WPS and WPQR: What is the Difference and How They Relate in Practice
Two Documents, One Relationship
In industrial welding, WPS and WPQR are frequently confused. They are distinct documents with opposite but complementary functions:
| Document | Full name | Function |
|---|---|---|
| WPS | Welding Procedure Specification | Work instruction — tells THE WELDER how to weld |
| WPQR | Welding Procedure Qualification Record | Test record — proves the procedure WORKS |
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The WPS — Procedure Specification
The WPS is a prescriptive document: it defines all parameters the welder must observe during execution. According to EN ISO 15614-1, it must contain:
Mandatory WPS content
- Welding process (e.g., 135 — MAG)
- Base material: ISO/TR 15608 group, thickness, diameter
- Filler material: classification, diameter, brand
- Welding position (ISO 6947)
- Joint type and groove geometry
- Shielding gas: type, flow rate (l/min)
- Electrical parameters: current, voltage, wire feed speed
- Travel speed (mm/min)
- Heat input (kJ/mm)
- Preheat and interpass temperature
- Post-weld heat treatment (if applicable)
- Number of passes and sequence
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The WPQR — Qualification Record
The WPQR is an evidence document: it records what happened during and after the qualification test. It includes:
- Actual welding conditions of the test piece (pWPS — preliminary WPS)
- Results of destructive and non-destructive tests:
- Visual examination (EN ISO 17637)
- Radiography or ultrasound (EN ISO 17636 / 11666)
- Tensile test (EN ISO 4136)
- Bend test (EN ISO 5173)
- Hardness test (EN ISO 9015-1)
- Macrographic examination (EN ISO 17639)
- Charpy impact test (if required)
- Range of qualification (thickness, diameter, position coverage)
- Examiner or inspection body signature
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The Logical Sequence
``` pWPS (preliminary) → Test piece welding → Tests → WPQR → Final WPS ```
- The welding coordinator draws up the pWPS with the planned parameters
- The welder executes the test piece according to the pWPS
- The inspection body carries out the tests and issues the WPQR
- If approved, the pWPS becomes the definitive WPS, referencing the WPQR
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Validity and Extension
- An approved WPQR underpins the WPS and defines the limits of application
- Changes to essential variables (thickness, process, material, position) invalidate the WPQR → new test required
- Changes to non-essential variables (consumable brand, electrical parameters within range) only require WPS revision — no new test
- The WPQR has no expiry date as long as the process and materials remain within the qualified limits
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