poor low temperature

conventional airless

curing ability; Multiple coats; Poor

equipment to apply; can

impact and flexibility

Pipe and joints

be brushed on

Cement mortar

Minimal health and

Easily damaged; Can't be applied in

safety or environmental

cold weather; Add significant

issues; fast to apply; no

weight to pipe; Reduces pipe

blasting; well proven

diameter and pipe capacity; Difficult

and documented

to use apply in fabricated pipe

history; inexpensive;

(elbows, fittings, etc.); poor abrasion

total applied cost is low

and chemical resistance

Polyethylene

Simple application;

encasement

Very economical

T Lock system

Mostly water pipe & interior

Restrict the subsequent use of cathodic protection; Easy

Exterior and DIP only

damageable

Cast in application; no

Limited success; Corrosion due to

surface preparation

damage of the sheet

Interior and concrete

Low temperature 100% solids rigid polyurethane

curing; Fast setting;

Need to use plural component

Excellent abrasion and

system; Application complexity;

impact resistance;

Sensitive to moisture

Adhesion

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Both shop and field; Mainline and joints

Chin and Lee (2004) developed a rehabilitation process for underground pipes using vacuum assisted resin transfer molding (VARTM) with glass fiber fabric, to overcome the disadvantages of present trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised with a flexible mold technology. Although the procedure have not been implemented, the laboratory test that were conducted on a 600 mm concrete pipe reflected that the developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies.

The steps of the resin transfer molding (RTM) process are graphically shown in Figure 4.12.

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Figure 4.12: Repairing processes of underground pipes with RTM: (a) preprocessing; (b) placing of the reinforcing element; (c) attaching of the covers and sealing; (d) removal of wrinkles and twists of the reinforcing element; (e) injection of polyester resin; (f) wetting of resin into the fiber preform and removing voids and excessive resin within the perform (Chin and Lee, 2004).

The proposed liner is a multi-layer system with a glass-fiber preform that is impregnated with resin after the liner have been slipped into the pipe and pressurized in place. On both sides of the glass fiber is a Pro-sol film, which has superior tensile strength (100 MPa).

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Figure 4.13: Schematic diagram of the repairing-reinforcing experiment with glass fiber fabric and unsaturated polyester resin using RTM and dielectrometry.

Figure 4.14: Configuration of the reinforcing element.

A low viscosity resin (0,2 Pa s), PC670 was used to impregnate the fiberglass by creating a pressure differential from the input side to the breather side. Figure 4.15 reflects the resin flow direction through the fiberglass, which was used to determine the flow characteristics of the resin. The flow characteristics proofed to be acceptable.

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Figure 4.15: Model for resin flow in the fiber preform used for resin wetting analysis A major quality control issue always remains to ensure that all the voids have been filled with resin and that the fiberglass has been properly wetted. Due to the opaque nature of the Pro-sol film the effective wetting of the fiberglass. The authors utilize dielectrometry and dielectric sensors to on-line monitor the resin flow and cure status in the pipe, from which the applied pressure and temperature were adjusted. The dielectrometry is a promising technique for continuous monitoring of thermosetting resins.

The dielectrometry procedure works on the principle that when an alternating electric field is applied to the two electrodes of the dielectric sensor embedded in the composite material (Figure 4.16(a)), the dipole and ions within the resin, which is a dielectric material, are aligned following an applied alternating electric field. At this time, the combination of two electrodes and polymeric resin can be modeled as a parallel equivalent circuit composed of resistance Rm and capacitance Cm as shown in Figure 4.16(b). The mobility of dipoles and ions has close relations with the cure state and the viscosity of resin within the composite material as shown in Figure 4.16(c), and can be expressed by the dissipation factor D, which represents the ratio of the energy loss by movements of dipoles and ions to the supplied electric energy.

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Figure 4.16: Principle working of the dielectrometry procedure

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5.

FIELD INVESTIGATIONS

Budget constraints and the Various complications and manufacturing This aspect has not been finalised and it is envisaged that once the final results have been obtained from the laboratory study, test sections will be renovated by Rand Water based on the findings of this research.

The selection of the suitable pipelines in which to install test sections of grouted linings was originally made to accommodate the Rand Waterâ&#x20AC;&#x2122;s pipeline strategic renovation programme, but due to changes could not be accommodated during this research period. The pipelines which were initially identified are listed Table 5.1.

Table 5.1: Pipelines targeted for investigation by Rand Water

Code

G7

Pipeline name

Outside

Total

Length to

diameter length

renovate

(mm)

Village-

610 and

Signal Hill

762

(m)

2 800

Turfontein G16

Nek-

1250

Booysens

4790

(m)

Minimum wall

thickness (years)

6.3

610mm

riveted

project

Lining type

(mm)

Âą 800 of

To suit

Age

9.5 riveted

84

Bitumen

66

Bitumen

When this research is continued these pipelines might still be included for the field work.

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6.

EXPERIMENTAL INVESTIGATIONS Objectives of the experimental work

6.1

The objectives set out for the experimental work was to: • • • •

Establish the ease of installation for liners which could be used for steel pipelines; Test the installation of joints; Establish how the liner performs under high internal pressure; and Determine if the liner could be installed along bends.

These objectives led to the following actions which were performed during this research: • • • • • • • • •

Identifying liners that are available and which could be used in high pressure conduits; Evaluating their inherent tensile characteristics; Assessing the bonding of the liner to the inside of the host pipe; Asses their ability to breach a hole in the pipeline; Defining an installation procedure and reviewing the ease of installation; Assessing the required grout characteristics and the ease to grout the annulus space; Establish the potential influence of thermal variations on the behaviour of the liner; Developing and test field joint systems; and Establishing the contribution of the liner to the strain characteristics of the pipeline.

Results of these investigations are covered in the following sections.

6.2

Identification of possible liners

Based on the understanding of the characteristics of a liner for the renovation of steel pipelines, the following two liner systems, which were available at the time of the investigation in South Africa, were selected for further testing: •

•

Anchor Knob System (AKS) – A South African manufactured product already widely used in low-pressure sewer lines to prevent corrosion. Two different thermoplastic materials are used in the manufacturing of the liner – HDPE or LLDPE. Cemlam – a thin polypropylene (PP) sheet with a PP mesh ultrasonically welded to the film, creating the capacity to mechanically bond with the mortar grout.

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Figures 6.1 shows some features of the two products.

