What Is a Welding Procedure Specification (WPS)?

A Welding Procedure Specification (WPS) is the controlled instruction sheet used to make a weld within approved limits. It identifies the welding process, base and filler metals, joint details, position, electrical settings, temperatures, shielding, technique, and other variables required by the governing code or project specification. It helps welders repeat an approved method, but it does not replace welder qualification, inspection, or workplace safety controls.

WPS Meaning and Core Purpose

A Welding Procedure Specification is a formal document that defines the welding process, base materials, filler metals, joint details, parameter ranges, and techniques needed for a specific range of production welding. It acts as a controlled recipe: it tells the welder what may be joined, how the joint must be prepared, and which variables must remain inside approved limits.

The WPS should be available to the welder or welding operator in a usable form. It may contain ranges rather than one fixed setting because normal production conditions vary. Those ranges must still remain within the limits allowed by the applicable code, supporting qualification record, engineering requirements, and project specification.

Common WPS content includes joint design, material group or specification, filler-metal classification, welding position, current type, polarity, amperage, voltage, travel speed, shielding gas, preheat, interpass temperature, postweld heat treatment, and bead-placement technique. For arc welding under the ISO system, ISO 15609-1:2019 addresses WPS content, while ISO 15607:2019 provides general rules for procedure specification and qualification.

Surface condition also matters. Oil, moisture, paint, scale, and coatings can affect weld quality and worker exposure. For example, proper zinc coating removal may be part of the approved preparation method, but coating removal must be combined with suitable ventilation, respiratory protection when required, fire control, and the applicable safety procedure.

WPS, PQR, and Welder Qualification

A WPS, a procedure qualification record, and a welder qualification record serve different purposes. Treating them as interchangeable can create approval, traceability, and inspection problems.

Why a WPS Matters for Weld Quality

A WPS reduces uncontrolled variation by giving the welding crew one approved method to follow. It also gives supervisors and inspectors a defined reference for checking materials, fit-up, consumables, temperature controls, machine settings, and technique.

How a WPS Improves Consistency and Inspection

The WPS does not determine the required weld size or connection strength by itself. Those requirements normally come from the design drawings, engineering documents, construction code, and project specification. Proper fillet weld sizing must therefore be coordinated with the approved procedure rather than selected from the WPS alone.

Compliance and Safety

A WPS is an important compliance document because it defines the method the organization has approved for the weld. However, it is not a complete safety program. It does not replace a job hazard analysis, hot-work permit, fire watch, ventilation plan, confined-space procedure, equipment inspection, or required personal protective equipment.

Welding can expose workers to metal fumes, ultraviolet radiation, burns, eye injury, electrical shock, fire, and other hazards. The Occupational Safety and Health Administration’s welding guidance explains common hazards and control measures. Local workplace law still applies, and legal requirements differ among countries, states, provinces, and territories.

In Australia, for example, model WHS laws and Codes of Practice may guide welding-risk controls, but their legal effect depends on the jurisdiction. In Canada, certified companies may have procedure-submission and approval duties under applicable CSA and CWB requirements. A project in another jurisdiction may use a different legal and certification structure.

Following the correct WPS can improve traceability, reduce avoidable rework, and make deviations easier to detect. It does not guarantee freedom from defects, eliminate liability, or prove that every production weld is acceptable.

What a WPS Must Include

The exact required fields depend on the code and welding process, but a useful WPS normally includes both document-control information and technical instructions.

Document-Control Fields

• WPS number and revision: Identifies the controlled document and prevents use of an obsolete version.
• Governing code and edition: States the code, standard, project specification, or contract requirement used.
• Supporting qualification: Lists the PQR, WPQR, SWPS, prequalified clause, or other qualification basis when applicable.
• Organization and approval: Identifies the manufacturer, contractor, responsible department, and required approvals.
• Date and scope: Shows when the WPS was issued and where it may be used.

