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Contents

Engineering Maintenance Solutions, June 2010

70/30 PHENOMENON - 5 SHIP BASED CONDITION MONITORING - 6 LATEST NEWS & PRODUCTS 8 - 33 GAS TURBINE MAINTENANCE - 33 - 38 HEALTH & SAFETY 44 - 47 PLUS: BUYER’S GUIDE VIBRATION MONITORING IR/THERMAL MONITORING October 2010 Publisher - Michael Dominguez Email: michael@engineeringmaintenance.info Editors/Contributers - Jon Barratt, Christer Idhammar, Alan France, Mick Saltzer, Mark Haarman

MAINTENANCE BEST PRACTICE HEAT EXCHANGERS + MORE

Email: editorial@engineeringmaintenance.info Ad Manager - Paul Clappison Email: paulc@engineeringmaintenance.info Online Sales Director - Paul Miles Email: paul@engineeringmaintenance.info Website: www.engineeringmaintenance.info MSL Group, Cobalt House, Centre Court, Sir Thomas Longley Road, Rochester, Kent, ME2 4BQ Tel: +44(0)1634 731646 Fax: +44(0)1634 731644 www.engineeringmaintenance.info

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70/30 Phenomenon When you ask front line supervisors or team leaders if all people in their teams are performing to the same standards or if some are doing more work and achieving more results than others, you will often get the same answer.

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ll over the world, the most common answer, after some analysis, verifies that about 30% of the people do 70% of the work. This is not only true for front line people like mechanics and electricians, but also for planners, engineers, and other salaried employees. However, our focus in this column is on the front line of maintenance. When I am involved in assessing maintenance performance for a customer, I always make an effort to talk one-on-one with individuals, but I also talk with a group of three to eight individuals. When you talk with people one-on-one, they are in most cases very open and honest about what they say. When you talk with a group of more than three, there will often be a change in attitudes. In a good work system with a homogenous group of strong performers, there is not much difference in talking with people in a group or on an individual basis. However, in a typical work situation, it is common to see a big difference. What I call "the griping level" is very high in a typical group. For example, in a group of nine, it is likely that three people will talk and complain about all the bad aspects of working in their plant, three people will show signs of support for the gripers, and three will say very little and remain passive. I have discovered that the silent few are often very good craftspeople that belong to the group of good performers, the ones doing 70% of the work. They are also sick and tired of hearing the gripers' constant complaints about everything that is wrong, especially when these gripers never do anything to improve the situation. As a manager, you should remember to listen to the good performers and to downplay comments

from the gripers. You should give much more time and attention to the best performers; otherwise, you risk losing them. When presenting observations and recommendations to a large, mixed group of people, I have often brought up the griping level as an improvement opportunity. After addressing this problem, I have had numerous craftspeople thank me for bringing it up. "If we could just get the 70% you talked about-and I believe you are correct with that figure in our organization-to pull their weight, we would do very well here," is a comment I have heard many times from individual crafts people. I have also had human resource, production, and maintenance managers thank me for addressing the griping level. The fact is that people's attitudes change quickly after such an open discussion, especially after talking about the group they belong to. It is not positive to be branded as a griper, so the griping decreases and people start talking about more productive and positive issues. Then, when they hear others say that they do not have enough resources for a task, their reaction becomes "we must each do our own part of the work before we complain about not having enough people."

get done and you won't need to worry about it anymore. However, to bring the whole team up to a high-performance level, you must make the effort to match the best performers with others when you assign work. It might take a little longer, but it pays off in the long run. The same principle is vital when a proposed flexible work system transfers from the negotiated contract to reality. Unfortunately, it is common to see that after long negotiations, strikes, and increased pay, the flexibility agreement is not implemented. Remember that you only get the flexibility you have trained people for through their work assignments. Christer Idhammar is a world renowned and awarded Reliability and Maintenance Consultant and Guru. He is the founder and executive vice president with IDCON, INC in Raleigh NC, USA; A reliability and maintenance training and consulting company to industry world wide since 1972. www.idcon.com

To really change the situation, supervisors or teams must start assigning work in such a way that all employees will have a chance to improve their performances. In a team environment, especially if teams are supposed to be self-directed, this can be difficult. In the pile of work orders that must be done, there are always jobs at the bottom of the stack that nobody wants. As a supervisor, it is understandably tempting to hand work to your best performers, because you know it will

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Easier Ship Based Machinery Condition Monitoring Most engineers acknowledge the usefulness of Vibration Analysis (VA) in the monitoring of machinery condition and fault diagnosis but unfortunately only a tiny minority have the necessary specialist skills or time available to apply it successfully.

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s a result machinery that is important to a vessels performance and revenue earning capability may be monitored only sporadically or not monitored at all and this falls far short of best practice. However there is an alternative to VA for detecting machinery degradation that is easy and quick to use by all engineering personnel. It has been in use in general industry for almost two decades where it has proved its effectiveness and sensitivity to faults, giving plenty of warning to allow maintenance activities to be planned and carried out with minimum disruption to operations and limiting the opportunity for costly secondary damage to occur. Furthermore it is well suited to routine marine use where it can put the power of Condition Monitoring into the hands of every ships’ engineer. Whereas VA requires a sophisticated diagnostic analysis to be carried out before the presence or absence of a fault can be confirmed, the Acoustic Emission (AE) technique in the guise of a ruggedised, portable MHC instrument can

MHC instruments are used on a particular fleet of platform supply vessels with periodic measurements being taken by ships’ engineers. On one vessel an increase in the proprietary Distress® parameter alerted to a problem arising on the gearbox starboard alternator PTO bearing (in service for 4 years). Measurements over the subsequent 6 So where’s the catch ? Well although with months tracked the deterioration and very little effort an MHC instrument can strip-down revealed clear damage within let you know where and when you need the bearing as shown in the accompanying to focus your maintenance, it does not photos. The bearing replacement resulted directly identify the specific nature of in one planned day out of service. the fault. In practice this is not as big a However it was evident that had the negative as it may first appear. Firstly, bearing further deteriorated considerable once you have been pointed in the right damage would have been caused to the direction you can often draw on standard gearbox itself resulting in much greater engineering skills and experience to repair costs and a minimum of 7 identify the problem and the headphones unplanned days out of service. The on the instrument are a great help in this estimated saving in this case was well in regard. Secondly, you could always use excess of £150,000. the MHC indication to initiate a full diagnostic analysis on just the machine of In fact MHC instruments are in use on concern at the time it needs it (based on around 30 platform supply vessels and VA and/or AE). However before assuming another fleet operator whose vessels have this will always be necessary consider the been monitored with on-board MHC following real life case study from a instruments for the last 7 years summed platform supply vessel : up the benefits as follows : a machine fault and enables easy trending during subsequent deterioration. Another benefit of the AE technique is that it can also monitor slowly rotating machinery where Vibration measurements become ever more difficult because of background noise issues.

“The information that this system provides to our engineering staff is invaluable in being able to plan in advance for overhauls … It also allows us to vindicate or extend / shorten the manufacturers recommended maintenance schedules based on the data collected …”. The MHC range is not restricted to portable instruments and includes permanently installed remote sensors for areas of difficult access as well as standalone programmable smart sensors for continuous surveillance. To find out more about an easier approach to condition monitoring visit www.holroyd-instruments.com or email us at sales@holroyd-instruments.com or phone us on +44 (0)1629 822060.

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ACCESS KEY ENERGY DATA WITHOUT LEAVING

YOUR DESK!

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ith the new SPC DTM data transfer module from Elcomponent, users of the company’s renowned SPC range of portable energy data loggers can now access information from instruments installed anywhere in the world, without leaving their desk. The SPC DTM module uses GPRS (General Packet Radio Service) to upload logger surveys to the web. As such the data is available at any location with a PC and an Internet connection. For users with data loggers on one or more remote sites, this means huge savings in time, money and carbon emissions as it is no longer necessary to visit those sites regularly to collect energy data. And, even for users who have instruments only on their local site, the ability to acquire data without leaving their desks is still a big time saver and a major aid to convenience.The new SPC DTM module, which communicates via the same GPRS wireless network that is used to provide data services on mobile phones, upholds Elcomponent’s strong tradition of producing devices that are dependable

and easy to use, even for those with no specialist knowhow. At the data monitoring location, be that in an office or any where in the world with web access, an internet connection is established using a PC running the same PowerPackPro software that was used to configure the module, and the data access facility is set up automatically. It’s not even necessary to enter the web address, as the software remembers this from the programming of the module. Unlike general-purpose data logger packages, the PowerPackPro software has been specifically designed to provide energy managers and engineers with the key information they need in the form that they need it. It allows, for example, almost instant creation of graphs and reports, so that energy cost savings and reductions in carbon footprint can start from day one, and it automatically converts volume data for gas or oil to energy and carbon values and seamless integration with Microsoft Office. www.elcomponent.co.uk and www.spcloggers.com

Prince learns about energy efficient rolling bearings at Start Wales Festival is Royal Highness spoke to Rich-

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food, transport, buildings and waste – at

ard Granger, Sales Engineer at

home and in the workplace.

more about Schaeffler’s range of rolling

More than 160 exhibitors attended the

and plain bearings that are helping engi-

event, including

neers to design more energy efficient

Schaeffler (UK) Ltd. A variety of different

wind, wave and tidal turbines.

rolling bearings and plain bearings were

Schaeffler (UK) Ltd, to learn

displayed on Schaeffler’s stand, many of HRH cut the ribbon at the very first Start

these designed to support specific types

Wales Festival. The event featured pres-

of renewable energy systems, including

entations and exhibits on the simple steps

wind, wave and tidal turbines.

we can all take to make better use of our natural

resources,

including

energy,

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EXCELLENCE EVERY INCH OF THE WAY

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ooper Roller Bearings is the inventor and world leader in the design, manufacture and development of split roller bearings and has been leading the market for over 100 years.

