Most API 510 candidates treat Domain II as a memory test on Section IX. It is a review job: someone hands you three documents and you decide whether the weld may go ahead.
What does Domain II of the API 510 exam cover?
Domain II is titled Welding Procedure and Qualification Evaluation, and it is based on ASME Section IX. The body of knowledge asks for familiarity with the basic requirements for qualifying procedures and welding personnel. It does not ask you to write a procedure from scratch.
You review three documents: the Welding Procedure Specification (WPS), the Procedure Qualification Record (PQR) and the Welder Performance Qualification (WPQ). Then you answer four questions about them. Do the records comply with ASME and any extra API 510 requirement? Have the essential and nonessential variables been addressed? Are the mechanical tests on the PQR the right number and type, and are the results acceptable? Is the welder qualified to make this production weld under this WPS?
Two further blocks sit beside the review. One is the general welding rules in Section VIII Division 1, Parts UW and UCS. The other is everything in API RP 577.
API 510 The distractor on this one catch four candidates out of five. Watch on YouTube · CertCrafter Our channel has a short on the distractor that catches most candidates, which is the same habit of mind you need here: read what the document says, not what you expect it to say.
How are the WPS, PQR and WPQ related?
The PQR is the proof. A coupon was welded, tested, and the results recorded. The WPS is the instruction a welder follows, and it has to be supported by that PQR. The WPQ shows that a particular welder can deposit sound weld metal using a qualified WPS.
API adds two small rules that become easy marks. The WPQ test coupon must be welded in accordance with a qualified WPS. And the PQR and WPQ must be certified by signing and dating. Editorial items such as the WPS number, the revision level, the company name, the date and the name of the testing lab are excluded, so a question will not turn on them.
Worked example: reviewing a record set in four steps
You are handed a WPS, its PQR and a welder’s WPQ for a repair on a carbon steel shell. Work through them in this order.
- Confirm the process. Is it one of SMAW, GTAW, GMAW or SAW, and is it only one?
- Check the base metal and filler. Is the metal in P-No. 1, 3, 4, 5 or 8, with one filler per process and no dissimilar metals or thicknesses?
- Read the variables. For each essential variable on the WPS, does the PQR support it? Are the nonessential ones addressed?
- Read the welder. Was the coupon welded to a qualified WPS, is the WPQ signed and dated, and does it cover the production weld?
A “no” at any step stops the review. The record is not compliant, and that is the answer the question is usually built around.
The API 510 Complete Exam Kit works more of these under timed conditions, with every answer explained.
What do inspectors check in practice?
On a real job the paperwork usually looks complete. The problem is the gap between the document and the weld about to be made.
A WPS that was qualified for one position, one thickness range or one filler gets used for a repair that sits outside it. A welder’s qualification has lapsed or covers a different process. A PQR is attached to the WPS but its mechanical tests do not match what the procedure now claims. Experienced inspectors read the WPS against the repair package, then the PQR against the WPS, then the WPQ against both, and they hold the weld until the chain closes.
Repair welding on an installed vessel brings a second question: heat treatment. Postweld heat treatment is sometimes impractical on a vessel that cannot be moved, and API 510 gives the engineer alternatives. The decision belongs to the engineer, and the inspector confirms it is what the repair record shows. One of the free questions below tests exactly that boundary.
Which limits does API 510 put on the weld review?
The exam narrows the field on purpose, and the narrowing is the study aid.
For P-No. 1, 3, 4 and 5, the body of knowledge fixes the lower transformation temperature at 1330 °F (720 °C) and the upper at 1600 °F (870 °C), so you do not need to look them up. It also says supplemental essential variables are not part of the WPS or PQR you review.
One rule cuts across the whole domain. Where API 510 has a welding rule, it takes precedence over the Section VIII Division 1 rule covering the same area. When two sources seem to disagree, API 510 wins.
Where do candidates lose marks on welding qualification?
Three habits cost the most.
The first is treating a filler change as automatically fatal. ASME Section IX groups electrodes by F number and A number, not by commercial classification. A change inside the same groups is not an essential change. One of the free questions below puts an E7018 against an E7016 to see whether you know that.
The second is confusing the procedure with the person. A procedure can stay valid while a welder needs a new performance qualification, and the reverse is not true.
The third is reading the PQR for what it contains and not for what it proves. Counting the tests and judging the results is a separate step from matching the variables.
Questions on this domain are framed as short cases: a named vessel, a repair, a shop asking to change something, and four options that each match a plausible slip. Several are open book, so the skill is knowing where to look and what the paragraph really says.
What to do next
Take any WPS, PQR and WPQ you can legally see, from your own site or a textbook, and run the four steps above on them. Write down which step stopped you, if one did.
For the shape of the exam day, the exam format, scoring and dates post covers the closed-book and open-book split, and common mistakes goes across all five domains. The certification guide holds the full body of knowledge summary, the free sample quiz shows where you stand today, and the six practice tests cover this domain in full. More API 510 posts go domain by domain.
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