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News Letter of Indian Society for Non-Destructive Testing - Mumbai Chapter

Keeping ntouchFor PRIVATE CIRCULATION ONLY

JAN - MAR 2013

Chairman Speaks...

1

Dear Friends,

Greetings!

Effective communication is imperative for the survival of any progressive society. It is the sincere effort by

SNT Mumbai Chapter to communicate with its members through this newsletter. I hope this will generate a

global interest among all members to strengthen and enrich this newsletter with their wholehearted participation by way of

contributing articles, case studies and work experience relating to NDT activities.NDT has reached a stage where it can address issues related to safety, besides quality requirements. Safety being of prime

mportance to the modern society, it needs attention from all of us. Technological development demands continuous efforts towards

the improvement of safety measures. Considering this, ISNT Mumbai Chapter suggests a new theme "Safety through NDT", to be

mplemented in all aspects of engineering.

The 14th Asia Pacific Conference on Non-Destructive Testing (APCNDT 2013) scheduled in the month of November this year

at Mumbai, is yet another milestone for ISNT. It will provide a common platform for sharing knowledge, experience and expertise

with NDTians and equipment manufacturers from different parts of the world. After the World Conference (WCNDT) held in New

Delhi in 1996, this will be another occasion where one can interact with NDT stalwarts and I am sure you would not miss this

opportunity!

Awaiting your valuable suggestions,

With regards,

S. P. Srivastava

National Workshop on Non- Destructive Evaluation of Structures, held on 8th - 9th March 2013, organized by ISNT Mumbai Chapter

along with Association for Structural Re-habilitation (ASTR), was a small step towards spreading the awareness regarding safety

and quality in civil and mechanical engineering.

In thisIssue...

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Chairman Speaks

Executive & AdvisoryCommittee 2012-2013

Eddy Current Testing ofFinned Heat ExchangerTubes

Use of DGS diagram forevaluating flaw sizes

Activity Report

Members Introduction

Executive & Advisory Committee 2012-2013

Executive Committee

Chairman

Shri S. P. Srivastava

Vice Chairman

Shri Prakash Mehta

Shri N. Sadasivan

Hon. Secretary

Shri Samir K. Choksi

Hon. Jt. Secretary

Shri Hemant Madhukar

Shri Mukesh Arora

TreasurerShri Anil V. Jain

Members

Shri D. J. Varde

Shri Dilip Takbhate

Shri N. V .Wagle

Shri B. K. Shah

Shri R. S. Vaghasiya

Shri Rajul Parikh

Shri K. B. Jetly

Shri Ashok Trivedi

Shri Krishna BhutaShri S. N. Roy

Shri P. P. Nanekar

Shri P. B. PatilShri Arbind Kumar

Shri N. P. Srivastava

Shri Sekar Jesudhason

Shri Ramesh B. Parikh

Shri P. G. Kulkarni

Shri L. M. Tolani

Prof. G. V. Prabhu Gaunkar

Dr. Dara E. Rupa

Shri P. Gopal

Shri Bansi Rele

Shri P. R. Parikh

Shri V. J. Thaker

Shri A. C. Jaju

Advisory Committee

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Introduction

To exchange heat from one fluid to another fluid is an important

process in chemical plants, fertilizer plants or power plants.

Heat exchanger is used either as waste heat recovery unit or to

heat the process fluids as per the requirements. Heat

exchangers are used as steam generators, condensers or

evaporators. Shell and tube type heat exchanger is the most

versatile heat exchanger used in industry. In shell and tube typeheat exchanger, the tubes are supported by tube support plate

nside the shell and by two tube sheet at both ends. Fins are

provided on the tubes in some of the heat exchangers to

enhance the heat transfer efficiency. Tubes face harsh

environment due to presence of corrosive fluid, high

temperature as well as flow induced vibration. Due to such

hostile conditions inside the shell, the tubes undergo various

types of corrosions such as pitting, crevice, stress corrosion

cracking, denting, fretting etc. The flaws are generated at the

nner or outer surface of the tube, under the tube support plate,

under the tube sheet and U-bend regions. The integrity of the

tubes is to be monitored using non-destructive test methods.

Eddy Current testing is used for detection of flaws during

service. Many spurious signals are observed during testing of

the heat exchanger tubes due to presence of tube support plate,

tube ID variation, local chemical composition variation, tube

sheet, presence of residual stress due improper heat treatment

of the tubes and chemical deposits. In finned tubes heat

exchanger, the spurious signals are also caused due to

presence of fins. The fins may be straight fins along the tubes,

spiral fins along the tubes, cage type fins or some other types of

fin. Sometimes corrugated tubes are also used for such

application.

