Frequently Asked Questions

Answer all of your questions

General FAQ


As a New Comer to NDT Field it's essential that the Knowledge you are getting are perfect to the industrial requirements and you are obtaining hands-on practicals from the institutional training itself.

it's noted that many centres in India and abroad are Just delivering some theoretical session as their own and issuing certificates on behalf of this. This is not considerable to a ideal practice but since majority of such institutions are offering SNT-TC-1A (ASNT) certificates, the responsibility of such certified person truly rely on the Employer if they finds such persons are competent companies many hire such competancies are evaluated now a days at every client location.

This bad practices root cause is the ethics violation of ASNT NDT Level 3's which Training and Certification industries are facing and the end user the Employers are also facing this issues.

To Scrutinize a BEST Value institution for your hard earned money is a systematic process...

Initially you need to Understand under which Certification Scheme the institution is providing certificate Like: PCN/ISO 9712/ SNT-TC-1A/ ANSI CP-189.

Once this is Analyzed ISO 9712 and PCN Training have it's on credibility since it's considered as a Thrid Party Certification but when it comes to SNT-TC-1A & CP 189 it's Second Party Certification and of this SNT-TC-1A is purely Employer Oriented and hence Quality Will be Less to that of a CP 189 Requirement. When CP 189 Requirements are met it's the Complete Responsibility of a Level 3 whom certified the individual that he know's the trained method very well to the level 2 training mark.

Both SNT-TC-1A and CP 189 demand a minimum Training Hour Requirment for both practical and theory for Each NDT Method Level 1/Level 2/Level 3 ( Total 16 Level 2 Methods Available as of 2016 Edition of SNT-TC-1A and CP 189 Recommended Practice)

Example: If you are Doing Magentic Particle Testing (MT) Level 2 the Minimum Training hours required for MT as per 2016 Edition of the Practice Standard is 

12 Hour for Level 1 and 8 Hour for Level 2 and if candidate is doing Direct Level 2 without any Examination in Level 1 then the total of Level 1 Hours + Level 2 Hours is required as a minimum requirement that gives you a total of 20 Hours for MT Level 2 of this 50 % is for Practical and 50% is for theory.

Likewise each 16 method has a explained minimum requirement of Training hours, if any organization is meeting this time requirement exactly then it can be considered as an ideal institution and good value for your money.

UT Level 2 Requires 80 Hours (If Only Level 2)

RT Level 2 Requires 80 Hours (if Only Level 2)

VT Level 2 Requires  24 Hours 

 To Know More about How to select the Best Training Institution for you NDT Training & Certification Contact Us or Call us at (+91)-0466-2214-333
No, experience can be gained either before or after training and examination. It is generally better to come on a course with some previous knowledge in the application, but in line with scheme documents, it is not essential.

We normally recommend the Appreciation of NDT Techniques course. This will show you:

  • How to appreciate the available methods
  • How to explain the basic principles of these methods
  • How to identify the advantages and disadvantages of these, both in application and defect detection capability
  • How to carry out basic hands-on applications for familiarisation purposes

Then we would suggest you attend the Penetrant Testing and Magnetic Particle Testing courses - they are the normal starting point for a career in NDT. These are the methods for detecting surface breaking defects and are used extensively to supplement radiography and ultrasonics, which are used to detect sub-surface defects. They have the advantage of having the shortest duration courses with the shortest experience duration needed which must be gained before full certification can be awarded. This is the fastest route to becoming a Level 2 NDT Inspector. Also, the number of NDT tickets you hold can reduce the experience requirements needed for attending future NDT courses.


Below are some of the websites carrying NDT job advertisements:

This Question is regularly asked by many freshers.

Decibel as a Pioneer provider for QA/QC, NDT, Piping and other Inspection courses in Kerala with world wide accredited certification we could clearly clarify this doubt.

QA/QC and NDT is different but NDT is a vital part in the life of a QC or QA Inspector.

NDT is only a Small but vital Part of a QC or QA Job responsibilities and duties but this depends upon the activities specifically applied by the Job holder and to which industry he is working for.