Figure 6.1: AKS liner system Subsequent to the selection of these two liners, information was obtained about the AGRU liner system (an Austrian Firm) that has been used by Gundle Plastic SA for low-pressure applications. This product was not further investigated.

6.3

6.3.1

Initial comparative test of the selected two liner materials

Purpose of the experiment for determining the tensile strength

Comparative tests were conducted on the selected two liner materials with reference to their behaviour under tensile forces, with the objective to establish which of the liners will have a comparable structural behaviour with that of the steel host pipe.

From these results a liner will be selected for further testing.

In this review it was also required to determine how homogeneous the material is and what the failure mechanism of the material is.

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6.3.2

Experimental set-up for the tensile test

Test samples were cut from the material provided by suppliers. The first samples were approximately 22 mm wide and 200 mm long. The samples were clamped into a tensile testing machine as can be seen in Figure 6.3.

Figure 6.3: Test setup for tensile testing (Cemlam) The samples were tested by deforming them at a constant rate while recording the elongation as well as the force required to achieve the elongation.

6.3.3

Results obtained for the comparative tensile tests

Examples of the typical load deformation behaviour of 22 mm wide strips of the two materials can be seen in Figure 6.4. These results clearly indicate that the Cemlam sample fails at a load which is only 35% of the failure load of the AKS. However Cemlam has a lower initial stiffness and deforms more than the AKS, before the maximum load is reached.

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The actual failure mechanism of the two materials differs significantly. The AKS elongates to about 2,5 times the initial length before the material starts tearing as can be seen in Figure 6.5. The plastic backing of the Cemlam started tearing before the peak load was reached and thereafter the strands in the woven net started failing one by one â&#x20AC;&#x201C; resulting in the ragged pattern of the load- deformation curve. Once the first strand fails, the rest of the net failure is brittle.

22mm wide liner strip 1600 1400 1200 Load (N)

Anchor knob

1000 Cemforce

800 600 400 200 0 0

50

100

150

200

Strain (%)

Figure 6.4: Load deformation comparison

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250

300

Figure 6.5: Deformation of AKS It could be argued that the liners do not have the same thickness and it would thus not be fair to compare the materials, not taking thickness into account. Material thickness can be taken into account by plotting the stress in the material as a function of the strain as indicated in Figure 6.6 and Figure 6.7 for the AKS and Cemlam respectively. From Figure 6.6 it can be seen that both AKS specimens tested started to deform plastically as soon as a stress of 20 MPa was reached.

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3mm Anchor knob liner 35 30

Stress (MPa)

25 20 15 10 5 0 0

50

100

150

200

250

Strain (%)

Figure 6.6: Stress strain behavior of AKS

Cemforce liner 35 30

Stress (MPa)

25 20 15 10 5 0 0

50

100

150

200

250

Strain (%)

Figure 6.7: Stress strain behavior of Cemlam The second test was stopped before the sample failed, but it can be seen that the behaviour of the two specimen were similar. The specimens will be able to sustain more than 80% of the maximum load even after large deformations have taken place.

There was no indication of tearing taking place around the anchor knobs and these knobs are not causing weak spots in the material.

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From Figure 6.7 it can be seen that the one Cemlam specimen started failing at a stress of 20 MPa but the stress increased to 25 MPa before failure took place. The second specimen failed without much warning at a stress of 32,6 MPa. The failure load of the one specimen is approximately 75% of the other, which indicates that the strength of this material is more variable than that of the AKS. Both specimens failed in a brittle manner and once failure commences, the residual strength is not a property that can be used.

Initially it was decided to use a white AKS with the hope that the sheets would be sufficiently transparent for the grout to be visible through the sheet. This would make it possible to identify voids in the grout visually. After initial testing it was concluded that it would not be possible to see through the liner and that any colour could be used. Material was sourced from AKS/EL and the new liner material was supposed to be thinner than the 3mm thick sheets initially tested, but accurate measurements indicated that there was no noticeable reduction in thickness.

Strength tests were conducted on the new AKS material and the results can be seen in Figure 6.8. Six specimens (26 mm wide and 100 mm long) were cut from the material that was actually used in the full scale liner test setup. The thickness of these specimens varied between 2,85 mm and 3 mm. The specimens were clamped into the test frame to have a test length of 75 mm. The stress strain behaviour of the six samples does not vary significantly. All six samples elongated more than 150% before failing and the stress that could be sustained after large deformations were more than 80% of the ultimate failure stress. The maximum stress induced in the specimens varied between 14,3 MPa and 15,5 MPa, which is significantly less than that of the previous specimens (more than 20 MPa). This material is clearly not identical to the previous sample and care will have to be taken to ensure that the material used by contractors has sufficient strength.

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20 18

Specimen A

Stress (MPa)

16 14

Specimen B

12

Specimen C

10

Specimen D

8

Specimen E

6

Specimen F

4 2 0 0

50

100

150

200

250

300

Strain (%)

Figure 6.8: Stress strain behaviour of second AKS sample The extent of the deformation that the HDPE AKS can sustain prior to failure can clearly be in Figure 6.9. The top specimen in Figure 6.9 gives an indication of the original spacing of the anchor knobs, while the total length of the bottom specimen contains only three anchor knobs. It can be seen that the material stretches around the knobs.

Figure 6.9: Extent of deformation of the AKS system (HDPE) prior to failure

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6.3.4

Conclusions and recommendations from the comparative tensile test

Although the Cemlam has a higher tensile strength than the HDPE AKS, the difference in thickness results in the 3 mm thick AKS yielding a higher load carrying capacity than the Cemlam. The AKS failure is less brittle and more repeatable than the failure of the Cemlam. The anchor knobs in the AKS do not cause weak points, where failure commences.

It is recommended that the AKS liner (HDPE) should be used in the other experimental tests. The relatively brittle failure of the Cemlam as well as the premature rupture of the plastic layer increases the risk of failure of a Cemlam lining system which was therefore not assessed further in these investigations.

A strength specification will be required to ensure that the material (HDPE) used for liners meets the expected levels.

6.4

Flat Plate test (Bondage between grout and steel pipe material)

6.4.1

Purpose of the flat plate experiment

The purpose of this part of the experimental program was to determine the effect of the bond between the steel plate, the mortar and the plastic liner. Six steel plates were prepared where two of the plates were new smooth steel, two plates were pre-treated with acid to enhance bond between the concrete and the steel and the last two plates were sand-blasted to produce some surface roughness.