The EC signals from tube support plate or tube ID variation can

be suppressed using multi-frequency EC Technique. However,

EC Signals from tube fins cannot be segregated using multi-

frequency EC techniques as these signals have no defined

pattern. They are zigzags.

The eddy current test coil design, selection of test parameters

and signal analysis carried out to address these issues are

discussed in the following paragraphs.

Eddy Current Testingof Finned Heat Exchanger Tubes

Arbind KumarQuality Assurance Division - Bhabha Atomic Research Centre

Trombay, Mumbai 400 085. e-mail : arbindk@barc.gov.in

Principles of Eddy Current Testing

Eddy Current test coil carries alternating current and associated

with changing primary magnetic field. This EC coil induces eddy

current in the conducting materials such as plates or tubes

when they brought near to it. The secondary magnetic field

associated with eddy current opposes the primary magnetic

field. The impedance of EC Coil changes due to variation in the

magnetic field associated with the coil and it is monitored interms of voltage on the screen of ECT Equipment.

Selection of Eddy Current Test

Parameters

Frequency is the only parameter that can be selected to change

the eddy current density as well as depth of penetration of eddy

current for testing of a particular tube. Multi-frequency can be

selected to suppress the unwanted signals due to support plate,

tube ID variation and foreign particle deposits. The numbers offrequencies selected should be one more than the numbers of

variables to be suppressed. For suppression of signals due to

fins, multi-frequency cannot be used as the patterns of EC

signal from the fins are haphazard. To suppress the OD fin

signals, the frequency is selected in such a way that the depth of

penetration is restricted to tube wall. At such high frequency, the

sensitivity of the testing will be more towards inner surface of the

tubes. The standard depth of penetration (SDP) depends on

conductivity, permeability and frequency. The SDP is calculated

using the following formula.

SDP () = (1/f) where =Magnetic Permeability,

=Electrical Conductivity and f=Test Frequency

Eddy Current Test Coil Design

The design of the eddy current test coil is one of the most

important tasks during eddy current testing. For testing of finned

heat exchanger tubes, differential bobbin coil is the best

configuration. Differential configuration of the test coil take care

the gross variation due to fins. It is more sensitive to localized

flaws. The diameter of the coil is selected to maintain the fillfactor around 90%. The groove dimensions are fabricated on

the bobbin as per the requirements of flaw size detection and

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number of turns of wire to be accommodated. Numbers of wire

turns are determined from the design frequency and inductance

of the test coil. It is calculated using the formulae given below.

L = 0.035a2N2/(6a+9b+10c) where L is inductance, a=coil

radius, N= No. of turns, b & c = Groove depth and width.

All these considerations have to be taken care to improve the

sensitivity and Q-factor of the coil.

Sensitivity Settings EC Equipment

Reference flaws such as flat bottom holes and through wall hole

were fabricated on the finned tubes. This reference tube was

used for setting the sensitivity of the EC equipment prior to

testing of the installed tubes during service.

Analysis of Eddy Current Test Signals

Eddy Current Test Signals are analyzed on the basis of

characteristics of signals such as amplitude, phase, start and

end direction and time required to complete the signal loop. The

signals due to fins are adjusted in horizontal direction. By proper

selection of test frequency, it is possible to get the signals from

the flaws at different angle than the signals from the fins. EC

signals were analyzed in Al-finned Tubes, Cupro-Nickel, finned

tubes and stainless steel finned tubes on the basis of said

characteristics of the signals. One case study regarding finned

cupro-nickel tubes is described here.

Case Study : Eddy Current Testing of

Cupro-Nickel Finned TubesFinned Cupro-Nickel Tubes are used for exchanging heat from

one fluids to another in Power Plants. Due to presence of fins,

eddy current testing is difficult. By proper selection test

frequency, these tubes were tested. Finned Cupro-Nickel tubes

are shown in Figure 1. The EC Signals observed from the fins

and through wall hole is shown in the figure 2.

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Fig 1 : Finned Cupro-Nickel Tubes Fig 2 : EC Signals from Fins and Through Wall Hole

EC Signals from Fins

EC Signals fromThrough Wall Hole Conclusions

Eddy Current testing is one of the best NDT Methods for testingof heat exchanger thin walled tubes. Multi-frequency EC

Technique is used to suppress the unwanted signals of a

particular pattern such as the signals from support plate, tube ID

variation and foreign particle deposits. The signals from fins are

not having a particular pattern can be suppressed using proper

selection of test frequency so that eddy current density is more

towards the inner surface of the tubes. This facilitates the

feasibility of testing of finned heat exchanger tubes.