  • Go to . On the bottom Right Corner under Students Portal Heading click on ‘Results’
  • Enter your Candidate number/Student ID, and press ‘Search’
  • You can See Updated listing for all your examination appeared

Please visit the The British Institute of Non-Destructive Testing (BINDT) Verification webpage:

or contact BINDT:
Tel: +44 (0)1604 89 3811
Fax: +44 (0)1604 89 3861


Learning from a Truly Global Training Provider and Expert in the Industry is a real advantage for Professionals who are striving to become the best of the industries
(Challenge) If any of the Institution in Your Geographical Region can demand a Practical facility, which exceeds the facilities in Decibel and to the course/standard requirements we will provide those students the CQC course entirely free of cost. We feel the best commitment will not be better than this. Our Multimillion Facilities available across the globe will really make you a professional not just a certified personnel.

Our Distinctive facilities and features listed below could portrait why to choose Decibel.

  • Decibel is Accredited to British Qualifications & Certification Services - Scotland
  • Decibel is Corporate affiliated to American Society for Non Destructive Testing,
  • International Section Affiliation with Saudi Arabia Section of ASNT,
  • International Section Affiliation with Qatar ASNT,
  • International Section Affiliation with UAE ASNT Chapter,
  • International Section Affiliation with South Korean ASNT,
  • International Section Affiliation with Singapore ASNT,
  • 50 Advanced Inspection Patents and a Dedicated R & D Division,
  • First Institution in India to provide TOFD, Phased Array, LRUT, AUT Courses.
  • First Indian Institute to offer NDE courses in 15 methods and 12 limited NDE Certification Courses
  • Member of American Welding Society,
  • International section affiliation with Kuwait Section of ASNT,
  • Member of Institution of Corrosion Engineers UK
  • Affiliated to American Petroleum Institute.
  • Global Presence, Global Recognition, Professional Labs
  • ANSI/ECNDT/ASNT based original training materials.
  • First institute in India to offer AUT interpreter Programs.
  • Technical Board with ASME reviews board members.
  • ASNT listed Training provider in India.
  • Only organization having 32 Level 3 examiners to monitor and direct the Entire training and certification scheme. Our Level 3 panel will certify only for Decibel and hence creditability, recognition and validity of certificates are assured.
  • Specialists in advanced NDE training for corporate companies.
  • Asia's Largest Third Party accredited certification provider for QC Programs.
  • First Remote Visual Training Provider in Asia.
  • First GPR Training Provider in Asia.
  • First Nuclear NDT Training Center in Asia.
  • First Aerospace NDT Training Provider in India.
  • Placement Desk & Representatives across the World
  • Practical Labs meeting EN/BS/ASME/API/ASNT requirements.
Decibel as an Internationally Accredited Training Provider for Various courses, each course examination will be in accordance to the norms and examination procedure of respective certification bodies. For SN-TC-1A and BQACS Examinations, all are conducted through Chief Examiner Approved Third Party Online Examination Portal as Online Examination which provides centralized evaluation and credibility in examinations. For ISO 9712 Courses Presently its in Paper Based Examination but in nearer future all such examination are gong to be Online. For ASNT Level 3 it's Online Examination at any Pearson Vue Testing Cerntre approved by ASNT For CSWIP/AWS Respective Certification body itself will be conducting direct examination at Pre-Scheduled Locations.

Technical FAQ

Many factors affect choice of consumable for cast iron, and the relative importance of each depend on the user's priorities. The most popular consumables for arc welding are nickel and nickel-iron alloys, which, while expensive, offer the most manageable weld metal properties. Copper-tin alloys are used for bearing and surfacing applications because of their good sliding properties.

The best colour match with the casting is achieved by depositing a cast iron weld metal. Oxy-acetylene welding is most effective in this respect, though it is possible to use arc welding successfully. Good colour matching is also possible with nickel-copper fillers.

