Let me start with something I tell every candidate who attends our UT Level II training in Bangalore.

Knowing how to perform an ultrasonic test — how to set up the instrument, calibrate the DAC curve, scan the weld, and find an indication — is half the job. The other half, equally important and far more frequently misunderstood, is knowing what to do with what you find. How long is too long? How strong an echo is too strong? When do you call a weld rejected — and when do you leave it in service?

Those questions are answered by acceptance standards. And for ultrasonic testing of welds in the ISO world, the primary acceptance standard is ISO 11666:2018 — Non-Destructive Testing of Welds — Ultrasonic Testing — Acceptance Levels.

In nearly three decades of doing and teaching UT in Indian industry, I have found ISO 11666 to be one of the most misquoted, misapplied, and misunderstood standards in the NDT practitioner’s toolkit. Engineers mix it up with ISO 17640 (the testing technique standard). They confuse its acceptance levels with those in ASME Section VIII. They apply AL2 where AL3 was specified — or vice versa — without understanding what the practical consequence is.

This article is my attempt to fix that. We will go through ISO 11666:2018 from beginning to end — the scope, the logic, the numbers, the practical application, and the relationship to every other standard in the ISO weld inspection family. By the end, you will be able to look at a UT test report referencing this standard and know exactly what it means.

What ISO 11666 Is — And What It Is Not

Before we go any further, let us establish clearly what ISO 11666 does and does not cover.

ISO 11666 tells you: Given an ultrasonic indication found during UT of a weld, what amplitude and length criteria determine whether it is acceptable or rejectable?

ISO 11666 does not tell you: How to perform the UT test. Which probes to use. How to calibrate the instrument. What scanning patterns to follow. All of those are covered by ISO 17640 — Non-Destructive Testing of Welds — Ultrasonic Testing — Techniques, Testing Levels and Assessment — which is the technique standard that ISO 11666 depends upon.

Think of it this way: ISO 17640 tells you how to look. ISO 11666 tells you what you are allowed to find. They work together — and you cannot apply one without the other. Every UT of a weld to ISO standards is a two-standard exercise: technique per ISO 17640, acceptance per ISO 11666.

Scope and Application — What This Standard Covers

ISO 11666:2018 was published in 2018 as the second edition, replacing ISO 11666:2010. As of 2025, a new committee draft (ISO/CD 11666) is under development — so a third edition is on the horizon. However, the 2018 edition remains the active international standard and is the version cited in the vast majority of current contracts and codes.

The standard applies to:

Full penetration welded joints in ferritic steels with thicknesses from 8 mm to 100 mm. This is the primary scope — the application that covers the overwhelming majority of welded pressure vessels, structural steel, pipelines, and process piping in Indian and international fabrication.

It can also be used for other types of welds, materials and thicknesses, provided the tests have been performed with necessary consideration of the geometry and acoustic properties of the component, and an adequate sensitivity can be employed to enable the acceptance levels of this document to be applied.

This second paragraph is more important in practice than the first. It is the clause that experienced practitioners use to apply ISO 11666 to austenitic stainless steel welds, aluminium alloy welds, and nickel alloy welds — always with the caveat that the UT technique must be appropriate for the material, and that adequate sensitivity to the relevant indication sizes must be demonstrably achievable.

What the standard does NOT apply to:

• Partial penetration welds — fillet welds, tee joints with partial penetration, overlay welds
• Welds in materials below 8 mm thickness (for thin section, other standards apply)
• Welds in materials above 100 mm thickness (special thick-section procedures are required)
• Austenitic stainless steel welds where specific acoustic problems preclude adequate sensitivity without specific additional provisions

The ISO Weld Inspection Standard Family — Understanding Where ISO 11666 Fits

To understand ISO 11666 properly, you need to understand the ecosystem of ISO standards it belongs to. These standards are not independent — they form a structured hierarchy.

ISO 5817:2014 — Welding — Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) — Quality Levels for Imperfections

This is the foundational document that defines what imperfection sizes and types are acceptable for different applications of welded joints. ISO 5817 defines three weld quality levels:

• Quality Level B — the highest quality; strictest limits on imperfection sizes
• Quality Level C — intermediate quality; moderate limits
• Quality Level D — the lowest quality; most permissive limits

These three quality levels are the starting point for everything in the ISO weld acceptance world. When a contract specifies “ISO 5817 Quality Level B welds”, it is saying: every weld in this project must meet the strictest permissible imperfection limits.

ISO 17640:2018 — Non-Destructive Testing of Welds — Ultrasonic Testing — Techniques, Testing Levels and Assessment

This is the testing technique standard. It defines how UT of welds shall be performed — probe selection, frequency, scanning technique, calibration, recording level, and how to determine the length of an indication. It defines four testing levels (A, B, C, and D) of increasing thoroughness, corresponding to the criticality of the application.

ISO 11666:2018 — Non-Destructive Testing of Welds — Ultrasonic Testing — Acceptance Levels

This is what we are discussing today. It takes the findings produced by a UT test performed per ISO 17640 and tells you whether those findings are acceptable or rejectable, at one of two acceptance levels that correspond to ISO 5817 quality levels.

The relationship is beautifully systematic: the quality of the weld (ISO 5817) drives the strictness of the testing (ISO 17640 testing level) which drives the strictness of the acceptance criteria (ISO 11666 acceptance level). Everything ties together.

The Two Acceptance Levels — AL2 and AL3

ISO 11666:2018 specifies two ultrasonic acceptance levels known as acceptance level 2 (AL 2) and acceptance level 3 (AL 3) for full penetration welded joints in ferritic steels, which correspond to ISO 5817:2014, quality levels B and C.

Let me be very specific about what these numbers mean and which is stricter — because this is where confusion consistently occurs.

Acceptance Level 2 (AL2) = ISO 5817 Quality Level B = The STRICTER level

Acceptance Level 3 (AL3) = ISO 5817 Quality Level C = The LESS STRICT level

The counterintuitive thing for newcomers is that a lower number (2) is the stricter acceptance level. This follows the ISO 5817 convention where Quality Level B (the best) is stricter than Quality Level C, which is in turn stricter than Quality Level D. The numbering reflects the ISO 5817 quality level letters: B = 2, C = 3.

An acceptance level corresponding to ISO 5817:2014, quality level D is not included in this document, as ultrasonic testing is generally not requested for this weld quality.

This is a logical and practical decision. ISO 5817 Quality Level D represents the most lenient weld quality — welds where relatively large imperfections are acceptable. For such welds, UT is typically not a contractual requirement because the quality level is low enough that the effort and cost of ultrasonic testing is disproportionate to the application’s criticality.

The Three Levels You Must Understand — Recording, Evaluation, and Acceptance

One of the most common sources of confusion in applying ISO 11666 is the distinction between three different amplitude thresholds that appear in the standard. These are not the same thing, and mixing them up leads to incorrect reporting.

The Recording Level (also called the Detection Level)

This is the amplitude threshold above which the technician must write the indication into the test record. Every indication that exceeds the Recording Level must be documented — its location, depth, length, and amplitude relative to the reference level. The recording level does NOT determine acceptance or rejection — it only determines what gets written down.

Per ISO 17640 and ISO 11666, the evaluation levels are expressed in dB relative to the reference DAC (Distance-Amplitude Correction) curve established from a reference reflector (typically a 3 mm side-drilled hole in the calibration block of the same material and nominal thickness as the test object).

Evaluation and Acceptance Levels

The Evaluation Level

This is the amplitude above which the technician must measure the indication’s length (using the 6 dB drop method or the specified echo-amplitude method) and assess it against the acceptance criteria. Indications above the recording level but below the evaluation level are recorded in full but their length does not need to be measured and they are not evaluated against the acceptance criteria tables.

In ISO 11666:2018, the evaluation levels for techniques 1 to 4 are given in ISO 11666:2018, Table A.1. These are expressed as dB values below the reference DAC level — typically in the range of DAC -10 dB or DAC -6 dB depending on the technique and thickness range.

The Acceptance Level

This is the maximum amplitude and maximum length that an indication may have while still being classified as acceptable. An indication that exceeds either the amplitude acceptance criterion OR the length acceptance criterion (or both) at its given evaluation level must be classified as rejectable.

Understanding the hierarchy — Recording → Evaluation → Acceptance — is the key to reading ISO 11666 correctly.

How the Acceptance Criteria Work — The Practical Application

The core of ISO 11666 is a set of tables that relate:

1. Wall thickness of the weld joint (which affects the amplitude reference level and the length acceptance criteria)
2. Amplitude of the indication (expressed in dB relative to the H0 reference level — the point on the DAC curve at the depth of the indication)
3. Measured length of the indication (determined by the 6 dB drop method or echo-amplitude method)

These three variables together determine whether an indication is accepted or rejected.

Let me work through this in practical terms.

Setting Up the Reference — What H0 Means

H0 is the amplitude reference point in ISO 11666 — it is the amplitude of the echo from the reference reflector (a 3 mm diameter flat-bottom hole or side-drilled hole, depending on the technique) at the same metal path distance as the indication being evaluated, as read from the DAC curve.

This is critical: H0 is not a fixed point on the instrument. It changes with depth. When you evaluate an indication at 20 mm depth, H0 is the DAC curve amplitude at 20 mm. When you evaluate an indication at 50 mm depth, H0 is the DAC curve amplitude at 50 mm. The DAC curve automatically accounts for sound attenuation with distance, so H0 always represents the same equivalent flaw size regardless of depth.

What the Acceptance Tables Tell You

For each combination of acceptance level (AL2 or AL3) and weld thickness range, the acceptance table gives you pairs of conditions. An indication must be evaluated against both conditions — amplitude and length — and must satisfy BOTH to be accepted.

In simplified practical terms, for a typical structural steel weld at Acceptance Level 2:

An indication is accepted if BOTH of the following apply:

• Its amplitude does not exceed H0 (the DAC curve amplitude at that depth), and Its measured length does not exceed a specified fraction of the wall thickness (typically t/4 for certain thickness ranges)

An indication is rejected if EITHER:

• Its amplitude exceeds H0 at any depth, OR
• Its length exceeds the maximum permitted regardless of amplitude, OR
• Its amplitude and length combination falls above the acceptance line in the table

The elegance of this system is that it mirrors real-world defect behaviour: large but shallow and short indications may be acceptable, while long continuous linear indications are rejectable even at relatively low amplitudes, because a long linear discontinuity (which could be a crack, a linear slag line, or a lengthy area of lack of fusion) is always more dangerous than an isolated point reflector.

The Amplitude-Length Relationship — The Key Insight

There is a principle embedded in the ISO 11666 tables that every practising UT inspector should internalise:

As an indication’s length increases, the maximum acceptable amplitude decreases.

Or stated another way: the longer the indication, the stricter the amplitude criterion. A short indication (length less than half the wall thickness, for example) may be accepted at full H0 amplitude. But a long indication — one whose length approaches or exceeds the wall thickness — must have an amplitude significantly below H0 to be accepted.

Why? Because length is a proxy for defect type and severity. A point-like porosity pore gives a short indication. A slag inclusion can give a moderate-length indication. But lack of fusion — particularly if it extends over a long run of the weld — gives a long indication. And lack of fusion, being a planar defect with potential stress-concentration effect, is far more dangerous in service than an equivalent-length chain of porosity. The amplitude-length relationship in the acceptance tables reflects this physical reality.

AL2 vs AL3 — When to Apply Which, and Why It Matters

The choice of acceptance level for a given weld is one of the most important decisions in a UT inspection contract. It is not a decision that should be made by the NDT inspector on site — it should be specified in the inspection contract, the design documentation, or the applicable product standard.

Here is the practical guidance:

Apply AL2 (the stricter level) when:

• The weld carries high stress or is in a fatigue-critical location
• The weld is in a pressure-retaining system (pressure vessels, boilers, pipelines) where failure could cause catastrophic release
• The applicable product standard or contract specifies ISO 5817 Quality Level B
• The weld joins safety-critical structural members — primary load-bearing joints in bridges, offshore platforms, or building frames
• Failure of the weld would have significant consequences for life safety or environmental integrity
• The design has been based on weld quality Level B assumptions

Apply AL3 (the less strict level) when:

• The weld is in a lower-criticality structural application
• The applicable product standard or contract specifies ISO 5817 Quality Level C
• The weld carries static (non-cyclic) loading and the design tolerates a larger imperfection
• The fabrication is categorised as standard quality rather than special quality

The critically important point: The contract or product standard determines the acceptance level. The inspector applies it — but does not choose it. If you receive a UT contract with no acceptance level specified, this must be resolved before testing begins. Applying AL3 where AL2 was required, or vice versa, is a significant quality failure — not just an administrative one. It can result in unsafe welds being accepted into service, or acceptable welds being unnecessarily rejected.

