Knowledge centre

Answers to the questions work planners, engineers and QC staff deal with every day. If your question is not listed, ask the Welding & Quality Assistant.

WPS, WPQR & qualifications

WPS versus WPQR: what is the difference?

WPS and WPQR are not the same document. Learn how the pWPS, the qualification record and the welding procedure specification relate under EN ISO 15614-1.

When do you need a WPQR?

When is a WPQR mandatory? A practical overview of the requirements in EN 1090-2, ISO 3834, the PED and client specifications.

How to determine whether an existing WPQR covers your application

Is your existing WPQR valid for a new job? How to check material group, thickness, process, position and joint type against EN ISO 15614-1, step by step.

Writing a pWPS: variables, sources and pitfalls

Writing a pWPS for a welding procedure qualification: the variables it must contain, where to source reliable values and the mistakes to avoid.

Welder qualification to ISO 9606-1

How welder qualification to ISO 9606-1 works: the structure of the standard, essential variables, ranges of qualification, test pieces and examination.

Validity and revalidation of welder qualifications

Validity and revalidation of welder qualifications under ISO 9606-1: the six-month confirmation and the three routes of clause 9.3 explained.

ASME IX vs EN ISO 15614-1: two systems for procedure qualification

ASME IX or EN ISO 15614-1? The differences in structure (PQR, WPS, WPQ versus WPQR), variables, testing and qualification ranges, and when each applies.

Qualification range for thickness and diameter under EN ISO 15614-1

How does the qualification range for thickness and diameter work under EN ISO 15614-1? The tables explained, and choosing a test piece for a wide range.

Operator qualification to ISO 14732 for mechanised and orbital welding

Operator qualification to ISO 14732 for robotic, mechanised and orbital welding: when an operator rather than a welder, qualification routes and validity.

WPQR cost and lead time: where the money goes and how long it takes

What drives the cost and lead time of a welding procedure qualification? The cost items of a WPQR, what delays the schedule and how to combine work.

The procedure qualification record (PQR): what it is and how it works

What is a procedure qualification record under ASME IX? How WPS and PQR relate, what a PQR contains, how it differs from a WPQR and the most common errors.

Welder certification compared: AWS, ASME IX and ISO 9606-1

Welder certification compared: AWS D1.1, the AWS Certified Welder program, ASME IX WPQ and ISO 9606-1. Who certifies, validity, continuity, portability.

Essential variables: what invalidates a qualification

Which changes invalidate a welding procedure qualification? The essential variables of ISO 15614-1 and ASME IX listed, with the common pitfalls.

Adopting a WPQR from a third party

Adopting a WPQR from a supplier, a sister company or a previous employer: when it is permitted, which conditions apply and where it goes wrong.

Execution classes under EN 1090-2: EXC1 to EXC4 explained

How execution classes EXC1 to EXC4 are determined under EN 1090-2 and what each class means for welding, qualifications, coordination and documentation.

ISO 3834 parts 2, 3 and 4: which part fits your company

ISO 3834 has three certifiable parts. Which part suits which company, what each part requires, and how the standard relates to EN 1090 and client demands.

The welding coordinator under ISO 14731: when, who and what

When a welding coordinator is required under ISO 14731, which tasks and responsibilities the role covers, and how to choose between IWE, IWT or IWS levels.

CE marking of steel structures under EN 1090-1

CE marking of structural steelwork under EN 1090-1: how the DoP and FPC work, the role of the notified body and the mistakes fabricators make most often.

ISO 5817 quality levels B, C and D: selecting and applying

What the ISO 5817 quality levels B, C and D mean, how to select the right level for your welded work and how the levels tie in with the EXC classes.

Welding under the PED 2014/68/EU: categories and approvals

What the PED 2014/68/EU requires for welding: categories, permanent joints, and approval of welding procedures and personnel by a notified body or RTPO.

AWS D1.1 versus the European standards: the key differences

How AWS D1.1 compares with EN 1090, EN ISO 15614-1 and ISO 9606-1: structure, prequalified WPSs and what it means for fabricators working to both systems.

Visual testing of welds to ISO 17637

Visual testing of welds to ISO 17637: lighting, viewing distance and angle, tools, timing of the examination, reporting and the link with ISO 5817 levels.

Material certificates 3.1 and 3.2 to EN 10204

Material certificates to EN 10204: the difference between 2.1, 2.2, 3.1 and 3.2, who signs, what to require under EN 1090 and the PED, and traceability.

NDT personnel to ISO 9712: levels, responsibilities and validity

Qualification and certification of NDT personnel to ISO 9712: levels 1, 2 and 3, who may do what, methods, validity, renewal and recertification explained.

Factory production control (FPC) under EN 1090-1

Factory production control (FPC) under EN 1090-1: what it must cover, how to set it up in practice, the notified body's role and links with ISO 3834.