Technical Welding Fields

1. Welding process and mode: SMAW, GMAW, FCAW, GTAW, SAW, or another approved process, including transfer mode or equipment details when required.
2. Base metals: Specifications, grades, group numbers, product form, diameter, and qualified thickness range.
3. Joint design: Groove angle, root face, root opening, backing, backgouging, fit-up tolerances, and joint sketch.
4. Filler metals: Specification, classification, trade designation when needed, electrode or wire diameter, flux, and consumable control.
5. Position and progression: Permitted welding positions and vertical-up or vertical-down progression where applicable.
6. Electrical characteristics: Current type, polarity, amperage, voltage, wire-feed speed, pulse variables, and other process controls.
7. Travel and heat control: Travel-speed range, heat-input limits or calculation method when required, preheat, minimum interpass temperature, and maximum interpass temperature.
8. Shielding and backing gases: Gas composition, flow range, trailing shielding, and purge requirements.
9. Technique: Stringer or weave beads, oscillation, contact-tip distance, torch angle, number of electrodes, cleaning between passes, peening restrictions, and bead sequence.
10. Thermal treatment: Postweld heat treatment, controlled cooling, or other thermal requirements.
11. Preparation and task controls: Surface cleaning, moisture control, alignment, tack weld treatment, sequence, and special handling instructions.

These details preserve the approved procedure and reduce guesswork. Understanding the main welding parameters helps a welder read the WPS, but an operator must not adjust a listed variable beyond the permitted range without authorized review.

Essential, Nonessential, and Supplementary Essential Variables

Many qualification codes classify variables according to what happens when they change. The exact classifications and ranges differ by code, process, material, and service.

• Essential variable: A change outside the qualified limit generally requires a new procedure qualification or another code-approved qualification basis.
• Nonessential variable: A change may require the WPS to be revised, but it does not normally require a new PQR under that code.
• Supplementary essential variable: A variable that becomes qualification-sensitive when notch toughness or another specified service condition applies.

Examples can involve the welding process, base-metal grouping, filler-metal grouping, thickness, position, shielding gas, heat treatment, electrical characteristics, or heat input. Do not assume that a variable has the same classification under AWS D1.1, ASME Section IX, API 1104, or an ISO qualification standard.

The qualified range comes from the governing code and the qualification basis—not from how close two welding jobs appear in the shop.

How to Draft and Qualify a WPS

Start by identifying the construction code, project specification, design requirements, service conditions, materials, joint, welding process, and inspection requirements. The correct qualification route must be selected before the test coupon is welded.

1. Confirm the governing requirements. Record the exact code or standard edition required by the contract, drawing, law, or client specification.
2. Choose the qualification route. Determine whether the procedure can be prequalified, adopted as an approved standard procedure, supported by existing qualification records, or qualified by a new test.
3. Prepare the proposed procedure. When the selected system uses a preliminary WPS, list the proposed materials, joint details, process, consumables, position, temperatures, settings, shielding, and technique.
4. Prepare the test assembly. Verify material identity, dimensions, joint preparation, fit-up, consumable condition, equipment calibration or verification, and required preheat.
5. Weld the coupon under controlled conditions. Record the actual variables used rather than copying only the proposed ranges.
6. Examine and test the coupon. Perform the visual examination, NDE, destructive mechanical tests, macro examination, impact testing, hardness testing, or other evaluations required by the governing document.
7. Complete the PQR or WPQR. Record the actual variables, test results, qualified ranges, supporting reports, and certification required by the code.
8. Write the production WPS. Set usable production ranges that remain inside the qualified limits and meet the design and project requirements.
9. Review and approve the document. Obtain the technical, quality, client, engineer, or regulatory approvals required for the project.
10. Issue and control the revision. Make the current WPS available at the point of use and remove superseded copies.

A suitable welding technique must match the selected process and code. A technique cannot be qualified simply because it has worked on another material, thickness, joint, or project.

Procedure Testing Versus Production Inspection

Procedure qualification tests show whether a procedure can produce the properties required within a qualified range. Production inspection determines whether the welds made on the project satisfy the applicable workmanship and acceptance criteria. They are related but separate activities.