6.4.2

Experimental set-up for the flat plate test

For each of the steel plates the plastic liner was placed on a Perspex plate and the steel plate was bolted to the back of the liner. The edges of the set-up were sealed and the opening between the plastic liner and the steel plate was filled with grout. The intention was to place the flat sheets in a rig that could be used to apply a tensile force on the steel (Figure 6.10). The stress in the plates as well as the strain would be recorded and the behaviour of the mortar observed.

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Figure 6.10: Flat plate test to determine the bonding of the grout and the pipe 6.4.3

Results obtained from the flat plate tests

The results from this experiment were contrary to the assumption that the system will function as a composite steel-mortar-liner panel. Delamination occurred when the Perspex sheet was removed. The mortar stuck to the plastic liner as can be seen in Figure 6.11. The mortar was uniformly distributed and the anchor knobs did not cause any irregularities in the mortar. Upon drying the mortar did not crack around the anchors or delaminate from the plastic. However the current test set-up is not suitable to deform the liner alone and it was decided that the behaviour of the composite would be determined from the actual behaviour in a 900 mm diameter test section subjected to 300 m water pressure.

Figure 6.11: Mortar stuck to the liner

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6 â&#x20AC;&#x201C; 10

6.4.4

Conclusions and recommendations

These tests were inconclusive and might have to be repeated in a follow-up project, in which an addition load that would reflect the influence of the internal pressure on such an installation.

6.5

Performance of AKS under internal pressure in areas without grout (circular sections)

6.5.1

Purpose of the experiment

It was established during the tensile testing of the liner samples that the AKS did not fail in a brittle manner and that the anchor knobs did not cause weak points in the liner. However the tensile tests were conducted by applying a one directional force in the plane of the material and in a pipeline the material would be subjected to both ring-tension and water-pressure, resulting in forces in the plane of the sheet and perpendicular to the liner. During the grouting of the annulus space between the liner and the host pipe, there is a possibility that the flow of grout is restricted in some areas resulting in small sections of liner that will remain unsupported by grout. In these areas the liner will have to sustain water pressures of up to 300 m without failing. The purpose of this part of the experiment is to establish the behaviour of the liner when loads are applied perpendicular to the liner.

6.5.2

Experimental set-up

For this part of the experiment a pressure chamber placed in a room with a temperature of 25oC and a relative humidity of 55% was used as indicated in Figure 6.12. The chamber was filled with water and the pressure was gradually increased gradually up to 300 m water pressure.

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Figure 6.12: Experimental components to verify the response of the liner without grouting support In the first part of the experiment the liner was backed by a solid steel plate, preventing movement of the liner beyond the bottom of the knobs (Figure 6.12). This would simulate the situation in a steel pipe, where the expansion of the liner would be limited by the containment of the steel pipe. Specimens were placed under constant water pressure of 100 m, 200 m and 300 m for 10 days each. Upon removal from the chamber the specimens were visually inspected for any signs of damage (Figure 6.13).

Figure 6.13: Deformation of the liner without backing (no grout) and a pressure of 100 m Similar results were obtained for the pressures up to 30 Bar. In none of these cases the liner leaked or tore.

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Figure 6.14 reflects the findings for a specimen that was pressurised up to 300 m for a 10 day period.

Figure 6.14: Deformation of the liner under a pressure of 300 m In the second part of the experiment a hole was cut in the centre of the steel plate which previously backed the liner, resulting in an unsupported circular area of AKS with a diameter of 80 mm. This would simulate the behaviour of the AKS liner in areas where small sections of the liner is supported by neither grout nor steel pipe.

During the second part of the experiment the specimen failed at a water pressure of 100 m. The failed specimen can be seen in Figure 6.15. The unsupported area of the specimen is clearly visible on the left section of Figure 6.15, while the insert on the right indicates the extent of the deformation (“blow-out”) that occurred when the pressure reached 10o m.

Figure 6.15: The burst disc that was pressurized to about 100 m

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6.5.3

Results obtained from the review of an un-grouted AKS liner experiencing high pressures

The AKS liner will not fail with 300 m water load if there are ungrouted areas that are supported by the host steel pipe. The liner will however burst at pressure as low as 100 m water pressure if there are areas of the liner (as small as 80 mm in diameter) unsupported by grout as well as the steel pipe.

6.5.4

Recommendations

Care should be taken to ensure that the liner is not used in areas where the steel pipe has large holes that could result in bursting of the liner due to insufficient support. A relationship of the whole size, internal pressure and liner material thickness and material characteristics need to be determined prior to the installation of the selected liner.

6.5.5

Review of the deformation of a larger unsupported AKS liner disc

An experiment was set up to determine the deformation-pressure relationship of a larger AKS liner disc. Figure 6.16 reflects the setup, while Table 6.1 provides the initial results of the deformation of the liner at different pressures and a constant temperature of 240C. Table 6.1: Details of the tests that were conducted on the AKS disc Disc dimension

Temperature

280 mm diameter

24 0 C

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Maximum pressure (m) 10,5 7,1

Maximum deformation (mm) 105 70

Figure 6.16: Setup for the deformation measurement of the disc 6.6 Installation of the liner Table 6.2 reflects the proposed steps for the installation of the AKS liner system in existing pipelines.

Table 6.2: Proposed steps for the installation of the AKS liner system Step

Description of action

1

Place the liner into the pipeline

2

Provide seals for the initial grout phase

3

Isolate the liner and pressurize the liner prior to grouting

4

Conduct the primary (initial) grout

5

Install the Steel and HDPE flanges

6

Conduct the secondary grout

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6.7 Primary grouting of the first pipe segment 6.7.1

Purpose of the experiment

The purpose of this part of the experiment was to establish whether it would be physically possible to grout the liner into a pipe. While the grouting of the annulus space between the liner and the host pipe, it is required to support the liner in position up to the time when the grout has reached sufficient strength.

6.7.2

Experimental set-up

In this part of the experiment an AKS liner was placed in a 3 m long section of 900 mm diameter pipe as can be seen in Figure 6.17.

Figure 6.17: The liner installed in a 3 m long steel section For the first section of pipe a bladder system was used to contain water in the pipe.

This water could be pressurised sufficiently to ensure that the liner did not collapse under the load of the wet grout during or immediately after grouting. A flat steel plate

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6 â&#x20AC;&#x201C; 16

was placed in each end of the pipe and these plates were tied to each other with a cable. A tractor tube was placed on the outside of each of these plates and steel rings were tied to the outside of the tubes to keep the tubes in place, shown in Figure 6.18.

