What Is a Welding Procedure Specification? WPS Explained

A fabricator finishes a 40-foot run of process piping on a Tuesday, gets it back with three rejected radiographs on Thursday, and discovers the crew had been running a procedure nobody had ever written down — just a habit passed from the old shop foreman to three different welders. The pipe was fine. The paper was not. That gap between ‘the way we always weld it’ and a written, code-compliant procedure is exactly what a Welding Procedure Specification exists to close.

What Is a Welding Procedure Specification (WPS)? A Plain-English Answer

Here is the plain-English version. A welding procedure specification is a written document that tells the welder, the inspector and the code exactly how a particular weld is to be made. It names the base and filler metal, the joint configuration, the process, the position, the technique, the electrical parameters, preheat and interpass temperatures, the cleaning method and any supplementary variables the governing code requires. It is an instruction, and the whole point is that the next weld comes out like the last one.

Take a run of process pipe. The crew that welded it did nothing wrong in the way a welder does something wrong. They simply welded the way the shop always welded that joint, which happened to sit outside what the code allowed, and nobody had ever written it down. A WPS would have caught that before the pipe was spooled, and it is the document an inspector pulls from the binder to answer one question: was this weld made the way the code says it must be made?

What the document actually contains

A complete WPS is not a one-page summary. It is a structured record, usually on a standard form:

• Identification — WPS number, revision, the code it is written to, and the material standard it applies under.
• Base metal — specification and grade (for example ASTM A106 Grade B), thickness range, diameter or size range, cladding or heat treatment condition.
• Joint design — groove type, groove angle, root face, root opening, backing, and whether the joint is a full penetration weld.
• Filler metal — AWS classification such as E7018 or ER70S-6, diameter range, number of passes, diffusible hydrogen or notch toughness requirement.
• Process and technique — SMAW, GMAW, FCAW, GTAW or SAW, welding position, progression, weave or stringer beads, interpass cleaning method.
• Parameters — amperage, voltage, travel speed, wire feed speed, shielding gas type and flow rate, each stated as a range.
• Thermal controls — minimum preheat, maximum interpass temperature, post-weld heat treatment.
• Supplementary variables — heat input per unit length, maximum weld size, reinforcement limits, and the inspection and acceptance criteria that follow.

For anyone learning position vocabulary, this guide to all-position welding rods shows what the position and technique fields on a WPS mean in the hand.

What a WPS is not

Three documents get tangled together so often that AWS publishes a self-paced course, WPS/PQR Explained, noting that the nature and use of a welding procedure specification and its supporting procedure qualification record are “commonly misunderstood.” Worth stating up front:

• The WPS is the instruction: the plan for how the weld will be made.
• The PQR (Procedure Qualification Record, ASME terminology) is the evidence: the parameters actually used on a test coupon plus the test results proving the procedure is qualified.
• The WPQ or WQTR (Welder Performance Qualification or Welder Qualification Test Record) is the evidence that an individual welder passed a performance test for a given process, position and material range.

Who writes it, who uses it

A WPS is normally written or approved by a welding engineer, a Certified Welding Inspector (CWI), a person holding the AWS Welding Procedure Qualifier endorsement, or a fabricator’s QA or quality department, working from the contract drawings and the governing code. Its users range from the welder at the torch and the inspector at the joint to the QA manager, the owner’s representative checking compliance, and the auditor who asks for it two years after the job closed. AWS B2.1 is the umbrella specification defining the WPS, PQR and WPQ document set in one place.

The three things a WPS actually does

1. It makes welds repeatable. Two welders on two shifts can produce the same joint because the variables are written down instead of remembered.
2. It makes welds inspectable against objective criteria. An inspector, an owner’s rep or an auditor can answer whether the weld was made as the code says. Without that written baseline, every rejection becomes a debate about intent.
3. It links the drawing, the code and the finished joint. The drawing says what the pipe must do, the code says how it must be built, and the WPS connects the two in metal that has already been poured.

That third point is why the paperwork is not optional. ASME B31.3, Process Piping, paragraph 328.2.1 requires that qualification of the welding procedures to be used shall conform to ASME Section IX. The code does not merely ask for a good weld. It asks for a procedure qualified to a published standard, and it expects you to show it.

What comes next

The rest of this guide covers the anatomy of a WPS, the two routes to qualification (prequalified code procedures versus coupon testing), the governing codes including ASME Section IX, AWS D1.1 and ISO 15614, a method for writing a WPS that survives a production schedule, the mistakes inspectors actually find, and what it means to the welder on the floor.

Why a WPS Matters: The Business Case and the Safety Case

Three rejected radiographs can cost more than the welds ever did. Once a joint comes back from the radiography house, money moves in every direction: the crew stands down, the pipe gets cut out or re-welded, the inspector opens a nonconformance, and the schedule slips. None of it shows up on a purchase order, and all of it lands on one line at the bottom of the year. That is the real question behind a welding procedure specification: what a shop gets back for the time it spends writing one.

The Business Case

A qualified procedure replaces guesswork with repeatable settings, and repeatable settings stop small variations from multiplying down a spool. Fewer rejected welds means fewer cuts, fewer repair cycles, fewer re-examinations and fewer return trips for the NDE crew.

Turnover is the benefit most shops underestimate. A documented procedure lets a new welder be productive on day one, because the daily answers are written down instead of passed down from the old foreman. For shops running SMAW as their workhorse process, the reasons advantages of stick welding keeps coming up are the same reasons a procedure matters: simple to qualify, tolerant of varied shop conditions, and entirely dependent on doing the same thing the same way every time. A shop that hires a few journeymen every season stops paying to rediscover the same answers.

Consistency across shifts and machines follows from that. Same procedure, different welder, different machine, same result. It matters most where the tolerance for improvisation is zero, such as aerospace welding, where the procedure is the contract.