With worldwide representation, vast experience and unbeatable know-how, Cooper is a full-service provider from bearing selection through installation, training to maintenance and repair. Our manufacturing plant is in King’s Lynn where the reliability of Cooper products and business processes is underlined by ISO 9001 and 14000 accreditation as well as registration with Lloyds and BSI. The Cooper split roller bearing is a simple product that can save you huge amounts of money by reducing downtime and increasing productivity. The split feature means inspection and maintenance is cut to a minimum while the superior sealing promotes longer bearing life. As a result, your business profitability is increased. When placing an order, please quote this code: engineeringmaintenance2010 Cooper Bearings Group Wisbech Road, King’s Lynn Norfolk PE30 5JX, England Tel.: +44 (0)1553 763 447 Fax: +44 (0)1553 660 494 Website: www.cooperbearings.com

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NSK’S MOLDED OILTM BEARINGS DELIVER SAVINGS IN DOWNTIME COSTS OF €38,400/yr FOR CONCRETE PIPE MANUFACTURER. NSK’s asset improvement programme has delivered an annual cost saving of €38,400 for a manufacturer of concrete pipes. This has been achieved by reducing failures on the blade support roller of a concrete pipe-slotting machine, replacing the original bearings, which were lasting 2-3 months on average, with NSK Molded OilTM bearings. To date, these bearings have operated for 12-months with not a single failure.

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he problem on the original

NSK for bearings used in remote

nated plastics - where the oil content is a

bearings, as identified by an NSK

locations, and/or where oil and grease

mere few percent by weight - by offering

applications engineer, was the

absorbing dust is produced.

a lubricating oil content of more than 50% by weight. This enables the material to

ingress of concrete dust. This is a common problem in the industry: the

Molded OilTM has been proven to

always maintain a good lubrication re-

dust combines with bearing lubricant to

transform the performance of bearings

gime, helped by the mechanism of oil

produce an abrasive mixture that causes

used in machinery and equipment - in

discharge from the matrix, which this is

premature bearing failure. In this

terms of reliability, maintenance free

temperature dependent: so the higher

instance, the dust- contaminated

intervals and operation - in environments

the heat generation, the higher the oil

lubricant was causing failures four-times

exposed to contamination. It also

discharge rate. Operating temperatures

per year, each failure resulting in 8-

enables plant operators to make real

are normally limited to 60°c

hours downtime, at a cost of €1,200/hr.

cost savings by replacing existing, and often costly, methods of lubricating

As a means of overcoming the problem,

machine parts.

the NSK engineer recommended using bearings equipped with Molded OilTM, a

A highly effective lubrication method,

solid lubricant technology developed by

Molded Oil differs from other oil impreg-

www.nskeurope.com


GREEN IS THIS SEASON’S COLOUR entrances, they will reduce

Capacity ACR Series air curtains for

the demands of air

additional power.

conditioning by preventing

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heat loss from the building

For the Marble Arch store building,

by 80%.

bespoke AC Series units were supplied. A corner entrance, it was specially

ew Look, one of the nation’s hottest fashion chains, has taken the lead on sustainability

at its new flagship Oxford Circus store on London’s Oxford Street and its popular Marble Arch premises, by installing revolutionary AC Series air curtains from Airbloc.

The energy efficient Airbloc air curtains will slash the energy consumption of the two stores. Situated above the main

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The significant green benefits of

designed to create an impressive effect

installing AC Series units are matched by

for customers. As such, it was essential

their other performance qualities. CE

that the air curtains fitted the design

approved, the versatile and hardwearing

seamlessly.

system can be installed either vertically or horizontally at doorways and entrances to meet any need.

At New Look’s Oxford Circus store, the main entrance featured overhead High

For further information, please contact Mr Keith Sprague Fens Pool Avenue Brierley Hill West Midlands DY5 1QA www.airbloc.co.uk marketing@airbloc.co.uk


New ABB online tutorial explains how to choose between mass and volume flow

ABB has released the latest in its series of online tutorial videos at www.youtube.co.uk/abbukinstrumentation, explaining the difference between mass and volume flow and how to decide which technique is appropriate for particular applications. Confusion often arises over the

ly select the right flow variable can

technologies, ABB is well placed to of-

difference between mass and volume

lead to significant improvements in

fer advice and guidance on the best

flow measurement and when a

process performance and cost effec-

flowmeter for your application. For

particular measurement should be

tiveness.

more information, please call 0870 600

applied.

The video tutorial is presented by Mark

6122 or email

Though both technologies will deliver

Allinson, Process Flow Specialist for

moreinstrumentation@gb.abb.com ref.

almost identical results under certain

ABB's UK instrumentation business,

'mass v. volume flow'.

conditions, the deviations that can oc-

who explains the differences between

cur where a process is subject to pres-

mass and volume flow measurement

sure and temperature changes makes it

and highlights the best technologies for

crucial to make the right choice from

specific applications.

the outset. Understanding the effects

As a leading manufacturer and supplier

of these deviations and how to correct-

of a comprehensive range of flowmeter

Recovering waste heat from compressed air systems ABAC’s Alup Energy Box converts the heat generated by most air compressors into hot water up to 70ºC, for industrial processes or washroom use.

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The amount of energy it is possible to recover using Energy Box can be significant.

Energy Box provides an easy to install packaged system that can be fitted to any make of oil injected rotary screw compressor up to 90 kW.

For instance, with a relatively small 37 kW compressor, the energy available for recovery can be up to 29.9 kW. which may equate to annual heating costs of over ÂŁ6000 (based on 4000 operating hours if conventional heaters or boilers are used to provide this energy).

s it replaces the energy normally used to fuel boilers or heaters, it saves significantly on fuel costs.

It recovers energy from the oil circuit on the compressor via a heat exchanger, allowing a return on investment (ROI) to be achieved very quickly.

The system is available in several sizes to suit any make of oil injected screw compressor from 11 to 90 kW, and operating with larger compressors or for longer periods can result in greater energy savings.

Further information: http://www.alup.co.uk/energybox.htm

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TEST ADAPTOR AVOIDS UNWANTED TRIPPING OF RCDs

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eaward’s latest PAT accessory is a special new adaptor for RCD testing. The adaptor has been designed to enable users to test a portable RCD or RCD protected extension lead without risk of tripping the main RCD in the installation.

installation which is RCD protected, the test may cause the main RCD to operate. The new compact RCD test adaptor eliminates this problem by providing an isolated mains supply. The Seaward RCD adaptor can be used easily and effectively with any make of PAT tester or RCD test instrument.

RCD testing has taken on greater significance since the introduction of the 3rd Edition of the IEE Code of Practice The new RCD test adaptor from Seaward which recommends that when an forms part of an extended range of extension lead or multiway adaptor is specialist PAT testers and accessories. fitted with an RCD, the RCD should be checked using an RCD test instrument to determine that the trip time is within the limits set out in BS 4293, BS 7288 or BS EN 61008. More details from: Most Seaward portable appliance testers are already equipped with an integral RCD trip time test. However, when testing a portable RCD using a mains outlet on an

www.seaward.co.uk

Nederman’s Free Grinder Nederman are offering a free high quality sander / grinder with all P160I portable dust extraction units absolutely free from 01st September to 31st December.

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ustomers also get one free cast metal sanding or grinding connection manifold and one hundred free abrasive discs,” said Mark Hodgens, Managing Director. “It’s a complete package, ready to use - all at a greatly reduced price.”

This versatility makes it an ideal entrylevel extraction solution for businesses looking to realise benefits including reduced abrasive costs, improved product quality and lower cleaning costs, all whilst protecting staff from harmful particles.

The P160I is available in 110V or 240V. The 1200W motor gives powerful performance from a light unit (19kg) that’s ideal for most general sanding and grinding applications. Automatic features include electrical start / stop and filter cleaning; a floor cleaning attachment is also included.

Further information is available at www.nederman.co.uk or by contacting Nederman on 08452 743434.

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Hansford Sensors highlight benefits of On-line monitoring using HS-423 Dual Output Sensors In the world of industry, pressure to deliver high productivity whilst keeping costs down has over the last two decades led to a rise in the implementation of machinery vibration monitoring programs with great success. Costly break downs and damage to machinery have in many instances been avoided and the required maintenance has been able to be scheduled for a convenient time.