Figure 6.18: Configuration of the setup during the primary (initial) grouting Nozzles were welded onto the lowest point of the bottom of the pipe for a grout entry point and at the highest point of the top of the pipe for a bleed point. Bicycle tubes were placed between the liner and the steel pipe and inflated to contain the grout.

The mixed composition that was used for the grout in the first pipe section is indicated in Table 6.3. During grouting test cubes were cast to establish the strength development of the grout. Three 100 mm cubes were cast for testing after 24 hours, 7 days, 14 days and 28 days, and the strength recorded in this report is the average strength of the three samples. The cubes were de-moulded 24 hours after casting and cured in 25oC water up to the time of testing.

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Table 6.3: Grout mix composition Type

RD

Kg/m3

PPC Cem 1 42.5R Condensed Silica Fume (CSF) GP Grout (Chryso) Silica Sand Premia 100 (Chryso) Optima 100 (Chryso)

3,14 2,2 2,75 2,65 1,19 1,19 1

57,96 34,78 1159,3 579,65 3,94 3,94 318,81

Density:

2158,38

Material Cementitious Sand Admixture Water

6.7.3

Results from the grouting of the first pipe section

The strength development of the grout, as established from the test, can be seen in Figure 6.19 where the compressive strength is plotted as a function of time. The 24 hour strength is 5 MPa and the 28 day strength is 60 MPa. It is normal concrete practice to specify a characteristic 28-day strength, which is defined as the strength which would be exceeded by at least 95% of the samples tested. Depending on the repeatability of the strength results, this mixture would probably have a characteristic

Compressive strength (MPa)

strength of about 50 MPa.

70 60 50 40 30 20 10 0 0

5

10

15

20

25

30

Time since casting (days)

Figure 6.19: Compressive strength of the grout The support of the liner was removed within 24 hours and the liner did not collapse, which indicates that the early strength is sufficient. It should be possible to use grout

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6 â&#x20AC;&#x201C; 18

with a lower ultimate strength, but that would have a negative effect on the early age strength. Currently the mixture contains a set-retarder (Optima 100), to ensure that the grout remains pumpable for as long as possible. The use of a retarder would however reduce the early strength and if the retarder is removed, it should be possible to aim for lower 28 day strength, without reducing the early strength significantly. This would however reduce the time that can be used to place the grout. The exact mix composition of the grout will have to be a function of the length of pipe to be grouted as one section.

During the grouting process the end plates kept on moving. The pipes were not perfectly circular, which resulted in the tubes â&#x20AC;&#x153;popping outâ&#x20AC;? as can be seen in Figure 6.20. This resulted in water leaking out, which caused the pressure to drop, thus enabling the liner to bulge into the pipe allowing the grout to congregate in the bottom of the pipe. In Figure 6.21 the bulge that formed, can be seen in the right hand bottom side of the pipe.

Figure 6.20: Bulging of the tube that was used to seal the liner

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Figure 6.21: Bulging of the liner due to the loss of internal pressure during grouting

6.8

Installation and grouting procedures

6.8.1

Grouting procedure

The concern about the potential heat damage to the liner, which could result from the welding of the steel flange onto the pipe, led to the following suggested installation and grouting procedure as suggested in Table 6.4.

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Table 6.4: Initial suggested installation and grouting procedure

Step

Description

Visual demonstration

Problems experienced with the proposed procedure

No problems were 1

experienced with the

Place the liner

installation in the straight

into the pipeline

section used in the experiment.

` Difficulties were experienced

Provide seals 2

to create a good seal between

for the primary

the steel pipe and the AKS

(initial) grout

liner. This procedure has to

phase

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be changed.

6 â&#x20AC;&#x201C; 21

Step

Description

Visual demonstration

Problems experienced with the proposed procedure Difficulties were experienced and it was concluded that

Isolate the liner 3

this procedure, to isolate the

and pressurize

section of liner to pressurize

the liner prior to

it prior to grouting, will not

grouting

be practical in large diameter pipelines.

4

Conduct the

No problems were

primary (initial)

experienced with the primary

grout

(initial) grouting

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Step

Description

Visual demonstration

Problems experienced with the proposed procedure

The thermal welding of the Install the Steel 5

and HDPE flanges

pre-manufactured flange Steel flange with a spool piece was slided

onto the liner was difficult

over the pipe section (not shown here)

and had to be conducted by an experienced (thermoplastic) welder.

6

Conduct the

No problems were

secondary grout

experienced

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6.8.2

Conclusions and recommendations

The support of the liner was removed within 24 hours and the liner did not collapse, which indicates that the early strength of 5 MPa is sufficient.

The bladder system did not work as it was impossible to maintain the water pressure in a pipe that was not perfectly circular.

It is recommended that: â&#x20AC;˘

The exact mix composition of the grout will have to be a function of the length of pipe to be grouted as one section.

â&#x20AC;˘

An alternative method of keeping the liner in place should be developed and for the second pipe section the pipe should be closed up (welded and bolted) before grouting takes place. This will make it possible to fill the pipe with water and use the valve system to contain the water while the grout is wet. Consideration should be given to weld up the flanges and provide a flange or dome to be able to charge the pipeline and pressurize the water on the inside of the liner to the required head to ensure that the liner is secured in the host pipe.

6.9

Preparation of the experimental setup for secondary grouting

6.9.1

Purpose of the experiment

The purpose of this experiment was to review the welding of the HDPE flange onto the liner, to determine if the steel flange could be welded onto the pipe if the liner is protected by the grout and define what would happen if the liner was not protected thermally by the grout. Further it was necessary to consider different mechanical seals between the steel flange and the HDPE flanges to ensure a watertight coupling.

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6.9.2

Experimental set-up

6.9.2.1 Positioning and welding of HDPE flanges onto the liner The HDPE liner was manufactured under instruction of EL from flat HDPE sheets.

The flange had a recess to accommodate the liner as is shown in Figure 6.22.

Figure 6.22: Inside view of the HDPE flange with the 35 mm recess for the liner

6.9.2.2 Welding of steel flanges The steel flanges were welded onto the pipe after the liner was in place. This resulted in the liner melting as can be seen in Figure 6.23 (indicated in red). This problem was overcome by placing a sprinkler system in the pipe during welding. In Figure 6.24 the heat generated in the steel as a result of the welding, can be seen on the reference line 2-3 on the side of the pipe. The presence of the water cools the liner down to below the melting point of HDPE. It is recommended that this will be an acceptable procedure for the welding of the steel flange and that the staged grouting procedure is not required.