Auditing is the quiet dividend. When an owner representative, third-party inspector or QA manager asks which procedure covers a joint, the answer is a document number and a revision, not a shrug. The same document gives a clean handoff between shop and field: the field crew reads the same ranges, filler metal and inspection criteria the shop worked to.

One counterpoint deserves stating plainly. Documentation costs time upfront and only saves money if the shop actually follows it. A WPS that sits in a binder, is never updated and never reaches the workstation is worse than none at all, because it manufactures confidence nobody earned. The savings are real, but conditional on enforcement.

The Safety Case

Safety here is not about paperwork, it is about heat, hydrogen and cleanliness. A qualified procedure controls heat input, interpass temperature, cleaning between passes and the order of operations. Those variables decide whether a joint cracks, whether hydrogen turns a sound-looking weld into a delayed failure, and whether the finished assembly distorts enough to break a fit-up or stress a nozzle connection later on.

The federal anchor is OSHA 29 CFR 1910.252, the general requirements for welding, cutting and brazing. A WPS does not replace that standard, but most shop-level controls of this kind get written down there:

• Paragraph (a)(2)(iii)(A) requires a fire watch when appreciable combustible material sits closer than 35 feet (10.7 m) to the point of operation, or when wall or floor openings within a 35-foot radius expose combustible material.
• Paragraph (a)(2)(iii)(B) requires that fire watch to be maintained for at least a half hour after welding or cutting stops, to catch and extinguish smoldering fires.
• Paragraph (a)(2)(vii) requires that, where practicable, combustibles be relocated at least 35 feet from the work site, or protected with flameproofed covers or metal guards when relocation is impracticable.
• Paragraph (a)(2)(xi) prohibits welding on a metal partition, wall, ceiling or roof that has a combustible covering, or on walls and partitions of combustible sandwich-type panel construction.

Paragraph (a)(1) points users to NFPA Standard 51B, Standard for Fire Prevention in Use of Cutting and Welding Processes, incorporated by reference into the OSHA rule. That reference shows how deeply codified this work has become. As the AWS standards library shows, the American Welding Society has authored more than 350 standards covering welding practices and procedures.

The real reason safety belongs here is sequence. A good WPS standardizes fit-up, cleaning, tacking, welding and inspection as one documented chain, so the safety engineer and the welding engineer work from the same page instead of two versions of the truth. A traveler that reads torch clean, tack in the root, weld out, clean between passes does safety work as much as quality work. When something goes wrong, the record of what was specified tells you whether the cause was the procedure, the consumable, the machine or the person. That is the difference between a weld that is inspected and a weld that is hoped about.

WPS vs. PQR vs. WPQ: Clearing Up the Acronyms

Three acronyms, three different jobs. A WPS is the instruction. The PQR is the proof that the instruction works. The WPQ is the proof that a particular person can execute it. Mix them up and the paperwork starts to lie to you.

That distinction matters more than it sounds. A shop can hold a beautifully formatted WPS, a binder of coupon results and welder tickets that expired years ago, and the job still fails.

WPS: the instruction

The Welding Procedure Specification tells everyone how a specific weld is made: base metal, joint design, process, position, filler metal, electrical parameters, preheat and interpass temperatures, cleaning requirements, and inspection and acceptance criteria. It is forward-looking. It describes what you are about to do.

PQR: the proof for the procedure

In ASME terminology, the supporting record is the PQR, the Procedure Qualification Record. It captures the actual parameters used when a test coupon was welded, plus the results: macro or micro examination, bend tests, tensile tests, and impact testing where the code calls for it. The coupon testing side is described in detail by organizations such as KTA-TWI. The PQR makes a WPS legitimate rather than aspirational.

WPQ / WQTR: the proof for the person

The WPQ (Welder Performance Qualification) or WQTR (Welder Qualification Test Record) shows that an individual welder passed a performance test for a given process, position and material range. It says nothing about the quality of the procedure itself.

Why the names collide

International shops get permanently tangled here. Under ISO 15614 practice, the procedure qualification record is called a WPQR, the Welding Procedure Qualification Record, while the welder’s own record is called a WPQ. The same four letters mean the procedure record in Europe and the welder record in North American usage, and plenty of projects mix both conventions.

AWS tried to fix this with a single umbrella document: AWS B2.1, Specification for Welding Procedure and Performance Qualification. It defines all three record types and states that the intent is for the specification to be referenced by codes, specifications, contracts, and quality control or quality assurance manuals. AWS also runs instructor-led training titled “WPS, PQR & WQTR” covering the other essential documents for welding and fabrication, plus its self-paced WPS/PQR Explained course. That training exists at all is an admission the confusion is endemic.

Side by side

Document	What it is	Who signs it	What it proves	Validity and use
WPS	Instruction for making a specific weld	Engineer, CWI or authorized procedure qualifier	Nothing alone; valid with a PQR or a prequalified code provision	Used until superseded
PQR	Coupon parameters plus test results	Shop welding engineer or third-party test laboratory	Procedure qualified, with exact proven ranges	Supports several WPSs at once
WPQ / WQTR	Individual welder’s performance test record	Shop inspector or test agency administering the test	Welder can weld that process, position and material range	Follows the welder; retest for a new process or position

One PQR, several WPSs

Qualification travels. One qualified PQR can justify multiple WPSs, as long as each stays inside the proven ranges for base metal, thickness, position, process and supplementary variables on that record. A PQR qualified on carbon steel at 60 to 110 amps can back a 3/8 inch line and a 5/8 inch line, because both sit inside the tested envelope. A WPS calling for 135 amps walks straight out of it.

TWI puts it plainly: essential variables define the edges of the qualified range, and anything outside those edges is unproven.

