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TECHNICAL BULLETIN OF INDIAN SOCIETY FOR NON-DESTRUCTIVE TESTING (ISNT) THIRUVANANTHAPURAM CHAPTER Vol.27 No.1

November 2012

www.isnttvm.org

Chapter activities June 2012 to September 2012

From Chairman’s Desk ......

1. AGM 2012.

Non destructive Testing is a part of our daily life. When we purchase an item or when we want to use an item we accept it based on visual inspection. Even though in most cases it works well, in good number of cases the assessment of quality by such inspection fails. This means that the reliability of the technique or the method adopted is not adequate. In industrial scenario we use more scientifi c methods for inspection which are more reliable. In the case of aerospace sector where design margins are low, and functional requirement of these components is very important, reliability plays a vital role. The methods and practice which we follow must have high degree of reliability. Adherence to NDT Standards is one way of achieving reliability. NDT practitioners also need to resort to procedures, which are well documented, to achieve better reliability of inspection. Expertise needs to be built up by way of training in various areas of NDT methods. Efforts are put in by ISNT in this direction to impart training to various NDT practitioners by way of various training programmes, workshops etc.

Annual General Meeting 2012 was conducted on 23rd June 2012 at Classic Avenue, Trivandrum. More than 90 ISNT members participated in the meeting. This was followed by family get together and entertainment programmes. 2. MR Kurup memorial lecture Dr. B. Venkatraman, Associate Director IGCAR, Kalpakkam delivered the MR Kurup memorial lecture on 23rd June 2012 at Hotel Classic Avenue. Various NDT methods and challenges in the area of NDT of nuclear power reactors were briefed during this lecture. 3. Annual Technical Meet Sri. Anil Kesavan, NLPTA certified trainer delivered the Annual Technical Meet lecture on 23rd June 2012 at Hotel Classic Avenue. The topic ‘Why we behave the way we do’ was well attended by both members and their families. 4. Executive committee meeting Three executive committee meetings were held during July, August and September 2012 to plan and execute various programs

With best wishes.

5. Seminar on He leak detection

S. ANNAMALAPILLAI Chairman, ISNT TVM Chapter

A seminar on ‘He leak detection and its techniques’ was organized by the chapter jointly with M/s Agilent Technologies India Ltd. on 10th September 2012 at Hotel Nandavanam Park Trivandrum. More than 100 people attended the lecture. 1


6. Member directory Draft of the member directory is getting ready at Press. Members are requested to send updated details immediately if already not sent 7. Academic institution program ISNT supported in arriving the specifications for procurement of NDT equipments for Department of Mechanical Engineering Barton Hill College of Engineering, Trivandrum

A view from the audience during the seminar

ISNT supports procurement of NDT equipments for

Barton Hill College of Engineering, Trivandrum jointly with the Department of Mechanical Engineering

Hon. Secretary presenting the report on chapter activities during the AGM 2012

MR Kurup memorial lecture delivered by Dr. B. Venkatraman, AD, IGCAR Kalpakam

Visual Inspection KR MOHAN ANANTHANARAYANAN DGM QUALITY CONTROL EXTERNAL VSSC

This issue of IMAGE onwards we are bringing out

‘Back to Basics’ series on Non-Destructive Inspection. No doubt the first topic is visual Inspection, an easily said and seen technique. Can we define visual inspection? It is

Dr. Pieter, He leak detection specialist, USA during the seminar

not that simple, it goes on like this “Visual inspection is the process of examination and evaluation of systems and components by use of human sensory systems aided only by mechanical enhancements to sensory input as magnifiers, dental picks, stethoscopes, and the like. The inspection process may be done using such behaviors as looking, listening, feeling, smelling, shaking, and twisting. It included a cognitive component wherein observations are correlated with knowledge of structure and with descriptions and diagrams from service literature.” [1]. Making it

Dr, S, Annamala Pillai, Chairman ISNT Tvpm Chapter delivering the welcome address during the seminar

short it is just sensing and believing. 2


Visual inspection is a normal Quality Control require-

Optical aids for visual testing range from simple mirror

ment in fabrication of welded and riveted structures and

or magnifying glasses to sophisticated devices such as

other machined components of launch vehicle hardware.

closed circuit television (CCTV), and coupled fiber optic

As an aeroplane lands and gets parked we might have

scopes. Some lists include devices such as optical and

seen airport personnel moving with flash light, checking

electron microscopes, optical comparators, and machine

the wings and other parts of the plane. It is a routine visual

vision systems. A listing that includes most optical aids

check that can prevent calamities. As the train rolls into

currently in use is:

a station its wheels and axles are checked, you could see inspectors crouching and looking at the wheels under

a. Mirrors (especially small, angled mirrors)

illumination. These are simple cost effective checks that

b. Magnifying glasses, eye loupes, multi-lens

can prevent failure.