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Figure 6.23: Positions where the liner has been damaged by the welding of the steel flange

Figure 6.24: The arc weld plasma shining through the liner

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6.9.2.3 Positioning and flogging of steel flanges The requirement to ensure a watertight seal between the steel flanges at the field coupling required that the bolts of the flanges had to be flogged by an experienced person.

6.9.2.4 Positioning of end domes Depending on the diameter and the pressure required to ensure that the liner is kept in position the last pipe will have to be fitted with a blank flange or dome. The requirement of a dome will be calculated for each such installation.

6.10 Testing of different seal arrangements at the couplings 6.10.1 Different seals During the experimental investigation different coupling seal options were evaluated with the objective to establish a workable configuration to be used during field installations.

6.10.2 Experimental setup to evaluate different seal arrangements In the experimental setup shown in Figure 6.25, the coupling configurations indicated in Table 6.5 were used.

Figure 6.25: Schematic layout of the couplings which were tested

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Table 6.5: Details of the setup at the coupling Coupling

Leftmost

1 2

Steel

3

Second layer Rubber insertion HDPE flange HDPE flange

Third layer HDPE flange HDPE flange O-ring

Fourth layer

Rightmost

None None

Steel

HDPE flange

The seals for the different couplings functioned as indicated in Table 6.6.

Table 6.6: Overview of the water tightness of the couplings Test Phase 3 4

Pressure (Bar) 21,3 18

Coupling Worst Best 1 2,3 1,2 3

Comment By tightening the bolts the initial leaks were fixed

6.10.3 Recommendation pertaining the field arrangements for a watertight coupling The performance of the different couplings indicated that the positioning of an O-ring between the two HDPE end flanges was required. Figure 6.26 reflects the proposed sealing system for the field joints.

Figure 6.26: Sealing arrangement at the field joints

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6.11 Determination of the pressure strain relationship of the pipeline with the liner

6.11.1

Testing procedures

It was decided to install strain gauges in the radial and longitudinal direction to measure the deformation during the filling and pressurizing of the pipeline.

Figure 6.27 reflects the installation, while Figure 6.27 reflects the installed strain gauge and Figure 6.28 shows some of the wiring that is required to record the data.

Figure 6.26(a): Installation of the strain gauge

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Figure 6.27: Installed strain gauge and LVDT mounting

Figure 6.28: Wiring of the instrumentation to conduct the measuring

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6.11.2

Pressure tests which were conducted

Table 6.7 reflects the pressure transducers that were used during the pressure testing.

Table 6.7: Pressure transducers installed to capture the internal pressure Distance Phase of Capacity Position above the testing Transducer (Bar) crown PT19 and 3 50 PT20 Eastern 218 and 392 Y111336 dome 4 40 Y111338 Western Dial gauge dome After the pipeline was grouted different tests were conducted as reflected in Table 6.8.

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Table 6.8: Details of the test phases that were conducted on the 900 mm pipe Date

Phase

Nov 06 to Feb 07

1 – Instrumentation

19 March 07 to 18 June 07

2 – Installation of liner

Sept 07 to Dec 07 Jan 08 to March 08

3 – Pressurization of lined system 4 – Pressurization of bare pipeline

Maximum pressure (Bar)

Comments Strain gauges were installed.

Not pressurised – just filled

21,3 18

Various leaks in the liner (joints) were experience, which was difficult to pinpoint. Liner collapsed in western pipe and the liner was removed.

The weak points were the couplings that had to be tightened.

6.11.3 Strain calculations and results Positions where the strain gauges have been installed are referenced in Figure 6.29 and Figure 6.30.

Figure 6.29: Reference positions along the pipeline stain gauges were installed

Figure 6.30: Reference positions where the stain gauges were positioned

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Table 6.9 reflects details of the pressure tests for which the strains in the pipeline were determined.

Table 6.9: Details of the pressure tests which were performed on the lined and unlined pipeline Test

Test

Liner

number

date

details

22

Liner

Nov

and

07

grout

1

Maximum

Figure numbers for the graphical results

head

Pressure

Pressure â&#x20AC;&#x201C; Strain

(m)

variation

relationship

213

6.31

6.32 to 6.34

6.35

6.36 to 6.39

6.40

6.41 to 6.43

22 1

2

Feb 08

No

26

liner

Feb 08

The graphical results are reflected in Figures 6.31 to 6.42 as reflected in Table 6.9.

Table 6.10 reflects the notation used for the reference positions where the strains were measured.

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Table 6.10: Notation used to reflect the positions where the strains were measured Position of alpha/numeric characters First two alpha/numeric characters P1 P2 Third and fourth alpha characters SW SC SE Fifth and sixth alpha characters CR NS I SS Seventh alpha character L C

Description General Pipe (Figure 6.29) General Position of the station (Figure 6.29) General Position around the circumference of the pipe (Figure 6.30) General Direction of the strain measurement

Detail Pipe 1 Pipe 2 Detail Station west Station centre Station east Detail Crown Northern spring line Invert Southern spring line Detail Longitudinal Circumferential

Test 1 Liner Grouted - 22 Nov 07 25

Pressure (Bar)

20

15

10

5

Test 1 Liner Grouted 0 08:24:00

09:36:00

10:48:00

12:00:00

13:12:00

14:24:00

15:36:00

16:48:00

Time (hms)

Figure 6.31: Pressure variation – Test 1 – Lined and grouted – 22 November 2007

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RW-WRC Pipe Test 1 - Liner Installed & Grouted - 22 November 2007 Measured and Predicted Pipe Circumferential Expansion 28

Internal Pressure, Bar

23

18

13

8

3

-2 -0.5

0.0

0.5

1.0

1.5

2.0

2.5

Circumferential Expansion, mm

Calc.Circ. Displ.

LVDT-P1-SW

LVDT-P1-SC

LVDT-P2-SC

Figure 6.32: Pressure-circumferential expansion – Test 1 – Lined and grouted – 22 November 2007 WRC - PIPE 1 STATION CENTRE Test 1 Liner Grouted - 22 Nov 2007 700 P1SCCR-L P1SCCR-C P1SCSS-L P1SCSS-C P1SC-I-L

600

Strain (Microstrain)

500 400

P1SC-I-C

300 200

P1SCNS-L P1SCNS-C Circum.