A quick scenario

Your shop qualifies one PQR for SMAW on carbon steel covering 3/8 to 5/8 inch wall thickness in 3G and 6G positions, using E7018. That record supports two WPSs: one for horizontal pipe runs, one for vertical risers. Welder A holds a 3G ticket; Welder B holds a 6G ticket, which means B also passed the 3G test. On the horizontal spools either welder can work; on the riser spool, only B can. One PQR, two WPSs, two welders, two WPQs.

The reverse trap is common too. A 6G SMAW ticket does not let a welder run GTAW on aluminum, and a 3G carbon steel ticket does not cover a stainless spool in a different material group. Qualification does not transfer to a different process, position or material group without separate performance qualification, even when the procedure itself is fully qualified. Strict requalification is the norm in sectors like aerospace welding, where a pipe test on carbon steel buys nothing on titanium.

Position also drives electrode handling. If the procedure calls for SMAW in 6G, running out and restarting a bead on a vertical joint deserves a refresher, and our all-position welding rod guide covers how the same consumable behaves when the joint keeps moving under the arc.

Short Note: File the three documents together in the shop library. When an auditor asks “prove this procedure is qualified,” the answer is one folder: the WPS in front, the PQR behind it, and the WPQ of the welder who ran it.

What’s Inside a Welding Procedure Specification: A Field-by-Field Tour

Most welders meet their first WPS clipped to a welding cart, folded down to the size of a lunch receipt, half of it hidden under tape. That is exactly how the pipe in our opening story got welded. The paper existed somewhere in a filing cabinet, but the range of amperage that was actually proven on the test coupon, the filler metal that was actually used, and the radiography that was actually required never made it to the workstation.

So read a WPS as a set of answers, not a set of blanks. Here is the field-by-field tour of what a real one contains.

1. Identification and metadata. WPS number, revision letter or date, the code basis (ASME B31.3, AWS D1.1, ISO 15614), the material standard, and usually the shop, welder, date and the PQR that supports it. This block is what makes the document traceable. A WPS without a revision field is a document nobody can supersede.
2. Base metal. Specification and grade, such as ASTM A106 Grade B seamless pipe, the type (plate, pipe, tube, forging), the thickness range, the diameter or size range, plus any heat treatment condition or cladding. The thickness range is the field that decides whether the procedure applies to your weld at all, so it is never left blank or vaguely stated as “typical.”
3. Joint design. Joint type, groove geometry, groove angle, root face, root opening, backing, and whether the joint is a complete joint penetration or partial penetration weld. This is where multi-pass work gets described: stringer or weave beads, number of passes, and whether back gouging is required. Back gouging to remove the root bead between passes is standard practice in heavy fabrication, and air arc gouging is the usual tool for it.
4. Filler metal. The AWS classification (E7018, ER70S-6, E71T-1 and so on), the diameter range, and the number of passes. For critical service you will also see a diffusible hydrogen limit and a Charpy V-notch toughness requirement. Reading the digits in a classification takes practice, and a practical all position welding rod guide helps decode what the “1” and the “8” actually promise.
5. Process and technique. SMAW, GMAW, FCAW, GTAW or SAW, plus the position (plate, pipe, horizontal-vertical fixed, 6G), the progression (uphill or downhill), weave or stringer, and the interpass cleaning method. These are not cosmetic. Change the process or the position and you have left the qualified envelope entirely. Each process has its own character and control requirements, from why SMAW still wins on field work to the tight, gas-controlled demands of aerospace TIG welding.
6. Electrical and travel parameters. Amperage and voltage ranges, travel speed, wire feed speed where applicable, shielding gas type and flow rate, and polarity. These are ranges, never a single number.
7. Thermal controls. Minimum preheat, maximum interpass temperature, and post-weld heat treatment if the code or the material demands it. Preheat and interpass maximum are mandatory entries on carbon steel work where the code calls for them, and blowing past the interpass maximum is one of the most common root causes of hydrogen-assisted cracking findings.
8. Supplementary variables. These are the extra controls the code adds on top of the essential ones: heat input per unit length, maximum weld size, maximum reinforcement and undercut limits, and sometimes interpass temperature. In structural work under AWS D1.1, leaving them off is one of the fastest ways to fail an audit.
9. Inspection and acceptance. Visual acceptance criteria, the NDE method and extent (for example, 10% radiography), and a reference to the code acceptance criteria that the results are judged against. A WPS that names the inspection but not the acceptance criteria leaves the inspector with nothing objective to work from.

Parameter	Setpoint only (weak)	Qualified range (correct)
Amperage	85 A	60–90 A
Travel speed	4 in/min	3–6 in/min
Interpass temperature	300 °F	Max 350 °F
Filler metal	E7018	E7018, 3/32 in and 1/8 in dia.

AWS organizes the details a procedure must record into a standard format, which is why so many fabricators build their internal WPS form around the AWS B2.1 structure, even when the governing contract code is ASME. If you would rather not design a form from scratch, AWS publishes free downloadable WPS forms and prequalified procedure resources on its Free Welding Resources page, which gives you a compliant starting structure instead of a blank sheet.

The classic mistake: copying a shop house sheet that records only the settings the floor likes to use, with no qualified ranges, no filler metal classification, and no inspection requirements. It looks like a WPS on the clipboard and it is worth exactly as much as the paper it is printed on. When a radiograph comes back rejected, a house sheet cannot tell you whether the amperage was inside the qualified band, and neither can the shop.

How Welding Procedures Get Qualified: Prequalified vs. Performance Testing

Writing a welding procedure specification does not qualify it. A WPS that comes off a word processor and goes into a binder is a statement of intent. It becomes usable only when something proves it, and there are two ways that proof happens. One leans on a code that already tested the joint for you. The other welds a real coupon, tests it, and lets the results define what your shop may weld. Knowing which route applies separates a procedure an auditor accepts from one that gets a job shut down.