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aintenance engineers have long known the benefits of monitoring vibration, however the virtues of what can be achieved are not always appreciated by their work colleagues and the valid warnings that are highlighted can be disregarded from management level to the shop floor with often catastrophic results. Chris Hansford, Managing Director at Hansford Sensors Ltd. tells that “Such a situation was reported to us via one of our overseas customers very recently. A Maintenance Engineer Team leader contacted our customer directly for advice on a potential equipment failure they had recently identified. The application was in a process application where the Maintenance Team had discovered that a conveyor pulley bearing had developed high levels of wear over a short period of time. The Production Department decided that, instead of instigating an unplanned shutdown, based on the recommendations of the Maintenance Team they chose to ignore the warning and continued to run the pulley until the planned shutdown date. The scheduled shutdown was due 3 weeks after the initial bearing fault detection”.

Chris continues “The maintenance team responsible for the monitoring of this production line was obviously concerned

with the possibility of a failure on this pulley, and on the recommendation of our customer they purchased a stock item sensor; HS-423 (Dual output -420mA acceleration into the PLC and AC output via a data collector). Within 24 hours these were delivered and installed on the conveyor pulley bearing that had been diagnosed with high levels of wear, thus giving Management at the facility instant warning if the problem progressed further”. As the date for the planned shut grew closer, the identified ‘g’ (acceleration) levels shown by the HS-423 sensor, monitoring the pulley bearing doubled. The HS423, being connected directly to the control room display, was sent into alarm as the detected levels surpassed previously specified warning parameters. These reading were further backed up by the acceleration readings taken via the department’s hand-held data collector. The levels increased substantially in the final hours before the failure. (See diagram)

Unfortunately, the operators did not heed the alarm warnings and continued their attempt to run the conveyor to the planned shutdown date. Consequently the bearing catastrophically failed, in turn catching on fire and resulting in high costs of damage to equipment and putting the lives of a number of employees at risk. This resulted in expensive repairs, a mountain of paper work with the fire it caused and shut down of the conveyor for over 24 hours. Hindsight is a wonderful thing, but at least a valuable lesson had been learned. Fortunately no-one was badly injured and the worth of the Maintenance Team has been put in the spot-light proving what a valuable job they carry out and the significance of their role in ensuring the safe, cost-effective management of industrial plant.

For more information, please contact:Suzanne Pearl Hansford Sensors Ltd. Tel:0845 680 1957 Fax:0845 680 1958 Email:suzanne.pearl@hansfordsensor s.com Web: www.hansfordsensors.com

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SIPOS takes district cooling to Doha A growing Middle East market for SIPOS Aktorik’s actuation solution for district cooling is being supported with a premium gold sponsorship package for the DC summit in Doha. The second annual district cooling event will run from 28-30 Nov 2010.

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isted as a key topic is a SIPOS Aktorik case-study on the implementation of SIPOS 5 variable speed actuators in district cooling plants in the UAE: Steffen Koehler, SIPOS Aktorik’s International Sales Manager will present a paper on this subject on the first day of the programme. The summit has been designed to attract delegates from a range of sectors including district cooling owners/operators, EPC/MEP and maintenance contractors along with water re-use/conservation companies plus WwTW and power utility organisations.

SIPOS will therefore be well placed to present its district cooling specialism to key target markets with a display that will highlight how its actuators control cooling water flow and protect hydraulics from water hammer. Successful district cooling installations for SIPOS in the Middle East include contracts in Dubai, Yas Island and Al Raha beach. As well as presenting a paper, SIPOS will have a presence in the exhibition area supported by local agent Torento Energy Systems.

Photocaption: SIPOS actuators aid district cooling

SIPOS Aktorik GmbH, Im Erlet 2, D90518 Altdorf, Germany Tel. +49 (0) 9187 / 9227- 0 Fax +49 (0) 9187 / 9227-5111 Web: www.sipos.de

Better connections, better seal New M8 connectors from ifm electronic ommonly used on small sensing

tightening of the thread, again leading to

devices, the M8 connector has

loss of seal of shaking loose. All this re-

become popular in recent years,

sulted in a lack of confidence in the M8

C

having developed from a simple push-fit

connector in many applications.

to more secure screw-on connectors. While conforming to EN 61076, the de-

Now with the new additions to their

sign was, however, ripe for the makeover

‘ecolink’ family sensor market leader ifm

now thoughtfully carried out by sensor

electronic have successfully addressed

market leader ifm electronic Ltd.

both of these issues at a stroke. Firstly, the sealing O-ring has been clev-

Having greatly improved the larger M12

erly replaced by a profiled seal. Normally

connector, the sensor Specialist Compa-

invisible in the female connector, this

ny turned their attention specifically to

seal has a vital role in keeping moisture

to the sawtooth incorporated in the

the seal of the M8. As the male part of

out of the connection, but the original

thread. This prevents the mated parts

the connector is designed with a taper –

design was not always capable. Now the

from shaking apart under high or pro-

originating from the push-fit days – it

cunning new design of shaped seal can-

longed vibration.

does not always sit well on the O-ring

not be displaced, and will always per-

supplied with the female counterpart,

form. This design achieves protection

For further information:

and in fact can ride up, losing any seal-

ratings of IP 67, IP 68 and even IP 69K

+44(0)20 8213-0000.

ing function. In addition, the small size

Secondly, the mechanical interlocking of

website www.ifm.com/uk

of the connector led often to insufficient

the two parts is now more stable thanks

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Telephone: or visit our


Rethinking Maintenance Procedures Using IR Noncontact temperature monitoring is an essential tool for ensuring the safety and reliability of equipment. As alternative solutions to portable thermal imagers, both portable and fixed infrared thermometers are gaining importance in preventive maintenance applications, the latter for example in OEM solutions and for the infrared monitoring of large plants with a multitude of measuring points.

T

he detection of defects in switchgear, fuses, motors or

inspection capability for temperatures

but doesn’t represent the true

from -32 to 900ÂşC.

measurement spot size.

The integrated laser sight with crosshairs

As a consequence, the temperatures

permits accurate targeting of the

readings for overheated objects are

measured object and indicates the real

lower than their real temperatures. So

measurement spot size.

if, for example, a small electrical

electrical connections is almost

impossible with the naked eye. But we do know that almost any electrical device will get warmer than normal very soon after an anomaly occurs. In

component experiences an overload

complement to portable thermal imagers, high-end portable infrared thermometers are now increasingly used for the detection of weak spots.

At the touch of a single button the

condition and heats up excessively, this

temperature reading appears on the

will only show as a minor temperature

display with a 0.1ÂşC resolution. An alarm

rise if the measurement spot is too large,

signal is output to indicate temperatures Fixed pyrometers are used predominantly in plants where electrical or mechanical components to be monitored are hard or impossible to reach.

Using portable precision pyrometers for preventive maintenance

above or below programmed limit values (MAX/MIN function) so that you can systematically scan the measured object and quickly pinpoint the source of the malfunction.

One major aspect to be taken into account for all measurements is whether

Fig. 1: Temperature measurements on highly stressed components of a welding robot using the optris LaserSight LS

the optics of the infrared thermometer The handheld infrared thermometer optris LaserSight LS enables you to verify critical components quickly and easily once you have identified them by means of a thermal imager. This gives you fast

actually are able to acquire the hot spots

so that potentially hazardous situations

properly. The optical resolution offered

will go undetected.

by commercially available infrared thermometers in the low price range is

Figure 1 shows a correct temperature

poor, and the dot laser featured by such

measurement procedure using the

instruments can be used for sighting only

laser/crosshairs technology for

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Fig. 3: Medium-voltage switchgear monitored by fixed pyrometers

Fig. 2: Detailed temperature measurement of an electrical control system using the integrated Close Focus optics of the optris LaserSight LS

for longer measuring distances, or

absolute safety can only be offered by a

exclusively for small measurement

fixed system providing full-time

objects. This forced customers to buy

continuous monitoring.

either several thermometer models or

The fixed pyrometer optris CS has been

replacement optics. The optris

specially designed for maximum

LaserSight LS is an all-in-one

versatility and is used for example to

instrument where you simply flip a

monitor shipboard electrical systems for

selector switch for close focussing.

loose bolted connections. Defective busbar and power breaker connections

Fixed measuring system for full-time monitoring of mechanical components on

monitoring

lead to increased contact resistances, causing overheating at these points.

a welding robot. The new two-lens precision optics of the optris LaserSight LS permit the measurement of very small objects. Switching to the Close Focus Mode enables you to accurately measure targets as small as 1 mm. Sighting is provided by two laser beams intersecting

In plants which are very expansive or comprise hard-to-reach electrical or mechanical equipment (large production

the market have been designed either

systems etc.) the use of portable instruments is very time-consuming and labour-intensive.

numbers of such critical points.

If temperature limits are exceeded an alarm signal is output to the control unit. This allows overheating conditions to be detected quickly and reliably and the

Also, such inspections can never be more than random spot checks and will only permit the detection of trends. Near-

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solution for the monitoring of large

facilities, high-rise buildings, shipboard

at the close focus point at a distance of 62 mm. So far, instruments available on

Fixed pyrometers are an affordable

electrical system to be cut-out instantaneously with very short response times (less than 1 second).