The Length Measurement Question — 6 dB Drop vs Echo-Amplitude Method

One area where ISO 11666 gives inspectors a choice — but a choice that must be consistently documented — is in the method for measuring indication length.

The 6 dB Drop Method

The probe is scanned along the weld axis until the echo from the indication drops to half its maximum amplitude (a 6 dB reduction). The distance between the two 6 dB drop positions along the scan axis is reported as the indication length. This method is straightforward, well-understood, and appropriate when the indication is reasonably distinct and not near the weld root or cap.

The Echo-Amplitude Method (DAC-based)

The inspector scans the probe along the weld until the indication amplitude falls below a specified threshold relative to H0, then reports the distance between those threshold-crossing positions as the indication length. This method tends to give shorter reported lengths than the 6 dB drop method for the same indication — which means that choosing this method rather than 6 dB drop for the same indication may be the difference between acceptance and rejection.

This is not a trick — it is a legitimate technical approach, and ISO 11666 permits both methods. But the method must be specified in the written procedure and consistently applied. An inspector who switches between methods depending on which gives a more convenient result for a marginal indication is not practising good NDT — and any competent reviewer of the test records would spot this immediately.

The Relationship with ISO 17640 Testing Levels — A Table Worth Understanding

In addition to possessing general knowledge of ultrasonic weld testing, personnel must also understand the testing challenges specifically associated with the type of welded joints under examination.

ISO 17640 defines four testing levels — A, B, C, and D — of increasing thoroughness and coverage. The choice of ISO 17640 testing level determines the scanning coverage, the probe angles used, and the number of probe positions. ISO 11666 acceptance levels are linked to ISO 17640 testing levels:

The important implication is that a contract specifying AL2 will almost certainly require ISO 17640 Testing Level B or C, because only the more comprehensive scanning coverage provided by those testing levels can reliably detect the smaller indications that AL2 is intended to control.

Conversely, a contract that specifies ISO 17640 Testing Level B but AL3 is a contract for moderately thorough scanning with moderately lenient acceptance — appropriate for secondary structural members in non-critical applications.

Transfer Correction — The Most Frequently Missed Step

Transfer differences, between test object and reference block, at a representative number of locations. ISO 16811 describes suitable techniques for this evaluation. When the differences are less than or equal to 2 dB, inspectors do not need to apply correction. The differences exceed 2 dB but remain less than or equal to 12 dB, inspectors must compensate for them. Transfer losses exceed 12 dB, inspectors must investigate the cause and carry out further preparation of the scanning surface.

This is one of the most practically significant provisions in the standard — and one of the most consistently overlooked in routine inspection work.

The calibration block has a smooth, flat surface. The inspected weld may have a rough surface due to the as-welded condition, scale, or minor corrosion. This surface roughness introduces additional sound attenuation, reducing the sound entering the weld compared with the amount that entered the calibration block. If inspectors do not measure and compensate for this transfer difference, the actual sensitivity becomes lower than assumed, causing the system to miss small indications that should have appeared above the recording level.

The correct procedure: after calibrating on the reference block, measure the DAC amplitude using the same probe on the actual weld surface at several representative locations. The difference between this reading and the calibration block reading is the transfer correction. If the difference exceeds 2 dB, inspectors must increase the instrument gain by the correction value before the test begins.

In my experience training UT Level II candidates, transfer correction is the step that separates the technician who follows a procedure from the technician who understands what the procedure is trying to achieve.

What the 2018 Revision Changed From the 2010 Edition

For those who have worked with ISO 11666:2010 and are updating their knowledge, the 2018 revision introduced several important clarifications and updates:

Clearer correlation with ISO 5817:2014: The 2018 edition more explicitly links AL2 to ISO 5817 Quality Level B and AL3 to ISO 5817 Quality Level C, making it easier to use the standard in conjunction with quality requirements specified per ISO 5817.

The revised Table A.1 aligns the evaluation level table with the updated ISO 17640:2018 technique definitions, particularly for the four standard techniques.

Expanded guidance on non-ferritic materials: The 2018 edition provides slightly more guidance on applying the acceptance criteria to non-ferritic materials where specific acoustic properties affect the validity of the reference calibration.

The 2018 edition clarifies that inspectors must establish the recording threshold before scanning begins and cannot retrospectively adjust it to change the documented results.

As of late 2024, the committee registered a new draft standard (ISO/CD 11666) to replace ISO 11666:2018 and initiated committee drafting in December 2025. The comment period closed in February 2026. This indicates that the committee is likely to publish a new edition within the next two to three years. NDT professionals working to this standard should monitor ISO’s publications for the DIS (Draft International Standard) — which will give advance notice of any significant changes to the acceptance criteria.

Applying ISO 11666 with PAUT — A Growing Practical Question

One of the questions that advanced UT practitioners ask me most frequently is whether they can apply ISO 11666 acceptance criteria to Phased Array Ultrasonic Testing (PAUT) results.

The short answer is: yes, with important conditions.

There is a document that specifies the application of the phased array technology for the semi- or fully automated ultrasonic testing of fusion-welded joints in metallic materials of minimum thickness 6 mm. It applies to full penetration welded joints of simple geometry in plates, pipes, and vessels, where both the weld and the parent material are low-alloy and/or fine grained steel.

The relevant companion standard for PAUT of welds is ISO 13588 — which covers the PAUT technique for weld inspection and references ISO 11666 acceptance levels. When inspectors use PAUT to perform weld UT in accordance with ISO 17640 technique requirements and express the results in equivalent amplitude terms relative to the same reference reflector (3 mm SDH or FBH), they can apply the ISO 11666 acceptance tables directly.

The critical condition requires the PAUT technique to demonstrate, through validation, that it achieves at least equivalent detection capability to the manual UT technique it replaces. The amplitude reference calibration must use the same reference reflector as specified for the manual technique. When PAUT produces results in S-scan or E-scan format, inspectors must properly extract the maximum amplitude at any point in the weld cross-section and compare it with the acceptance criteria.

PAUT done properly to ISO standards is a powerful tool — faster, more reproducible, and often more sensitive than manual UT for complex weld geometries. PAUT done without proper calibration and without attention to the acceptance standard requirements is just impressive-looking data that may not mean what the client thinks it means.

A Worked Example — From DAC Calibration to Accept/Reject Decision

Let me take you through a realistic scenario — the kind of situation that comes up on the shop floor regularly.

The Setup:

• Butt weld in carbon steel pressure vessel
• Wall thickness: 30 mm
• Acceptance level specified: AL2 (ISO 5817 Quality Level B)
• Testing per ISO 17640, Testing Level B
• Technique: Angle beam, 60° probe, 4 MHz, single angle
• Calibration: DAC curve from 3 mm SDH in reference block, 30 mm thickness, same material

The Calibration: You establish the DAC curve. At the 30 mm metal path depth, your DAC amplitude corresponds to the response from the 3 mm SDH. You set this as H0 at that depth. You adjust sensitivity to bring this point to 80% full screen height (FSH) — a standard reference point.

The Scan: You scan the weld. You find an indication at approximately 22 mm depth (metal path). The maximum echo amplitude from this indication is 72% FSH. You note that it exceeds the recording level, which you set below DAC—perhaps at DAC -10 dB, equivalent to about 25% FSH. You stop and evaluate.

Reading H0 at 22 mm depth: From your DAC curve, at 22 mm metal path, the DAC is — let’s say — 78% FSH. So your indication amplitude of 72% FSH is below H0. In dB terms, it is approximately 0.7 dB below H0. This means the indication is below the maximum amplitude acceptance criterion of H0.

Length Measurement: You measure the indication length using the 6 dB drop method. The amplitude drops from 72% FSH to 36% FSH (half) at two positions along the weld axis. The distance between these positions: 18 mm.

Applying the Acceptance Table

For AL2 with a 30 mm wall thickness and an indication amplitude below H0, what maximum length does the standard permit?

The ISO 11666:2018 Table gives maximum indication lengths that depend on the amplitude relative to H0 and the wall thickness. For an indication at or below H0 in a 30 mm wall, the standard typically expresses the maximum permitted length as a fraction of the wall thickness.Approximately t/2 for the amplitude level under discussion—which corresponds to 15 mm.

Our indication is 18 mm long. The acceptance criterion is 15 mm. AL2 rejects this indication.

Evaluators would need to reassess the same indication against the AL3 acceptance criteria to determine whether the less stringent level would accept it. Although that assessment remains academic from a contractual standpoint if the contract specifies AL2. It belongs in a fitness-for-service assessment, not the inspection report.

The Most Common Mistakes I See in ISO 11666 Application

After reviewing test reports and conducting audits for fabricators and inspection companies across India, these are the recurring errors:

Mistake 1 — Applying AL3 instead of AL2 because it is “easier to pass” The acceptance level is specified in the contract. Applying the wrong level — intentionally or through carelessness — is a quality system failure. Any reputable inspection company that discovers this has happened must issue a corrected report and notify the client.

Mistake 2 — Not performing transfer correction The calibration block surface is different from the weld surface. If the difference is more than 2 dB, correction is mandatory. Many inspectors on site skip this step because it adds time. It compromises the sensitivity of the inspection.

Mistake 3 — Measuring length by eye rather than by the 6 dB drop method “It looks about 15 mm long” is not a length measurement. Inspectors must use and document the 6 dB drop method or the echo-amplitude method.

other Common Mistakes That Needs Consideration

Mistake 4 — Confusing the evaluation level with the acceptance level. Inspectors must assess an indication that exceeds the evaluation level; they cannot automatically reject it. Many technicians incorrectly treat exceeding the evaluation level as a rejection. It is a threshold that triggers length measurement and acceptance assessment.

Mistake 5 — Using calibration blocks of the wrong material ISO 17640 and ISO 11666 require that the calibration block be of the same material group. As the test object.

Using a carbon steel calibration block for a 316L stainless steel weld inspection will give incorrect sensitivity because the acoustic properties differ.

Mistake 6 — Failing to specify the acceptance level in the test report. Every UT weld test report should clearly state the applied acceptance level (AL2 or AL3). The evaluation level in dB, the recording level in dB, and the reference reflector used. Reports that omit this information are incomplete and non-compliant with ISO 17640 reporting requirements.

How ISO 11666 Relates to Other Major UT Acceptance Standards

For practitioners who work across multiple code environments, here is the orientation table that I share in our UT Level II training:

The important thing to note: ASME and ISO acceptance systems are fundamentally different in their approach. ASME uses a simpler reject/accept binary based primarily on whether the indication exceeds the DAC curve. A DAC-crossing indication is typically rejectable (with some additional evaluation criteria). ISO 11666 uses a more nuanced system in which amplitude and length together determine acceptance. Thus allowing inspectors to accept certain above-DAC indications if their length remains within permissible limits.

This means you cannot substitute one for the other without understanding which is more conservative for a given indication. ASME might reject a short but high-amplitude indication that ISO 11666 AL3 would accept.While certain ASME interpretations might accept a long but moderate-amplitude indication that ISO 11666 AL2 would reject. Know your code, and apply it correctly.