A qualification coupon may require bend, tension, macro, impact, hardness, fracture, nick-break, or other tests. Visual, radiographic, ultrasonic, magnetic-particle, or liquid-penetrant examination may also be required or permitted. The exact combination must come from the governing code rather than a generic checklist.

Prequalified, Standard, and Qualified WPSs

WPS terminology varies among codes, so there is no universal list of four types. The following descriptions cover the most common qualification routes.

Prequalified WPS

A prequalified WPS does not require a new procedure-qualification test when the governing code permits prequalification and every applicable condition is satisfied. The organization must still write and control the WPS. Materials, processes, filler metals, joint details, preheat, technique, and other variables must remain within the code’s prequalified provisions.

AWS D1.1/D1.1M:2025-AMD1 is one example of a structural welding code that addresses procedure qualification, welder qualification, fabrication, inspection, and acceptance for structural steel. A procedure is not prequalified merely because it uses a familiar steel or a common electrode.

Standard WPS or SWPS

A standard welding procedure specification is a published procedure supported by qualification records and issued for use under stated conditions. AWS explains that its SWPSs are supported by reviewed PQRs and are intentionally limited to defined applications. Under the ISO system, ISO 15612:2018 addresses qualification by adoption of a standard welding procedure specification.

The user must still confirm that the governing application standard permits adoption and that the organization, material, process, thickness, joint, equipment, and other conditions meet every restriction.

Procedure-Tested or Qualified WPS

A procedure-tested WPS is supported by a PQR or WPQR developed under the applicable qualification rules. It is normally required when prequalification is unavailable, the variables fall outside prequalified limits, the service has special property requirements, or the contract specifically requires testing.

• Use a prequalified WPS only when the selected code allows it and every prequalification condition is satisfied.
• Use an SWPS only when the governing requirements permit adoption and the published procedure covers the application.
• Use a procedure-tested WPS when qualification testing is required or the job falls outside another accepted route.
• Request engineering or code review when the material, joint, position, process, heat treatment, toughness requirement, or service condition creates doubt.

A MIG welder troubleshooting guide can help identify equipment problems, but repairing a machine or restoring wire feed does not authorize a departure from the WPS settings, polarity, transfer mode, or shielding requirements.

How a PQR Supports a WPS

A Procedure Qualification Record documents the actual conditions used to weld a qualification coupon and the results of the required tests. If the results satisfy the governing rules, the record establishes a qualified range that can support one or more WPSs.

The PQR does not function as the normal shop instruction sheet. It records what actually happened during qualification. The WPS converts the permitted qualified range into clear production instructions.

Not every WPS has its own PQR. A code-compliant prequalified WPS may use a qualification route that does not require a procedure test. An SWPS may rely on qualification records developed and reviewed by another organization. The WPS must identify its correct basis.

PQR Test Coupons

1. Verify the coupon material, thickness, diameter, joint geometry, backing, and preparation.
2. Confirm the consumables, equipment, shielding, preheat, position, and welding sequence.
3. Weld the coupon while recording the actual amperage, voltage, travel speed, temperatures, filler metals, gases, and other required variables.
4. Inspect the completed coupon as required before removing test specimens.
5. Prepare and test the specimens using the methods required by the governing code.
6. Record all results, including failures, retests, supporting laboratory reports, and the final qualification disposition.

The root opening should match the proposed joint and qualification requirements; it should not simply be made “tight.” Likewise, a coupon does not pass because the bead looks smooth. It must satisfy every required examination and test criterion.

Understanding the advantages and limitations of welding processes can help during procedure development, but the final qualification decision must follow the governing document.

Validating Procedure Variables

The qualification record must show the variables that were actually used. Depending on the code and process, these may include base-metal group, filler classification, electrode diameter, gas composition, polarity, transfer mode, position, thickness, preheat, interpass temperature, postweld heat treatment, amperage, voltage, wire-feed speed, travel speed, and calculated heat input.

If the required results are not achieved, the organization must evaluate the cause, revise the proposed procedure when necessary, and complete any retest or new qualification required by the code. Failed results should not be hidden by rewriting the PQR to match the desired outcome.