Fig. 5: Typical monitoring locations at points of contact

The optris CS measures temperatures

industrial environments and ensures very

Medium-voltage switchgears fitted with

from -20 to 350掳C, being only 87 mm

good electromagnetic compatibility

the instrumentation described above will

long and 12 mm in diameter it can be

performance. The electronics package is

no longer require any additional routine

installed in confined spaces and

integrated in the instrument together

checks of contact points. This improves

tolerates ambient temperatures up to

with an intelligent sighting aid.

the protection of your equipment, reduces maintenance costs and ensures

75掳C. It is attractively priced and combines excellent quality and high

It also features a scalable analog output

measuring accuracy with a rugged,

(0 - 10 V or 0 - 5 V) and protection

superior mechanical design. It has been

against short circuits and polarity

designed for deployment in harsh

reversal.

the health and safety of your personnel.

For Further information please CONTACT:

Optris GmbH Ferdinand-Buisson-Str. 14 路 D -13127 Berlin 路 Germany Tel. +49 30 500197-0 Fax +49 30 500197-10 E-mail : sales@optris.com www.optris.de

Fig. 4: optris CS pyrometer

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A&G Heat Exchangers Ltd A&G Heat Exchangers was established as a partnership business in 2003 by two engineers who saw potential in market share to supply heat exchanger solutions and services. Pooling their knowledge and skills together the business soon established itself and further enhanced its capabilities by employing a dedicated team upon which a platform for growth was soon established.

F

ocusing on customer satisfaction and meeting all requirements soon saw the order book grow and by the end of the first year of trading a firm customer base had been established and growth soon followed. Following four years of exceeding all planned growth projections the business was incorporated as a limited company in April of 2007. Further investment then enabled the re-location to new premises to cater for the increase in growth demand within the market place. Today that growth continues and further investment is being planned to be ready to meet future challenges and continue to meet all customer needs and expectations. A&G Heat Exchangers Limited is a leading supplier of heating and cooling solutions. Utilising the most up to date design software our engineers are able to evaluate all customer requirements and offer the most cost effective design solutions to ensure effective serviceability whilst fully complying with PED regulations. Along with the annual growth came the ability and capability to meet ever more demanding requirements set by our customers. Detailed above is a service list that we currently offer.

Turn key projects including skid mounted equipment and complete supply and installation of pipe work and controls Is also part of the service we offer. We also specialise in the supply and assembly of kit form heat exchangers where there are access restrictions to final installation locations. Welding All welding is carried out by coded operators qualified to ASME IX and BS EN 287

The health and safety of all persons connected with our operations is paramount. This fact is confirmed by our commitment to enrolling with the CHAS Contractors Health and Safety Assessment scheme. Our procedures for ensuring the welfare of all have been confirmed as fully compliant and will continue to be so. A&G Heat Exchangers Ltd welcomes all enquiries. We are fully committed to supplying a service that fully complies with all our customer requirements and meets all needs and expectations. We look forward to being of service.

Operations All operations are governed by our ISO 9001:2008 accredited status. Supply of a quality service and delivery of a quality product is confirmed by the feedback we receive from satisfied customers. All our systems are controlled in accordance with the standard and are audited continually for compliance.

A&G Heat Exchangers Limited Tel:00 44 (0)121 788 2450 Fax:00 44 (0)121 788 2587 Web: www.aandgheatexchangers.com


® Vibxpert

II

A New Portable Vibration Analyzer — with Full Colour Display, fast data acquisition and powerful diagnostics tools.

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he VIBXPERT II handheld vibration analyzer combines the advantages of a rapid processor with a brilliant energy-efficient colour VGA display. Enhanced with an Fmax of 51KHz and up to 102,400 Lines of Resolution, all machinery problems can be captured and easily analyzed on the VIBXPERT II large colour screen. The VIBXPERT II Basic platform is a 1-channel vibration data collector which can be upgraded at any time to 2 individually configured channels via a special pass code it’s user upgradable and does not require hardware changes.

standards are visually identified with proven leaders the aid of coloured LEDs. technology.

maintenance

VIBXPERT II is lightweight vibration meter —only 1.2Kg! Its robust housing is dustproof and water resistant (IP65). VIBXPERT II is delivered with a carrying pouch with includes a breakaway shoulder strap for safety during data collection.

Optionally available:

The VIBXPERT II vibration analyzer features modular functionality including dynamic balancing, extended time waveform recording, transient data capture, UFF file export, Modal/ODS support and more.

For details and our free 180 page guide to Condition Monitoring, Laser Shaft Alignment and Dynamic Balancing contact Pruftechnik Ltd, Plant Lane Business Park, Burntwood WS7 3GN or phone 01543 448350, Fax 01543 275472, email pposte@pruftechnik.co.uk

As with all Pruftechnik vibration data collectors with the new VIBXPERT II All forms of machine vibrations, you will enjoy the benefits of free bearing conditions, process data and updates, low ownership cost and visual inspection information can be unlimited tech support from the collected and stored on the expandable Compact Flash Card (up to 8 gigabyte) for report generation or for later transfer to the OMNITREND software for further analysis, reporting and archiving. The VIBXPERT II vibration analyzer provides an easy-to-use icon driven platform that offers comprehensive analysis functionality for the diagnosis of simple or very complex vibration problems. Capabilities include order spectrum, phase, cepstrum, crosschannel phase, orbits, run-up and coast-down measurements, bump test, negative averaging and more. Analysis tools, including various cursor types, machine-specific frequency markers, signal post processing, and extensive bearing databases are included for evaluating each spectrum. Alarm notifications based on ISO standards or user-defined

of

Modules for Dynamic Balancing, Recording, Modal Analysis and Operation Deflection Shape (ODS) and VIBCODE automatic measurement location identification.


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Protor Vibration Condition Monitoring System Installed in Three Thermal Power Plants in Spain for Iberdrola IBERDROLA has launched a renewal plan for the existing condition monitoring systems in their plants in Spain. This plan will be implemented gradually and PROSIG was selected to install their PROTOR Vibration Condition Monitoring System in three IBERDROLA power stations. The contract was awarded to PROSIG in partnership with Aries Ingeniería y Sistemas, who are PROSIG’s representative in Spain.

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ROSIG have already successfully commissioned and installed the PROTOR system in the Lada (Asturias, Spain) and the Pasajes (Guipúzcoa, Spain) power plants. The work primarily consists of the supply, installation and signal cabling of the PROTOR systems together with training of the IBERDROLA staff. PROSIG will complete the third installation at the Velilla power plant, located in Palencia, Spain in September 2010. The monitoring and diagnosis of rotating equipment based on vibration analysis measurement is at the core of predictive maintenance systems. This type of system allows the condition and health of machines to be assessed. During operation, rotating equipment experiences dynamic stress caused by hydraulic, mechanical or electrical forces that induce vibrations and contribute to both ageing and wear of machines. The damage level of a rotating machine is reflected in several measureable factors. The PROTOR Vibration Monitoring System, designed and manufactured by PROSIG, provides reliable on-line monitoring of turbine generators, main boiler feed pumps and other auxiliary plant equipment. It provides both real-time and long-term historical access to the important vibration factors together with various plant process parameters which indicate the machine state. Without information on the condition of primary equipment, such as turbines, pumps and associated plant, impending faults go unnoticed and develop into severe conditions that could result in failures. Failures may lead to unscheduled outages or more serious equipment damage with consequent loss of revenues. tel: +44 (0)1329 239925 http://www.prosig.com prosig@prosig.com

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Vista Data Vision (VDV) If logging data, use Vista Data Vision (VDV) for automatic data handling, including data base storage, trend lines, alarms and reports

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DV software is used for professional handling of data from technical projects like Wind Farms, Ambient Weather and Water and Sewer infrastructures. VDV automatically imports data from files collected from your data-logger(s)

and stores in its built-in database. With access to the database, VDV becomes the front end of your data allowing you to easily and quickly view graphs, histograms, wind roses and trend lines. Virtual variables can be used to create new calculated results. Validation limits and alarm limits can be set for individual sensors. With VDV, there are endless possibilities of making logged data visible and easy to understand. Users include Government Agencies, Universities, Municipals and Engineering firms.

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Full Web-access to all data is accomplished using comprehensive Access Control. VDV natively supports the full range of Campbell Scientific data-loggers and most other brands of data-loggers via its File Converter. See http://demo.vistadatavision.com for real data from various industries. For more information, please contact Vista Data Vision - Vista Engineering, Hofdabakka 9c, IS-110 Reykjavik, Iceland, tel +354587-8889 email vdv@vistadatavision.com, www.vistadatavision.com,


TURBINE MAINTENANCE

Maintenance of Gas Turbines There are many types of failures associated with a gas turbine, since these units are very complex in their overall makeup. The Gas Turbines are the heart of large Combined Cycle Power Plants.