Writing the ISO 11666 UT Test Report

The ISO 17640 reporting requirements (which govern the test report for UT of welds using ISO 11666 acceptance criteria) specify that every compliant test report must include:

• Name of the testing organisation and name of the inspector
• Inspector’s qualification level and certification scheme
• Name of the client and identification of the tested object
• Material specification, dimensions, and condition of the weld
• Testing standard: ISO 17640, testing level specified
• Acceptance standard: ISO 11666:2018, acceptance level applied (AL2 or AL3)
• Reference reflector: type (SDH or FBH), diameter, location in calibration block
• Probe details: type, frequency, angle, size, manufacturer, serial number
• Instrument type and serial number
• Calibration date and reference (instrument must be in calibration)
• Recording level, evaluation level, and acceptance level in dB relative to H0
• Transfer correction applied (value in dB, or statement that correction was less than 2 dB)
• Scanning pattern and coverage achieved
• For each recorded indication: location, depth, measured length, maximum amplitude (relative to H0), assessment (Accepted/Rejected)
• Overall conclusion: Accepted or Rejected
• Date of testing
• Authorised signature — minimum UT Level II per applicable certification scheme

A report that is missing any of these elements is incomplete by the standard’s requirements. For NABL-accredited reports (as issued by Trinity NDT WeldSolutions), additional requirements per ISO/IEC 17025 — including measurement uncertainty statement, NABL logo and accreditation number, unique report reference, and non-modification statement — also apply.

The Bigger Picture — Why Acceptance Standards Matter More Than Many Realise

Let me close with something that goes beyond the technical detail.

I started in NDT in the late 1990s, and early on, a conversation with a senior inspector who had worked on refinery piping for two decades struck me deeply. He said something that stayed with me: “The acceptance criterion is not just a number. It is a statement about what humanity has collectively agreed is safe enough.”

That sounds philosophical for an NDT standard. But think about what is behind ISO 11666:2018. The acceptance levels are not guesses or conservative rule-of-thumb estimates. They are the product of decades of fracture mechanics research — understanding how cracks and other weld discontinuities behave under load, how they grow under cyclic stress, at what size they become critical under the design loading conditions of real structures. Research grounds the ISO 5817 quality levels, which in turn drive the ISO 11666 acceptance levels.

When you apply AL2 and reject a weld with an indication that slightly exceeds the acceptance criteria, you are making a decision that the research says that particular combination of amplitude and length represents a risk that the design did not account for and cannot reliably tolerate. When you accept a weld with a 14 mm indication where the limit is 15 mm, you are making a decision that the research says this particular size, in this material, at this depth, is below the threshold at which fracture mechanics predicts failure at the design stress.

This is why the acceptance criterion matters. It is not negotiable based on convenience or client pressure. Every UT inspector who applies ISO 11666 should understand — not just memorise — the principles behind the numbers.

Our UT Testing and Training Services at Trinity NDT

At Trinity NDT WeldSolutions, we provide NABL ISO/IEC 17025:2017 accredited Ultrasonic Testing services for welds in pressure vessels. Also, piping, structural steel, and aerospace components — to ISO 17640 and ISO 11666, as well as ASME Section V, AWS D1.1, API 1104, and other applicable codes. Trinity NDT issues all UT test reports with NABL accreditation. Wherever they fall within scope, giving your quality system independently verified confidence in the results.

Trinity NDT also conducts UT Level I and Level II certification training—both online (live virtual via Zoom) and offline (in-person at its Peenya, Bangalore facility)—covering ISO 11666, ISO 17640, and ASME Section V acceptance criteria in detail using real production radiographs and UT test records.

If you have a specific question about ISO 11666 application — which acceptance level is appropriate for your application. How to handle a borderline indication, or how to write a compliant UT procedure referencing this standard. I am happy to discuss it. That is exactly the kind of technical consultation that we provide as part of our ASNT Level III NDT consulting service.

WhatsApp: +91 98441 29439 | Email: info@trinityndt.com

About the Author: Ravi Kumar Thammana is the CEO and Co-Founder of Trinity NDT WeldSolutions Pvt. Ltd., Bangalore. He holds ASNT Level III certification in all six NDT methods (UT, RT, MT, PT, VT, ET), International Welding Engineer (IWE) from IIW India, NAS 410 Level III (Aerospace NDT), and Radiological Safety Officer (RSO) from AERB/BARC. Trinity NDT holds NABL ISO/IEC 17025:2017 accreditation (TC-5934) and NADCAP Aerospace Merit accreditation. He blogs at materials-testing.blogspot.com.

The post ISO 11666:2018 — Acceptance Levels for Ultrasonic Testing of Welds: Everything You Need to Know appeared first on Trinity NDT WeldSolutions Private Limited.

There are jobs in this work that go exactly as planned. You set up the equipment, run the procedure, the readings drop, and the component goes out the door. The client is happy, the report is signed, and you move on to the next job. We are about to know an interesting demagnetization case study.

And then there are days when a component gives you a fight.

Today was one of those days — and the component that decided to be stubborn was a steel shaft that arrived at our Peenya laboratory carrying over 10 Gauss of residual magnetism and an absolutely determined resistance to losing it.

This is the story of that shaft, how it got to 10 Gauss, why that is a serious problem for any rotating machine, and what it took to bring it back down below the 3 Gauss threshold that industry standards demand.

First — Why Was This Shaft Magnetised?

The client who brought this shaft to us had previously sent it for Magnetic Particle Inspection (MPI) at another facility. MPI — also called Magnetic Particle Testing (MPT) — is one of the most effective methods for detecting surface and near-surface cracks in ferromagnetic components. During MPI, a strong magnetic field is intentionally induced into the component using either a yoke, a prod, a coil, or a bench-type stationary machine. This magnetisation is what makes the test work — it creates the flux leakage that attracts magnetic particles to crack locations and makes them visible.

The problem is that steel has memory. When a magnetic field is applied and then removed, ferromagnetic materials do not simply return to a neutral state. They retain a portion of the induced magnetic field — what we call the residual magnetism or remnant field. In some steels — particularly high-carbon and alloy steels with high coercivity — this residual field can be surprisingly strong and surprisingly stubborn.

On this particular shaft, the MPI inspection had clearly been performed using a high-magnetisation technique. The resulting residual field measured over 10 Gauss on our calibrated digital Gaussmeter when the shaft arrived at our facility.

Why Does 10 Gauss Matter? Why Not Just Leave It?

This is a question we hear regularly. “It’s invisible. It doesn’t affect how the shaft looks. Why does it matter?”

The answer is: because residual magnetism causes damage in ways that are both subtle and accumulative. Let us walk through exactly what happens when a magnetised shaft enters service.

Bearing damage from arc discharge. In a rotating shaft running in electrical equipment, a residual magnetic field creates a voltage potential that can discharge through the bearing races as a tiny electrical arc — sometimes called Electrical Discharge Machining (EDM) pitting of the bearing. Over time, this pitting destroys bearing surfaces, increases noise and vibration, and eventually causes bearing failure. A shaft with 10 Gauss of residual magnetism in a motor or generator is a bearing damage accelerant.

Chip and swarf attraction in machining. If a magnetised shaft goes into a subsequent machining operation — grinding, turning, or polishing — it attracts metallic chips and swarf directly to the surface being machined. These particles become embedded in the surface or cause scoring. The machined finish is compromised, dimensional tolerances suffer, and the component may need to be scrapped.

Interference with precision instruments. Any precision measuring instrument — a CMM probe, a dial gauge, a digital calliper — that comes close to a strongly magnetised shaft will give false readings or suffer calibration drift. In a quality-controlled manufacturing environment, this is unacceptable.

Other Issues with Residual Magnetism

Welding arc blow. If a magnetised shaft or component is to be welded, residual magnetism causes arc blow — a deflection of the welding arc away from the intended joint. The result is poor fusion, irregular bead geometry, and increased weld defects. For shaft repair or hardfacing welding, demagnetisation before welding is a mandatory first step.

Compass and navigation interference. In marine, aviation, or defence applications, a magnetised component near a compass or navigation instrument can cause heading errors. This is not a theoretical risk — it is a documented failure mode in marine engineering.

For all of these reasons, the standard practice across industries — from automotive and power generation to aerospace and defence — is to specify a maximum residual field of 3 Gauss or less before a component is approved for final assembly or further processing. At 10 Gauss, this shaft was more than three times above the acceptable limit.

The Challenge — Why This Shaft Was Difficult

Image 1: Initial residual field measurement on the shaft — 10+ Gauss. The Gaussmeter probe is positioned at the shaft surface, showing the elevated reading that indicates significant retained magnetism from the previous MPI inspection.

When our Senior Demagnetization Technician first ran the Gaussmeter over the shaft, the reading was immediately concerning — not just for the magnitude, but for the distribution of the field. In a straightforward demagnetisation job, the residual field is fairly uniform across the component surface. You set up the coil, run the procedure, and the readings drop evenly.

This shaft was not straightforward.

The field was distributed asymmetrically across the shaft length — stronger at one end, relatively weaker at the midpoint, and elevated again at the other end. This told an experienced technician something specific: the MPI technique used at the other facility had likely involved multiple separate magnetisation shots at different zones of the shaft, possibly with a prod or yoke technique applied at several points rather than a single coil or through-the-bar technique. Each of those separate magnetisation applications had created its own domain alignment, and those domains were not pointing in the same direction. This is the hardest type of residual magnetism to remove.

Our Senior Technician’s first demagnetisation pass — a standard AC coil technique with slow withdrawal — brought the field down at the shaft midsection but the end zones remained stubbornly high. A second pass produced only marginal improvement. The steel’s coercivity — its resistance to magnetic reversal — was working against us.

This is the point in a demagnetisation job where an inexperienced operator might either declare it “good enough” or escalate unnecessarily. Our technician did neither. He went back to fundamentals.

The Technique That Worked

Without disclosing the specific proprietary parameters of our demagnetisation procedure, here is what the correct technical approach involved for this component:

Step 1 — Reassessment of field distribution. Before running any further demagnetisation attempts, our technician methodically mapped the field across the shaft length at 5 cm intervals, recording the reading at each point. This field map told him exactly where the strongest retention zones were and gave him a basis for assessing whether each subsequent treatment pass was making progress.

Step 2 — Frequency optimisation. The AC demagnetisation coil was set to a frequency and field intensity matched to the shaft’s cross-section diameter and estimated material coercivity — not the default setting, but the calculated optimal parameter for this specific geometry and steel type.

Step 3 — Zone-specific treatment. Rather than treating the entire shaft as a single unit, the technician worked on the high-retention zones separately, using a slower and more controlled coil pass rate in those regions. The field map was re-run after each zone treatment to verify progress.

Step 4 — Final pass — complete shaft. After the zone-specific treatment had brought the problem areas down to a manageable level, a final full-length coil pass was performed to unify the field reduction across the entire shaft length.

Step 5 — Final verification. The Gaussmeter was used to re-survey the entire shaft surface, not just spot-check it. Every measurement point was recorded on the test record.

The result: residual magnetism below 3 Gauss across all measurement points.

The Result — Below 3 Gauss

Image 2: Final residual field measurement after successful demagnetisation — below 3 Gauss. The same shaft, the same Gaussmeter probe, the same measurement location as Image 1. The residual field has been reduced to within the industry-standard acceptance limit, and the shaft is now cleared for assembly, machining, or further processing.

The comparison between Image 1 and Image 2 is the complete story of today’s job. A reading that was well above any acceptable limit, brought back to compliance through methodical technique, the right equipment, and the experience to recognise when a standard approach is not working and adapt.

The client’s shaft left our facility with a formal Demagnetisation Test Record documenting:

• Component description and identification
• Initial residual field readings (mapped at multiple points along the shaft)
• Demagnetisation method, equipment, and parameters used
• Post-demagnetisation residual field readings (verified below 3 Gauss at all points)
• Operator identification and certification
• Date and time of service

That document is the client’s proof — for their quality records, for their client, and for any regulatory or inspection body that might ask — that the demagnetisation was done correctly and was verified.

What the 3 Gauss Specification Means — And Where It Comes From

The 3 Gauss (0.3 mT) maximum residual field requirement is the most widely cited acceptance criterion in industrial demagnetisation. It appears in:

• ASTM E1444 — Standard Practice for Magnetic Particle Testing (the primary MPI standard in the USA and widely followed in India for ASME-coded work)
• AWS D1.1 — Structural Welding Code, which references maximum residual field requirements before welding repairs
• MIL-STD-1949 — Military standard for magnetic particle inspection
• NAS 410 — Aerospace NDT standard (for aerospace-grade components, residual field requirements can be stricter than 3 Gauss)
• Various OEM and end-user specifications for bearing and gear manufacturers

Some specific applications — particularly in precision bearing assemblies, compass-critical components, and aerospace rotating machinery — specify maximum residual fields of 1 Gauss or even below 0.5 Gauss. When clients bring such requirements, our demagnetisation procedure is adjusted accordingly and the verification threshold is tightened to match.