Shri Arbind Kumar is M.Tech. in Metallurgy from IIT Kanpur. Presently, he is a Scientific Officer (G) at QualityAssurance Division, Bhabha Atomic Research Centre, Trombay, Mumbai. He is involved in research and

development of eddy current test techniques, design of eddy current test probes, and standardization of eddy current

test procedures for flaw detection and characterization in tubes, rods and plates. He is ISNT Level III in Eddy Current

Testing. He has specialized in quality control of Nuclear Fuels and In-Service Inspection of Nuclear Reactor Core

Components. He has received ISNT Mumbai Chapter NDT Awards in R&D Category, ISNT National NDT Award in

R&D Category, Scientific and Technical Excellence Award and 5 Group Achievement Awards conferred by

Department of Atomic energy, Government of India.

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Asia Pacific Conference on Non-Destructive Testing (APCNDT) started in 1976 with

the first conference been held in Japan. Over the last three decades, APCNDT has made

considerable progress and has provided the international forum for highlighting the

accomplishments in the field of non-destructive testing.

November 18 - 22, 2013

Hotel Renaissance, Powai, Mumbai

NiDiT

and NOW

14th APCNDT - 2013

at Mumbai, India

14th APCNDT - 2013

at Mumbai, India

Are you ready

for the most important eventof Asia Pacific...?

www.apcndt2013.com

Indian Society

for

Non Destructive Testing

(ISNT)

City of Mumbai attracts so many people,

not just from other parts of the country but

from the entire globe.

The Corporate headquarters of

major business houses of India are

located in Mumbai.

Mumbai also has large number of

NDE professionals working

in research and academic organizations,

industrial units and service industries.

1st APCNDT-1976at Tokyo, Japan

2nd APCNDT-1978

at Seoul, Korea

3rd APCNDT-1980

at Tokyo, Japan

4th APCNDT-1983

at Sydney, Australia

5th APCNDT-1987at Vancouver, Canada

6th APCNDT-1990

at Auckland, New Zealand

7th APCNDT-1993

at Shanghai, China

8th APCNDT-1995

at Chinese Taiwan

9th APCNDT-1998at Anaheim, USA

10th APCNDT-2001

at Brisbane, Australia

11th APCNDT-2003

at Jeju Island, Korea

12th APCNDT-2006

at Auckland, New Zealand

13th APCNDT-2009at Yokohama, Japan

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Use of DGS diagramfor evaluating flaw sizes

by N. Sadasivan, NDT Level III

n any NDT method, sensitivity can be defined as the ability of

the technique to detect the critical flaw which may be

detrimental for the performance. Therefore, it is essential to

ensure the sensitivity before starting the examination. In

Ultrasonic testing, we use artificial discontinuity such as side-

drilled holes, notches or flat bottomed holes (FBH) created in an

acoustically similar material specimen for setting the sensitivity.

Echo height from the discontinuity is compared with the

response from a specified size of artificial discontinuity. Dr.

Joseph Krautkramer evolved DGS diagram, a novel way of

doing away with creation of costly and time consuming

reference specimen. DGS diagram has been widely used in

European countries.

DGS (Distance-Gain-Size) method of evaluating the

discontinuities make use of the test specimen directly or

standard blocks such as IIW V1/V2 for setting the sensitivity.Echo height plays a decisive part while evaluating the

discontinuity. Echo from a discontinuity is compared to a disc-

shaped reflector (known as DSR). Echo heights (H) are

2proportional to the area of reflection i.e. H d . For example,

echo height from a 4mm FBH is 4 times higher (+12dB) as

compared to that from a 2mm FBH. Echo height depends on

orientation, geometry (shape) and surface quality of the

discontinuity.

While using DGS diagram/scale, we need to keep in mind

certain cautions:

a) More effective in non-attenuating material such as steel

plates, forgings & carbon/low alloy steel welds. Attenuating

materials such as steel castings can be evaluated subject

to giving a correction for attenuation. Anisotropic materials

such as austenitic welds cannot be evaluated using this

technique. Instruments with built-in DGS scales may not

read the equivalent flaw size correctly unless attenuation

correction is applied.

b) Useful for evaluating flaws which are within beam width

c) Discontinuities such as shrinkages, which absorbs the

sound waves, cannot be effectively evaluated. This is one

reason why most of the specification for Steel Castings

specifies loss of back wall echo (rear-wall attenuation) as

an additional acceptance rejection criteria.

d) While examining cylindrical objects such as round bars withcentral bore, a correction is required when you use the back

echo from bore as reference echo. Diameter of the

specimen shall be approximately greater than 3.7 times

near field of the probe used.

Author is an NDT Consultant renderingNDT Services under the name MaterialsEvaluation Services (Mumbai) P. Ltd.