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ombined Cycle Power Plants were originally designed to operate as base-loaded units, however, recently most of these units that operate are cycled weekly or daily and during the day the plants are further cycled from about 40% - 100% power load. Most operators and OEM’s work on an equivalent hour basis, which takes into account the number of starts, and the percent load and time at which they are operated. The gas turbine failures range from control system problems, which are the most frequent but the down time accompanying these failures usually is the smallest averaging a few hours, the problems with combustors, rotors and blade failures are less frequent but the down time and costs accompanying those failures could extend to several weeks, and several million dollars in costs. The hot section failures used to far outnumber the problems in the compressor due to the high temperatures associated with the hot section, however in today’s advanced gas turbine a blade failure in the compressor can cause extensive downstream failures. Recent reports published Based on information from “Moderne Gas Turbinen-Technologie, Risiken und Schaden, Dr. J. Stoiber, Allianz Zentrum Fur Technik Gmbh, VGB PowerTech 2/2002, divides the problems for gas turbines into sizes larger than 150 MW, and gas turbines less than 170 MW. Figure 1 and Figure 2 show the major problems areas experienced in Gas turbines than less 150 MW and larger than 150 MW, respectively. In the smaller size turbines, the problems are concentrated in the hot section, as has been traditionally experienced. The interesting point as seen in Figure 2 is that the compressor problems are greatly increased as the turbine ratings increase.

Figure 1 – Major Failures in Gas Turbines Smaller Than 170 MW In fact, the compressor problems are slightly larger than the turbine problems. This is related to the high flow and high pressure in the larger turbines, and the air coolers for compressor air used for turbine cooling. The failures of the gas turbine in the compressor section are usually in the Inlet Guide Vanes, at the transition between the low pressure and high pressure compressors and due to rubbing in stages usually upstream of the bleed flow sections. The larger units have very high pressure ratios per stage, and have both low pressure and high pressure compressors and have high exit temperatures all leading to problems in the compressor section. The compressor

exhaust air coolers in some systems are part of the Heat Recovery Steam Generator Systems (HRSG), adding further complexity to the system.

Figure 2 – Major Failures in Gas Turbines Sizes Larger than 150 MW

The last twenty years has seen a large growth in Gas Turbine Technology. The growth is spear headed by the increase in compressor pressure ratio, advanced combustion techniques, the growth of

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TURBINE MAINTENANCE materials technology, new coatings and new cooling schemes. In other words the technology envelope is being pushed so that many of the components are operating in uncharted waters. Gas Turbine maintenance is dependent on the operational characteristics of the plant. The large Combined Cycle Power Plants were developed as Base Load Operating Units (1 start in every 1000 hours of operation). The reality has been very different and most combined cycle power plants are operating under cyclic conditions where the load at off prime time could be as low as 40-50% of the base load. Many of these plants now shutdown for the weekends. These changes in operation in many cases require the maintenance and inspection changes. Maintenance of most gas turbines depends on Equivalent Engine Operating Hours (EOH) and the number of starts. The Equivalent Operating Hours (EOH) are based on calculation of the number of starts or stops, number of trips, firing temperature, the variation in firing temperature, the type of fuel and the total actual operating hours.

Fired Starts 400 800 1200

1600

Inspection Combustor Inspection Hot Gas Path Inspection Combustor Inspection Full Turbine Maintenance Performance degradation in a gas turbine can be categorized as recoverable and non-recoverable. Recoverable performance is the deterioration in a gas turbine performance that can be recovered by engine cleaning or other wise known as an on-line and off-line water wash. Non-recoverable degradation is the performance deterioration of a gas turbine caused by internal engine component wear. The only way to recover the non-recoverable degradation is by performing a shop inspection and engine overhaul. Deterioration in turbine performance is indicated by one or more of the following conditions: Slower engine acceleration Engine compressor surge or stall

Inspection intervals are in most cases based on EOH, but some manufacturers also want to base these intervals on a combination of EOH and number of starts. Table 1 shows the typical gas turbine intervals for various types of inspections.

TABLE 1 Typical Gas Turbine Inspection time Intervals.

Lower power output Loss of engine compressor discharge pressure

Increase in compressor discharge temperature Figure 3 is a typical non-recoverable Power and Heat Rate degradation curve

Equivalent Operating Hours 8,000 16,000 24,000 32,000 40,000 48,000 Type of Inspection Combustor Inspection Combustor and First Stage Nozzle vanes and blades* Hot Gas Path Inspection Combustor Inspection Combustor and First Stage Nozzle Vanes and Blades* Full Turbine Maintenance

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power and an increase in the turbine heat rate during the first 5000 equivalent operating hours. These losses are non-recoverable in most cases, and would require the turbine to be returned to the shop, and outfitted with most new components, as well as special machining of the casing. Compressor Section Increase in overall gas turbine efficiency depends on pressure ratio and firing temperature. Therefore advanced gas turbines operate at very high pressure ratios. Pressure ratios in industrial gas turbines have increased from about 7:1 in the 1950’s to as high as 30:1 in the late 1990’s. Aero-engines in operation today have pressure ratios as high as 40:1. This increase in compressor pressure ratio decreases the operating range of the compressor, and thus the stability of the compressor. The operating range of the compressor is defined as the flow range at a constant speed line stretches from the surge point at the low flow end to the choke point at the high flow end. The stability of the compressor is defined as the ratio of the difference between the surge point and the design point to the design point: Stability (%) = ( Design Point- Surge point)/ Design point The compressor of a gas turbine consumes over 55%-60% of the power generated by the turbine, thus problems with the compressor can be very costly as to power produced and the loss of overall thermal efficiency of the gas turbine. Figure 4 shows the effect of compressor fouling on overall cycle efficiency. The effect of fouling of the compressor which reduces the compressor efficiency, leads to a reduction in the overall efficiency. The higher the pressure ratio of the compressor, the greater the reduction in the overall thermal efficiency of the turbine as can also be seen. Figure 4

Effect of Compressor Efficiency Drop on the Overall Thermal Efficiency as a function of Equivalent Engine Operating Hours (EOH). With an increase in equivalent engine operating hours there is a sharp drop in delivered

Reduction Table 2 indicates the various fouling mechanisms that affect the compressor


TURBINE MAINTENANCE near the eleventh to fourteenth compressor stages and therefore are more susceptible to out of roundness of the casing. Figure 6 shows the bleed chambers in a typical compressor. Measurements of the casing should be taken to determine blade tip clearances at eight points on the inner circumference of the compressor casing. Comparison of these clearance readings with those at installation or at some previous time will indicate if rubs have occurred and whether or not the casing is warped. It will also indicate whether or not the rotor is below its original position and requires further investigation at the overhaul period..

section of the Gas Turbine. The table indicates the effect that various types of fouling mechanisms have on the entire compressor section from the Inlet Guide Vanes to the Exhaust Guide Vanes*. The table deals with the effects on the variable and fixed compressor stator vanes, and the rotating blades. Table 2 Axial flow compressor performance is sensitive to the condition of the rotor blades. The compressor’s major problems are caused by dirt on the blades, due to poor filtration and maintenance practices. On-line water washing recovers majority of the performance deterioration. During a major inspection, all blades should be cleaned and checked for cracks with a dye penetrant test. If cracks are found in any blade, that blade should be replaced. Occasionally, small cracks can be blended out, tests conducted on blended blades have shown that if 75% of the blade tip chord length is intact then the compressor will suffer minimal loss of pressure and efficiency, and the blades can be used. The maximum and minimum chord lengths should be recorded and reported to the manufacturer, who in turn should be able to report the performance loss occasioned by wear and the decrease in structural strength. Leading edge blade erosion, as seen in Figure 5, is caused by the impact of water droplets from inlet evaporative and fogging systems commonly used in large gas turbines as an aid to power augmentation during the hot summer months. It should be noted that in many cases the benefit of Evaporative Cooling outweighs the cost of rejuvenating the leading edge of these blades. Figure 5

Coating Erosion Found on the First Stage of the Compressor Blade in units using Evaporative Cooling Systems The trends for the advanced axial flow compressors are towards fewer, thinner, larger, three Dimensional and controlled diffusion shaped airfoils (3D/CDA), with smaller clearances and higher loading per stage. Table 3 shows the technology in Axial flow Compressor blading of the new advanced gas turbines.