Both routes share one idea. TWI summarizes it directly: essential variables are detailed in the relevant specification and typically include material type, welding process, thickness range and sometimes welding position. Change an essential variable and you have stepped outside the qualified envelope, so you requalify. Set the other category, supplementary essential variables, and nothing is requalified, but the values must still be recorded and controlled. Heat input, maximum weld size and interpass temperature usually live in that second bucket. The AWS B2.1 specification for welding procedure and performance qualification defines both routes in detail.

Route one: prequalified procedures

Structural codes publish prequalified welding procedures for common joint configurations, and AWS D1.1 is the best-known example. If the base metal, joint design, process, filler metal, position, preheat and interpass conditions all fall inside the prequalified provisions, a fabricator may use that procedure without a separate qualification test. The joint is not your invention, and neither is the test behind it. The current AWS standards listings show which structural documents carry this machinery.

Prequalified does not mean no paperwork. It means the testing burden is replaced by strict compliance. Every supplementary essential variable still has to be recorded on the WPS and controlled in production, and in AWS D1.1 work that means heat input per unit length, maximum weld size and interpass temperature. Miss one and the prequalified status evaporates even though nothing about the joint changed. Treat prequalification as a shortcut and you end up welding outside the code with a document that says you did not.

Route two: qualified by performance testing

Under ASME Section IX the ordinary path is a physical coupon. The fabricator welds the coupon using the procedure it intends to use, records the actual parameters on the PQR, then subjects it to the prescribed testing before the WPS is written. Typical testing includes visual examination, macro or micro examination, bend tests, and fracture or tensile tests of the weld metal, with impact testing or nondestructive examination called in for certain materials and services. Piping work follows the same structure, since ASME B31.3 points welding procedure qualification back to Section IX. KTA’s overview of procedure qualification testing walks through the coupon testing sequence in more detail.

ISO 15614-1 runs the same logic with a WPQR instead of a PQR, and it defines qualification ranges for thickness and positions that form the basis of the EN 15614 qualification tables used across European practice. The output is a proven range with a WPS written to stay inside it. In aerospace, where a single coupon can trigger a full material and process qualification campaign, the cost of that route becomes obvious, and the aerospace welding standards and career guide is a good primer on how tight those requirements are.

Why the qualified range is not the same as the test value

A coupon welded at 95 A does not mean you can only weld at 95 A. The coupon proves a range around the tested values, and that range is the envelope you may use in production. Section IX is fairly tight here: for SMAW, QW-252 permits a qualified amperage range of plus or minus 10 percent of the coupon value when voltage is not a controlled factor, so 95 A supports roughly 86 to 104 A. Other specifications control heat input and weld size instead and permit wider bands. In practice shops write the band they will actually run, so a WPS may list 60 to 110 A, or be narrowed to 80 to 100 A so welders stay comfortable. Wider is faster to set up; narrower is easier to hit on the first try. The case for stick welding often rests on exactly that kind of forgiving operating window, which is why position and electrode choices matter as much as the numbers.

Positions deserve special mention, because a change of position is a change of essential variable. A coupon qualified in one position does not cover another, which is why a guide to all-position electrodes matters when you plan what to qualify next.

Factor	Prequalified procedure	Qualified by performance testing
Rules come from	Code provisions, such as AWS D1.1	ASME Section IX QW-200 series, ISO 15614-1
Test coupon	Not required	Required, plus mechanical and NDE testing
Record produced	WPS with supplementary variables recorded	WPS plus PQR or WPQR with test results
Speed and cost	Fast, inexpensive	Slower: coupons, lab fees, possible travel
Flexibility	Limited to prequalified configurations	Nearly any joint, material or position
Main risk	Conditions drifting outside the limits unnoticed	Writing a WPS broader than the coupon supports

The trade-off is straightforward. Prequalified is faster and cheaper but only available for the joints a code author thought to cover. Performance testing costs real money and calendar time but it will qualify an unusual groove, an awkward material or a position nobody publishes. Check the AWS free resources and our welding guide before you commission testing, since much of the prequalified ground is already mapped out.

The Codes That Govern Your WPS: ASME Section IX, AWS D1.1, and ISO 15614

Every qualified welding procedure specification traces back to a code. Not a house standard, not a preference, not the memory of a retired foreman. A code. And the single most common confusion among shop owners, QA managers, and even experienced welders is which code is actually in charge of their paperwork.

Here is the useful distinction. A construction code tells you what to build and what acceptable weld looks like. A qualification code tells you how to prove your welder and your procedure are capable. Most shops need both, and they are written by different organizations.

ASME Section IX: The Qualification Engine

ASME BPVC Section IX, titled Welding, Brazing, and Fusing Qualifications, is the qualification half of the puzzle, and it is organized in three clean blocks:

• QW-100 — General requirements. Defines the scope, the personnel categories (welding procedure specification, procedure qualification record, welder performance qualification, and the supporting records), and the general obligations that apply to everything that follows.
• QW-200 — Qualification for welding procedures. This is where the WPS lives. It sets out the essential variables for each welding process (SMAW, GMAW, FCAW, GTAW, SAW and others), defines what counts as a supplementary essential variable, and states the ranges that must be recorded and controlled. QW-200 is the clause a procedure writer lives inside.
• QW-300 — Performance qualification for welders and welding operators. This is the clause that governs the WPQ or WQTR, including continuity requirements and the retest provisions.

Now the part people miss. Section IX does not tell you what to build. It tells you how to qualify. It has no opinion about pipe schedule, wall thickness, design pressure, or service temperature. Those come from the construction code, and for piping that means B31.1 for Power Piping, B31.3 for Process Piping, Section VIII for Pressure Vessels, and Section I for Power Boilers.

