Welding procedure specification WPS: the welder’s guide

Every company or plant that has some production process needs to have rigorously described documentation for each link in it, in order to ensure repeatability and match governmental standards of the final product.

If such a process includes a weld as a part of it, the whole welding procedure must be carefully described, as well, since the quality of each welding seam in the construction contributes to its overall reliability and sturdiness.

The ultimate quality of the desired weld shouldn’t depend on the welder’s experience and identity, and a welding procedure specification (WPS) is the key element in securing production process flexibility. You’ll find out some general info on WPS from the text below.

welding procedure specification

Welding procedure specification WPS and its subtypes

According to AWS A3.0 – the American National Standard, welding procedure specification WPS can be aimed at underqualified welders – preliminary WPS (prequalified WPS) and at qualified welders – QWPS (qualified WPS).

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Simply put, these two types of welding procedure specification WPS pursue the same goal: standardization of a technological process, but imply different welds’ complexity, hence different welders’ proficiency levels required.

The whole welding process is described by parameters called welding variables. Variables determine every aspect of the welding procedure that is more or less significant for the final seam.

Welding variables are the central element of welding procedure specification, since following it a welder or a welding operator understands what type of welding, filler metal, and base material must be used, a joint’s position, post-weld heat treatment, etc.

The whole list of code requirements for welding variables can be found in any welding code (for instance, ASME – American Society of Mechanical Engineers or API – American Petroleum Institute).

In general, three types of required welding variables can be distinguished: essential, supplementary essential, and non-essential (as per ASME section IX).

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Essential variables (QG-105.1, QW-251.2 as per ASME) and supplementary essential variables (QG-105.3, QW-401.1) are the types of variables, which are crucial for the basic properties of conjunctions.

The major difference between these two types is in toughness tests – supplementary essential variables are used only when toughness testing of the joint is required.

The electrical characteristics, filler metals, base materials, inert gas usage, and the like: all those parameters are essential variables.

Supplementary essential variables determine the parameters of a toughness test coupon if such testing is needed. These variables describe the coupon group number, its thickness, etc.

Nonessential Variables (QG-105.4, QW-251.3) are less significant in terms of a joint’s sturdiness, that’s why their implementation is largely at the discretion of a welder.

The amperage and the voltage, for example, are not quite crucial for the joint’s sturdiness, therefore, their values may fluctuate within a relatively wide range, in accordance with a welder’s convenience.

Nevertheless, changes in non-essential variables must be mentioned in a welding procedure specification.

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Welding procedure specification development

First of all, developing a welding procedure specification needs a strong comprehension of the welding process.

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An engineer must be aware of welding principles and modes, base materials’ characteristics, welding machines and equipment, and safety measures as well.

The Preliminary welding procedure specification (PWPS) is the draft project of the welding procedure specification WPS, and at this step, the welding engineer assumes standard values to be tested for the welding procedure qualification record (PQR).

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The figures for welding codes and materials must correspond to standard values from welding code charts (ASME, Section IX).

Once the preliminary welding procedure specification is finished, the welding engineer has to run a series of tests, like tension and bend tests for samples.

Welding types and codes

All data received is put into PQR tables, and the test results match standard ranges.

Tests for PQR are of two kinds: destructive and non-destructive testing.

Non-destructive testing, obviously, doesn’t imply sample damage, whereas destructive test coupon is being destroyed during the test.

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Visual welding inspection, radiography and ultrasonic examination, liquid penetration, and magnetic particle examinations are the most commonly run non-destructive testing.

Most of the mechanical testing like tension and bending tests, as well as the aggressive environment and corrosion tests, are destructive.

Welding procedure specification is designed for precise implementation of constructions in a workshop, it’s strongly bonded with other production chain links, and a workshop welder has to closely follow the written document.

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Only meticulously organized processes can provide production meeting the highest standards, and the reliability of quality welds is the key element in 0verall output quality.

At times, when a production process requires especially high reliability of weld joints, final tests may be done. In general, the more manufacturing there is, the more rigorous and sometimes redundant testing is done, although it depends on the company’s responsibility.

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Only highly professional welders or welding operators must be eligible to run pre-production testing. If the results received from the final tests do not agree with the standards, the welding procedure specification must be adjusted or redone.

Welding procedure specification is a standard item, and there are analogs in most countries across the world. For example, Australian ISO 15621 and ISO15609 are quite similar to ASME Section IX.

Every big company producing some commodities comprised of quality welds has a wide range of their own WPS for each item.

Most workplace health programs require welding procedure specification development as well, since using correct welding codes and techniques ensures welders’ and welding operators’ safety in a workshop.

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Unsurprisingly, there are many companies specializing in developing welding procedure specifications, working out the most common welding processes in detail, and running all the necessary non-destructive and destructive tests.

Outsourcing the development of such important documents is a good choice for small companies without a well-prepared base for testing and welding engineers.

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Here are some of the ASME articles, essential for welding:

Article I (general welding conditions):

QW-150 – QW -182 basic tension, bending, toughness tests, their description, and normal ranges.

QW-183 – macro-examination procedure.

Article II (WPQR):

QW-200 – QW-250 – testing parameters, variables, and general description.

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Article II (all basic welding info):

QW-400 – QW-470 – welding variables, filler metals, positions, type, preheat, and other gritty data.

Article V – Standard Welding Procedure Specifications (SWPSs) – contains general info on standard WPS and their scope.

Using standard WPS: there are many WPS templates and forms developed for most of the common welding types, so in most cases such WPS will perfectly fit some non-unique weld joints.

Although, some joints may be so unobvious to implement that it’ll take an engineer much time to develop a completely new WPS.

One important thing to mention is that WPS determines the workshop’s welder’s proficiency, reducing or excluding occasions of the work done by an underqualified welder.

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Summary

Welding procedure specification is about the standardization of production processes, the written document that every big manufacturer has.

Reliable weld joints contribute to the overall output quality more than others, that’s why only the most experienced engineers, welders, and welding operators must be eligible for WPS development.

There are plenty of WPS templates and forms, which can become the basis of your own specification. As a rule, there’s no need to develop all the WPS by yourself, you can either just take the standard template entirely, or adjust it to your needs.

FAQs

What is standard Welding Procedure Specification?

A welding procedure specification, a WPS is a document that describes standard welding processes and welding procedures.

Like any recipe used for welders, this procedure provides a guideline that will allow your welders to create a quality product that is in line with industry standards.

What are the 5 essentials for proper welding procedures?

The proper electrode sizes. Proper arc length and voltage. Good travel speeds. A proper welding position of the electrode. Any welding process implies variants of these characteristics.

What is the difference between PQR and WPS?

WPS or PQCr are necessary documentation for fabrication for welding when certain standards are specified. WPS is an instruction manual for welding operations, and PQR is an inspection checklist to verify compliance with the instructions. The document for PQR has to be drafted for the creation of WPS.

What is ASME standard Welding Procedure Specification?

A welding procedure specification (WPS) describes the formal writing of welding procedures that gives guidance to welding operators in making reliable production welds in accordance with code requirements.

Aron Russell

If you have come to my page, then you are trying to learn the correct technique for welding various parts. I can confidently say that you can trust me. I have been studying multiple welding techniques for 20 years. In my youth, I got a job at a factory, where my acquaintance with this technique began.

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