Authoritries to give a brief account of theproblems associated with attenuatingmaterials and use of DGS diagram.

Email: sadasivan.n24@gmail.com

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NDTS India (P) Limited

619 & 620 The Great Eastern Galleria

Plot No.20, Sector 4, Nerul, Navi Mumbai 400 706

Tel.: +91-22 6138 0600, 2770 3913, 2770 3923, 2772 9077

Fax: +91-22 2770 3903 | Email: info@ndts.co.in

www.ndts.co.in

Remote Visual Inspection (RVI) / Boroscopy

Tube Testing - Eddy Current / RFT / MFL

Wire Rope Testing

Advance ServicesINSPECTION

Time of Flight Diffraction /Ultrasonic Phased Array

Infrared Thermography

Thickness Mapping of Boiler Tubes

High Temperature Thickness Gauging

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ISNT, Mumbai Chapter Activities Report

1. ISNT conducted Welding Inspector Examination at BITT,

Mahim on September 02, 2012. The Examiners were Shri L. M.

Tolani and Shri S. P. Srivastava.

2. ISNT conducted AGM-2012 on September 08, 2012 at Hotel

Chakra, Sakinaka. Around 180 members attended the meeting.

Lecture on Stress Management by Dr Shriniwas Kashalikar

was also conducted during AGM.

3. ISNT conducted General NDT Course for ONGC Engineers from

September 10, 2012 to September 14, 2012 at Hotel Atithi.

4. EC Meeting held on September 28, 2012 at ISNT, Mumbai

Office.

5. Evening Technical Lecture held on the topic Leak Testing-

Basics & Advance on November 05, 2012 from 6.30 pm to

8.30 pm at the Multipurpose Hall, BARC Training School.

Speakers were Shri S. P. Srivastava and Shri Yatin Nakhare.

The lecture was followed by a demonstration of the TMP and

Advance Leak Detectors. Around 90 members attended.

6. 18 Life Members and 1 Associate Member were enrolled to ISNT,

Mumbai Chapter from April 2012 till date .

7. A workshop on Wire Rope Testing was organised at Hotel

Oasis, Deonar on December 14, 2012. Speaker was Mr.

Alexander Mironenko from Intron Plus Ltd., Russia. Around 50

members attended the workshop which was sponsored by NDTS

India (P) Limited.

Members Introduction

Editor & Publisher may or may not subscribe to opinions/articles printed in this publication and are not responsible for any of them.Editor: PARITOSH NANEKAR Co-Editor : MUKESH ARORA Publisher: ISNT, Mumbai Chapter

303, Lok Centre, Marol Maroshi Road, Andheri (E), Mumbai 400 059. Email: isntmumbai@gmail.com Website: www.isnt.org

LM-5415

Vijay Madhusudan JoshiAdjunct ProfessorVivekanand Education Society'sInstitute of Technology (VESIT)Chembur, Mumbai 400 074Cell.: +91-98331 45947Email: mrvijayjoshi@yahoo.com

Role in NDE:Research and Development of Advanced UltrasonicTesting (UT) and Imaging Systems.

LM-5285

Shyamal Kumar RoyAsst. General Manager (NDE)Larsen & Toubro Ltd.Powai, MumbaiCell: +91 99308 20429

Role in NDE:UT Level III in Ultrasonic Testing

8. ISNT conducted RT Level-I Course & Examination for ONGC

Engineers from January 07 - 12, 2013 at IQM, Jogeshwari.

9. Welding Inspector Examination held on 13th January 2013 at

BITT, Mahim.

10. PT Level- I course on February 02 & 03, 2013 and Examination

on February 05, 2013 at ISNT Mumbai office.

11. A workshop on Surface Array & Tube Testing was organised at

Hotel Oasis, Deonar on February 12, 2013. Speaker was Mr.

Aaron Greenbank from Eddyfi, Canada. Around 100 members

attended the workshop which was sponsored by NDTS India (P)

Limited.

Materials

Evaluation Services

(Mumbai) Pvt. Ltd.

Services Offered:Non-Destructive Testing(UT, MT, PT)

Training & Certification in NDTNDT Level III

Consultancy Services

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JasonInstitute of Technology

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Training facility from 6 pm to 9 pm at Vikhrolion all working days.

Our Address: Jason Institute of TechnologyTagore Nagar, Vikhroli Mumbai-400 083

Phone: 98201 13341, 98202 67834

Training Certification courses in NDTLevel 1 and Level 2

ASME Codes Radiography Testing

Welding Ultrasonic Testing

NDT Magnetic Particle Testing

Quality Control Penetrant TestingTime Of Flight Diffraction(TOFD)

Phased Array UltrasonicTesting (PAUT)

courses in