The delegation is explicit. ASME B31.3 paragraph 328.2 refers welding procedure qualification back to ASME Section IX, and the U.S. Department of Energy’s published comparison of EN 13480 and ASME B31.3 documents that same structure clearly: each construction code delegates qualification to its own qualification standard, with B31.3 pointing at ASME IX. As The Fabricator has pointed out, this is why most shops end up owning both documents, because the code itself does not cover welding qualification as such.

For shops working in nuclear and energy sectors, Los Alamos National Laboratory’s ASME B31.3 Process Piping Guide documents that reference structure in detail, and it is worth reading if your work sits anywhere near that world.

The AWS Side: Structural, Aluminum, Bridge, Sheet Metal

AWS codes fill the same role for structural and aluminum work. The current AWS standards listings show AWS D1.1/D1.1M:2025-AMD1 for structural steel welding and AWS D1.2/D1.2M:2026 for aluminum. Other workhorse documents include D1.5 for bridge welding, D9.1 for sheet metal, and A3.0 for tube mill products. Because AWS revises these on a rolling cycle, fabricators should always confirm the edition named in their contract specifications rather than assuming the newest print.

For aluminum specifically, the material behavior changes everything about how you qualify. Our guides on aluminum MIG welding and aluminum flux core welding cover the practical side, but the paperwork side follows D1.2, which treats process and filler selection differently than the steel codes do.

Overarching all of it is AWS B2.1, Specification for Welding Procedure and Performance Qualification. AWS states plainly that B2.1 is intended to be referenced by other documents such as codes, specifications, contracts, and quality control or quality assurance manuals. That is why you will see it named in purchase orders and QA manuals even when the job itself is governed by B31.3 or D1.1. B2.1 goes through periodic revision cycles, so check which edition your documents cite.

ISO 15614 and the European Route

Across Europe, ISO 15614-1 covers the specification and qualification of welding procedures for arc welding of steels, and EN 13480 is the pressure piping standard that points back to it. The vocabulary differs from ASME, and this is where confusion starts: ISO uses WPS for the instruction and WPQR for the welding procedure qualification record, whereas ASME calls that same record a PQR. Identical documents, different names. The TWI job knowledge on welding procedure qualification explains the mechanics of essential variables under ISO practice, and the concepts map cleanly once you translate the labels.

Which Code Governs Your Work

Industry / Work	Typical Governing Code	Qualification Standard
Structural steel buildings and bridges	AWS D1.1/D1.1M (structural), AWS D1.5 (bridge)	AWS D1.1 / D1.5, AWS B2.1
Process piping	ASME B31.3	ASME Section IX
Power piping	ASME B31.1	ASME Section IX
Pressure vessels	ASME Section VIII Div. 1	ASME Section IX
Boilers	ASME Section I / Section VIII Div. 1	ASME Section IX
Pipeline transmission	ASME B31.4 / B31.8	ASME Section IX
Aluminum structures	AWS D1.2/D1.2M	AWS D1.2, AWS B2.1
Sheet metal fabrication	AWS D9.1	AWS D9.1, AWS B2.1
Aerospace	AWS D17.x series, customer specifications	AWS D17.x, customer specs
Offshore and marine	AWS D1.1, D1.6, D3.6, ASME codes as specified	AWS B2.1 and ASME IX as invoked
European pressure piping	EN 13480	ISO 15614-1

One more thing that catches people: a single job can sit under several codes at once. A pipeline crossing a refinery boundary might have API 5L materials, ASME B31.4 design and construction, and owner-specific QA requirements that add to both. Always read the contract specifications before you read the code, because the contract is what tells you which code edition and which qualification route apply to your specific weld.

Next, we get practical. Section 7 walks through how to actually write a WPS that survives a Monday morning on the shop floor.

How to Write a WPS That Actually Works on the Shop Floor

A WPS is easy to write badly: fill in the header, type one amperage value, sign the bottom, file it. That satisfies a clerk and fails an inspector. Writing one that survives production takes a specific order of operations, and the order matters more than the formatting.

1. Read the governing documents first. Pull the contract drawings, the code of construction and the project specifications before you touch a form. Build a joint list: joint type, base metal specification and grade, wall thickness range, diameter, service conditions (pressure, temperature, corrosion, cycling) and client additions such as radiography extent or impact testing. In process work, ASME B31.3 and the project specification are the usual pair.
2. Inventory what you already have. Check the PQR library, prequalified procedures published inside codes like AWS D1.1, and proven shop history on comparable work. A qualified procedure that already covers the joint is free; a new coupon is not. Reuse before you re-test.
3. Decide the route. If the joint matches a prequalified configuration in the code tables, use it and record every supplementary essential variable. If it does not, performance qualify by coupon. Prequalified is not paperwork-free: it trades testing for strict compliance with conditions you must document.
4. Choose the process and filler metal deliberately. Let service conditions decide: corrosion resistance, operating temperature, toughness, dissimilar metal, welding position and access. SMAW still wins in dirty or confined joints and on field piping, while GTAW or GMAW often beats it on thin material and cosmetic work. Electrode selection for all-position work is covered in this all-position rod guide.
5. Set parameters from proven data, not instinct. Establish the wire feed to amperage relationship, the voltage window, the travel speed, and the preheat from material thickness and carbon equivalent. Heat input per unit length must be calculated from travel speed, voltage, current and the process efficiency factor. It is one of the most frequently mishandled values on shop forms, and it is a calculation, not a guess.
6. Validate on a test coupon and record the actual values. Weld the coupon, run the required testing, and write the real numbers onto the record. Then define the qualified range conservatively inside what the test proved. Coupon testing and examination follow published requirements, and TWI explains why the essential variables define the edges of that range.
7. Write it on a structured form with no blanks. A WPS form with blank fields is an audit finding. Write N/A or None instead. AWS B2.1 supplies the reference structure for the procedure record, so building internal forms around its layout reduces rework when a project specifies a B2.1-based submission package. Start-up forms and prequalified resources are available through AWS free resources.
8. Review, approve, control and distribute. Have a qualified welding engineer or an AWS Certified Welding Inspector review it independently and sign it. Then set up revision control, get copies to the shop floor and post the current version at the workstation. Consumables get controlled the same way: name the classification, specify diffusible hydrogen limits where the code requires them, and verify the certificate of conformity on each filler metal lot.