If your component’s specification does not state a residual field limit but you need demagnetisation, our default acceptance criterion is below 3 Gauss — consistent with ASTM E1444. We always record the actual achieved reading so you have the documented evidence, not just a pass/fail statement.

When Is Demagnetisation Required?

Based on the range of jobs we handle at our Peenya facility, these are the most common situations where demagnetisation is needed:

After Magnetic Particle Inspection (MPI/MPT): This is the most frequent reason. Every MPI inspection magnetises the component. If the component is going into service in a bearing, a gear train, an electrical machine, or a high-precision assembly — demagnetise before dispatch.

Before welding or hardfacing: A magnetised component causes arc blow during welding. If you are repairing a shaft, hardfacing a gear, or welding any ferromagnetic component that has been through an MPI inspection, demagnetise before welding.

Before precision machining: Swarf and chip attraction to a magnetised surface is a real problem in precision grinding and turning. Demagnetise before finish machining operations.

Before assembly into precision equipment: Electric motors, generators, turbines, compressors, and gear boxes all contain components that can be affected by residual magnetism in adjacent parts. Demagnetise before final assembly.

Before calibration or use with precision measuring instruments: If a magnetised shaft or component is to be measured with contact gauges or CMM probes, demagnetise first to ensure measurement accuracy.

The Equipment We Use — Why It Matters

Not all demagnetisation equipment is equal, and not all operators are equally skilled in using it.

Our demagnetisation facility at Peenya uses a combination of AC coil demagnetisers sized for different component geometries — from small precision parts to large shafts — and portable yoke-type demagnetisers for in-field and on-site demagnetisation of large structures and weldments.

The verification instrument is a calibrated digital Gaussmeter — not a compass or a simple field indicator, but an instrument that gives precise, quantitative residual field measurements in Gauss or milliTesla, with calibration traceable to national standards. The readings in Image 1 and Image 2 above are real Gaussmeter readings — not estimated, not guessed, not assessed by feel. Measured. Recorded. Reported.

Our demagnetisation technicians are NDT professionals — the same team that performs Magnetic Particle Testing (MPI/MPT) for our clients every day. They understand the physics of magnetism and demagnetisation not just as a procedure to follow, but as a principle they can apply intelligently when a standard approach is not producing the required result. Today proved why that depth of knowledge matters.

A Note on the MPI and Demagnetisation Relationship

One question we hear from clients: “If MPI causes residual magnetism, why do some MPI reports come without a demagnetisation service?”

The answer is: sometimes the residual field left after MPI is already below the 3 Gauss acceptance limit. Particularly when AC yoke technique is used, since AC magnetisation naturally has a partial self-demagnetising. This effect is due to the alternating nature of the field. In those cases, a separate demagnetisation step may not be necessary.

But when high-field DC magnetisation is used. Bench machines with high amperage, or prod techniques. the residual field can be substantial, as this shaft demonstrated. In those cases, a formal demagnetisation step with verified measurement is not optional. It is part of professional MPI service delivery.

At Trinity NDT, our Magnetic Particle Testing (MPI) service routinely includes a residual field check at the conclusion of the inspection. If the field is above the specified limit, our technicians proceed to demagnetisation as part of the job.Not as an afterthought or an add-on.

For components that arrive from other MPI facilities — as this shaft did today. We provide standalone demagnetisation as a specialist service. We measure, treat, verify, and document. The client leaves with both the demagnetised component and the formal test record.

Our Demagnetisation Service — What We Offer

If you have a component that needs demagnetisation. Whether it has just come through MPI, is going into assembly, or is heading for welding repair. Here is what our service includes:

Initial residual field measurement: Full mapping of the component surface before treatment. Not a single spot check, but a systematic survey at multiple points. This gives the baseline reading and identifies zones of concentrated retention.

Treatment: AC coil and/or portable yoke demagnetisation using parameters optimised for the component’s dimensions, geometry, and material. If a standard single-pass treatment is insufficient — as today’s shaft demonstrated — we adapt the approach until the result meets the specification.

Post-treatment verification: Full re-survey of the component surface with the calibrated Gaussmeter. Every measurement point recorded.

Formal Demagnetisation Test Record: Issued with every job. Contains all readings, equipment identification, operator details, treatment parameters, and final acceptance statement. Suitable for inclusion in your Material Data Report (MDR) or quality records.

On-site service available: For large structures, installed equipment, or high-volume production requirements, our technicians can come to your facility with portable demagnetisation and Gaussmeter equipment. We operate from our NDT Labs across Peenya, Bangalore, and across India.

Enquire about our Demagnetisation Service →

Also see: Magnetic Particle Testing (MPI) Services →

The Shaft Leaves. The Learning Stays.

By end of day today, the shaft that arrived carrying 10 Gauss of residual magnetism left our facility in compliance. Below 3 Gauss, verified, documented, and ready for assembly.

The client had been worried. They had an MPI certificate from the inspection facility, but when they measured the shaft on their own floor. The field reading alarmed their assembly engineer. They called us, brought the shaft in, and we sorted it.

This is exactly the kind of problem that a dedicated, experienced demagnetisation team is here to solve. Not every job goes perfectly on the first pass. The steel doesn’t care about your procedure document — it only responds to the physics. Understanding those physics, and having the patience and skill to apply the right technique until the reading drops, is what separates a professional demagnetisation service from one that hands back a still-magnetised component with a rubber stamp.

If your components carry residual magnetism — or if you are simply not sure whether they do — call us or WhatsApp us at +91 98441 29439 and we will advise you on the fastest and most cost-effective path to getting them into compliance.

About Trinity NDT WeldSolutions: Trinity NDT WeldSolutions Pvt. Ltd. is India’s NABL ISO/IEC 17025:2017 accredited and NADCAP Aerospace Merit accredited NDT laboratory at Peenya Industrial Area, Bangalore. We provide Ultrasonic Testing, Magnetic Particle Testing, Liquid Penetrant Testing, Radiographic Testing, Eddy Current Testing, Visual Testing, Positive Material Identification, Hardness Testing, Demagnetisation, Ultrasonic Cleaning, Vapour Degreasing, and advanced NDT (PAUT/TOFD). NDT Level I & II certification training since 2001. 4.8★ Google Rating | 1,200+ reviews | 45+ countries served.

📞 +91 98441 29439 | 📧 info@trinityndt.com | www.trinityndt.com | Peenya Industrial Area, Bangalore 560058

The post The Shaft That Refused to Let Go — A Demagnetization Case Study from Our Lab appeared first on Trinity NDT WeldSolutions Private Limited.

Here is the complete blog post — written in the authentic voice of a 30-year welding engineering veteran:

When Is PWHT Mandatory for Carbon Steel Welds? A Welding Engineer’s Practical Guide

By Ravi Kumar Thammana | IWE | ASNT Level III | CEO, Trinity NDT WeldSolutions Pvt. Ltd., Bangalore Published: March 2026 | Reading Time: 8 minutes

I want to start with a story.

A few years ago, a fabrication shop in Pune called us in a panic. They had completed a pressure vessel for a petrochemical client — P265GH carbon steel, 38mm wall thickness, fully welded, hydrotest passed, NDT cleared. The vessel was sitting in their yard, ready for dispatch.

Their client’s inspector arrived and asked one question:

“Where is your PWHT record?”

The fabricator had not performed PWHT. Nobody had told them it was required. The WPS didn’t mention it. The shop supervisor assumed that because the material was ordinary carbon steel — not chrome-moly, not stainless — PWHT wasn’t needed.

That vessel had to be stress-relieved before dispatch. Two weeks of delay. ₹4 lakh in additional cost. A near-miss on a critical delivery.

In 25 years of welding engineering, I have seen this mistake more times than I can count. And it almost always comes from the same assumption:

“It’s just carbon steel. PWHT is for exotic materials.”

That assumption is wrong. Dangerously wrong in some applications.

Let me explain exactly when PWHT is mandatory — and why — in plain engineering language.

What Is PWHT and What Does It Actually Do?

Post Weld Heat Treatment (PWHT) is a controlled thermal process in which a completed weld joint is heated to a specified temperature, held at that temperature for a specified time, and then cooled at a controlled rate.

For carbon steel, the typical PWHT temperature range is 595°C to 650°C (1100°F to 1200°F) — well below the lower critical transformation temperature (Ac1), so no metallurgical phase transformation occurs. This is purely a stress-relief operation.

What it achieves:

1. Residual Stress Relief Welding generates intense, localised heat followed by rapid cooling. The surrounding cold metal restrains the contracting weld metal, creating residual tensile stresses — often approaching the yield strength of the material. These stresses are invisible, unmeasurable by conventional NDT, and do not cause immediate failure. But combined with service loads and certain environments (especially hydrogen and wet H2S), they become a primary driver of cracking. PWHT reduces these residual stresses by 85–90%.

2. Hydrogen Diffusion Welding processes — particularly SMAW (stick welding) and FCAW — introduce atomic hydrogen into the weld metal and HAZ. Hydrogen causes delayed cracking (also called cold cracking or hydrogen-induced cracking), which can occur hours or even days after welding is complete. Elevated temperature accelerates hydrogen diffusion out of the joint. PWHT at 200–250°C (dehydrogenation heat treatment) or full PWHT at 595°C+ removes this risk.

3. HAZ Softening and Tempering The heat-affected zone of carbon steel welds, particularly in thicker sections or higher-carbon materials, can contain hard martensitic and bainitic microstructures. These are brittle and susceptible to stress corrosion cracking. PWHT tempers these hard zones, improving toughness and ductility.

4. Dimensional Stability For components that will be machined after welding, PWHT reduces distortion and improves dimensional accuracy.

When Does the Code Say PWHT Is Mandatory?

This is where most fabricators get confused — because the answer is not a single rule. It depends on which code governs your job, the material, the wall thickness, and the service conditions. Let me go through each major scenario.

1. Wall Thickness — The Universal Trigger

Regardless of service conditions, every major fabrication code mandates PWHT above a certain wall thickness. For carbon steel:

Let me emphasise B31.1 and B31.3 here — the threshold is 19mm, not 38mm. I have seen fabricators apply the Section VIII 38mm rule to their B31.1 piping jobs. That is incorrect and non-compliant. Always check the specific code governing your job.

2. Carbon Equivalent (CE) — The Often-Ignored Trigger

Carbon equivalent is a formula that combines the effect of carbon and other alloying elements on hardenability. High CE materials are more susceptible to hydrogen cracking, harder HAZ formation, and brittle fracture.

The most common formula (IIW):

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

For carbon steel, when CE exceeds 0.45, both preheat and — in thicker sections — PWHT become critical. Many “standard” carbon steels like IS 2062 Grade B or ASTM A516 Grade 70 can have CE values of 0.42–0.48 depending on the heat. Always get the material test certificate (MTC) and calculate CE before writing your WPS.

3. Sour Service / Hydrogen-Containing Environments — Non-Negotiable

This is where PWHT transitions from a code requirement to a metallurgical necessity.

NACE MR0175 / ISO 15156 — the governing standard for equipment exposed to wet H2S (sour service in oil and gas) — mandates strict hardness limits: maximum 22 HRC (248 HBW) anywhere in the weld metal, HAZ, or base metal.

In practice, for carbon steel welds in sour service, achieving sub-22 HRC in the HAZ is extremely difficult without PWHT — especially in wall thicknesses above 12–15mm. The rapid cooling rates in the HAZ during welding promote hard microstructures, regardless of preheat.

For any carbon steel component that will be in contact with produced fluids, process streams containing H2S, or any wet sour environment — treat PWHT as mandatory, regardless of thickness. The consequence of getting this wrong is not a delayed delivery — it is catastrophic cracking, leaks, and potential fatality.

4. Impact Testing Requirements

When a design requires Charpy impact testing (toughness qualification) at low temperatures — such as for pressure vessels operating below 0°C, or LNG-related applications — PWHT is typically required as part of the WPS qualification to achieve the required toughness values in the HAZ.