TABLE 3 Comparison of Design Characteristics of the New Advanced Gas Turbine Blades to the Many of the new high performance compressors suffer from tip rubs. The smaller clearances (20-50 mils) and high pressure ratios tend to increase the probability of encountering rubs. These tip rubs can lead to blade failures at the trailing edge of the tip section of the blades. Most of these tip rubs do usually occur near the bleed sections which are usually positioned around the first bleed valve section which are close to the fourth to seventh compressor stages and the second bleed valve section which are

Figure 6 Typical Bleed Ports in an Axial Flow Compressor The advanced compressor blades also usually have squealer sections on the blade tips, which are designed to wear in a safe manner if the blades are in contact with the casing. These rubs, if severe can lead to tip fractures and overall destruction of the downstream blades and diffuser vanes due to domestic object damage (DOD), as seen in Figure 7.. Figure 7 Compressor blade Damage due to Domestic object damage (DOD) due to blade tip failure due to rubbing The very high temperature at the exit of the compressor, which in some cases exceeds 1000ºF (538 ºC), causes a very hot compression section, which also requires the cooling of the bleed flows before they can be used for cooling the turbine section. This also limits the down time between start-ups of the turbines. Design margins are set by Finite Element Modeling (FEM) at the

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TURBINE MAINTENANCE element level which results in lower safety margins than previous designs. The costs of these larger, thinner, lessrub tolerant, and more twisted-shape airfoils are usually higher. When several of the major characteristics of advanced gas turbines are examined from a risk viewpoint (i.e., probability and consequences of failure), there are no characteristics which reduce the probability of failure and/or decrease

income in power as well as the cost of labor to do so and equate it against the extra energy costs. Cleaning the turbine compressor with the online wash system should be a routine, and scheduled maintenance function. The on-line water wash system is based on injecting atomized demineralized water or a mixture with a cleaning fluid. Water quality for both on-line and offline water washes must be stringent, so as to ensure that impurities are not introduced. Table 3 gives a detailed specification of the quality of the water

The DLN/DLE combustors have multiple fuel nozzles in each combustor chamber, One center pilot fuel nozzle and from 5-8 secondary fuel nozzles in a circle around the pilot nozzle. These nozzles are “staged” i.e. pilot nozzle is on all the time, while the surrounding nozzles, which may be connected in two or three groups of fuel nozzles, come on and off at various speeds during start-up. The fuel is pre-mixed in the fuel nozzles before it enters the combustor liner where combustion occurs. The DLN/DLE combustors have stability problems and are very susceptible to any liquids in the fuel gas system, which lead to a phenomenon known as flashback. Flash back is caused by the combustion flame moving from the primary combustion zone on to the fuel nozzles, causing a melt down of the fuel nozzles as shown in Figure 8.

the consequence of failure. Figure 8 Figure 7 indicates typical blade failures in blades around the fifth to seventh stage of a typical axial flow compressor in an advanced gas turbine. Note the number of blades downstream which have suffered from DOD. If the air inlet is subjected to salt-water contamination, the rotor and stator blades should be checked for pitting. Severe pitting near the blade roots may lead to structural failures. The manufacturer should be informed of severe pitting. Coating compressor blades is highly recommended and the extra cost is paid back in the first year by the fuel savings. On line cleaning is a very important operational requirement. On-line cleaning is not the answer to all compressor fouling problems since after each cleaning cycle full power is not regained, therefore a time comes when

the unit needs to be cleaned off-line, as seen in Figure 3 Figure 3 Effect of Compressor Water Wash on Power Output The time for off-line cleaning must be determined by calculating the loss of

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required to complete a successful water wash. TABLE 3 WATER SPECIFICATION Combustor Section Gas Turbine Combustors can be “Can Annular Type Combustors” where about 10-14 individual combustor cans are positioned in an annular configuration. The can annular chambers are connected to each other by the use of cross-over tubes which are there to ensure that the combustion pressure is maintained evenly in all the combustor cans. The other configuration of the combustor can is a “Single Annular Combustor”. Furthermore each of the above two type combustors can be classified into two types of combustion chamber characteristics: “Diffusion Type Wet Combustors”, and the “Dry Low NOx (DLN) Combustors”, or sometimes known as “Dry Low Emission (DLE) Combustors”., and furthermore there are different configurations of the combustor chambers, the most common being the annular and can annular combustors. Diffusion type combustors inject the fuel through a single fuel nozzle into the primary combustion zone where it mixes with about 8-10% of the compressed air flow, and stoichiometric combustion occurs. The rest of the compressed air is used for cooling and mixing in the combustor liner. Water or steam is injected in the stoichiometric zone to cool the temperature of combustion and reduce NOx emissions. The amount of water is between 80-100% of the fuel flow rate.

Combustor Nozzles Burnt due to Flash Back Problems in a DLN Combustor Can-Annular type combustors and the small side combustors can be easily removed without removing the casing and the combustion liners and nozzles are easily inspected for cracks and burned areas without having to remove the turbine casing. Silo Combustors can also be easily examined after they have cooled and technicians can enter the combustors to examine the combustor tiles. The best way to examine the annular combustors is with the use of borescopes. Short, individual cracks especially in diffusion combustors are not uncommon and need no immediate attention. However, if the cracks are grouped such that their continuance or the beginning of another crack could cause the loss of a piece of metal, then a repair should be made. Cracks of this nature normally can be welded with a type of welding rod recommended by the manufacturer, depending on the kind of metal involved. Burned or warped areas in combustion chambers or baskets can be cut out and new sections welded. However, burned areas should be studied with regard to location, pattern, or repetition in all chambers to determine the cause of the burning.


TURBINE MAINTENANCE Table 4 indicates the various fouling mechanisms that affect the combustor section of the Gas Turbine. The table indicates the effect that various types of fouling mechanisms have on the entire combustor section including Diffusion and DLN combustors, fuel nozzles, cross-over-tubes, and the transition pieces. The table deals with the effects on can-annular and annular combustors. Table 4 Flash Back

This is a phenomenon

common in DLN combustors, and is accelerated if there is any liquids in the fuel gas No problem in diffusion combustors Major problem in these type of combustors. Caused by flame being moved back to the fuel pre-mix nozzles which destroys these nozzles, also accompanied by High vibration and pulsation Dual Fuel Liquid Fuel and natural gas. Operation at various percent mixture settings. Good operation at all percent mixture settings. Changes of percent on line possible On-line change of fuel not possible. Unit has to be shutdown and new fuel nozzles must be inserted. Individual burned areas may indicate a dirty or faulty fuel burner nozzle or misalignment of the combustion chamber. Similar burned areas in various chambers may indicate abnormally high firing temperatures during starting due to excessive fuel use. They may also be the result of "slugs" of liquids entering with the fuel gas, excessively rapid starts, or overloading of the turbine. In the case of DLN combustors problems with “flash backs” due to liquids in the fuel gas destroy the fuel pre-mix nozzles. The combustion chamber positions as well as the actual chambers or baskets should be permanently numbered, and a complete record should be made for each basket regarding hours of service,

repairs, or replacements made, and their location in the turbine at each inspection date. The basket ends or at places where they are supported should be inspected for excessive wear from vibration or expansion and contraction movement. Repair of these parts should be made by cutting out and welding in new materials or replacing spring seals if necessary. The Combustor Cans are connected to the “Transition Piece” which then connects to the turbine casing. The Transition pieces are exposed to the highest temperatures in the gas turbines. The transition pieces should be inspected for cracking and wear at points of contact. Transition pieces are now being coated with a TBC. Wear usually occurs between the transition piece and the combustion liner sleeve, and also at the first-stage nozzle fit. The cylindrical section of the transition piece may be replaced if the wear is excessive; wear at the nozzleend of the transition piece is more serious because it allows excessive vibration of the transition piece, which might lead to cracking. Transition pieces should be replaced if 50% of the inner or outer seal is reduced to half the original thickness. If the transition piece is in otherwise excellent condition, the seals may be ground off and replaced. Floating seals which join the transition piece to the turbine casing near the first stage nozzle vanes should be examined closely. Transition pieces should be replaced if cracks are found in the body. It is highly recommended that the combustor liners and the transition pieces be lined with a thermal barrier coating, so as to reduce the metal temperatures. Turbine Section The gas turbine consists of three to five stages, each stage consists of a circular row of nozzle vanes followed by a row of turbine blades. The first two row of turbine blades usually are non-shrouded, while the last few stages where the blades are long are also shrouded as seen in Figure 9. In this figure the first two rows have Thermal Barrier Coating (TBC). These coatings for each mil of coating thickness reduces the metal temperature by about 14 ºF (8 ºC). Figure 9 A Typical Gas Turbine’s Axial Flow Turbine Section The first-stage turbine nozzle vanes can be superficially inspected by the use of a borescope for bowing by entering the

turbine through the combustion chamber areas or by removing inspection plates. In certain turbines (and by somewhat difficult maneuvering) the last row of turbine rotating blades can be inspected by entering through the turbine discharge duct. The opportunity should be taken to measure, if possible, the blade tip clearance at eight points on the circumference. Comparison of these clearance readings with those at installation or at some previous time will indicate if rubs have occurred and whether or not the casing seal ring is warped and out of round. It will also indicate whether or not the rotor is below its original position and requires further investigation at the overhaul period. As the hot sections become exposed, preliminary inspection for cracks or bowings should be undertaken to estimate work to be done. Cracks are usually noted at the trailing edge of the blades at around 1/3 the blade height from the blade platform. The high temperature in the new blades have caused major failures at the blade platforms and due to leakages of the high temperature air the labyrinth seals or the honeycomb seals have had major blade failures. Incomplete combustion or excess fuel During start-up the fuel is not combusted and collects in the stationary vanes, which act as flame holders. Ensure that the control system has a rate of acceleration shutdown mode Hot Corrosion Type I (over 1500ºF) Rapid form of oxidation, caused by the reaction of Na in the air or fluid, sulfur which is usually in the fluid, and oxygen. Intergranular attack, sulfide particles and a denuded zone of base metal.