A Worked Example: 6-Inch Schedule 40 Carbon Steel Process Line

Assume a root and fill joint on 6-inch Schedule 40 ASTM A106 Grade B piping. The procedure reads: SMAW root and fill, E7018 electrodes at 3/32 inch, stringer beads uphill, 60 to 90 amps, 20 to 24 volts, preheat per material thickness requirement, interpass cleaning with a wire brush and acetone, visual inspection on 100 percent of welds and radiography on 10 percent. Note what it does not say. It does not say “60 amps.” It says the qualified range, so every welder, inspector and auditor reads the same number. The 10 percent RT extent comes from the project specification, not from the welder’s memory.

Parameter Starting Points

Process	Typical filler	Indicative starting values
SMAW	E7018 (3/32 in)	60 to 90 A, 20 to 24 V, stringer beads uphill
GMAW	ER70S-6, C25 shielding gas	Wire feed 250 to 350 in/min, 18 to 22 V, 60 to 90 A
FCAW	E71T-1C	Wire feed 200 to 350 in/min, 19 to 24 V, 70 to 130 A

Build the Library and the People Behind It

A single WPS is a snapshot. A shop really needs a controlled library with revision history, a rule that every NCR triggers a procedure review, and at least one person whose actual job is writing and updating these documents. AWS certification paths map directly onto that work: Certified Welding Inspector (CWI), Certified Welding Supervisor (CWS), Certified Welding Engineer (CWENG), Certified Robotic Arc Welding (CRAW) for automated cells, plus the Welder Performance Qualifier (WPQ1) and Welding Procedure Qualifier (WPQ2) endorsements. WPQ2 exists specifically for people who write and qualify procedures. AWS also runs a self-paced WPS/PQR Explained course because, as AWS puts it, these documents are commonly misunderstood. Train someone properly, give them revision control, and the shop stops reinventing procedures every time an inspector asks a question.

Common WPS Mistakes and How to Fix Them

Most WPS problems are not welding problems. They are documentation problems that finally show up as welding problems, usually three radiographs and one very expensive week later. Here are the ten errors that inspectors and QA auditors find over and over, and the fix for each one.

1. Using a WPS that does not cover the joint you are welding. A procedure covers only what it lists. If the qualified thickness range, welding position, process, joint configuration or supplementary variables exclude the production joint, the weld sits outside the procedure no matter how carefully it was made. Fix: qualify the actual condition. Never widen the paperwork to fit the weld you already made.
2. Recording one set of parameters instead of a qualified range. A WPS that lists “115 A, 22 V” and nothing else tells the welder nothing about what else is allowed. Fix: transcribe the full qualified range from the PQR or WPQR, with the limits your test actually proved, as described in the AWS B2.1 qualification specification.
3. Filling the form with “typical” values from a handbook. These look authoritative and prove nothing. Fix: every number has to trace to a test coupon you ran or a prequalified code table you satisfied.
4. Omitting supplementary essential variables. In AWS D1.1 prequalified work, heat input per unit length, maximum weld size and interpass temperature are essential variables you must record and control even though no coupon is required. Fix: pull them from the prequalified provision in the current AWS structural welding standards, and record them on the WPS.
5. Leaving the joint design vague. No root face, root opening, groove angle, backing or joint configuration means the welder is improvising the geometry that was never qualified. Fix: add a joint detail drawing or a precise written description to the WPS.
6. Omitting filler metal traceability. Record the classification and, where required, the lot or heat number alongside the manufacturer’s certificate of conformity, so the consumable can be tied back to the weld. Fix: build lot traceability into your receiving process; regulated work such as aerospace and nuclear welding expects this from day one.
7. Confusing the WPS with the shop instruction sheet. If the only document at the workstation is a traveler that says “weld per WPS,” the ranges and acceptance criteria never reach the welder. Fix: derive a readable work card from the WPS, with the limits printed on it. See our guide to all-position welding rods for how much procedure detail actually matters at the stinger.
8. Copying another shop’s WPS. It looks complete and was never qualified for your base metal specification, your joint or your test conditions. Fix: treat a borrowed form as a template only, then qualify it for your work.
9. Assuming repair and rewelding are already covered. They usually are not. Repair, rewelding and gouging need their own qualification or a code-approved repair procedure, and gouging carries its own hazards under OSHA 1910.252. Fix: qualify them separately. Our overview of air arc welding and carbon arc gouging covers the process side.
10. Ignoring revision control. Obsolete WPS versions sit at the workstation long after the code, the filler metal or the procedure changed. Fix: date and number every issue, withdraw old copies physically, and audit what is actually posted.

Troubleshooting Path: When a Weld Gets Rejected

Work the symptom back to the variable. This mapping is standard practice in welding troubleshooting and is what turns a rejected coupon into a fixable procedure.

