IIW IWI-S common mistakes
IIW IWI-S · Understand the traps and how to avoid them.
Writing a WPS/PQR answer that states the essential variables were 'within range' without naming which variables changed and how each is re-qualified or covered by a supporting PQR.
Candidates memorize that a WPS needs qualification but study the variable lists as isolated facts, so under exam pressure they give a generic reassurance instead of applying the specific-variable logic to the scenario given.
What to do instead
Practise a fixed drill: list the essential, supplementary essential and non-essential variables for the process in the question, mark which one the scenario alters, then state whether a new PQR, a re-test, or only a WPS revision is required, citing the applicable standard clause. Do this for at least five processes so the pattern becomes automatic.
Confusing a defect with an imperfection and answering that any indication found by NDT is a rejectable defect.
The words are used loosely in daily workshop language, so candidates carry the colloquial meaning into the exam and skip the acceptance-criteria step entirely.
What to do instead
Anchor the definition: an imperfection is any discontinuity; it becomes a defect only when it exceeds the acceptance criteria of the applicable standard or specification. On every NDT question, first identify the standard and acceptance level, then compare the measured size or character against that limit before writing the verdict.
Choosing an NDT method by habit (usually radiography or visual) without matching it to the discontinuity type, orientation, location and material.
Candidates learn each method in isolation and never build a comparison table, so they cannot quickly discriminate between surface-breaking, planar, volumetric or sub-surface indications.
What to do instead
Build and memorize a matrix: method versus detectable discontinuity type, typical orientation sensitivity, surface versus sub-surface capability, and material restrictions (for example magnetic methods only on ferromagnetic material). Answer by reading the discontinuity described in the question and selecting the method that column supports.
Treating hydrogen-assisted cold cracking as a single-variable problem and blaming only the hydrogen level, ignoring restraint, hard microstructure and stress.
The four-factor interaction is taught as a list rather than a mechanism, so candidates pick the most familiar factor and stop.
What to do instead
Rehearse the mechanism as four interacting contributors: diffusible hydrogen, susceptible microstructure (carbon equivalent and cooling rate), tensile stress (restraint), and temperature/time. For scenario questions, state which factors the proposed measure actually changes and whether the others remain uncontrolled.
Answering heat-input or preheat questions with a formula result but no discussion of how it was derived or what assumptions apply.
Candidates memorize a single equation and plug in numbers without tracking units, thermal efficiency or the difference between heat input and arc energy.
What to do instead
Write out the calculation with units at each step, state the thermal efficiency factor used and where it comes from, and distinguish heat input (per unit length of weld) from arc energy. Practise dimensional checking so a wrong unit is caught before the answer is committed.
Describing a welding procedure or inspection sequence in the wrong order, for example placing post-weld heat treatment before final NDT or omitting intermediate inspection.
Candidates know the individual steps but have not sequenced them as a fabrication route, so the answer reads as a list of activities rather than a process.
What to do instead
Draw the fabrication sequence for each common joint type from fit-up through root, fill and cap, then NDT, then any heat treatment, then final inspection and documentation. Practise questions by writing the numbered sequence first and only then answering, so ordering errors are exposed before the exam.
Giving a generic safety answer such as 'follow the risk assessment and use PPE' when the question asks about a specific hazard mechanism such as fume, arc radiation, or confined-space atmosphere.
Safety is treated as common sense rather than as technical content with its own mechanisms, exposure limits and controls, so candidates default to slogans.
What to do instead
For each hazard, learn the mechanism, the route of exposure, the relevant occupational exposure limit or threshold, and the hierarchy of controls from elimination down to PPE. Answer by naming the specific control that interrupts the specific mechanism in the scenario, not the general principle.
Confusing quality control with quality assurance and misplacing documents such as the inspection and test plan, the WPS, the welder qualification record and the NDT report in the wrong part of the quality system.
The terms overlap in everyday use, and candidates have not mapped which documents are planning documents, which are records, and which are verification activities.
What to do instead
Build a document map: policy and planning level (QA, ITP, specifications), execution level (WPS, welder and procedure qualification records, NDT instructions), and verification level (inspection reports, NDT reports, traceability records). Classify each document in the question against this map before answering.
Writing inspection reports that record a result without the traceability chain, so the joint, the procedure, the welder and the instrument calibration cannot be linked.
Candidates focus on the measurement and treat identification, calibration status and reference documents as clerical detail rather than part of the technical record.
What to do instead
Use a fixed report skeleton: item and joint identification, applicable WPS and revision, welder identification, NDT method and standard with acceptance level, equipment and calibration validity, results with measurements, and a clear accept or reject statement with the responsible person. Practise writing short reports to this skeleton until every element is habitually included.
Applying a general rule of thumb to a specific material group (for example austenitic stainless steel, aluminium, or duplex) without adjusting for its particular behaviour during welding.
Most study time goes to carbon and low-alloy steel, so candidates over-generalize thermal conductivity, expansion, oxide formation and sensitization behaviour to materials where those assumptions fail.
What to do instead
For each material family, write a one-page profile covering thermal conductivity, coefficient of expansion, oxide and surface condition, typical cracking mechanisms, and the resulting changes to process, shielding, cleaning and heat input. Review these profiles before the exam and answer material questions by reading the family first, then applying its profile.