If your WPS was qualified without PWHT and your job now requires impact testing, your WPS is not valid for that application. A new WPS with PWHT must be qualified.

5. Specific Materials — Even at Low Thickness

Certain carbon and low-alloy steels require PWHT at much lower thicknesses due to their chemistry:

• P-No.1 Group 2 (higher carbon content, e.g. A516 Gr.70 thick plates, A105 flanges) — some specifications require PWHT above 16mm
• Chrome-Moly steels (P-No.4, P-No.5) — PWHT is always mandatory regardless of thickness, though technically these are low-alloy steels, not plain carbon steels
• High-carbon content repair welds on castings or forgings — always require PWHT

Common Misconceptions I Encounter Every Week

“Our material is A36 structural steel — PWHT is not needed.” Correct for general structural work under AWS D1.1. Incorrect if the same structure carries cyclic loads, operates in a corrosive environment, or has specific code requirements imposed by the end-user.

“We did preheat — that means we don’t need PWHT.” Preheat and PWHT serve different purposes. Preheat controls cooling rate during welding and reduces hydrogen cracking risk. PWHT relieves residual stresses after welding is complete. In thick sections and sour service, you need both — they are not interchangeable.

“The weld passed UT and RT — there are no defects, so PWHT is unnecessary.” RT and UT detect existing defects. They cannot detect residual stress magnitude. A weld can be completely clean on RT and UT and still fail in service due to stress corrosion cracking if PWHT was not performed. These are different failure mechanisms.

“PWHT will distort our component.” Possible — but manageable with proper fixturing, controlled heating rates, and engineering. The distortion risk from PWHT is far smaller than the integrity risk from skipping it in a mandatory application.

Practical Checklist — Should Your Carbon Steel Weld Be PWHT’d?

Work through this list before finalising your WPS:

☑ Identify your governing code — ASME VIII, B31.1, B31.3, EN 13445, AWS D1.1, or client spec ☑ Check wall thickness against code mandatory threshold (19mm for B31.1/B31.3; 38mm for Section VIII Div.1) ☑ Calculate Carbon Equivalent (CE) from MTC — above 0.45 warrants serious PWHT consideration ☑ Confirm service environment — any H2S, wet sour, hydrogen-containing service = PWHT mandatory ☑ Check design temperature — sub-zero service requires impact testing, which typically requires PWHT qualification ☑ Review client specification — client specs often impose PWHT at lower thresholds than code minimum (always check) ☑ Review repair weld requirements — repair welds on existing equipment often have stricter PWHT requirements than original fabrication

If you answer YES to any of the above — PWHT is required. Do not proceed without it.

PWHT Parameters for Carbon Steel — Quick Reference

When PWHT is required for P-No.1 carbon steel per ASME BPVC:

Final Thought

PWHT is not a bureaucratic formality. It is not something you do to satisfy an inspector and forget about. It is a critical metallurgical process that directly determines whether your weld joint will survive its intended service life — or fail prematurely, sometimes catastrophically.

The 30-year-old pressure vessel still in service. The pipeline that has never leaked. The aircraft component that has never cracked. These outcomes are not accidents. They are the result of engineering decisions made correctly at the fabrication stage — including the decision to perform PWHT when the code, the material, and the service conditions demand it.

When in doubt — perform PWHT. The cost of a stress-relief cycle is a fraction of the cost of a failure investigation, a recall, or a tragedy.

Ravi Kumar Thammana is the CEO and co-founder of Trinity NDT WeldSolutions Pvt. Ltd., Bangalore — India’s only NADCAP and NABL dual-accredited NDT and welding centre. He holds ASNT Level III certifications in UT, RT, MT, PT, VT, and ET; NAS 410 Level III for aerospace NDT; and is an International Welding Engineer (IWE) certified by the International Institute of Welding. With over 25 years in welding engineering, NDT, and quality assurance across aerospace, oil & gas, pressure vessels, and structural fabrication, he has qualified over 16,000 NDT and welding professionals across 45 countries.

📞 Training & Consulting: +91 98441 29439 | 🌐 www.trinityndt.com | ✉️ info@trinityndt.com

Free WPS, PQR, and NDT procedure templates available for download at www.trinityndt.com/ndt-procedures-and-report-formats

Tags: PWHT | Carbon Steel Welding | ASME B31.3 | Pressure Vessel Fabrication | Weld Procedure | Sour Service | Hydrogen Cracking | Residual Stress | ISO 3834 | Welding Quality | NDT India | Trinity NDT

The post When Is PWHT Mandatory for Carbon Steel Welds? A Welding Engineer’s Practical Guide appeared first on Trinity NDT WeldSolutions Private Limited.

The post ASTM E1444 Key Changes from 2016 to 2025 edition | Trinity NDT Blog appeared first on Trinity NDT WeldSolutions Private Limited.

Guide for Industrial Radiography Artifacts

All indications appearing in a radiograph are to be interpreted. Interpretation requires analysing the indication as to whether it is a true indication due to discontinuities or a false indication due to problems with film manufacturing, mishandling of film or poor storage. The interpreter should be able to distinguish a relevant discontinuity from a false indication.

No image in the area of interest must obscure the true indication. All false indications appearing in the area must be re-radiographed for interpretation. All true indications are interpreted and characterized.

In Industrial radiography, false indications are also called artifacts, which may form due to improper handling of film, lead screens or cassettes during any stage of the radiographic process. Common artifacts include: 

Static marks

Branchlike, jagged dark lines or irregular dark spots originating from rapid loading or unloading of film.

Pressure marks

produced by extreme pressure on an area of film.• Chemical stain – streaks on the film caused by inadequate removal of chemicals between processing stages or insufficient agitation of the film hanger.

Crimp marks

Caused by abrupt bending of film; typically crescent shaped. • Water mark – circular pattern caused by water droplets drying on the film surface. 

Reticulation

Formation of a network of wrinkles or cracks in a photographic emulsion. 

Dichoric fog

A stain visible under reflected or transmitted light due to improper development. 

Frilling of emulsion

Loosening of the emulsion from the film base due to warm or exhausted fixer solution, high temperature of processing solutions or prolonged washing in warm water. 

Scratches

Caused by abrasive materials or rough handling, including fingernails.

Damaged lead screens – Includes scratches on lead foil screens

Damaged or reused cassette – may cause a false indication to reappear after processing if the same cassette is used. However, the indication will probably move slightly because cassette placement is usually not exact.

Conclusion

The above guide may not be complete and exhaustive. Radiography Film Artifacts are common while processing the films. As long as they do not interfere with interpretation they can be ignored. If the artifacts are masking the relevant flaw indications it is better to re-shoot the same spot radiography.

Artifacts are not only appear in manual processing. There are artifacts in automatic processing such as PI Lines due to scratched on the rollers.

Proper precautions can minimize the artifacts in Industrial Radiography service and may not be completely avoidable. Visit us to know more about NDT testing services.

The post Guide for Industrial Radiography Artifacts appeared first on Trinity NDT WeldSolutions Private Limited.

The post Guide for Industrial Radiography Artifacts appeared first on Trinity NDT WeldSolutions Private Limited.

Types of Weld Repairs

Weld repairs can be divided into two specific areas:
1 Production
2 In-service

Reasons For Weld Repair

The reasons for making a repair are many and varied, from the removal of weld defects induced during manufacture to a quick and temporary running repair to an item of production plant. In these terms, the subject of welding repairs is also wide and varied and often confused with maintenance and refurbishment where the work can be scheduled.

Repair Welding is Unplanned

With planned maintenance and refurbishment, sufficient time can be allowed to enable the tasks to be completed without production pressures being applied. In contrast, repairs are usually unplanned and may result in shortcuts being taken to allow the production programme to continue. It is, therefore, advisable for a fabricator to have an established policy on repairs and to have repair methods and procedures in place.

Welding Processes for Repairs

The manually controlled welding processes are the easiest to use, particularly if it is a local repair or one to be carried out on site. Probably the most frequently used of these processes is MMA as this is versatile,
portable and readily applicable to many alloys because of the wide range of off-the-shelf consumables. Repairs almost always result in higher residual stresses and increased distortion compared with first time welds. With C-Mn and low/medium alloy steels, the application of pre and post weld heat treatments may be required.

Key Factors to be Considered Before Weld Repairs

There are a number of key factors that need to be considered before undertaking any repair. The most important being a judgement as to whether it is financially worthwhile. Before this judgement can be made, the
fabricator needs to answer the following questions:
• Can structural integrity be achieved if the item is repaired?
• Are there any alternatives to welding?
• What caused the defect and is it likely to happen again?
• How is the defect to be removed and what welding process is to be used?
• Which NDT method is required to ensure complete removal of the defect?
• Will the welding procedures require approval/re-approval?
• What will be the effect of welding distortion and residual stress?
• Will heat treatment be required?
• What NDT is required and how can acceptability of the repair be demonstrated?
• Will approval of the repair be required – if yes, how and by whom?

How difficult to carryout weld repairs?

Although a weld repair may be a relatively straightforward activity, in many instances it can be quite complex and various engineering disciplines may need to be involved to ensure a successful outcome.
It is recommended that ongoing analysis of the types of defect is carried out by the QC department to discover the likely reason for their occurrence (material/process or skill related).

Things to be considered before carrying out weld repairs

In general terms, a welding repair involves:
• A detailed assessment to find out the extremity of the defect. This may involve the use of a surface or sub-surface NDT methods.
• Cleaning the repair area, (removal of paint grease etc).
• Once established the excavation site must be clearly identified and marked out.
• An excavation procedure may be required (method used ie grinding, arc/air gouging, preheat requirements etc).
• NDT testing to locate the defect and confirm its removal.
• A welding repair procedure/method statement with the appropriate* welding process, consumable, technique, controlled heat input and interpass temperatures, etc will need to be approved.
• Use of approved welders.
• Dressing the weld and final visual inspection.
• NDT procedure/technique prepared and carried out to ensure that the defect has been successfully removed and repaired.
• Any post repair heat treatment requirements.
• Final NDT procedure/technique prepared and carried out after heat treatment requirements.
• Applying protective treatments (painting etc as required).
*Appropriate means suitable for the alloys being repaired and may not apply in specific situations.

Production Weld repairs

Repairs are usually identified during production inspection. Evaluation of the reports is carried out by the Welding Inspector, or NDT operator. Discontinuities in the welds are only classed as defects when they are
outside the range permitted by the applied code or standard. Before the repair can commence, a number of elements need to be fulfilled.

Analysis before commencement of Weld Repair

As this defect is surface-breaking and has occurred at the fusion face the problem could be cracking or lack of sidewall fusion. If the defect is found to be cracking the cause may be associated with the material or the welding procedure, however if the defect is lack of sidewall fusion this can be apportioned to the lack of skill of the welder.

Assessment

In this particular case as the defect is open to the surface, magnetic particle inspection (MPI) or dye penetrant inspection (DPI) may be used to gauge the length of the defect and ultrasonic testing (UT) used to gauge the depth. In addition for volumetric type flaws such as blow holes and slag it is good opt for X-ray radiography testing.

A typical defect is shown below:

Excavation – Removal of Defective area prior to weld repair

If a thermal method of excavation is being used ie arc/air gouging it may be a requirement to qualify a procedure as the heat generated may have an effect on the metallurgical structure, resulting in the risk of cracking in the weld or parent material.

Is Preheat Necessary?

To prevent cracking it may be necessary to apply a preheat based on carbon content of the base material and filler materials. High carbon and high alloy steels needs preheat to avoid cracking at later stages of repair.
The depth to width ratio shall not be less than 1 (depth) to 1 (width), ideally 1 (depth) to 1.5 (width) would be recommended (ratio: depth 1 to width 1.5).

Cleaning of the excavation

At this stage grinding of the repair area is important, due to the risk of carbon becoming impregnated into the weld metal/parent material. It should be ground back typically 3 to 4mm to bright metal.

Confirmation of Removal of Defective area

At this stage NDT should be used to confirm that the defect has been completely excavated from the area.

Re-welding of the excavation

Prior to re-welding of the excavation a detailed repair welding procedure/method statement shall be approved.

NDT confirmation of successful repair

After the excavation has been filled the weldment should then undergo a complete retest using the same NDT inspection techniques as previously used to establish the original repair.

