pWPS generator
A preliminary welding procedure specification to EN ISO 15609-1: give the process, parent material group, thickness and position, and the generator drafts the sheet with edge preparation, filler, gas, current and thermal regime. The sheet downloads as a table and you fill in the rest.
Short answer
A pWPS is the same sheet as a WPS, only before the test: the same fields, but nothing in them is proven yet. You write it, weld a test piece to it, and after the WPQR report it becomes a WPS. The generator below drafts that sheet from your data: edge preparation, filler, gas, current and thermal regime.
Where the numbers come from
The parameters come from the same tables that print the MIG/MAG, TIG and manual metal arc current data elsewhere on the site: filler diameter, current, voltage and gas flow are picked by thickness. Edge preparation is worked out by the same function as the groove calculator — the angle, gap and root face in the sheet are the ones you get there. What the generator adds of its own is the choice of filler and shielding gas by material group, and the arrangement of all of it into the rows of EN ISO 15609-1.
It does not work out heat input: travel speed goes into that, and travel speed is measured on the test piece — the sheet leaves an empty row for it. It does not know your heat: the preheat here is typical for the group and thickness, and the exact figure comes from EN 1011-2 through the carbon equivalent. It does not cover aluminium: that needs 131 and 141 and different parameters, and the site has no tables of that kind yet — guessing numbers in a document that goes to inspection is not on. And above all: it does not qualify the procedure.
From pWPS to WPS
The order is this: you write the pWPS, weld a test piece to it, submit that for testing, get the WPQR report — and only then does the same sheet become a WPS. Until the report exists the document stays preliminary, however carefully it is filled in.
Qualification covers a range rather than a single combination: other thicknesses, diameters and positions that fall inside it need no separate WPQR. That is exactly why the test piece is chosen not for ease but for the range it buys.
How to fill in a pWPS, field by field
The generator sheet has five blocks in the same order as EN ISO 15609-1. The generator fills the first four; the fifth is yours. Below is what each line means and where the paper most often drifts away from what actually happens at the booth.
Joint and material
Process to ISO 4063 is a number, not a name: 111 (covered electrode), 135 (MAG with solid wire), 136 (flux-cored wire with gas), 141 (TIG). The pWPS carries the number because the range of qualification hangs on it: for acceptance, 135 and 136 are two different processes. Material group follows ISO/TR 15608: 1.1 is steel with a yield strength up to 275 MPa (S235, S275), 1.2 up to 360 MPa (S355). Take the group from the plate’s inspection certificate, not from the drawing. Edge preparation, included angle α, root gap b and root face c come from the same function as the edge preparation calculator; for a fillet weld those three lines stay empty because the edges are not bevelled. Position is written as an ISO 6947 symbol (PA, PB, PC, PF, PG, H-L045): “vertical” is not enough, since it does not say up or down. The symbols are explained on the welding positions page.
Filler and gas
Write the filler designation in full, with the standard number: “EN ISO 14341-A G 42 2 M21 3Si1”, not “SG2 wire from the stores”. A trade name may sit next to it, but acceptance checks the classification. Diameter and gas flow come from the parameter table by thickness. Gas is written as an ISO 14175 symbol (M21 — argon with 18 % CO₂); for stainless steel with 135 the generator gives M12, because with more CO₂ the weld picks up carbon from the gas.
Parameters and thermal regime
Current and voltage are ranges, not single values: the exact point is set on the test piece, and that point is what goes into the report. The number of runs on the sheet is the single-run / multi-run split, because that is how the range of qualification splits them. Preheat is typical for the group and thickness — for the actual heat, work it out with the preheat calculator using the carbon equivalent from the certificate. Interpass temperature is an upper limit: the generator writes 250 °C for groups 1 and 2, 200 °C for 3.1 and 150 °C for stainless 8.1.
What you fill in yourself
The pWPS number, manufacturer, welder, date, signature — and heat input. That last one comes after the test piece: measure run length and time, then put current and voltage into the heat input calculator. The “WPQR reference” line stays empty until there is a report.