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TURBINE MAINTENANCE Hot Corrosion Type II ( between 1100ºF1450ºF) Caused by low melting eutectic compounds resulting from the contamination of sodium sulfate and some of the alloy constituents such as nickel and cobalt. Layered type of corrosion scale Hot Gas Erosion Oxidation Caused by small solids in the air or the fuel. By poor combustor pattern, excessive EGT pattern Blade Tip Rubs Due to very small tip clearance, and high metal temperatures in the blades Blade Fretting Erosion Fretting in the dove tails/ fir trees is caused by the rocking action of the blades. Peaking turbines are highly susceptible to this problem Blade and wheel Rupture Failure This failure occurs in high temperature and highly loaded blades (highly stressed) and disks. Disk failure can be catastrophic. Caused by inadequate cooling due to blockage of cooling passages. Foreign Object Damage / Domestic Object Damage FOD occurs from materials coming from an external source to the gas turbine, and DOD occurs from failure of internal components. Low Cycle Fatigue (LCF) Turbine disks, and first stage turbine suffering from low steady state stress, also due to thermomechanical fatigue problems. Peaking turbines more susceptible. High Cycle Fatigue Can occur in any blades or vanes due to blade resonance frequency being excited. This usually occurs in blades where there are no tip or mid-span shrouds. Turbine blades should be closely inspected for erosion and cracks. The most critical areas in the turbine rotor are the fir-tree section, where the blades are attached to the rotor, and the trailing edge of the blade near the hub. The trailing edge of the turbine blade is usually the hottest section of the blade, and cracks usually start at the trailing edge at about 1/3 the height of the blade from the base. These areas should be carefully cleaned and checked for cracks with spray penetrant. The coatings should be stripped. They should then be inspected minutely for cracks by means of red dye or black light. The first-stage nozzle vanes will probably need attention, which can be done on the job. In older design vanes bowing on the trailing edge, if any, can be taken out by inserting a spacer piece of correct cross-sectional area between the vanes, heating the top vane to red

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heat with a torch, and forging the vane edge flat with a hammer and flatter. The cracks, if less than 1.5 inches long, can be grooved out and welded, providing the crack does not run under the end-supporting rings. In this case the vane must be removed and welded or a new vane fitted in place. As the vanes are welded, they must be continually checked for new cracks, which in turn must be grooved and welded and checked again. The new advanced nozzle vanes have thousands of cooling holes through out the vanes. These vanes have the hottest section at the leading and trailing edges of the vanes. Figure 10 shows a new design nozzle vane with a burnt leading edge and a burnt trailing edge. These vanes due to the very high temperature of over 2400ºF (1316 ºC) also require cooling of the nozzle platforms. A. Leading Edge Vane

Internal degradation is caused by microstructual changes, which result from extended exposure at high temperature under stress. The microstructural changes are responsible for the reduction in mechanical properties. Three forms of internal degradation have been verified: (1) precipitate coarsening or overaging, (2) changes in grain boundary carbides, and (3) cavitation or void formation. Normal reheat treatment can partially restore blade properties; however, it does not appear to be capable of full property recovery, although the miscrostructures are comparable to new blades. This shortcoming implies that cavitation may be present and was not removed by conventional reheat treatment. Hot isostatic pressure (HIP) processing is an alternative that ensures void removal. It has demonstrated its ability to remove even gross internal shrinkage porosity in investment castings.

B. Trailing Edge Vane The new advanced nozzle blades, because of their single crystal structure, or directionally solidified vane structure, and very complex cooling sections can not be repaired. The older alloy blades (IN 738) can be rejuvenated. Before rejuvenation the blades must be inspected for damage. There are two distinct types of damage can be recognized: surface damage and internal degradation. Surface damage may be due to either mechanical impact or corrosion and is generally confined to the blade airfoil. In both cases light damage can be removed by blending or dressing, and then applying coating for surface smoothness and temperature protection. Blending of the trailing edges and leading edges should not leave the chord at the blade tip less than 75% of the original blade chord length. Blades with severe surface damage or cracks usually are scrapped. When properly applied, these coatings can increase the life of the blades considerably, in some cases even more than when they were new. Advances in high temperature coatings for severe hot corrosion service have resulted in the low unit cost feature of pack cementation and the economy of electroplating to yield multiple element coatings containing precious metal aluminides. These coatings are available in several combinations of platinum, rhodium, and aluminum for application to cobalt and nickel based vanes and blades. Most of the newer first two stages of blades are coated with TBC coating. These coatings were optional on the old turbines but they are now necessary to maintain the blade metal temperature below 1350ºF (732ºC).

While repairing the older first-stage nozzle vanes, the upper and lower vane section should be bolted or clamped together, and the entire ring should be placed on a flat, level surface, or sufficiently supported in the horizontal plane to prevent heat warpage or bowing of the ring due to heating of the vanes during their repair. After straightening or taking out any bowing in the trailing edges of the vanes (partitions), perpendicular distances between the trailing edges of each vane and the surface of the next should be carefully measured. An average of these distances should be made and then corrected to a plus or minus percentage approved by the manufacturer. This method will help to assure equal distribution of gas flow to the first stage rotating blades for elimination of blade vibration. Turbine rotating blades cannot be field repaired if they are cracked. If one or two blades are damaged mechanically, the manufacturer may recommend field repair or replacement of the damaged blades. However, if several blades are fatigue cracked, it is recommended that the entire set be replaced, since the remaining blades have been exposed to the same operating conditions and, therefore, have little fatigue life left. Dr. Meherwan P. Boyce, P. E., C.Eng. FELLOW: ASME(USA), I.MechE(UK), IDGTE(UK) THE BOYCE CONSULTANCY GROUP, LLC. PHONE: 713-807-0888 FAX: 713-807-0088


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Hydraulic Servicing Allison Hydraulics has provided a service to UK Industry for over 30 years, starting from its base in the Leeds/Bradford area and later expanding with another service facility in Washington Tyne & Wear.

W

orking with our partners Hydrastore, Atos & MP Filtri we offer not only a Preventative Maintenance Service but our experienced engineers can offer advice on improvements to filtration, solutions to system overheating and more general fault diagnosis. A routine part of hydraulic servicing is to establish the condition of the hydraulic fluid and its suitability for continued use. This is done on-site, without interrupting production, using our Laser Particle Counter. If necessary, more detailed analysis can be carried out from samples taken.

repair or complete remanufacture for hydraulic and pneumatic cylinders. Allison Hydraulics Ltd Unit 2 Factory Lane Off Rooley Lane Dudley Hill Bradford BD4 9NW Tel 01274 687327 Allison Hydraulics Ltd 13B Harvey Close Crowther Ind Estate District 3 Washington Tyne & Wear NE38 0AB Tel 0191 416 1260 Email: sales@allisonhydraulics.com Please visit: www.allisonhydraulics.com

To complement our service we carry large stocks of replacement hydraulic components, including valves, pumps and filters. Our extensive workshops are equipped for all types of hydraulic repairs including

41


Do not disturb!

Key points: · AC and DC measurements with 1mA accuracy/resolution · Non-invasive current measurement – no need to break connections · Full accuracy maintained in harsh electrical environments · Lightweight, singlehanded operation

rue-RMS clamp meter measures down to 1mA with no circuit disturbance.

T

display: full-scale readings are up to 4A

difficult-to-reach location, remove the

or 40A, with auto-ranging and auto-zero

CP41 from the test site, and to bring it

functions. GMC-I PROSyS also offers a

back into clear view still displaying its

GMC-I PROSyS has introduced the CP41

second variant of the CP41, the CP410,

current reading.

AC/DC True RMS Clamp Meter, , a hand-

which measures higher currents: its auto-

held unit that combines simplicity of

range full-scale limits are up to 40A or

The CP41 and CP410 meet the Safety

operation and convenience with non-

400A. The GMC-I PROSyS CP41 uses

requirements of EN61010-2-032:2002 and

invasive measurement of current to an

compensated Hall-Effect sensing in a

the EMC specifications of EN 61326-2-

accuracy of ± 1% of reading and

patented magnetic circuit, to detect the

2:2006, and provide safe operation on

resolution of 1mA.

magnetic current generated by the

uninsulated conductors carrying voltage

current of interest; this technology

of up to 300V with respect to ground.

Measurement capability in the mA range

allows measurement of both DC and AC

They measure 194 x 74 x 25mm, weigh

permits verification of 4-20mA current-

currents. AC currents are measured over

235g, and operate for 15 hours from a

loops in process-control systems, while

a frequency range of 15 to 400 Hz.

standard 9V alkaline battery.

light-industrial and residential electrical

In operation, the user opens the jaws of

installations. The CP41 measures,

the probe, which have a 25-mm

selectably, DC or AC currents with a

aperture, and closes them around the

resolution of 1mA and, on its AC ranges,

conductor carrying the current of

with true-RMS current indication.

interest: advanced design of the

About GMC-I PROSyS GMC-I PROSyS designs, develops and manufactures current probes, clamp meters, handheld instruments and systems for current and voltage measurement, as well as measurement and processing of electrical parameters.

the meter is equally applicable to testing

magnetic circuit means that location of It maintains accuracy even in electrically

the conductor within the aperture is non-

noisy environments, featuring excellent

critical and errors due to off-centre

rejection of external magnetic fields

positioning are negligible. The CP41’s

together with a very high level of

design supports safe, single-handed

immunity to interference from voltage

operation in hazardous areas, assisted by

transients. The meter is battery-

a display-hold function which allows the

powered, and has a 4-digit liquid-crystal

user to take a measurement in a

42

For more information visit: www.i-prosys.com. For further information, please contact: Ahmet Selcuk, GMC-I PROSyS Tel: +44 1695 567280 ahmet.selcuk@i-prosys.com


43


Pilz Automation Technology and SCA Display UK co-develop innovative safety solution for hand-fed platen press

W

ith the Health & Safe-

A collaborative development project be-

Part of SCA, SCA Display UK’s Shenstone

ty Executive about to

tween two UK-based companies has re-

plant employs around 80 staff and manu-

commence on-site

sulted in a much safer working

factures a wide variety of point-of-sale

inspections of hand-

environment for operators of a hand-fed

and POD products, mostly custom de-

platen (die cutting) press.

signed products made from cardboard.

fed platen presses, users of this highrisk machinery need to ensure that their presses meet the required safety standards. By working closely together, two companies have developed a novel, high integrity safety solution for a hand-fed platen press, which uses an array of light beam sensors and a modular safety control and monitoring system.