This is carried out to ensure no further defects have been introduced by the repair welding process. NDT may also need to be further applied after any additional postweld heat treatment has been carried out.

In-service Weld Repairs

Most in-service repairs can be of a very complex nature as the component is very likely to be in a different welding position and condition than it was during production.

It may also have been in contact with toxic or combustible fluids hence a permit to work will need to be sought prior to any work being carried out. The repair welding procedure may look very different to the original production procedure due to changes in these elements.

Other factors may also be taken into consideration, such as the effect of heat on any surrounding areas of the component, ie electrical components, or materials that may become damaged by the repair procedure. This may also include difficulty in carrying out any required pre- or post-welding heat treatments and a possible restriction of access to the area to be repaired.

For large fabrications it is likely that the repair must also take place on site without a shutdown of operations, which may bring other elements that need to be considered. Repair of in-service defects may require consideration of these and many other factors, and as such are generally considered more complicated than production repairs.

Joining technologies often play a vital role in the repair and maintenance of structures. Parts can be replaced, worn or corroded parts can be built up, and cracks can be repaired.

When a repair is required it is important to determine two things: Firstly, the reason for failure and, secondly, can the component be repaired? The latter point infers that the material type is known.

For metals, particularly those to be welded, the chemical composition is vitally important. Failure modes
often indicate the approach required to make a sound repair. When the cause-effect analysis, however simple, is not followed through it is often the case that the repair is unsafe –- sometimes disastrously so.

In many instances, the Standard or Code used to design the structure will define the type of repair that can be carried out and will also give guidance on the methods to be followed. Standards imply that when designing or
manufacturing a new product it is important to consider a maintenance regime and repair procedures. Repairs may be required during manufacture and this situation should also be considered.

Normally there is more than one way of making a repair. For example, cracks in cast iron might be held together or repaired by pinning, bolting, riveting, welding, or brazing. The method chosen will depend on factors such as the reason for failure, material composition and cleanliness, environment and the size and shape of the component.

It is very important that repair and maintenance welding are not regarded as activities, which are simple or straightforward. In many instances a repair may seem undemanding but the consequences of getting it wrong can be catastrophic failure with disastrous consequences.

Is welding the best method of repair?

If repair is called for because a component has a local irregularity or a shallow defect, grinding out any defects and blending to a smooth contour might be acceptable.

It will certainly be preferable if the steel has poor weldability or if fatigue loading is severe. It is often better to reduce the so called factor of safety slightly, than to risk putting defects, stress concentrations and residual stresses into a brittle material.

In fact brittle materials – which can include some steels (particularly in thick sections) as well as cast irons – may not be able to withstand the residual stresses imposed by heavy weld repairs, particularly if defects are not all
removed, leaving stress concentrations to initiate cracking.

Is the repair like earlier repairs?

Repairs of one sort may have been routine for years, but it is important to check that the next one is not subtly different.

For example, the section thickness may be greater; the steel to be repaired may be different and less weldable, or the restraint higher. If there is any doubt, answer the remaining questions.

What is the composition and weldability of the base metal?

The original drawings will usually give some idea of the steel involved, although the specification limits may then have been less stringent, and the specification may not give enough compositional details to be helpful.

If sulphur-bearing free-machining steel is involved, it could give hot cracking problems during welding.

If there is any doubt about the composition, a chemical analysis should be carried out. It is important to analyse for all elements, which may affect weldability (Ni, Cr, Mo, Cu, V, Nb and B) as well as those usually, specified
(C, S, P, Si and Mn).

A small cost spent on analysis could prevent a valuable component being ruined by ill-prepared repairs or, save money by reducing or avoiding the need for preheat if the composition were leaner than expected. Once the
composition is known, a welding procedure can be devised.

What strength is required from the repair?

The higher the yield strength of the repair weld metal, the greater the residual stress level on completion of welding, risk of cracking, clamping needed to avoid distortion and more difficulty in formulating the welding
procedure. In any case, the practical limit for the yield strength of conventional steel weld metals is about 1000N/mm2.

Can preheat be tolerated?

Not only does a high level of preheat make conditions more difficult for the welder; the parent steel can be damaged if it has been tempered at a low temperature. In other cases the steel being repaired may contain items which are damaged by excessive heating.

Preheat levels can be reduced by using consumables of ultra-low hydrogen content or by non-ferritic weld metals. Of these, austenitic electrodes may need some preheat, but the more expensive nickel alloys usually do not. However, the latter may be sensitive to high sulphur and phosphorus contents in the parent steel if diluted into the weld metal.

Can softening or hardening of the HAZ be tolerated?

Softening of the HAZ is likely in very high strength steels, particularly if they have been tempered at low temperatures. Such softening cannot be avoided, but its extent can be minimised. Hard HAZs are particularly
vulnerable where service conditions can lead to stress corrosion. Solutions containing H2S (hydrogen sulphide) may demand hardness below 248HV (22HRC) although fresh aerated seawater appears to tolerate up to about
450HV. Excessively hard HAZs may, therefore, require PWHT to soften them but provided cracking has been avoided.

Is Post Weld Heat Teatment (PWHT) practicable?

Although it may be desirable, PWHT may not be possible for the same reasons that preheating is not. For large structures, local PWHT may be possible, but care should be taken to abide by the relevant codes, because
it is too easy to introduce new residual stresses by improperly executed PWHT.

Is PWHT necessary?

PWHT may be needed for one of several reasons, and the reason must be known before considering whether it can be avoided.

Will the fatigue resistance of the repair be adequate?

If the repair is in an area which is highly stressed by fatigue and particularly if the attempted repair is of a fatigue crack, inferior fatigue life can be expected unless the weld surface is ground smooth and no surface defects are left.

Fillet welds, in which the root cannot be ground smooth, are not tolerable in areas of high fatigue stress.

Will the repair resist its environment?

Besides corrosion, it is important to consider the possibility of stress corrosion, corrosion fatigue, thermal fatigue and oxidation in-service.

Corrosion and oxidation resistance usually require the composition of the filler metal is at least as noble or oxidation resistant as the parent metal. For corrosion fatigue resistance, the repair weld profile may need to be
smoothed.To resist stress corrosion, PWHT may be necessary to restore the correct micro-structure, reduce hardness and the residual stress left by the repair.

Can the repair be inspected and tested?

For onerous service, radiography and/or ultrasonic examination are often desirable, but problems are likely if stainless steel or nickel alloy filler is used; moreover, such repairs cannot be assessed by Magnetic particle Inspection. In such cases, it is particularly important to carry out the procedural tests for repairs very critically, to ensure there are no risks of cracking and no likelihood of serious welder-induced defects.

Indeed, for all repair welds, it is vital to ensure that the welders are properly motivated and carefully supervised.

As-welded repairs

Repair without PWHT is, of course, normal where the original weld was not heat treated, but some alloy steels and many thick-sectioned components require PWHT to maintain a reasonable level of toughness, corrosion
resistance, etc. However, PWHT of components in-service is not always easy or even possible, and local PWHT may give rise to more problems than it solves except in simple structures.

The post Weld Repairs during Production and In-service Maintenance appeared first on Trinity NDT WeldSolutions Private Limited.

Basic Standard for QMS

   ISO 9001 -2000

Manufacturing

   ISO 3834, EN 1011, ISO 5817

Personnel

   ISO 9606, EN 287, ISO 14731, ISO 14732

Procedures

   ISO 15607 – 15614

Testing and Inspection Personnel

   ISO 9712, EN 1289

Basis for ISO 3834  series of welding standards

As is well known, weld quality is achieved by sound welding, not by inspection. Inspection, however, provides a check of the reliability of the product, but cannot improve poor quality. Therefore, welding requires continuous control and/or to follow documented procedures. Certifications such as ISO3834 can build a robust quality management systems thus attracting more customers.

Genesis of ISO-3834

A member of the International Union of Technical Associations and Organisations (UTAO), IIW is a part of the International Council for Engineering and Technology (ICET), one of the twelve key formal umbrella organisations associated with UNESCO.

The experts of International Institute of Welding (IIW) have supplied the technical basis of the great majority of welding standards issued by the International Standards Organisation – ISO.

Since 1989, IIW has been recognised by ISO as an International Standardisation Body to prepare the final texts of international welding standards.

Criteria of selection of part of  the standard

• Financial loss
• Loss to human life
• Repair cost
• Loads- static and dynamic

Application of ISO 3834

• Certification of companies in accordance with ISO – 3834 Parts 2, 3 or 4
• Certification of personnel in accordance with ISO 14731

What is ISO 3834?

ISO3834 is an international standard created by welding professionals. ISO 9001 provides the requirements for a quality management system; it does not establish requirements for products. The standard on the other hand, does provide the quality requirements for a welded product.

It specifies requirements relating only to the quality of the welded product. Encourages a proactive process orientated approach to managing and controlling welding   product quality in a workshop or on site. Also, gives a Factory Control System to control activities for the manufacture of the product.

Why adopt ISO 3834 when we have ISO 9001?

ISO 9001 is a comprehensive standard that lays down quality management system requirements for any organisation. However, the standard does not prescribe specific details for “special processes”. Welding is regarded as a ‘special process’. ISO 3834 was developed to identify all factors that could affect the quality of welded product and which need to be controlled at all stages, before, during and after welding.

What are the benefits of specifying the ISO 3834 Standard for the purchaser & supplier?

• More assurance of contract delivery dates
• Greater assurance of the quality of welded products
• Greater reliability and performance of plant
• Reduction in maintenance costs
• Reduction or elimination of third party inspection costs
• More competent suppliers of welded products

What are the benefits of using the ISO 3834 Standard for the manufacturer?

• Less rework
• Jobs completed on time
• Local and international recognition as a competent organisation
• Meet the welding-related requirements of ISO 9001
• More efficient coordination of welding activities
• More pro-active and responsible workforce
• Increased opportunities and capability to bid on jobs
• Cost savings – more efficient technology
• Reduced surveillance audits and inspections by purchasers with significant savings

What are the benefits of using the ISO 3834 Standard for the individual employees?

• Helps to do the job more satisfactorily
• Greater job security
• Higher regard by other people
• Professional recognition
• Satisfied employer and customer
• More rewarding job position
• Develops team spirit

How important are welding personnel?

A key feature of ISO 3834 is the requirement to ensure that people with welding responsibilities are competent to discharge those responsibilities. This is achieved by incorporation of another standard, namely, ISO 14731 “Welding coordination – Tasks and responsibilities”. The specifying of minimum requirements for personnel dealing with welding coordination and welding inspection personnel.

What is the definition of a manufacturer as per standard?

ISO 3834 defines a manufacturer as a ‘person or organization responsible for the welding production’.

The Standard uses this term to describe any such organisation, including manufacturing organisations supplying welding services, either for new products or for repair and maintenance, as well as others where the application of the requirements of ISO 3834 are relevant.

A manufacturer may be involved in manufacture, fabrication, construction, repair or maintenance.

What are the types of manufacturing organisation that ISO 3834 can be applied to?

Fabrication companies

• Construction companies – on-site work

• Repair and maintenance contractors

• Manufacturers of products

• Welding workshops on sites under the same technical and quality management

• Owners of plant with their own workshop(s)

What are the types of other organisation that ISO 3834 can be applied to?

Asset owners without own workshops, both private and government

• Project management companies

• Design companies

• Consultants

• Government agencies

Those which, though not creating welded product themselves, are specifying or requiring such work from others and are thus involved in weld design, contract development, and review of technical requirements and competencies of subcontractors

How many parts does ISO 3834 have?

• ISO 3834: 2005 “Quality requirements for fusion welding of metallic materials” consists of 6 parts:
• ISO 3834-1:2005, Criteria for the selection of the appropriate level of quality requirements
• ISO 3834-2:2005, Comprehensive quality requirements
• ISO 3834-3:2005, Standard quality requirements
• ISO 3834-4:2005, Elementary quality requirements
• ISO 3834-5:2005, Applicable documentation (not full title)
• ISO/TR 3834-6:2007, Guidelines on implementing ISO 3834

How does ISO 3834 link in with ISO 9001?