This documentation provides traceability and allows an inspector or reviewer to connect the production WPS to the evidence supporting its qualified range.

How to Read and Use a WPS

Before welding starts, compare the WPS with the drawing, traveler, weld map, material identification, filler-metal issue record, and current project specification.

1. Check the document number and revision. Confirm that the copy at the work area is current and approved for the project.
2. Confirm the code and supporting record. Verify the qualification basis and any client restrictions.
3. Match the base metal. Check grade, group, product form, thickness, and diameter against the WPS range.
4. Check the joint. Verify groove angle, root face, root opening, backing, fit-up, and required backgouging.
5. Confirm the filler metal. Match the specification, classification, diameter, flux, storage, conditioning, and issue controls.
6. Set the process variables. Use the permitted polarity, amperage, voltage, wire-feed speed, gas, flow rate, and travel range.
7. Verify temperatures. Measure preheat and interpass temperature with a suitable method at the required location.
8. Follow the technique. Use the stated progression, bead type, cleaning, sequence, and pass restrictions.
9. Stop when the job does not match. Obtain an authorized revision, alternative WPS, or technical disposition rather than improvising.

Key Standards for Welding Procedure Specifications

The applicable code depends on the product, industry, jurisdiction, service, contract, and joint application. Always use the exact edition incorporated by the governing document rather than assuming that the newest edition automatically applies to an existing project.

• AWS D1.1: Commonly used for structural steel welding. The current AWS product page identifies D1.1/D1.1M:2025-AMD1.
• ASME BPVC Section IX: Contains rules for qualification of welding, brazing, and fusing procedures and personnel when invoked by an applicable construction code or specification. The current ASME product page lists the 2025 edition.
• ISO 15607: Provides general rules for specification and qualification of welding procedures for metallic materials.
• ISO 15609 series: Addresses required WPS content for specified welding processes, including ISO 15609-1 for arc welding.
• ISO 15612: Covers qualification by adoption of an SWPS under stated conditions.
• ISO 15614 series: Contains procedure-test rules for different processes and material groups.
• API Standard 1104: May be specified for welding pipelines and related facilities.
• Canadian requirements: Projects may invoke CSA W47.1, W47.2, W59, W186, or CWB certification and procedure-approval requirements.

ASME BPVC Section IX is a qualification standard, not a substitute for the construction code that sets design, fabrication, examination, and acceptance requirements. Likewise, an AWS, API, CSA, or ISO document should be used only within its stated scope.

Understanding welder certification requirements is useful, but personal qualification does not replace procedure approval or project-specific code review.

When You Need a Custom WPS

You need a custom Welding Procedure Specification when a prequalified or standard procedure does not cover the project’s material, joint, process, position, thickness, diameter, heat treatment, toughness, or performance requirements.

Common triggers include dissimilar metals, unusual joint geometry, nonstandard filler metals, restricted access, repair welding, hardfacing, overlay, special corrosion requirements, impact-tested service, high-restraint joints, new welding processes, and variables outside a published procedure’s permitted range.

A custom WPS can define base metals, filler, joint geometry, preheat, interpass temperature, travel speed, heat input, shielding gas, technique, sequence, and postweld heat treatment for the specific application. When the governing rules require procedure testing, it must be supported by a properly completed PQR or WPQR.

Tailoring the procedure to the job can improve quality assurance and traceability. It does not remove the need for welder qualification, production inspection, engineering review, or workplace controls. Use the required ventilation, fire prevention, electrical precautions, and PPE setup for the actual welding environment.

Common WPS Mistakes

• Using the wrong revision: An older shop copy remains in circulation after the approved WPS changes.
• Assuming similar materials are interchangeable: The material grade or group falls outside the qualified range.
• Ignoring process details: The crew changes polarity, transfer mode, shielding gas, flux, electrode classification, or wire diameter without review.
• Copying target values onto the PQR: The record should contain actual qualification variables and results.
• Confusing design and procedure requirements: The WPS is used to choose weld size even though the drawing or engineering specification controls it.
• Using a welder qualification as procedure evidence: A welder test does not replace a required PQR.
• Assuming a procedure transfers between codes: A WPS qualified under one standard is used under another without checking acceptance and ranges.
• Treating NDE as the only qualification test: Required destructive or mechanical tests are omitted.
• Leaving ranges too broad: The WPS includes settings that are impractical, unsupported, or outside the qualified limits.
• Skipping field verification: The WPS is technically valid, but the material, joint, consumable, or position at the work area does not match it.