44

The factory uses a wide range of machinIn November 2009, machinery safety specialist Pilz Automation Technology and SCA Display UK, a manufacturer of Pointof-Display (POD) products for retail customers, began working together to improve the safety of a hand-fed platen press at SCA Display’s production plant in Shenstone.

ery, including digital and silkscreen printers, die cutters, folding & gluing machines and platen presses. Most of the


die cutting uses semi-automatic presses,

ensure that additional operator safety

during normal production. In both cases,

but one of the presses is hand-fed, which

measures.”

the hand-fed machine was being used in the dwell mode and the power to the

is used for short runs and one-off cusHSE Safety Alerts and Inspections

platen was not isolated before the inter-

Ian Clews is not alone in his views on

vention occurred and so the safety de-

Ian Clews, Facilities Manager at Shen-

the need to improve the safety of

vices fitted to the machine did not

stone, has been working with platen

hand-fed platen presses. In the UK, the

prevent the platens closing on the oper-

presses for more than 30 years and SCA

Health & Safety Executive (HSE) has

ator.

are members of the Confederation of

recently issued safety alerts to users of

Paper Industries, where machinery safe-

hand-fed platen presses. It is estimated

“During the setting process, waste re-

ty is high on the agenda. “Quite frankly,

that in the UK alone, there are be-

moval, replacement of lay stops or mis-

the use of these machines has been a

tween 1,000 and 2,000 such presses

feed retrieval, even with the most safe-

concern for many years, particularly in

that require safety upgrades, mostly

ty conscious operators may try to beat

the dwell mode. With two fatalities in

operated by companies in the printing

the dwell and climb onto the platen

the UK in recent years, users of these

and packaging industries. Most of the

press bed or lean into the machine.

machines need to review their safety

high-risk machines fall into the 1.4m to

Whilst between the fixed and moving

systems.”

2m-width range.

platen beds the operator is not detected

“A typical hand fed platen press closes

The HSE is currently considering issuing

with a tremendous force, often with the

alerts to users in order to raise aware-

operator’s body in close proximity. This

ness of the potential dangers of whole

According to the HSE, the latest hand-

means that operator safety is extremely

body access between the platens of

fed platen presses are much larger than

critical. At Shenstone we have a continu-

these machines when operating in the

their predecessors and many users now

al improvement policy which instigated

‘dwell’ mode. The alerts are in re-

use the machine’s dwell mode to either

further upgrades to our platen press to

sponse to two fatalities since 2008 in

give them more production flexibility or

the UK, where operators were crushed

to speed up the machine’s output, as

between the platens as they intervened

this mode can often double the speed of

tomer specials.

by any of the usual safety systems,” explains Ian Clews.

45


operation. On most hand-fed platen

tect employees. Ian Clews contacted Pilz

array of light beam sensors that would

presses, climbing onto the platen from

Automation Technology to discuss possi-

monitor the side and platens in order to

the normal operating position in front of

ble safety solutions.

detect any violation of the machine’s danger zone whilst the press was closing.

the machine can be done without operating the safe edge that is normally fitted

“By this time, I had already devised sev-

As far as we are aware, the solution

to the leading edge of the lower platen.

eral concepts for upgrading the safety of

we’ve developed is the only one of its

This means that if a safe system of work

the platen press, but needed to talk to a

kind in the UK, where light beam sensors

is not followed, including isolating the

machinery safety specialist supplier such

are being used to monitor the area di-

machine, the platen may then continue

as Pilz about how the solution could be

rectly above the moving platen.”

to cycle if it is being used in the dwell

realised from a technological viewpoint.

mode and the protective devices will not

I also wanted the solution to be modular,

The overall safety solution is based on

automatically be triggered.

enabling a best option for employee pro-

Pilz’s PNOZmulti modular safety system.

tection rather than a cost option. It was

PNOZmulti is multifunctional, freely con-

Further investigation by the HSE has

critical that we worked with a supplier

figurable and is ideal for monitoring

showed that standards of guarding and

that had in-depth knowledge of current

safety functions such as Emergency-Stop,

working practices on many existing, larg-

machinery safety legislation and stand-

safety gates and light barriers, as well as

er hand-fed platen presses need to be

ards, but with the ability to then apply

performing standard control functions.

improved significantly. HSE has an-

that knowledge to developing the most

Rather than hard wiring, safety circuits

nounced that it will commence on-site

appropriate safety system for our ma-

can be generated on a PC using

inspections of hand-fed platen presses in

chine,” says Ian Clews.

PNOZmulti’s intuitive configuration software. This configuration can then be

October 2010. Chris Sloan (Area Sales Engineer) and

stored on a memory card and download-

In his presentation to a group of machin-

Stewart Robinson (Consultant Engineer)

ed to the PNOZmulti base unit.

ery safety suppliers at the HSE’s Birming-

at Pilz Automation Technology have

ham offices on 12th July 2010, Tim Small,

worked closely with Ian Clews on the

The solution incorporates a PNOZmulti

HM Principal Inspector at the HSE, stat-

platen press project since early 2010.

base unit, with input and output expan-

ed: “The HSE deems hand-fed platen

Chris Sloan says: “Initially we visited

sion modules to control all aspects of

presses as high risk machines. Enforce-

Shenstone to assess and analyse the plat-

machine safety and control. “We wrote a

ment action will be taken against any UK

en press and to discuss safety issues and

functional specification for the press,

firms that aren’t taking appropriate ac-

potential solutions. SCA wanted a work-

then engineered a solution based on

tion to meet these new safety expecta-

ing solution based on a modular safety

these functional safety requirements. We

tions.”

platform that would include all the nec-

supplied all the hardware, including the

essary hardware and software, tailored

light beam array and safety controller, as

to suit the machine.”

well as writing all the software code for

Employee Safety-Driven Approach

the application,” states Stewart Robin-

In November 2009, SCA Display UK decided to improve the safety of its hand-fed

Stewart Robinson adds: “One of Ian

platen press at Shenstone to better pro-

Clews’ favoured concepts was to use an

46

son.


It should be remembered that this solu-

The hand-fed platen press at Shenstone

We quickly resolved this issue by devel-

is fitted with a number of general pur-

oping more robust bearing mountings,

tion must be accompanied with robust,

pose safety devices such as trip bars,

which enable the sensors to be adjust-

safe systems of work, training, regular

interlocked guards, right and left hand

ed more easily. We also developed an

maintenance and risk assessments.

emergency stops, safety mat, front safe

infra-red sighting device that simplifies

edge, lumbar bar, safety gate key

the alignment of the sensors.”

“The services provided by Pilz were exceptionally good and I cannot fault them

switch, left and right side light curtain. All these devices have the same func-

The light beam array now detects a

at all. Any modifications or software up-

tional safety requirements, which are to

violation of the danger zone whilst the

dates were carried out quickly as and

prevent all hazardous movement by en-

press is closing. This is achieved by se-

when required and technical support

suring that the clutch safety valve is

quentially muting the laser beams as

from Pilz engineers was excellent.

de-energised and that the main motor is

the press closes.

stopped, and to prevent unintended

The working relationship was very close If any beam is broken before it has

and has resulted in a truly collaborative

been muted, the press clutch safety

solution. The project itself was complet-

valve is de-energised immediately

ed successfully on the 16th of July and

bringing the hazardous movement to a

the press was handed over to our pro-

stop. Once the final beam has been

duction team two weeks later,” Ian

SCA’s Safety Solution

broken (press closed) the beams re-

Clews concludes.

The machine now uses an array of

main muted until the press cam switch

PSENop4S light beams supplied by Pilz.

has operated, signalling that the press

restart. The target safety integrity level for each General Safety Function is SIL 3 (EN 62061), equivalent to PLe according to EN ISO 13849-1.

is at the ‘home’ position.

Please email v.smith@pilz.co.uk for

As Ian Clews explains: “We did have a

more information about the project or

few teething problems based around

The muting points are derived from the

alignment of the sensors, but this was

simulation of press position carried out

telephone 01536 460766 or visit

down to the original machine mount-

within the PNOZmulti control system.

www.pilz.co.uk

ings, which were not robust enough to

The application also includes checking

provide a solid foundation for the light

that the press cam switch operates cor-

beam sensors.

rectly in each press cycle.

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EMS OCTOBER 2010  

EMS MAGAZINE

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