ISO 3834 does not replace ISO 9001 as a quality management system. However, it contains many attributes that will be important for a welding manufacturer, in both workshops and at field installation sites, seeking ISO 9001 certification. Elements of ISO 9001 should be considered when implementing ISO 3834 quality requirements and seeking ISO 3834 certification. The specific complementary elements of ISO 9001 are detailed in ISO 3834.

What are the main welding requirements covered in ISO 3834 ?

Review of requirements

• Technical review

• Subcontracting

• Welding personnel

– Welders and welding operators, Welding coordination personnel

• Inspection & testing personnel

– Welding Inspection personnel; Non-destructive testing personnel

• Equipment

– Production and testing equipment; Description of equipment; Suitability of equipment; New

equipment; Equipment maintenance

Welding and related activities

– Production planning; Welding procedure specifications (WPS); Qualification of the welding

procedures; Work instructions; Procedures for preparation and control of documents

• Welding Consumables

– Batch testing; Storage and handling

• Storage of parent materials

• Post-weld heat treatment

Inspection and testing

– Inspection & testing before welding; Inspection & testing during welding; Inspection & testing after

welding; Inspection & test status

• Non-conformance and corrective actions

• Calibration and validation of measuring, inspection and testing equipment

• Identification & traceability

• Quality records

Selection of Welding Quality Requirement as per ISO:3834

Comparison of Welding quality requirements with regard to ISO 3834-2, 3834-3  & 3834-4

How do Manufacturers select the Appropriate Part of ISO 3834?

A balanced decision needs to be taken based on the following, related to products & processes:

• The extent and significance of safety-critical products
• The complexity of manufacture
• The range of products manufactured
• The range of different materials used
• The extent to which metallurgical problems may occur
• The extent to which manufacturing imperfections e.g. misalignment, distortion or weld imperfection, affect product performance
• Service condition (Dynamic loading, fatigue, low/high Temperature, corrosion)
• The welding processes adopted, their level of sophistication and automation

Suggested Steps for Implementation of ISO 3834 by an Organisation

• Gap Analysis to identify action areas for  System, training and resources
• Upgradation of System based on above
• Personnel Training for competence
• Assessment of additional Resources if any
• Internal Audit to close NCR’s
• Management Review
• Trial operation to stabilise system
• Application for Certification to Certification Body

Gap Analysis internally by the Organisation against requirements of ISO 3834 & ISO 14731

• ISO 9001 systems if existing or desired and compare with the present system.
• System requirements for applicable part of 3834 (2, 3 or 4) as determined previously and detailed in next three slides.
• Identify each area as per check list for gaps between required/desired level and actual status recorded.
• May take assistance from Consultants or Certifying bodies for this step
• Management corrective action to close the non conformities

To check for Gaps –

Requirements in ISO 3834 & Essential Tasks of  Welding Coordination Personnel in ISO 14731

1.Review of requirements & Technical review to understand parent material specification and welded joint properties, quality and acceptance requirements, etc.

2.Subcontracting Supplier to be treated as extension of manufacturers facility

3.Welding personnel Welders and welding operators, Welding coordination personnel

4.Inspection & testing personnel Welding Inspection personnel; Non-destructive testing personnel

5.Equipment: Production and testing equipment; Description of equipment; Suitability of equipment; New equipment; Equipment maintenance

6.Welding and related activities: Production planning; Welding procedure specifications (WPS); Process Qualification of the welding (WPQR); Work instructions;

7.Welding Consumables: Batch testing; Storage and handling

8.Storage of parent materials

9.Post-weld heat treatment

10. Inspection and NDT testing: Inspection & testing before welding; Inspection & testing during welding; Inspection & testing after welding; Inspection & test status

11.Non-conformance and corrective actions ¬ Learning from experience

12.Calibration and validation of measuring, inspection and testing equipment

13.Identification & traceability

14.Quality records

How important are welding personnel?

A key feature of ISO 3834 is the requirement to ensure that people with welding responsibilities are competent to discharge those responsibilities.

This is achieved by incorporation of another standard, namely, ISO 14731 ‘Welding coordination – Tasks and responsibilities’

The specifying of minimum requirements for personnel dealing with welding coordination and welding inspection personnel

The Human Resource

­Without an appropriate specific technical competence (intended as a combination of knowledge, experience and attitude) no management system can be successful in the manufacturing of any product. ­

A great importance has been entrusted to the Welding Coordinator, who has become the real “key element” around whom all the welding production process works.

ISO 14731 Requirements for Welding Co-ordination Personnel

Welding Co-ordination :

   – Manufacturing operations for all welding and welding related activities

  – The sole responsibility of the manufacturer

  – May be sub-contracted

  – May be carried out by more than one person

Welding Co-ordinator

– Responsible and competent person

– Specified tasks and responsibilities

– Qualified for each task

Welding Inspection

– Is part of welding co-ordination

Role of the Responsible Welding Co-ordinator

The company shall nominate at least one Responsible Welding Co-ordinator ( RWC ). He must be competent to make decisions and sign on behalf of the manufacturer.

The RWC must be authorised with the overall responsibility for monitoring welding activities as well as taking action when welding has not been correctly performed. May also be responsible for the work of other welding co-ordinators in the in the same department / site.

RWC may be to an individuals normal job title eg, Technical Manager, QC Manager, Production Manager etc.

IIW International Diploma Qualifications for Welding Co-ordination Personnel

International Welding Engineer ( IWE )

International Welding Technologist ( IWT )

International Welding Specialist ( IWS )

International Welding Practitioner ( IWP )

International Welding Inspection Personnel (IWIP)

International Welded Structure Designer ( IWSD )

International Welder ( IW ) – Diploma awarded for Specific process and material & at 3 levels

In India, ANB-India of IIW India is authorised to award the above diplomas. Contact IIW India.

ISO 14731 Gradation of Responsible Welding Coordinators

Three different levels of RWC are given. The selection of RWC depends mainly on the variability and technical complexity of the welding procedures required.

How can Trinity NDT Can Help you in ISO3834 certifications?

Center of Welding – Trinity NDT provides comprehensive consulting services for ISO3834 certifications. Being an associate of The Indian Institute of Welding – IIW India, can hand hold organizations in the process of certification.

This includes, quality manual preparation, establishing wps, documentation, QMS implementation, Gap analysis from ISO9001 to ISO3834, NDT Level II personnel certification. Also provide welding coordinator services by our IWE experts. Also an IBR approved Welding & NDT Lab in Bangalore.

Let us know your requirement. Contact Trinity NDT today.

The post ISO3834 Quality Management in Welding Companies appeared first on Trinity NDT WeldSolutions Private Limited.

Penetrant Testing(PT) is also called as Dye Penetrant inspection(DPT) or Fluorescent Inspection FPI Testing in Aerospace is one of the most widely used Non-destructive Evaluation – NDE method. DPT testing is suitable for inspecting steels, aluminium, stainless steels and other materials for surface opened flaws. In brief, this NDT method is suitable for any non-porous material.

Also, a very reliable method for crack testing on Aerospace components and Aircraft structures. However, detectability depends on technique and penetrant sensitivity. For example: When compared to S2 penetrant, S3 will give better sensitivity. Similarly, fluorescent penetrants give better sensitivity when compared to visible penetrants.

Penetrant inspection method is one of the NDT methods for inspection of Welds, Castings, Forgings and Valves. Also, a very reliable method for in-service inspection to find fatigue cracks on automobile, aerospace, oil and gas pipe lines at economical cost.

Of the surface NDT methods, DPT testing is simple in principle and versatile method. To carry the test, the inspector should have proper level of training and certification in Penetrant testing.

Trinity NDT has compete testing labs for penetrant testing up to aerospace standards and procedures. The unique Aerospace NDT Labs at Bangalore India can perform Method A, C and D and sensitivities S2, S3 and S4. In addition, fluorescent and visible penetrant testing also available to offer. The penetrant testing FPI testing labs have accreditation as per ISO17025:2017 from NABL, Delhi, India.

Penetrant – Type, Methods & Sensitivity | Trinity NDT Labs

Even though it is treated as the simplest NDT method, the test results vary greatly in terms of techniques and sensitivity levels employed. Selection of PT technique normally depends on application of component and sensitivity desired. Penetrant inspection techniques are categorized broadly in to

• Type 1 – Fluorescent Penetrants
• Type 2- Visible Penetrants

And, based on method of removal classified as

• Method A – Water Washable
• Method B – Post Emulsifiable, Lipophilic
• Method C – Solvent Removable
• Method D – Post Emulsifiable, Hydrophilic

Also Penetrant Sensitivities are classified as

• ½
• 1
• 2
• 3
• 4

Developer Types

• Dry
• Wet – Aqueous
• Wet – Non Aqueous

Dry Developers are preferred for Aerospace NDT applications. Solvent removable, Wet Aqueous and Non Aqueous developers also available and used based on NDT procedure. That is to say, contact us with your test sensitivity, we have complete range of testing solutions.

As we are serving Aerospace NDT, our laboratory services have all the above types of penetrants and sensitivities to cater to need based inspections.

NABL ISO17025:2017 Accreditation for our FPI Testing Labs

Accreditation of NDT Labs gives additional confidence in test results to customers. Therefore, Our FPI labs are NABL ISO17025 accredited and meets international standards. In addition, the aerospace FPI testing equipment meets ASTM E 1417 and ASTM E 165. One major advantage with Trinity NDT is, all penetrant testing techniques including Fluorescent, Visible penetrants, Water washable, Post Emulsifiable, Solvent removable penetrants up to sensitivity Level 4 are available. So that we are the one stop solutions providing NDT agency trusted by over 500 customers across India.  

Quick Contact us for your requirements on NDT

Stationery FPI equipment | Aerospace NDT Lab in India

Aerospace sector uses altogether high standards of Penetrant materials. Starting from pre cleaning to final cleaning controlling the parameters in each step is vital. Therefore, PT equipment, procedures, training of personnel has clear impact on test results.

We have the best infrastructure to carry FPI testing of aerospace components. The state of art modern Aerospace FPI testing set up is catering to the needs of customers. Our aerospace penetrant testing lab is one of the best facility available in India.

Pre-cleaning procedures include Ultrasonic Cleaning, Alkaline cleaning and solvent cleaning solutions.

Our NDT facility undertakes Dye penetrant testing DPT testing both onsite and off-site. We have expertise in DP testing of Welds, Pressure vessels and boiler components, cross country pipe lines, Castings, Valves, gears, Turbine blades and critical aircraft engine components. Timely calibrations, Daily control checks using TAM/PSM panels ensures the process controls are intact.

Aerospace FPI Testing Agency In Bangalore India

Our Aerospace FPI testing labs are providing services to CEMILAC, Government of India, HAL, L & T Aerospace and many more. Contact us to outsource your NDT Testing to us. We assure to deliver the best to meet your expectations in terms of Timely delivery, professional services at affordable cost.

Know more about Aerospace NDT FPI testing facilities.

Codes, Standards On Liquid Penetrant Testing

Even though there are numerous standards on Penetrant testing such as ASTM E 165 and ASTM E 1417. Also ASME Section V – Non-destructive Examination, API Codes, AWS codes, BS Standards, EN standards provide acceptance criteria. Trinity NDT – Testing Labs uses procedures that meets international standards, codes and customer specifications.

NDT PT Level II Technicians | PT FPI Services

Trinity NDT maintains its Written practice that meets ASNT SNT TC 1A. We engage only Dye penetrant testing / FPI testing Level II technicians. All the DPT testing procedures are duly approved before starting testing by in house ASNT NDT level III. 

NAS410, ASNT NDT Level III Services | Penetrant Inspection

Trinity NDT have in-house Penetrant Testing ASNT Level III. Every NDT procedure is approved by the Level III to meet client needs. We also provide ASNT NDT Level III services such as preparing NDT procedures, Written Practice for personnel certification and layout setting up of penetrant testing facility.

Why do you need to choose Trinity NDT Labs in Bangalore India ?