Frequently Asked Questions

What are the four types of WPS?

There is no universal list of four WPS types. Common terms include preliminary WPS, prequalified WPS, procedure-tested or qualified WPS, and standard WPS. Their meanings and acceptance depend on the governing code. A welding procedure data sheet may be used by some organizations, but it is not a universal fourth category.

Why is a WPS required?

A WPS turns an approved welding method into repeatable production instructions. It controls important variables, helps the crew work consistently, supports traceability, and gives inspectors a documented reference. Whether it is legally or contractually required depends on the code, jurisdiction, client, and project.

Who can write a Welding Procedure Specification?

There is no single job title that applies worldwide. The manufacturer or contractor normally owns and controls the WPS. A welding engineer, welding coordinator, supervisor, inspector, or other technically competent person may prepare it, but required review, approval, and professional qualifications depend on the governing code and jurisdiction.

How long is a WPS valid?

A WPS does not have one universal expiry period. It remains usable only while its qualification basis, code acceptance, approvals, and document-control status remain valid. Review it after code or contract changes and whenever an essential variable, material, process, joint, position, service condition, or other controlled requirement changes.

Can you use one WPS for every welding job?

No. Each WPS has a defined scope and set of limits. Confirm the code, base metal, filler metal, process, joint, thickness, diameter, position, preheat, heat treatment, shielding, and service requirements before applying it to a job.

Does every WPS need a PQR?

No. A procedure qualified by testing is normally supported by a PQR or WPQR. A code-permitted prequalified WPS may not require a separate procedure test, while an adopted SWPS may rely on qualification records developed by another organization. The WPS should identify its qualification basis.

Does following a WPS guarantee an acceptable weld?

No. The WPS controls the method, but the welder must still execute it correctly. Material condition, fit-up, equipment, consumable handling, access, workmanship, and inspection also affect the result. Production welds must meet the acceptance criteria required by the governing code and project.

Sources

1. American Welding Society — AWS D1.1/D1.1M:2025-AMD1 — structural steel procedure, personnel, fabrication, and inspection context.
2. ASME — BPVC Section IX, 2025 — welding, brazing, and fusing procedure and personnel qualification.
3. ISO 15607:2019 — general rules for welding-procedure specification and qualification.
4. ISO 15609-1:2019 — WPS content requirements for arc welding.
5. ISO 15612:2018 — qualification by adoption of a standard welding procedure specification.
6. OSHA — Welding, Cutting, and Brazing Hazards and Solutions — welding health and safety hazards and controls.

Conclusion

A welding procedure specification gives the welding crew a controlled path to consistent, code-compliant work. It defines the process, materials, joint, position, temperatures, settings, shielding, and technique that may be used for a stated application.

A qualified procedure may be supported by a PQR or WPQR, while a prequalified or standard procedure follows a different code-approved route. None of these documents replaces welder performance qualification, production inspection, engineering requirements, or workplace safety controls.

Before a critical weld begins, confirm the WPS number and revision, code edition, material, joint, filler metal, position, parameter ranges, temperature limits, and qualification basis. Stop and request technical review whenever the job falls outside those limits.

Related Guides

Automotive Welding Guide ⏱ 13 min read

How to Keep a Welding Journal to Track Your Progress

Jun 2026 Read → How to Keep a Welding Journal to Track Your Progress

Automotive Welding Guide ⏱ 15 min read

How to Build a Simple Welding Table for Auto Body Work

Jun 2026 Read → How to Build a Simple Welding Table for Auto Body Work

Automotive Welding Guide ⏱ 15 min read

How Much Does It Cost to Learn Automotive Welding?

Jun 2026 Read → How Much Does It Cost to Learn Automotive Welding?