Visual inspection is the most often specified

c. Microscopes (optical and electron)

technique for airframes, power plants and systems in

d. Optical flats (for surface flatness measurement)

aviation. The FAA’s Advisory Circular 43-204 (1997)

e. Borescopes and fiber optic borescopes

1 on Visual Inspection for Aircraft quotes Goranson and

f.

g. Photographic records

h. Closed circuit television (CCTV) systems (alone

Rogers (1983) to the effect that over 80% of inspections on large transport category aircraft are visual inspections [4].

magnifiers, measuring magnifiers

Optical comparators

and coupled to borescopes/ microscopes)

Classification of visual inspection: It can be

i.

Machine vision systems

classified as Direct and Remote Visual inspection. In

j.

Positioning and transport systems (often used

the case of direct, as the name implies, we can see the

object directly with or without the aid of magnification.

In the case of remote visual inspection direct access is not

k. Image enhancement (computer analysis and

available. For the inspection of a recess or an assembled

with CCTV systems) enhancement). [2]

turbine blade we need to have equipments like borescope

Pre-requisites for visual inspection :

and fiberoscopes to carry out the visual inspection.

Visual aids for visual inspection: Visual inspection is carried out with mechanical and optical aids. These aids

To the extent possible visual inspection has to be

carried out after thorough cleaning of the object under

help in having a better view with magnification of the test. Visual inspection plan has to be prepared taking into imperfections and to assess them with respect to size and

account the functional requirement of the product and the

location. Marking and reporting of defects are also done

type of processes involved in its production. Spe-

with the help of these aids.

cific references to codes and standards if specified have to be complied with. When visual inspection is specified

Mechanical aids include:

it means that the inspection is carried out by a certified

a. Measuring rules and tapes

b. Calipers and micrometers

c. Squares and angle measuring devices

Contents of a visual Inspection Plan:

d. Thread, pitch, and thickness gages

e. Level gages (liquid and laser) and plumb lines

f.

inspector.

The plan should provide what, when and how to in-

spect. Reference to section of relevant codes and standards

A variety of weld gages.

has to be made in the plan. 3


What to inspect?

When to inspect?

There are different type of surface imperfections that

Stages of inspection have to be specified in the plan.

are looked for. Surface finish verification of machined

In machined components visual inspection is carried out

parts has even been developed, and classification can be

at the final stage to ensure that there are no surface imper-

performed by visual comparison to manufactured finish

fections like dents, scratches and other handling marks. In

standards. In the fabrication industry weld size, contour,

the case o-rings, visual check helps in identifying sharp

length, and inspection for surface discontinuities are

corners in the groove that can cut the o-ring resulting in

routinely specified. Forgings and castings are normally

a functional failure. Improper chamfers in a component

inspected for surface indications such as laps, seams, cold

may result in assembly difficulties. Untouched portion

shuts, mismatch, and other various surface conditions. In

during machining can been seen and reported. In some

service inspection of nuclear power systems visual

cases a visual inspector can even find out an area of weld

inspection is carried out in welds, hangers, valves, pumps,

build up in a machined component. In the case of welds

pipe restraints, supports, snubbers, spring sway braces,

Inspection is carried out for cleanliness of the set up,

and integral components attached to critical systems.

mismatch before welding and the bead surface condition

Many of these inspections are used to identify erosion,

after welding. Lack of root penetration, underfills, arc

corrosion, loose or missing parts, adjustments, and set-

strikes, spatter and even a crack that opens to surface can

tings. This type of inspection is applicable for aerospace

be seen. Figures attached provide certain cases wherein

structures also. Visual inspection is the predominant tool

defects are visually seen.

in the coating industry. The cleanliness of the base metal

Look at the following figures. All of them are visual observations on machined components and welds.

before plating is to be seen. After coating, visual inspection is performed to identify under thickness, sags, mud cracking, blistering, delamination, pores, peel off and numerous other conditions that may be present in the top coating layer. Checking for proper identification marking, painting and packing can also form a part of visual inspection.

Visual inspection of fasteners typically includes the

action of feeling for fastener/structure relative movement.