Symptom	Check this WPS variable first	Look for
Porosity	Cleanliness, shielding gas, consumable moisture	Mill scale, rust, paint, oil, damp electrodes, wrong gas flow
Undercut	Amperage, travel speed, arc length	Too much current for the bead, slow travel, a wandering arc
Lack of fusion	Heat input and bead placement	Cold starts, wrong bead sequence, contaminated surfaces
Excessive reinforcement	Maximum weld size, heat input per unit length	A supplementary variable exceeded on a D1.1 prequalified joint
Cracking	Hydrogen control, preheat, interpass temperature	Wet consumables, no preheat, interpass too high
Poor profile or spatter	Wire feed speed against amperage	Settings outside the qualified window, a worn gun or liner

Notice how the same root cause shows up in several rows. A WPS that says nothing about interpass temperature or preheat is not a neutral document. It leaves the welder free to drift into a condition the procedure never controlled, and the crack or the rejection follows later.

Treat Every Nonconformance as Data

A rejected weld is not a failure, it is a free measurement. Feed it back into the procedure, the consumable control plan, the equipment maintenance schedule or the welder’s qualification, whichever the symptom points to. Shops that treat nonconformances as a source of information get better welds. Shops that treat them as paperwork to be closed out just get the same rejection again next quarter. Prequalified procedure resources and blank WPS forms are available through the AWS free resources page if you need a clean starting point rather than a copy of somebody else’s history.

What the WPS Means for the Welder on the Floor

A procedure gets written and qualified in a lab, but the weld is made by someone standing over a hot joint in a shop colder than the drawings assume. What does that mean for the person holding the stinger?

The answer is simpler than most people expect: the WPS is the welder’s reference. Before the arc is struck it says what you are allowed to do: electrode, amps, travel speed, interpass heat, and where the inspector wants to look. A good procedure lets a welder run the job right the first time, without phoning QA mid-bead.

Two Documents, One Job

Mature shops run two versions of the same information. The full WPS goes to QA, the inspector, the client, and the project file. The condensed version, a work instruction, traveler, or WPS card, is posted at the welding station with the essentials: joint, process, filler metal, amperage and voltage ranges, preheat, maximum interpass temperature, cleaning method, and hold points where inspection must happen before the weld is closed out.

If the card and the WPS ever disagree, the card is wrong. The controlled document wins and the card gets reissued.

Working Inside the Qualified Range

A WPS states ranges, not single numbers, and staying inside them is the welder’s real job.

• Amperage, voltage and travel speed. These three drive heat input, and heat input drives weld shape. High amperage gives undercut and heavy reinforcement; low amperage gives a cold, sluggish bead that risks lack of fusion.
• Consumable handling. Electrodes live in a dry rod holder or holding oven, not a wet cart. Re-dry them per the manufacturer’s instructions and keep lot numbers for traceability. Selection and handling details are worth a look in this all-position welding rod guide, and if you are on stick, the case for it is laid out in why SMAW still wins.
• Preheat. Maintain it between passes, not just at tacking. A torch that cools the joint faster than the procedure expects changes the weld.
• Cleaning between passes. Remove slag, spatter and oxidation to the standard the WPS names. Most slag inclusions start with an uncleaned pass.

The Safety Context Belongs in the Procedure Too

A procedure specification covers the conditions of the work, including PPE and the surroundings. OSHA 29 CFR 1910.252 is the governing standard, and its requirements are worth reading in full.

• Paragraph (b)(2)(ii)(A) requires helmets or hand shields for all arc welding or arc cutting except submerged arc welding, plus eye protection for helpers and attendants. The filter-shade guide in (b)(2)(ii)(H) lists shade 10 for shielded metal-arc welding with 1/16- to 5/32-inch electrodes, shade 12 for SMAW with 3/16- through 7/32-inch electrodes, and shade 12 for gas-shielded arc welding of ferrous metals.
• Paragraph (c)(1)(iii) requires local exhaust or general ventilation to keep toxic fumes, gases and dusts below the maximum allowable concentration specified in 1910.1000. Fume fever comes from the metal, not the flux. Paragraph (c)(1)(iv) requires employers to fold hazardous materials in fluxes, coatings, coverings and filler metals into their Hazard Communication program, with labels and safety data sheets available to employees.
• Paragraph (c)(1)(v)(B) sets the minimum container notice for filler metals and fusible granular materials: “Do not use in areas without adequate ventilation. See ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes.”
• Keep combustibles 35 feet clear of the work area and maintain a fire watch for at least 30 minutes after the last arc is cut.
• Paragraph (b)(4)(vii) requires the welder to mark hot metal or warn other workers after completing operations in a confined space.

Deviations Are Not a Welder Decision

This is where shop culture gets tested. If the joint, position, thickness or machine setup falls outside the WPS, the welder cannot fix it by adjusting the knobs. It takes an engineering change, a new qualification, or both. Outside the qualified range, nobody knows what the weld looks like until it is proven on a coupon.

AWS B2.1 sets out the qualification framework governing both the procedure and the welder’s ticket, and a copy is worth keeping at the station. AWS B2.1 is the reference shops cite when a question comes up about what was and was not qualified.

New Hires and What Good Discipline Buys You

A shop with clean procedures can welcome a new welder without months of shadow training. The new hire reads the card, sees the ranges, and learns the craft instead of copying somebody’s habits. That is why aerospace welding school style programs, and the AWS Certified Welder track in general, put so much weight on running to a qualified procedure. The payoff shows up in turnover, consistency between shifts, and audits that stop being a scramble.

The reference the welder actually holds is the WPS. Everything else, from the traveler to the safety rules, exists to make sure that one document is followed.

Conclusion: Building a WPS Program That Survives Contact With Production

Strip away the forms and the acronyms and the whole subject rests on three documents that have to agree with each other. A welding procedure specification is the written, code-compliant instruction for how a weld is to be made. A PQR (called a WPQR in ISO 15614 practice) is the record proving that procedure was actually qualified on test coupons. A WPQ or WQTR proves the individual welder is qualified for that process, position and material range. One tells the crew how to run the arc, one proves the recipe works, one proves the person on the stinger can run it. Leave any one of them out and the other two stop meaning anything.