100

Long.

0 -100 0.0

5.0

10.0

15.0

20.0

25.0

Pressure (Bar)

Figure 6.33: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 1 – Lined and grouted – 22 November 2007

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WRC - PIPE 2 STATION CENTRE Test 1 Liner Grouted - 22 Nov 2007 700 P2SC-CR-L

600

P2SC-CR-C

Strain (Microstrain)

500

P2SC-SS-L

400

P2SC-SS-C P2SC-I-L

300

P2SC-I-C 200

P2SC-NS-L

100

P2SC-NS-C Circum.

0

Long.

-100 0

5

10

15

20

25

Pressure (Bar)

Figure 6.34: Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 1 – Lined and grouted – 22 November 2007 Test 1 - No Liner - 22 Feb 08 20 18 16

Pressure (Bar)

14 12 10 8 6 4

Test 1 - No liner - 22 Feb 08

2 0 09:50:24

09:57:36

10:04:48

10:12:00

10:19:12

Time (hms)

Figure 6.35: Pressure variation – Test 1 – Unlined – 22 February 2008

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10:26:24

RW-WRC Pipe 1 - Test 1 No Liner - 22 February 2008 Measured and Predicted Pipe Circumferential Expansion 20

Internal Pressure, Bar

18 16 14 12 10 8 6 4 2 0 -0.5

0.0

0.5

1.0

1.5

2.0

Circumferential Expansion, mm Calc.Circ. Displ.

LVDT-P1-SW

LVDT-P1-SC

Figure 6.36: Pressure-circumferential expansion – Test 1 – Unlined – 22 February 2008 WRC PIPE 1 - STATION CENTRE - Test 1 - 22 February 2008 600

500

Strain (Microstrain)

400 P1SC-CR-L P1SC-CR-C

300

P1SC-SS-L P1SC-SS-C P1SC-I-L

200

P1SC-I-C P1SC-NS-L

100

P1SC-NS-C Circum.

Long.

0

-100 0

2

4

6

8

10 Pressure (Bar)

12

14

16

18

20

Figure 6.37: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 1 – Unlined – 22 February 2008

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WRC PIPE 2 - STATION CENTRE - Test 1 - 22 February 2008 600

500

P2SW-CR-L

Strain (Microstrain)

400

P2SW-CR-C P2SW-SS-L 300

P2SW-SS-C P2SW-I-L P2SW-I-C

200

P2SW-NS-L P2SW-NS-C Circum.

100

Long.

0

-100 0

2

4

6

8

10

12

14

16

18

20

Pressure (Bar)

Figure 6.38: Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 1 – Unlined – 22 February 2008 Test 2 - No Liner - 26 Feb 08 30 25

Pressure (Bar)

20 15 10

5

Test 2 - 26 Feb 08 0 10:33:36

10:48:00

11:02:24

11:16:48

11:31:12

11:45:36

12:00:00

-5

Time (hms)

Figure 6.39: Pressure variation – Test 2 – Unlined – 26 February 2008

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12:14:24

RW-WRC Pipe - Test 2 No Liner - 26 February 2008 Measured and Predicted Pipe Circumferential Expansion

Internal Pressure, Bar

28 23 18 13 8 3 -2 -1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Circumferential Expansion, mm Calc.Circ. Displ.

LVDT-P1-SW

LVDT-P1-SC

LVDT-P2-SC

Figure 6.40: Pressure-circumferential expansion – Test 2 – Unlined – 26 February 2008

WRC - PIPE 1 : STATION CENTRE Test 2 26 Feb 08 1000 P1SCCR-L P1SCCR-C P1SCSS-L P1SCSS-C P1SC-I-L

900

Strain (Microstrain)

800 700 600

P1SC-I-C

500

300

P1SCNS-L P1SCNS-C Circum.

200

Long.

400

100 0 0

5

10

15

20

25

Pressure (Bar)

Figure 6.41: Strain-Pressure relationship at centre station (CS) of Pipe 1 – Test 2 – Unlined – 26 February 2008

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WRC - PIPE 2 : STATION CENTRE Test 2 26 Feb 08

1000 900

Strain (Microstrain)

800

P2SC-CR-L

700

P2SC-CR-C P2SC-SS-L

600

P2SC-SS-C

500

P2SC-I-L P2SC-I-C

400

P2SC-NS-L

300

P2SC-NS-C Circum.

200

Long.

100 0 0

5

10

15

20

25

Pressure (Bar)

Figure 6.41(a): Strain-Pressure relationship at centre station (CS) of Pipe 2 – Test 2 – Unlined – 26 February 2008

6.11.4

Conclusions and recommendations based on the results from the strain assessment of the experimental set-up

It is clear from the results graphically represented results above, that: •

The shortness of the pipe segments (3 m) in the experimental set-up as well as the thick flanges and unsupported end domes, complicates the comparison of the results with the theoretically calculated results on unrestrained steel pipe;

•

The measurement of the circumferential variation gauged by a LVDT at the centre station of pipe 1 (LVDT-P1-SC) is questioned; and

•

That the anticipated contribution of the liner to stiffen and hence restrain the pipe to deform could have been reduced by the matrix type crack formation between the anchor knobs on the back of the AKS liner.

The question of whether it is possible to conduct a design assessment for the composite pipe consisting of the host pipe and in this case the grouted liner, could not be addressed by the results which were obtained this far. To obtain a thorough understanding of the crack propagation, bonding of the liner to the host pipe and the restraining characteristics of the grouted liner (AKS), a detailed assessment is required.

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7.

SELECTION OF AN APPROPRIATE LINER SYSTEM

Linings are used to extend the economic life of the pipeline network. It is inevitable that a large variety of host pipe condition and installation difficulties like non-manentry and no surface access, complicates the formulation of installation criteria.

The need for pipe renovation can be classified into four main groups: structural, hydraulic, water quality and risk. Examples of typical conditions which could prevail in a pipeline and the requirements of liner systems could include the following: â&#x20AC;˘

The pipeline might have holes (leaks) that need to be bridged by the lining while in other circumstances the requirement might only be to prevent alkalinity leaching from cement mortar;

â&#x20AC;˘

Hydraulic roughness of the aged pipeline needs to be improved to restored some of the hydraulic capacity; and

â&#x20AC;˘

The integrity of the lining system under negative internal pressure and an external high water table requires that the lining should bond to the pipe and not fail under these circumstances. This requires that the outside surface of the lining should be treated, deformed or be a composite that will bond to the cement grout. In addition, the cement grout needs to be of sufficient thickness to provide an interlocking self-arching annulus, and/or it needs to adhere to the steel pipe inside surface.

