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WPS essential variables checklist builder
A welding procedure specification is only evidence when every variable the framework treats as essential is written in it, and when each written value can be traced back to the qualification record that supports it. This builder lists the variable categories that apply to one combination of framework family, process and joint, records the state of each one, and reports how much of the document exists.
No range of qualification is built into the page, and no variable is classified here as essential, supplementary essential or non-essential. Both of those live in the framework edition you hold, they change between editions, and the checklist stays correct across editions precisely because it names the variable and sends you to the clause.
What the builder counts, and what it refuses to decide
applicable = categories that apply to this framework family, process, joint, product form and toughness requirement
completeness = 100 × documented / applicable
traceability = 100 × traced / applicable
documented = the value is written in the WPS, traced or not · traced = the value is written AND the qualification record and clause behind it are referenced next to it, so every traced category is also a documented one and the two percentages can never cross · a category you mark not applicable leaves both the numerator and the denominator, and is reported separately so the exclusion stays visible
That is the whole of the arithmetic, and it is deliberately small. Counting is the part a page can own. The part it must not own is the range: the qualified band around every variable below comes from the value recorded on the qualification record — the WPQR under the ISO 15614-1 family, the PQR under the ASME IX family — together with the variables clause of the edition you hold. Neither of those numbers is on this page, and neither should be quoted from a web page in a document somebody welds to.
The second refusal is less obvious and matters more. Whether a given variable is essential, supplementary essential or non-essential is not a property of the variable: it depends on the process, on the framework, on the edition, and on whether impact toughness or hardness testing is called up by the application standard. That mapping is the framework’s own variable table. The builder therefore treats every category as something the WPS has to document, which is the safe direction of error — documenting a variable that turns out to be non-essential costs a line of text, and omitting one that is essential costs a requalification.
How to build a WPS essential variables checklist
From a blank procedure specification to a list you can hand to whoever signs it.
- Set the scope. Framework family, welding process, joint and product form, plus whether the application standard calls for impact toughness or hardness testing. Two of those selections change which categories are counted — pipe adds the diameter category, a toughness requirement adds the supplementary set — and the framework family changes the wording of every line and the record each value is traced to.
- Copy in the values the WPS states. Parent thickness, outside diameter, minimum preheat and maximum interpass, in whichever unit system you work in. They are optional, they ride along into the export, and the only check performed on them is that the preheat minimum sits below the interpass maximum.
- Mark each category. Not documented yet, written in the WPS, written and traced to the qualification record, or not applicable. Everything starts at not documented, so the percentage only moves when you move it.
- Read the two percentages apart. Completeness says the document has nothing blank. Traceability says each value can be shown to come from the qualification record and the clause. An audit finding almost always lands on the second, not the first.
- Work the outstanding list. Each remaining category is written out below the results with what it has to contain and where its range comes from. Fill them, then export the CSV as the working record of the review.
- Written and traced are different states, and the second is the one that gets asked about. A range present in the WPS satisfies a reader. A range whose qualification record and clause are named next to it satisfies an auditor. The two percentages are reported apart because a document routinely reaches full completeness while half its values have no visible provenance.
- The content requirement and the qualification are two different documents. On the ISO branch, what a WPS must contain is set by ISO 15609-1 and the range around each value by the procedure test in ISO 15614-1. On the ASME branch both live in the same section but in different clauses. Confusing the two is how a WPS ends up complete and unqualified, or qualified and unusable.
- A category marked not applicable is your declaration, not the framework’s. The tool excludes it from both percentages and then names it back to you in a badge, because an exclusion nobody can see is the easiest way to reach a hundred per cent on a document that is not finished.
- Preheat and interpass are one category with two numbers, and they can contradict each other. Entering a minimum preheat at or above the maximum interpass temperature leaves the welder no working window; the tool flags that, and only that, because it is the document disagreeing with itself rather than with a standard. The preheat calculator handles the separate question of what the minimum should be.
- Heat input is the variable that drifts without anybody deciding to change it. Travel speed carries the error, weave breaks the range invisibly, and a WPS that states a band with no way to record what was delivered leaves nothing to compare against afterwards. The heat input calculator puts the number on paper and WeldTrace records what the arc actually did on each pass.
- The procedure is one of two qualifications the joint needs. The welder is the other, with its own essential variables and its own ranges — the ISO 9606-1 range of qualification checker covers that side, and digital WPS and PQR records cover keeping the pair straight across a fabrication.