Recommended applications for each filler type are:

Filler type Typical application
Cast iron Oxyacetylene and arc welding of grey, ductile and blackheart malleable irons where good colour match is required. Different consumables give either a flake or a nodular graphite structure.
Ni Joining and repair of grey irons and for surfacing high dilution welds in stronger grades. Produces a soft peenable deposit. Special electrode coverings are available to help repair deep cavities and blow holes
NiFe Joining and repair of ductile, blackheart malleable and higher strength grey irons. Also used to join cast iron to dissimilar metals and for welding austenitic irons. Can also be used on irons with high sulphur and phosphorus levels.
NiFeMn Similar applications to NiFe fillers, but a stronger more crack resistant deposit is produced.
NiCu Used when a soft peenable deposit with good colour match is required on grey, nodular and blackheart malleable irons. Also useful for welding castings of unknown type and composition.
CuSn Mostly used for its good sliding and anti-seizing properties, i.e. for surfacing applications, particularly on grey irons.
CuAl Similar applications to CuSn but with poorer surfacing properties, but higher strength.
CuMnNiAl Similar application to CuAl fillers, but used where higher strength is required.

A number of Non-Destructive Testing (NDT) techniques have been investigated over the years for inspecting electrofusion (EF) joints, including radiography, thermography and ultrasound. Radiography has been demonstrated in the laboratory as having potential, but it is not well suited for use in the field and thermography has only been capable of detecting gross flaws.

The state-of-the art for volumetric inspection of EF joints is by using Phased Array Ultrasound Testing (PAUT). This technique has been shown to be capable of detecting all common defects in EF joints, including lack of fusion, particulate contamination, pipe under-penetration and cold welds. TWI is a world-leader in PAUT of electrofusion welds in PE pipes and has developed the PolyTest system, specifically for inspecting welded joints in PE pipes

Eddy current penetration depends on:

The frequency of current in the search coil ( )

The conductivity of the specimen ( σ )

The permeability of the specimen ( µ )

As frequency increases so the depth of penetration decreases. This is known as skin effect. Furthermore, the intensity of eddy currents decreases exponentially with depth. There is a specific depth beyond which the eddy current intensity is too small to be useful for detection of defects. This depth is known as the standard depth of penetration. It is defined as the depth below the surface at which the intensity of the eddy current field has been reduced to a value of 37% of its intensity at the surface.

This depth can be calculated from a number of formulae. One of the most commonly used expressions is:-


δ - Standard depth of penetration, mm 
f - frequency, Hz 
σ - conductivity, m/ Ω mm 2 
µ - relative permeability

A practical inspection has been known to penetrate to a depth of approximately 40mm through about 14 layers of material.

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Radiographic quality is assessed using the four criteria shown below:

  • Density
  • Contrast
  • Definition
  • Sensitivity
Density: The log of the ratio of the intensity of light incident on the film to the intensity of light transmitted through the film defines density:

Density =


The technician reads the calculated density of the radiograph on an instrument called a densitometer, which provides a numerical value of the amount of light transmitted. 

Contrast: Degree of density difference between adjacent areas on a radiograph.

Low contrast
Low contrast
High contrast
High contrast

Definition: Sharpness of the dividing line between different density fields also referred to as Geometric Unsharpness (Ug) or Penumbra,


f     =     size of the radiation source

ofd     =     the thickness of the specimen being radiographed

fod     =     distance from the radiation source to the item being radiographed


Sensitivity: Objective measurement of radiographic quality.

An object referred to as a penetrameter is included within the radiographic image. The penetrameter contains either holes or wires of known dimensions and sensitivity is determined by relating the thickness of the thinnest wire or hole present to the thickness of the specimen being radiographed as shown below. The lower the value obtained the better.

%Sensitivity =

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Every piezoelectric element in a phased array probe behaves exactly like a piezoelectric crystal in a standard UT probe. Furthermore, if all the elements in an array are excited at the same time, the ultrasonic beam produced is closely similar to that produced by a single crystal of the same dimension. The difference between the beam produced by a phased array probe and that produced by an equivalent standard single crystal probe does not lie in the physical shape or size of the piezoelectric elements, but in the electronic management of the excitation of the elements in the array.


By introducing a unique time delay in the excitation of every single element in the array to two nanosecond precision (2x10 -9 sec), the ultrasonic wavefront experienced by the specimen being tested is now angled. For all inspection purposes, the phased array probe is now operating as a standard single crystal angled probe of the same dimensions as the array. This manipulation is generally known as 'beam steering'.