Ease of installation in non-man-entry and man-entry size pipe will require different equipment, instrumentation and procedures and is an important criterion to be assessed.

Gumble et al. (2004) indicated that liners can be grouped according to the characteristics of the pipeline as is reflected in Table 7.1.

Grouted linings for renovating steel pipelines

7-1

Table 7.1: Grouping of the liners based on the characteristics of the pipeline

As discussed in the previous sections and in agreement with the characteristic status of the host pipeline as reflected in Table 7.1, the following steps needs to be considered in selecting an appropriate liner to be used: •

Description of the current status of the pipeline;

•

Establish the current and future operation of the pipeline;

•

Determine the strategic importance of the pipeline;

•

Review the access to conduct the required renovation;

•

Identify suitable and available liners and their respective installation requirements;

•

Obtain a description of the required skills to install the liners;

•

Determine the availability of the liners and knowledge available on potential problem areas;

•

Review all the functional and physical limitations of the liner material;

•

Select alternative liners which could probably be implemented;

•

Conduct the required economic analyses to reflect the costs and benefits;

Grouted linings for renovating steel pipelines

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•

Select the appropriate liner system and undertake the required design review of all aspects;

•

Derive an installation criteria which will have to define the different quality assurance tests;

•

Establish the pre- and post-installation assessment;

•

Produce Tender documentation for the provision and installation of the liner;

•

Appoint an experienced contractor and contract an experienced person for site supervision;

•

Ensure water tightness prior to grouting of the annulus space; and

•

Develop a performance appraisal system for the liner as well as a management reporting system.

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8.

FIELD JOINTS

During this research, experience was gained pertaining the installation of HDPE liner in steel pipelines. The development of a workable field joint system, which could operate at pressures of about 300 m, reduced some problems during installation.

Figure 8.1 reflects the proposed field joint system while Table 8.2 indicates the different steps during the installation of the field joint.

Figure 8.1: Proposed field joint system The notation used on the above drawing is shown in Table 8.1.

Grouted linings for renovating steel pipelines

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Table 8.1: Description of the components of the field joint Reference number on

Description of the item

Figure 8.1 1

Host pipe.

2

Liner installed in the pipeline.

3

Steel flange shifted over the host pipe.

4

Pre-fabricated HDPE flange piece to be thermally welded onto the liner which protrudes out of the host pipe.

O-ring to provide a watertight seal between the two HDPE

5

flanges which are compressed by the bolts through the steel flanges.

Clamp-on device which could be used to reshape the host pipe to

6

acceptable roundness for the installation of the steel flange and collar prior to the welding of the HDPE liner.

7

Bleed hole in the collar to allow the air to be displaced during the grouting of the annulus space.

Heat shield to be installed in the annulus space between the liner

8

and the host pipe to prevent heat damage to the liner during the welding of the steel collar onto the pipe.

Grouted linings for renovating steel pipelines

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Step

Graphical presentation

Description

Pull the liner into the pipeline and allow it to extrude long enough for the welding

1

of the HDPE flange.

Install the heat shield and use the clampon equipment to improve the roundness

2

of the host pipe.

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Step

Graphical presentation

Description

Slide the prefabricated collar and flange over the host pipe to allow free access to

3

the liner.

Cut of the liner to the correct length and

4

Grouted linings for renovating steel pipelines

weld the HDPE flange onto the liner

8-4

Step

Graphical presentation

Description

Move the steel flange into position.

Provide a water spray on the inside of the liner while the steel collar is now welded 5

onto the steel pipe. The other side of the pipe end will be equipped similarly and the distance between the two end pieces will be made up with a spool piece.

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9.

FUTURE RESEARCH

9.1

Introduction

Mainly due to the inability to manufacture the proposed 600 mm diameter test facility and the rescheduling of the rehabilitation on the identified pipelines of Rand Water, all the deliverables, intended for this project, were not achieved.

However, it is still important to continue with further investigations to review more recent products and to develop â&#x20AC;&#x153;test procedureâ&#x20AC;? for the material testing, pre installation inspection, post installation assessment and operational performance of installations.

This could be achieved if a test facility could be set up as proposed in the next section.

9.2

Setting up a facility

To increase the operational life of the aging infrastructure, it is required to conduct the appropriate testing of new products. Figures 9.1 to 9.3 provide schematic detail of such an experimental setup. A feature which has to be included is to review the installation of the liners at bends and for this reason the bends have to have the functionality to withstand the test pressures, but also need to be removable.

Figure 9.1: Side view of the proposed experimental setup at the University of Pretoria

Grouted linings for renovating steel pipelines

9-1

Figure 9.2: Plan view of the proposed experimental setup at the University of Pretoria

Figure 9.3: Isometric view of the proposed experimental setup at the University of Pretoria

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9.3

Field work

The intended installation on a test section by Rand Water will provide valuable knowledge and understanding and it is proposed that the University of Pretoria remains involved in the work and that the performance evaluation of the liner, after installation, should be researched.

The development of a real time leak detect system for such liner systems, needs to be set as a focus.

………………………….

DDP TREBICKI Project leader COMPILED BY: ……………………………

PROF S J VAN VUUREN Main Researcher 27 May 2010 C:\Research\K5 1448 Liners\Reports\2010\Summary Report 2010\Final Summary\K5-1448 Summary Report 020610.doc

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10.

REFERENCES

Abraham, D.M. and Gillani, S.A. (1999). Innovations in materials for sewer system rehabilitation. Trenchless Technology Resources. Volume 12, pp 43-56.

Ahammed, M. (1997). Prediction of remaining strength of corroded pressurized pipelines. International Journal Pressure Vessels & Piping. Volume 71, pp 213-217.

Barber, M.E., Bakeer, R.M., Sever, V.F. and Boyd, G.R. (2004). Effect of close-fit sliplining on the hydraulic capacity of a pressurized pipeline. Tunneling and Underground Space Technology. Article in press 2004.

Boot J.C. and Toropova I.L. (1999). Polyethylene thin-walled linings for water mains: Development of structural design guidelines. Tunneling and Underground Space Technology, Volume 14, pp 13-28.

Boot, J.C., Guan Z.W. and Toropova, I. (1996). The structural performance of thinwalled polyethylene pipe linings for the renovation of water mains. Trenchless Technology Resources, Volume 11, pp 37-51.