Rusting and pitting on critical machined surfaces

This involves active attempts, using the fingers, to move the fastener. In human factors, this would be classified as tactile or more generally haptic inspection. A different example is checking control cables for fraying by sliding a rag along the cable to see whether it snags. Other examples include the sense of smell (fluid leakage, overheated control pivots), noise (in bearings or door hinges) and feel of backlash (in engine blades, also in 5 hinges and bearings). The point is that “visual� inspection is only partially defined by the visual sense, even though vision is its main focus.

Discoloration on Rocasin surfaces and rusting on metallic surface 4


Typical weld visual inspection with the aid of

illumination and magnifying glass.

As seen from the figures visual inspection can detect

a good number of surface imperfections. It also means that one should know where to and how to look for defects.

Minor scratches

Tool mark and dents

How to look for imperfections?

Visual inspection with optical aids provide better

results. Remote visual inspection is required for inaccessible areas. While making a request for visual inspection it is better to provide the details of illumination and magnification required. Some requirements that are given by ASME codes are reproduced below: Lighting requirements shall be as follows:

For general examination a minimum of 50 foot

candles of light. A standard two (2) cell flashlight fully charged will produce 50 foot candles at approximately 18mm distance for the point of observation.

lack of root fusion and

Undercut

Incomplete root penetration and

For the detection or study of small anomalies a

minimum of 100 foot candles of light . For comparison, a 100 W incandescent bulb produces about 1750 lumens or 137 foot-candles, a 23 watt fluorescent light produces about 1600 lumens or 125 foot-candles

• Excessive root penetration

For direct general visual examinations, resolution and

lighting shall be considered sufficient when a black line

Crack

1/32” wide on a 18% neutral gray card can be resolved under the worst conditions of lighting, angles or positions of the inspection to be encountered.

A gray card is a flat object of a neutral gray color that

derives from a flat reflectance spectrum. A typical example is the Kodak R-27 set, which contains two 8x10” cards and one 4x5” card which have 18% reflectance across the visible spectrum, and a white reverse side which has 90% reflectance. Note that flat spectral reflectance is a stronger condition than simply appearing neutral; this flatness ensures that the card appears neutral under any illuminant. 5


Mirrors and magnifiers may be used to assist in the

the recent years. Interestingly, vision testing has changed

examination when necessary. Visual examination may

little over time. Table 1 illustrates the different vision re-

begin immediately after completed welds have cooled

quirements that have been based on the present governing

except visual examination of welds in ASTM A514 and

standards. Note that little has been done to standardize

A517 steels shall be performed no less than 48 hours after

any of the vision tests used in the industrial sector.

completion.

Table 1 - Different vision requirements

Combined with lenses and placed in rigid tubes, we

Industry Study

have borescopes that enable us to see inside specimens

Color Vision

Brightness

Discrimination SNT-TC-1A 1992 J2* - Differentiate SNT-TC-1A 1975 J2 - Differentiate SNT-TC-1A 1968 J1 - Differentiate NAVSEA 250-1500 J1 - Differentiate RT contrast MIL-STD-271 J1 - Differentiate RT contrast MIL-STD-2132 J1 - Differentiate ASME SECTION III J1 20/20 Differentiate ASME SECTION XI J1 20/20 Differentiate 0.79 mm (0.31 in.) Line on gray card MIL-STD-410E J1 - Differentiate AWS D1.1-96 20/40 20/40 Differentiate -

such as jet engines, nuclear piping and fuel bundles, and complex machinery. When the rigid borescope cannot reach the desired area, flexible bundles of optical fibers often fill the bill. The fibers must be in exactly the same position at the inlet and outlet of the bundle to keep the image intact. Also, the fibers must be very small to provide the best image clarity. Some of the flexible borescopes have devices that permit the observation end of the scope to be moved around by a control at the eyepiece end. Some are also connected to CCTV systems

*Ortho-rater 8 equivalent , J1- Jaeger Number 1

so that a large picture may be examined and the inspection recorded on videotape. The CCTV systems may be used

ISO 9712, “Non-Destructive Testing - Qualification and

in regular inspections to help keep the inspector, looking

Certification of Personnel” or JAA JAR-66, “Certifying

at the right area and to prevent distractions. Sometimes

Staff Maintenance.” Provides the requirements for visual

the systems can also reduce eye fatigue. When the video

calibriation as given below:

systems are combined with computers, the images can be improved and details not observable in the original

image can be seen. These systems have been developed

DT personnel should receive documented vision and

color blindness testing at reasonable intervals (one to two

from our need to improve images received from space

years, shorter preferred). The NDT inspector shall have

satellites and explorers. But again, these systems add

documented evidence of satisfactory vision in accor-

considerable to the cost, as do special devices like optical

dance with accepted medical standards to be considered a

comparators and machine vision systems.

qualified NDT inspector. Vision examinations can either precede or accompany the initial determination of quali-

Vision testing standards

Near Far

fication to perform NDT. Vision examinations shall be administered by personnel in accordance with the stan-

The most important tool in unaided visual inspection

dard to determine qualification.

is the eye. No doubt there should be regular vision tests to prove the inspector’s capability to use his eyes properly.