Worked example: process 135, 10 mm plate, fillet weld in PB
Settings: 135, group 1.1, thickness 10 mm, diameter 0 (plate), fillet joint, position PB. The generator fills the sheet like this:
| Line | Value | Source |
|---|---|---|
| Edge preparation | fillet weld, no preparation; α, b, c empty | joint type |
| Filler | EN ISO 14341-A G 42 2 M21 3Si1, Ø 1.2 mm | group 1.1 + MAG table, row 8–10 mm |
| Gas | M21 — ArC-18, 16–18 l/min | ISO 14175 + MAG table |
| Current, voltage | DC+, 220–280 A, 26–29 V | MAG table, row 8–10 mm |
| Runs | multi-run | fillet joint, plate over 4 mm |
| Preheat / interpass | not required / 250 °C | group 1.1 up to 25 mm |
| PWHT | not required | group 1.1 |
How to read it. The current range comes from the table row for 8–10 mm and relates to thickness, not position: in PB the pool sags onto the lower leg, so the working point is chosen on the test piece so that the vertical leg is not undercut. The chosen point — an actual current and voltage — goes into the test record, not into the pWPS. The generator enters no preheat because the threshold for group 1.1 lies at 25 mm; but if the certificate shows a high carbon equivalent, the preheat calculator decides, not the sheet.
Before welding the test piece, check the range: the WPQR range calculator gives plate from 5 to 12 mm for a 10 mm fillet weld. If production also has 15 mm plate, weld a thicker test piece now rather than a second WPQR later.
What to do with the pWPS next
- Move the table (CSV button) into the company template, give it a number, add the manufacturer.
- Check the range of qualification and choose the test piece so that it covers the thicknesses and positions used in production.
- Weld the test piece to the pWPS with the examiner present; record the actual current, voltage, travel speed and temperatures.
- Send it for testing to EN ISO 15614-1 (visual, penetrant or magnetic particle, radiography or ultrasound, destructive tests — the set depends on the joint).
- After a pass you get the WPQR; on its basis you issue a WPS for production with parameters inside the range.
More on the document itself and its lines — in the article on the preliminary procedure pWPS.
Common pWPS mistakes
- A trade name instead of the filler classification. “1.2 wire from the supplier” gives no way of checking whether the filler suits the material group. Write the designation with its standard.
- One number instead of a range. “250 A” on a pWPS binds you to weld the test piece at exactly 250 A. A range leaves room for setting up, and the actual value ends up in the report anyway.
- Position in words. “Vertical” is PF or PG, and the difference changes the range: a PF test piece does not cover vertical-down PG, and with impact or hardness requirements uphill also runs at higher heat input than downhill.
- Material group from the drawing. The drawing says S235, the certificate says S355J2 — because that is what was in stock. What gets qualified is what was actually welded.
- The “easiest” test piece. 6 mm plate in PA is convenient but covers little. Choose the test piece for the production range.
- A pWPS on the shop floor instead of a WPS. Until there is a report, a pWPS is used for the test piece only.
Frequently asked questions
How does a pWPS differ from a WPS?
In its fields, not at all — they are the same. The report makes the difference: a WPS has a WPQR behind it confirming that the sheet produces a sound weld, and a pWPS does not have one yet. That is why you weld a test piece to a pWPS, not a product.
Can I weld production work to a pWPS?
Only where a qualified procedure is not required at all. The moment the work is accepted to EN 1090 or ISO 3834 and the client asks for a WPS, a WPQR report is needed — without it the sheet is not a document but an intention.
Why is the heat input row left empty?
Because travel speed goes into it, and travel speed cannot be derived from thickness: it depends on the welder, the position and how the pool runs. The generator gives you current and voltage; you measure the speed on the test piece and work out heat input with the separate calculator.
Why is there no aluminium?
Because it needs different processes (131 and 141), different fillers and different parameters, and the site has no parameter tables for aluminium yet. Putting steel figures here would mean handing inspection a document with wrong data.
Who signs a pWPS — can the welder sign it?
A pWPS belongs to the manufacturer, not the welder: it is drawn up and signed by whoever is responsible for welding technology — in a shop working to ISO 3834 or EN 1090, the welding coordinator. The welder signs the “welder and stamp” line only when the test piece is made, because it is the welder’s hand that the tests will check.
Does a pWPS have to follow a set form?
No. EN ISO 15609-1 lists what information the document must contain and gives a sample form in an annex as an example, not an obligation. That is why the generator table works as a starting draft: move it into your company template and add the number, the manufacturer and the signature.
What thickness range will a test piece welded to this pWPS cover?
It depends on the joint and the number of runs. For the example on this page — a fillet weld on 10 mm plate — the WPQR range calculator gives plate from 5 to 12 mm. A multi-run butt weld test piece of 10 mm would cover 3 to 20 mm. Check this before you weld the test piece, not after the tests.
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