The logic travels well across code families. ASME B31.3 delegates welding procedure qualification back to ASME Section IX, and EN 13480 does the same job through ISO 15614 in Europe. Whichever book sits on your table, the sequence never changes: qualify the procedure, qualify the welder, then accept the weld.

Five Habits That Separate Living Documents From Paperwork

1. Build a master library with real revision control. One indexed register of every qualified procedure, tied to its supporting PQR, its revision date and its applicable range. Nothing lives on a clipboard or a shared drive folder named “WPS old.” If a procedure is superseded, the obsolete copy is pulled from the workstation the same day.
2. Mine the data. Every nonconformance, every coupon result and every repair is free information about where your procedure is weak. Log it, then act on it. A recurring undercut complaint is not a welder problem until you have checked the amperage and travel speed the procedure actually permits.
3. Review on triggers, not on schedule. Any change of base metal specification, welding machine, position, or consumable should send the procedure back for a look. So should every NCR that cites a parameter. TWI’s guidance on qualification ranges explains why: a procedure is only proven inside the envelope the test established, so anything that shifts the conditions is a reason to look again. That is also why qualification is transferable. Qualify once, inside a stated range, and you can deploy that procedure across many jobs instead of re-testing on every contract.
4. Produce two formats, not one. The full WPS belongs in the QA file where an auditor can trace it. The welder gets a condensed, readable card derived from it. A shop still running SMAW on structural and pipe work will get more from a clear practical guide to stick welding than from a photocopy of the form.
5. Train and certify the people who write procedures. This is the habit most shops skip and the one that causes the rest to fail. AWS treats procedure qualification as a distinct, certifiable skill, with a Welding Procedure Qualifier (WPQ2) endorsement sitting alongside the Welder Performance Qualifier (WPQ1) on its certification and education menu. AWS also supports employers building structured qualification programs through its Welder Program (CWP) instead of informal shop habit.

Where this is heading is not more paperwork. Robotic cells increasingly load a qualified parameter set directly into the machine recipe, which is why AWS maintains a dedicated Certified Robotic Arc Welding (CRAW) credential for operators working those systems. In additive manufacturing, the parameter set effectively becomes the product specification, and in sectors such as aerospace welding the traceability trail is already contractual. Meanwhile owner QA regimes keep tightening, treating documentation as a deliverable rather than an administrative courtesy. Shops that build the habit early will find that the WPS is simply how they work, not a separate paperwork exercise.

A good WPS is not bureaucracy. It is the difference between a weld that is inspected and a weld that is hoped about.

Frequently Asked Questions

What is the difference between a WPS and a PQR?

A WPS is the instruction telling how a weld is to be made — process, materials, parameters, positions and inspection criteria. A PQR is the record showing the procedure was qualified: it captures the actual settings used on a test coupon plus the test results. The PQR is the evidence; the WPS is the rule derived from that evidence.

Do I legally need a WPS to weld?

For most hobby and general fabrication work, no — OSHA’s welding standards in 29 CFR 1910 Subpart Q govern safety practices, ventilation and PPE, not procedure documentation. WPS requirements come from the contract, the governing design code (ASME, AWS D1.1, API 1104) or the owner’s quality system. Code-governed pressure work, structural steel to AWS D1.1 and nuclear or offshore fabrication do require qualified procedures.

What is a prequalified welding procedure?

It is a procedure published inside a code, such as AWS D1.1, that you may use without running your own qualification coupon — provided every condition of the prequalified provisions is met and all supplementary essential variables, like heat input and maximum weld size, are recorded and controlled. Prequalified means the testing burden is replaced by strict compliance, not that paperwork is optional.

How long does it take to qualify a welding procedure?

It depends on the route. Using an existing prequalified procedure takes hours of paperwork. Qualifying by performance testing means welding coupons, having them machined and tested (bend, tensile, macro or micro), then writing the WPS — commonly a few weeks, and longer if the lab turnaround or a failed coupon is involved. A failed coupon is normal and simply means you adjust and repeat.

Can I use a WPS written by another company or supplier?

Only if it genuinely covers your work and you can prove it. Many suppliers publish shop procedures with wide, well-qualified ranges, which are genuinely useful for common joints, but you must confirm the base metal specification, joint design, process, position and thickness all fall inside the qualified limits, and that the document was produced under a code your project accepts. Never assume; read the ranges.

What is a WPQ and how is it different from a WPS?

A WPS qualifies the procedure — the way the weld is made. A WPQ (or WQTR in ASME language) qualifies the person — it records that an individual welder passed a performance test for a given process, position and material range. A shop can have a perfectly qualified WPS and still be unable to assign the job if no welder holds the matching WPQ.

Which welding code should my WPS follow?

Follow the code named in the contract specifications first, since it governs the acceptance criteria you will be judged against. In general, ASME Section IX qualification with ASME B31.1, B31.3 or Section VIII governs pressure work; AWS D1.1 governs structural steel; API 1104 governs pipeline; and ISO 15614 governs European practice. When the contract is silent, ask the engineer of record rather than guessing.

What happens if a weld is made outside the WPS?

It is a nonconformance, and it usually means the weld is rejected until disposition. The inspector’s options typically include repair or removal and rewelding under a qualified repair procedure, or engineering evaluation and acceptance. That is why deviations must go through an engineering change or a new qualification, never an informal decision at the workstation.

Do I need a WPS for a small shop or farm-style repair work?

Formal code qualification is usually unnecessary, but writing down your own settings as a standard work instruction is still worthwhile — it makes the work repeatable, stops two welders from doing it two different ways, and helps the next person after yours. Treat it as a shop standard rather than a code document, and revisit it when the material, machine or position changes.