Another very important feature attainable by electronically manipulating the excitation of the elements in the array is the focusing of the beam. By carefully calculating the time delays of the single elements in the array on the basis of Snell's refraction law, it is possible to obtain constructive interference at a desired locus following Huygen's principle. The beam has now been electronically focused. The focal spot size is generally equal to, if not smaller than, that of a conventional focused probe.


A combination of beam steering and focusing is also easily attainable. In this way, a phased array system can closely simulate a single probe inspection which would otherwise require various standard probes at different beam angles and focusing depths.

It has to be noted that, although the beam produced by a phased array is almost identical to that of conventional probes, low amplitude diffraction grating lobes are created in addition to normal probe side lobes due to the constructive interference principle. If incorrectly specified, phased array generated ultrasonic beams can have very poor signal-to-noise performance.

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In general, the number of flaws in a weld depends on the skill of the welder and the specific parameters of the welding process and procedure. There can be considerable variations in skill and hence the number of flaws between two welders with the same welder approval. Welds fabricated using modern automated welding techniques with controlled set-up would be expected to have a lower number of flaws than those fabricated using manual processes.

Welding parameters influencing the number of flaws include the process variables, type of materials and consumables, heat input, pre-heat, access, fit-up, position, restraint, location (shop or field), section thickness and run length. Welds have different susceptibilities to flaws of different types (slag, pores, hydrogen cracks, solidification cracking, liquation cracking, reheat cracking, lack of fusion, lack of penetration etc). Flaws may be associated with an individual bead or, in the case of a multi-pass weld, with the weld itself.

The number of flaws is a weld is often expressed as a frequency of flaws per unit length of bead laid or per unit length of the completed weld. The susceptibility of the weld to each flaw type is determined by the underlying mechanisms by which they can be formed and the associated metallurgical and process factors. A number of studies have been made to determine flaw frequencies from inspections and examinations of welded equipment.

Much attention has focused on thick-section submerged arc welds used for early reactor pressure vessels in the nuclear industry. These studies suggests that the frequency of large flaws (>0.5in) in pressure vessels manufactured in the early 1970s to Class 1 standards is on average about 0.4 flaws per vessel containing around 20 weldments [e.g. Marshall (1982), Smith and Warwick (1981)]. More recent Class 1 pressure vessels would be expected to have a lower frequency of flaws as improvements in welding technology, quality assurance and mechanistic understanding of the ways in which flaws have translated into practice.

From examining inspection reports, Thurlbeck et al (1996) and Baker and Kountouris (1989) have derived estimates for the frequency of fabrication flaws in submerged-arc welds used for offshore jacket structures manufactured since 1970. Wagner and Watchett have published data for girth weld defects requiring repair in mechanised GMA field welded pipelines. They found the repair rate due to flaws was around 1 repair per 10m of weld laid.

Welds are routinely inspected after fabrication and this can lead to the detection of significant flaws and their removal and repair. New flaws can initiate before service by mechanisms such as reheat cracking or arrested brittle fracture. Further changes to the flaw population can occur in service as new flaws are created by mechanisms such as fatigue, creep or stress corrosion cracking. The frequency of flaws in a weld may therefore change with time.



  • Baker M J and Kountouris I S, Defect assessment analysis of the dimensions of defects detected by ultrasonic inspection of an offshore structure. CESLIC Report OR8:1989.
  • Chapman V, Simulation of defects in weld construction, ASME PVP Conf. 1992
  • Marshall W, Report of the Study Group on LWR Pressure Vessel Integrity. HMSO Publications 1976, 1982.
  • Smith T A, Warwick R G, A survey of defects in pressure vessels in the UK for the period 1962 to 1978 and its relevance to nuclear pressure circuits, UKAEA Report SRD R203, 1981
  • Thurlbeck S D, Stacey A, Sharp J V, Nichols N W. Welding fabrication defects in two offshore jacket structures. OMAE Conf., Florence, 1996
  • Wagner M J and Watchett B M, Girth weld defects in mechanised GMA field welded pipelines. Welding Journal, 75 - 82, June 1991.
  • Wintle J B, Sanderson R M, and Hart P H M, A review of methods for determining nthe frequency and size distribution of welding flaws in steel fabrications, TWI core research report 749/2002, June 2002.


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