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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...
1
2
6
8
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 : [email protected]
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: [email protected]
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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: [email protected]
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: [email protected] Website: www.isnt.org
LM-5415
Vijay Madhusudan JoshiAdjunct ProfessorVivekanand Education Society'sInstitute of Technology (VESIT)Chembur, Mumbai 400 074Cell.: +91-98331 45947Email: [email protected]
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
3072, Bhandup Industrial EstateLBS Marg, Pannalal CompoundBhandup West, Mumbai 400 078
JasonInstitute of Technology
Training, Consultancy & Inspection
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