CEN (2001), Final Draft European standard prEN 13689

â&#x20AC;&#x153;Guidance on the

classification and design of plastics pipeping system used for renovationâ&#x20AC;?

European Committee for Standardization, Brussels.

Chin W S, Kwon J W, Lee D.G. (2002). Trenchless repairing of underground pipes using RTM and dielectrometry. 3rd International Conference on Composites in Infra-Structures, San Francisco, USA, June 2002.

Chin, W.S. and Lee, D.G. (2004), Development of the trenchless rehabilitation process for underground pipes based on RTM. Composite Structures. Article in press 2004.

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Derr, H.R.K. (2003). An Opinionated Review of Trenchless Technologies for Pipeline Rehabilitation. Proceedings of the pipeline division specialty conference: Pipelines 2003. ASCE. El-Sawy, K.M. and Elshafei, A.L. (2003). Neural network for the estimation of the inelastic buckling pressure of loosely fitted liners used for rigid pipe rehabilitation. Thin-walled structures, Volume 41, pp 785-800.

Guan, S.W. (2003). 100 % Solids Rigid Polyurethane Coatings Technology and Its Application on Pipeline Corrosion Protection. Proceedings of the pipeline division specialty conference: Pipelines 2003. ASCE. Gokhale, S. and Hastak, M. (2000). Decision aids for the selection of installation technology for underground municipal infrastructure systems. Trenchless Technology Resources, Volume 15, pp 1-11.

Gumbel, J. (2001). New approach to design of circular liner pipe to resist external hydrostatic pressure. Proceedings of the pipeline division specialty conference: Pipelines 2001. ASCE. Jeyapalan, J.K. (2001). Unified Design method for most no-dig rehabilitation liners. Proceedings of the pipeline division specialty conference: Pipelines 2001.

ASCE. Kiefner, J.F. and Vieth, P.H. (1990). PC program speeds new criterion for evaluating corroded pipe. Oil and Gas Journal. p91-93.

Lienberger, G.L. (2003). Design considerations for improving system efficiency and maximization of service life. Proceedings of the pipeline division specialty conference: Pipelines 2003. ASCE. Marshall, W. F. (2001). Pipeline evaluation and repair steel pipelines. Proceedings of the pipeline division specialty conference: Pipelines 2001. ASCE.

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Marshall, G.P., Thomas, D.L. and Pearson, D. (1990). Techniques for the Installation and Rehabilitation of Water Mains using Plastics Pipe Systems.

Construction and Building Materials. Volume 4, No 2, pp 73-77.

McAlpine, G. (2003), Fully deteriorated Design in Rigid Pipe Rehabilitation with Flexible Liners. Proceedings of the pipeline division specialty conference: Pipelines 2003. ASCE. Nassar, R. and Yousef, M. (2002). Analysis of creep failure times of cured-in-place pipe rehabilitation liners. Tunneling and Underground Technology, Volume 17, pp 327-332.

No-Dig Conference, San Diego. April 2007. Hosted by the Association of International Trechless Technology Oâ&#x20AC;&#x2122;Grady II, T.J., Hisey, D.T. and Kiefner, J.F. (1991). Method for evaluating corroded pipe addresses variety of patterns. Oil and Gas Journal pp 77-82.

Oâ&#x20AC;&#x2122;Grady II, T.J., Hisey, D.T. and Kiefner, J.F. (1992). Pressure calculation for corroded pipe developed. Oil and Gas Journal. p84-89.

Plastic Pipe Institute. (1993). Pipeline Rehabilitation by sliplining with Polyethylene pipe. The society of Plastic Industry, Inc. Schrock, B.J. (ed.). (1994) Existing sewer evaluation and rehabilitation. In ASCE Manual and Report on Engineering Practice. No. 62: Water Environment Federation Manual of Practice, FD-6. Prepared by the Joint Task force of the Water Environment Federation and the American Society of Civil Engineers, 1994.

Schrock, B.J. (2001). Annulus grouting of slipliner rehabilitation. Proceedings of the pipeline division specialty conference: Pipelines 2001. ASCE.

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Suydam, T., Woods, P.E.J., Stewart, E. and Shift, M.T., Custom Build Installation Equipment for Relining Pre-stressed Concrete Cylinder Pipes Minimize Construction Schedule Saegrov, S., Baptista, J.F.M., Conroy, P., Herz, R.K., LeGauffre, P., Moss, G., Oddevald, J.E., Rajani, B. and Schiatti, M. (1999). Rehabilitation of water networks â&#x20AC;&#x201C; Survey of research needs and on-going efforts, Urban Water. Volume 1. P15-22.

Thèpot O. (2000). A new design method for linings non-circular sewer. Trenchless Technology Resources, Volume 15, p25-41.

Trypus, J., Darrow, W. and Mattigly, J. (2003). The road to Rehabilitation of a 42 Inch Diameter Interceptor. Proceedings of the pipeline division specialty conference: Pipelines 2003. ASCE. Wood, P. (2003). Presentation: CEMPIPE pressure pipe renewal. 15th International conference on pipeline protection. Germany.

Youssef Diab, Y. and Morand, D. (2001). An Approach for the Choice of Rehabilitation Techniques of Urban Sewers. Proceedings of the pipeline division specialty conference: Pipelines 2001. ASCE. Zhao, J.Q. and Daigle, L. (2001). Structural performance of sliplined water main.

Canada Journal of Civil Engineering, Volume 28, pp 969-978.

Zhu, M. and Hall, D.E. (2001). Creep induced contact and stress evolution in thinwalled pipe liners, Thin-Walled structures, Volume 39, pp 939-959.

Prof S J van Vuuren

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Articles of interest but not referenced in Section 4 Creig-Smith S, To refurbish or replace steel water pipelines, that is the Question, Advanced Engineering and Testing Services, MATTEK, CSIR, Private Bag X28, Auckland Park 2006, South Africa McAlpine G, Rehabilitation of Fully Deteriorated Rigid Pipes by Flexible and Rigid Liners, , Danby of North America, Inc. P.O. Box 5127, Cary, NC 27512 Tel: 919-467-7799; e-mail: danby@mindspring.com; Fax: 919-467-7754 Salvo P and Michael J. Willmets M J, Case Study â&#x20AC;&#x201C; Two Watermain Rehabilitation Techniques on One Project, Crystal Beach, City of Ottawa.

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