• We are the best Liquid dye penetrant inspection services provider in Bangalore.
• Modern testing equipments with S2, S3 & S4 sensitivity penetrants. Water washable, post Emulsifiable penetrants for high sensitivity Aerospace NDT FPI testing. Also suitable for components upto 600mm in size.
• UV black light kits for fluorescent inspection
• Liquid penetrant testing technicians with PT Level I, II ASNT SNT-TC-1A and or IS:13805 certified by ISNT. Also have NAS410 Level 2 in Penetrant testing for Aerospace FPI inspections.
• In house NAS410 & ASNT NDT Level III consultants and experts for providing NDT procedure preparation, approval and consultancy services.
• NDT Level III trainers for conducting NDT Level 1, 2 training and certification courses on Liquid dye penetrant testing and other NDT inspection methods. Read more about Liquid Penetrant Testing Personnel Certifications.
• Strong team of NDT Level 2 certified Technicians and inspectors to provide PT and NDT services across India
• Sales and Supply of Dye penetrant inspection (DPT) chemicals kit, penetrants, cleaners, solvents, developers in Peenya Bangalore. If you want to buy DPT chemicals kit, we are the suppliers in Bangalore with ready stock today. Read more about sales of Liquid Penetrant inspection chemicals kit and consumables.

What is the principle of Dye Penetrant testing?

Dye penetrant testing works on principle of capillary action and blotting action (reverse of capillary action). While Capillary action allows penetrant to enter the surface opened flaws, blotting action brings back penetrant from inside of flaws. As capillary action can work in any direction irrespective of gravity forces, therefore cracks of any direction can be easily detected in DPT testing. Earlier the method is called as ‘Oil and whiting method’.

Dye Penetrant inspection | Applications

Penetrant inspection NDT method has many applications. Following a few of them.

• DPT of weld root run to find root flaws before proceeding for next welding layers
• Castings DP testing to find shrinkage at raisers and other areas
• Pipeline and pressure vessel weld joints after final welding
• Leak testing using penetrant testing for gross leaks
• In-service inspection of gears, shafts, valve castings, forging and plates
• Penetrant Inspection after bending to required angle to find cracks
• PT testing of Boiler tubes, pipes, headers and power plant machinery
• FPI testing of turbine blades for aerospace
• Aircraft Structural skin testing using FPI testing

Training Courses | Penetrant testing PT Level 2 and 3

Want To Learn And Get Certified To NDT Level / II after training course on Penetrant Inspection? You hear it right. We would like to share our experience through QA/QC courses organized at our Training Centre in Bangalore India. We offer these NDT courses since 2001 in Hosur and Mysore as well for the industries in these areas.

Trinity Institute of NDT Technology is a training division of Trinity NDT. The institute in India offers world class NDT courses on Penetrant inspection and other NDT testing methods. The training meets written practice and framed to the requirements of ASNT SNT TC 1A. For upcoming Training & certification schedule on PT inspection Level II course visit our Training Calendar page, fee structure, eligibility criteria for the training courses and register for the courses.

Participants from over 40 countries have benefited from our courses. The following are participants from countries whom the institute trained so far in India. Read reviews on Youtube channel

Sale And Supply Of Penetrant Testing Chemicals

Dye Penetrant and fluorescent penetrant chemicals – Solvent removable penetrants, solvent cleaners, developers, accessories and aluminium cracked samples are stocked and supplied for ready use. Items can be hand picked from our office or couriered with prepayment. Quick Contact us for your requirements on PT chemicals sales

Quick Contact us for your requirements on NDT

The post Penetrant Testing Principle, Types, Techniques and Services appeared first on Trinity NDT WeldSolutions Private Limited.

Penetrant Testing(PT) is also called as Dye Penetrant inspection(DPT) or Fluorescent Inspection FPI Testing in Aerospace is one of the most widely used Non-destructive Evaluation – NDE method. DPT testing is suitable for inspecting steels, aluminium, stainless steels and other materials for surface opened flaws. In brief, this NDT method is suitable for any non-porous material.

Also, a very reliable method for crack testing on Aerospace components and Aircraft structures. However, detectability depends on technique and penetrant sensitivity. For example: When compared to S2 penetrant, S3 will give better sensitivity. Similarly, fluorescent penetrants give better sensitivity when compared to visible penetrants.

Penetrant inspection method is one of the NDT methods for inspection of Welds, Castings, Forgings and Valves. Also, a very reliable method for in-service inspection to find fatigue cracks on automobile, aerospace, oil and gas pipe lines at economical cost.

Of the surface NDT methods, DPT testing is simple in principle and versatile method. To carry the test, the inspector should have proper level of training and certification in Penetrant testing.

Trinity NDT has compete testing labs for penetrant testing up to aerospace standards and procedures. The unique Aerospace NDT Labs at Bangalore India can perform Method A, C and D and sensitivities S2, S3 and S4. In addition, fluorescent and visible penetrant testing also available to offer. The penetrant testing FPI testing labs have accreditation as per ISO17025:2017 from NABL, Delhi, India.

Penetrant – Type, Methods & Sensitivity | Trinity NDT Labs

Even though it is treated as the simplest NDT method, the test results vary greatly in terms of techniques and sensitivity levels employed. Selection of PT technique normally depends on application of component and sensitivity desired. Penetrant inspection techniques are categorized broadly in to

• Type 1 – Fluorescent Penetrants
• Type 2- Visible Penetrants

And, based on method of removal classified as

• Method A – Water Washable
• Method B – Post Emulsifiable, Lipophilic
• Method C – Solvent Removable
• Method D – Post Emulsifiable, Hydrophilic

Also Penetrant Sensitivities are classified as

• ½
• 1
• 2
• 3
• 4

Developer Types

• Dry
• Wet – Aqueous
• Wet – Non Aqueous

Dry Developers are preferred for Aerospace NDT applications. Solvent removable, Wet Aqueous and Non Aqueous developers also available and used based on NDT procedure. That is to say, contact us with your test sensitivity, we have complete range of testing solutions.

As we are serving Aerospace NDT, our laboratory services have all the above types of penetrants and sensitivities to cater to need based inspections.

NABL ISO17025:2017 Accreditation for our FPI Testing Labs

Accreditation of NDT Labs gives additional confidence in test results to customers. Therefore, Our FPI labs are NABL ISO17025 accredited and meets international standards. In addition, the aerospace FPI testing equipment meets ASTM E 1417 and ASTM E 165. One major advantage with Trinity NDT is, all penetrant testing techniques including Fluorescent, Visible penetrants, Water washable, Post Emulsifiable, Solvent removable penetrants up to sensitivity Level 4 are available. So that we are the one stop solutions providing NDT agency trusted by over 500 customers across India.  

Quick Contact us for your requirements on NDT

Stationery FPI equipment | Aerospace NDT Lab in India

Aerospace sector uses altogether high standards of Penetrant materials. Starting from pre cleaning to final cleaning controlling the parameters in each step is vital. Therefore, PT equipment, procedures, training of personnel has clear impact on test results.

We have the best infrastructure to carry FPI testing of aerospace components. The state of art modern Aerospace FPI testing set up is catering to the needs of customers. Our aerospace penetrant testing lab is one of the best facility available in India.

Pre-cleaning procedures include Ultrasonic Cleaning, Alkaline cleaning and solvent cleaning solutions.

Our NDT facility undertakes Dye penetrant testing DPT testing both onsite and off-site. We have expertise in DP testing of Welds, Pressure vessels and boiler components, cross country pipe lines, Castings, Valves, gears, Turbine blades and critical aircraft engine components. Timely calibrations, Daily control checks using TAM/PSM panels ensures the process controls are intact.

Aerospace FPI Testing Agency In Bangalore India

Our Aerospace FPI testing labs are providing services to CEMILAC, Government of India, HAL, L & T Aerospace and many more. Contact us to outsource your NDT Testing to us. We assure to deliver the best to meet your expectations in terms of Timely delivery, professional services at affordable cost.

Know more about Aerospace NDT FPI testing facilities.

Codes, Standards On Liquid Penetrant Testing

Even though there are numerous standards on Penetrant testing such as ASTM E 165 and ASTM E 1417. Also ASME Section V – Non-destructive Examination, API Codes, AWS codes, BS Standards, EN standards provide acceptance criteria. Trinity NDT – Testing Labs uses procedures that meets international standards, codes and customer specifications.

NDT PT Level II Technicians | PT FPI Services

Trinity NDT maintains its Written practice that meets ASNT SNT TC 1A. We engage only Dye penetrant testing / FPI testing Level II technicians. All the DPT testing procedures are duly approved before starting testing by in house ASNT NDT level III. 

NAS410, ASNT NDT Level III Services | Penetrant Inspection

Trinity NDT have in-house Penetrant Testing ASNT Level III. Every NDT procedure is approved by the Level III to meet client needs. We also provide ASNT NDT Level III services such as preparing NDT procedures, Written Practice for personnel certification and layout setting up of penetrant testing facility.

Why do you need to choose Trinity NDT Labs in Bangalore India ?

• We are the best Liquid dye penetrant inspection services provider in Bangalore.
• Modern testing equipments with S2, S3 & S4 sensitivity penetrants. Water washable, post Emulsifiable penetrants for high sensitivity Aerospace NDT FPI testing. Also suitable for components upto 600mm in size.
• UV black light kits for fluorescent inspection
• Liquid penetrant testing technicians with PT Level I, II ASNT SNT-TC-1A and or IS:13805 certified by ISNT. Also have NAS410 Level 2 in Penetrant testing for Aerospace FPI inspections.
• In house NAS410 & ASNT NDT Level III consultants and experts for providing NDT procedure preparation, approval and consultancy services.
• NDT Level III trainers for conducting NDT Level 1, 2 training and certification courses on Liquid dye penetrant testing and other NDT inspection methods. Read more about Liquid Penetrant Testing Personnel Certifications.
• Strong team of NDT Level 2 certified Technicians and inspectors to provide PT and NDT services across India
• Sales and Supply of Dye penetrant inspection (DPT) chemicals kit, penetrants, cleaners, solvents, developers in Peenya Bangalore. If you want to buy DPT chemicals kit, we are the suppliers in Bangalore with ready stock today. Read more about sales of Liquid Penetrant inspection chemicals kit and consumables.

What is the principle of Dye Penetrant testing?

Dye penetrant testing works on principle of capillary action and blotting action (reverse of capillary action). While Capillary action allows penetrant to enter the surface opened flaws, blotting action brings back penetrant from inside of flaws. As capillary action can work in any direction irrespective of gravity forces, therefore cracks of any direction can be easily detected in DPT testing. Earlier the method is called as ‘Oil and whiting method’.

Dye Penetrant inspection | Applications

Penetrant inspection NDT method has many applications. Following a few of them.

• DPT of weld root run to find root flaws before proceeding for next welding layers
• Castings DP testing to find shrinkage at raisers and other areas
• Pipeline and pressure vessel weld joints after final welding
• Leak testing using penetrant testing for gross leaks
• In-service inspection of gears, shafts, valve castings, forging and plates
• Penetrant Inspection after bending to required angle to find cracks
• PT testing of Boiler tubes, pipes, headers and power plant machinery
• FPI testing of turbine blades for aerospace
• Aircraft Structural skin testing using FPI testing

Training Courses | Penetrant testing PT Level 2 and 3

Want To Learn And Get Certified To NDT Level / II after training course on Penetrant Inspection? You hear it right. We would like to share our experience through QA/QC courses organized at our Training Centre in Bangalore India. We offer these NDT courses since 2001 in Hosur and Mysore as well for the industries in these areas.

Trinity Institute of NDT Technology is a training division of Trinity NDT. The institute in India offers world class NDT courses on Penetrant inspection and other NDT testing methods. The training meets written practice and framed to the requirements of ASNT SNT TC 1A. For upcoming Training & certification schedule on PT inspection Level II course visit our Training Calendar page, fee structure, eligibility criteria for the training courses and register for the courses.

Participants from over 40 countries have benefited from our courses. The following are participants from countries whom the institute trained so far in India. Read reviews on Youtube channel

Sale And Supply Of Penetrant Testing Chemicals

Dye Penetrant and fluorescent penetrant chemicals – Solvent removable penetrants, solvent cleaners, developers, accessories and aluminium cracked samples are stocked and supplied for ready use. Items can be hand picked from our office or couriered with prepayment. Quick Contact us for your requirements on PT chemicals sales

Quick Contact us for your requirements on NDT

The post Penetrant Testing Principle, Types, Techniques and Services appeared first on Trinity NDT WeldSolutions Private Limited.