For the qualification test behind these variables in long form, read the EN ISO 15614-1 welding procedure qualification test guide.
Questions engineers ask about this calculation
What must a welding procedure specification actually document?
Everything a welder or a welding operator needs to reproduce the joint that was qualified, and everything an inspector needs to check that they did. In practice that resolves to a fixed set of categories: the process and its transfer mode, the parent material with its group, the thickness and, on pipe, the diameter, the joint preparation and backing, the position and progression, the consumable classification, the shielding and backing gas or flux, the electrical parameters, the heat input or arc energy, preheat and interpass temperature, post-weld heat treatment, and the run technique. Both framework families ask for the same categories in different words. This builder lists them for one combination and records which of them your document already carries.
What is the difference between an essential variable and a supplementary essential variable?
An essential variable is one whose change beyond its qualified range invalidates the procedure and requires requalification. "Supplementary essential" is the ASME IX wording for a variable that only carries that weight once the construction code calls for notch-toughness testing; the ISO family expresses the same idea differently, as additional requirements and tighter ranges that come into force when impact or hardness testing is required. Either way the practical consequence is identical: the same variable can be essential on one job and not on another depending on what the application standard asks for, which is why the toughness selection on this page changes the checklist rather than the arithmetic. Which specific variables fall into which class for your process is set by the framework variable table and is not reproduced here.
Where does the qualified range for each WPS variable come from?
From two documents together, never from one. The qualification record — the WPQR under the ISO family, the PQR under the ASME family — states the value that was actually welded and tested. The framework variables clause states how far around that value the qualification extends. A range written into a WPS without both of those behind it is a number somebody chose. That is why every checklist line on this page ends with the same instruction rather than a figure: the range lives in your qualification record and your edition of the framework, and it changes between editions.
Why does this checklist not show the range of qualification for my process?
Two reasons, and the second matters more. The ranges are copyrighted table content, so reproducing them here would be a copyright problem regardless of how convenient it is. More importantly they are edition-specific: a page that quoted a range would keep quoting it after the edition changed, and somebody would build a procedure on it. A checklist that names the variable and sends you to the clause stays correct across editions; a table baked into a web page does not. The same principle governs every calculator on this site — a comparison value is typed in by the engineer who holds the specification.
Can one qualification record support more than one welding procedure specification?
Yes, and it usually does. A single qualification record fixes a set of ranges, and any number of procedure specifications can be written inside those ranges — a thinner joint, a different position within the qualified set, a narrower parameter window for a particular fabrication. What it cannot do is support a WPS that sits outside any one of those ranges, and each range has to be checked separately: a document comfortably inside the thickness range can still be outside the position or the consumable range. The traceability column on this page exists for exactly that reason, because tracing each value to the record is what makes the check possible at all.
What happens when production runs outside a variable range the WPS states?
The weld was not made to a qualified procedure, and that is a nonconformity to be raised rather than an observation to be filed. The usual sequence is to stop, record the actual condition, assess the joints already made against the property the variable protects, and decide between acceptance on evidence, repair, or requalification. The failure mode worth planning for is the silent one: heat input, interpass temperature and travel speed drift without anybody choosing to change them, and a document that states a range with no way to record what was delivered leaves nothing to compare against afterwards.
Do the ISO and the ASME framework families ask for the same variables?
They ask about the same physics with different structures and different words, so a WPS written for one is not a WPS for the other. The category list overlaps almost entirely — both want the process, the material group, the thickness, the consumable, the gas, the position, the thermal conditions and the technique — but the grouping designations differ, the ranges differ, the classification of a given variable as essential or supplementary differs, and the required tests behind the qualification differ. Selecting the framework family on this page changes which record the checklist asks you to trace each value to, and the wording of every line, for that reason.
What does the completeness percentage on this page actually measure?
Only whether a category has been recorded as present in your document, out of the categories that apply to the combination you selected. It is a drafting-progress figure, not a compliance verdict: the tool cannot see your WPS, cannot check that a stated range is inside the qualified one, and does not know whether the framework treats a given variable as essential for your process. A hundred per cent means the document has nothing obviously left blank. It does not mean the procedure is qualified, and nothing on this page should be quoted as if it did.
A WPS states a range. Something still has to prove the range was held.
WeldTrace records current, voltage and wire feed speed at 25 kHz, and gas flow at 10 Hz, on every production pass, so the heat input and parameter variables this checklist asks you to document carry their own evidence instead of a signature.