(a) Near Distance Vision Requirements:

Vision testing of inspectors has been in use for about

40 years. Along with the development of the present day

standards and specifications, many changes have taken

The NDT inspector shall have natural or corrected

near distance acuity in at least one eye capable of

place in the testing methods. New revisions have incor-

reading the Jaeger Number 1 Test Chart or equivalent at

porated much of the new technology developed during

a distance of not less than 30 cm (12 in.). 6


(b) Color Vision Requirements:

Despite advances in other NDT technologies, visual inspection will likely remain the fi rst inspection method

The NDT inspector shall be able to differentiate

used in many fi eld applications. Visual inspection will

among colors used in the NDT method(s) for which the

continue to be an important NDE inspection approach

inspector is qualifi ed.

that will often identify areas of structures or components where more advanced NDE methods need to be applied.

(c) Vision Examination Documentation Requirements:

Following initial qualifi cation, the documented References : near distance and color vision examinations shall be administered as required above, and records thereof

[1] F.W. Spencer, Visual Inspection Research Project

retained by the employer.

Report on Benchmark Inspections, U.S. Department of Transportation, Federal Aviation Administration,

You may wonder what this Jaeger chart is. When our

Washington, DC, 1996.

eyes are checked by Ophthalmologist, a Snellen chart is used. The Snellen eye chart is familiar chart with the big

[2] Nondestructive Testing Handbook, Volume 8: Visual

E 20/200 at the top and progressively smaller letters at the

and Optical Testing, Technical Editors M.W. Allgaier and

bottom of the chart down to 20/20 or better. This is a chart

S. Ness, American Society for Nondestructive Testing,

for measuring visual acuity at a distance - in other words,

Columbus, OH, 1993

how well you can see things that are far away.

[3] Back to Basics: Testing Visual Acuity with the Jaeger

The Jaeger eye chart is used for reading up close and

Eye Chart by S. L. Weatherly*

for determining your near vision, which is an important issue if you are viewing X-ray fi lm or looking for a crack in a part held in your hands. When reviewing the chart,

[4] GOOD PRACTICES IN VISUAL INSPECTION - Colin G. Drury Applied Ergonomics roup Inc. Jean

you will see the notation J1 next to the paragraph with

Watson Federal Aviation Administration Flight Standards

the smallest text and each progressive paragraph of larger

Service May 2002

text is noted with an increase in the J number. Also centered above each paragraph is a number. The number 15 is centered above the smallest text line noted as J1. This number represents 20/15 vision. J2 has the number 20, for 20/20 vision. As you progress to larger lettered paragraphs, the lettering size increases for lesser visual acuity. Normal test distance is 30cm from the eye. Eye chart is given below.

The Jaeger eye chart is commonly used to test near vision of NDT technicians [3] 7


ATTENTION !..

Asia Pacific Conference of Non Destrucctive Testing

Members are requested to inform their present address with e-mail and

Theme :

Phone number to

Excellence with relevance thro NDE

Secretary, ISNT,

Venue :

Thiruvananthapuram Chapter,

Renaissance Mumbai Convention Centre Hotel, India

C/o. RPP, VSSC, ISRO PO, Trivandrum 22 e-mail : binu_thomas@vssc gov.in,

November 18 -22, 2013, Mumbai, India

Phone : 0471 - 2565245

• Important Dates • Abstract Submission: August 15, 2013 • Conveying the acceptance of paper for presentation (oral/ poster) September 15, 2013 • Submission of full text October 31, 2013 • Author Registration Deadline: October 15, 2013 • Conference Secretariat •

CHAPTER WEBSITE

Members are requested to visit Chapter website

www.isnttvm.org.

• Indian Society For Non Destructive Testing 303, Lok Centre, Marol Maroshi Road, Andheri (E), Mumbai - 4001 059 - India

Welcome your suggestions for further improvement

T: +91 22 29207521 E: info@apcndt2013.com W: www.apcndt2013.com www.apcndt2013.in

Published on behalf of Editorial committee, ISNT,Trivandrum chapter Editor: Dr. M R Suresh Members: S Remakanthan , Ratheesh S 8


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