AWS D1.1 prequalified WPS: rules, limits and common mistakes

AWS D1.1 prequalified WPS explained: when you can skip procedure testing, when a PQR is required, and the process, material and joint limits that apply.

ASME Section IX explained

ASME Section IX explained: QW and QB, P-numbers and F-numbers, essential and supplementary variables, WPS, PQR and WPQ, plus B31.3 and Section VIII.

ISO 15614-1: the welding procedure test explained

How does a welding procedure qualification to EN ISO 15614-1 work? Test coupon, testing programme, level 1 and 2, and the range of qualification.

EN 13445: unfired pressure vessels

EN 13445 explained: testing groups, joint coefficient, NDT extent and the relationship with the PED. Why the testing group determines your wall thickness.

EN 15085: welding of railway vehicles

Certification to EN 15085-2 for welding railway vehicles: certification levels CL1 to CL4, weld performance classes and the role of the welding coordinator.

Image quality in radiography: ISO 19232

Wire indicators, duplex wire indicators and the required image quality class: how to demonstrate that a radiograph is sensitive enough.

Choosing the right NDT method for a welded joint

Which NDT method suits which welded joint? VT, PT, MT, UT and RT compared on application, strengths and limitations, with practical selection rules.

Visual weld inspection: from preparation to report

How does a proper visual weld inspection work? Preparation, measuring tools, assessment against ISO 5817 and reporting, explained step by step for practice.

How to write an ITP that works in practice

How to write an ITP (inspection and test plan): structure, hold, witness and review points, responsibilities and client agreement, explained for daily practice.

The quality control plan for your fabrication project

What belongs in a quality control plan (QCP) for fabrication projects, how it differs from an ITP and how to set one up without creating a paper tiger.

The MRB and MDR: building the project dossier properly

How to build an MRB or MDR: which documents belong in it, in what order, and why you should compile the dossier digitally during the project, not afterwards.

Weld map and weld log: traceability for every weld

Why a weld map and weld log are essential: traceability per weld, what to record, and how to set them up practically and keep them current during fabrication.

FAT and final inspection without surprises

How to prepare a FAT and final inspection: checklist, the role of the independent inspector, digital release and the mistakes we see most often on the job.

Vendor inspection abroad: control of quality at a distance

Vendor inspection abroad: the typical risks, the right inspection stages, reporting and desk expediting, and what a structured approach delivers for you.

Punch list management: from open item to clean handover

How to manage a punch list: classify items as A, B or C, record them clearly, follow them up and close them out, so handover does not end in disputes.

Weld defects: recognition, causes and prevention

How to recognise common weld defects, from porosity and lack of fusion to cracks and undercut: causes, prevention and classification to ISO 6520-1.

The NCR: recording, resolving and learning from non-conformities

Writing an NCR (non-conformity report): when to raise one, what it must contain, the dispositions use as is, repair, rework and reject, and root cause.

CWI vs IWI: welding inspector certification compared

Welding inspector certification compared: AWS CWI, IIW IWI, CSWIP 3.1 and ISO 9712 VT. Levels, validity, regional recognition and what clients can expect.

Radiographic testing (RT) of welded joints

How radiographic weld testing works: X-ray versus gamma, image quality to ISO 19232, digital radiography and the acceptance criteria of ISO 10675-1.

Ultrasonic testing (UT) of welded joints

Ultrasonic weld testing to ISO 17640: angle probes, testing levels, calibration and why UT finds cracks better than radiography.

Penetrant testing (PT) of welded joints

Penetrant testing to ISO 3452: method, dwell times, colour contrast versus fluorescent, and the acceptance levels of ISO 23277.

Magnetic particle testing (MT) of welded joints

Magnetic particle testing to ISO 17638: yoke technique, field strength, cross magnetisation and the acceptance levels of ISO 23278.

Phased array and TOFD

Phased array (PAUT) and TOFD as a replacement for radiography: how they work, what ISO 13588 and ISO 10863 require, and when to choose them.

Hardness testing of welded joints

Hardness testing to ISO 9015 and ISO 6507: where to measure in weld and HAZ, which limits apply, and the difference between laboratory and portable testing.

Ferrite measurement in stainless and duplex weld metal

Why ferrite content in austenitic and duplex weld metal is measured, how the ferritescope works and which limits apply in practice.

Preheating in welding: when is it required

When is preheating required in welding? Carbon equivalent, thickness, hydrogen control, practical execution and verification, in line with EN 1011-2.

Calculating and controlling heat input

How to calculate welding heat input: the formula, thermal efficiency factors per process, and why control matters for fine grain steels and stainless.

PWHT: post weld heat treatment explained

Post weld heat treatment: when PWHT is required, which temperatures and holding times apply, and how to execute and record the treatment correctly.

Welding duplex stainless steel: key considerations

Welding duplex stainless steel: ferrite austenite balance, the heat input window, filler selection and testing with ferrite measurement and ASTM G48.

Heat tint on stainless welds: pickling and passivation

Heat tint on stainless steel welds: what the colours mean, acceptance criteria, backing gas with oxygen monitoring, and restoring resistance by pickling.

MAG welding process 135 and cored wire processes 136 and 138

Welding process 135 (MAG) and the cored wire processes 136 and 138: metal transfer modes, shielding gases, strengths, common pitfalls and typical uses.

TIG welding (141) and orbital welding of pipework

TIG welding (141) and orbital welding of stainless and titanium pipework: when to choose TIG, backing gas, quality control and ISO 14732 qualification.

Submerged arc welding (121): productive and controllable

Submerged arc welding (121): high deposition, applications from tanks to cladding, wire flux combinations, key quality points and qualification explained.

Preventing hydrogen cracking: mechanism and measures

How to prevent hydrogen cracking and cold cracking: mechanism, risk factors and countermeasures, from preheat and low hydrogen consumables to NDT delay.

Controlling weld distortion: causes, types and measures

How to control weld distortion: how shrinkage arises, types of distortion, and how welding sequence, presetting, restraint and design keep parts in shape.

Robot welding: qualification and control

Qualifying robot welding to ISO 15614 and ISO 14732: operator qualification, programme control, seam tracking and the repeatability that delivers the gain.

Welding fume: limits and duties

Welding fume and occupational health law: limits for chromium VI, manganese and nickel, mandatory local exhaust and what an employer must record.

Welding austenitic stainless steel: 304 and 316

Welding 304 and 316 without distortion, carbide precipitation or loss of corrosion resistance: filler choice, heat input, backing gas and cleaning.

Welding aluminium: 5083 and 6082

Welding aluminium calls for a different approach than steel: oxide film, hydrogen porosity, strength loss in the HAZ and the right filler wire for 5083 and 6082.

Welding fine grain steel: S460 to S690

Welding S460, S550 and S690: keeping heat input inside the window, preheat, low hydrogen practice and the pitfalls of thermomechanically rolled steel.

Welding nickel alloys and Inconel

Welding Inconel 625, 825 and Alloy 59: sluggish weld pool, hot cracking, dilution in overlay welding and strict heat input control.

Welding titanium

Welding titanium demands full shielding until below 400 degrees: trailing shields, chambers, colour assessment to AWS D18.2 and the pitfalls.

Welding cast iron

Repairing cast iron by welding: grey versus ductile iron, cold welding with nickel electrodes, hot welding and when you are better off not welding.

Welding wear resistant steel

Welding wear plate such as Hardox 400 and 500: preheat, heat input, undermatching consumables and the softened zone in the HAZ.

Dissimilar metal welds: stainless to carbon steel

Welding stainless to carbon steel: choosing filler metal, controlling dilution, carbon diffusion and the pitfalls at elevated temperature.

Welding galvanised steel

Welding galvanised steel: zinc fume and metal fume fever, porosity, liquid metal embrittlement and restoring the zinc coating.

Selecting filler metal

How to select the right filler metal: reading the classification, matching versus undermatching, hydrogen class and electrode storage.

Selecting shielding gas

Which shielding gas for which material and process? M21, C1, I1 and the mixtures, with their effect on penetration, spatter and impact values.

Welding copper and bronze

Welding copper, brass and bronze: thermal conductivity, preheat, oxygen free copper and the fumes from zinc and cadmium bearing alloys.

Joint preparation: which form when

V, X, U or J: which joint preparation do you choose and why? Included angle, root face, gap and their influence on weld metal volume and shrinkage.

Reading welding symbols to ISO 2553

Welding symbols explained: the reference line, arrow side and other side, a and z dimensions, length and pitch, and how ISO differs from AWS.

Calculating the throat thickness of a fillet weld

Throat or leg length? How to calculate the required throat thickness of a fillet weld to EN 1993-1-8, the ratio to z, and the most common mistakes.

Full penetration: when required and how to prove it

When is full penetration required, when does a partial penetration or fillet weld suffice, and how do you demonstrate penetration through testing and qualification?

Selecting the weld quality level: B, C or D

How to choose between quality levels B, C and D of ISO 5817 with justification: balancing loading, consequences of failure and cost.

Fatigue of welded joints

Why welds fail under fluctuating load: detail categories to EN 1993-1-9, the role of the weld toe, and post-treatments that extend service life.

Tolerances to EN 1090-2

Essential and functional tolerances in EN 1090-2: what is mandatory, what is negotiable, how to measure and what to do when exceeded.

Planning the welding sequence

A considered welding sequence saves more than the best straightening: balanced welding, back stepping, fixturing and when to release.

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