Introduction

In industries where strength, precision, and safety are non-negotiable, high quality welds are the foundation for structural excellence. The integrity of a weld can make or break the performance of a structure or component. That’s where Welding Procedure Specifications (WPS) come into play. A WPS is a technical document that ensures every weld meets its intended purpose.

In the UK, though WPSs are not a direct legal mandate, however, they are mandatory under various industry codes such as BS EN ISO 15614, BS EN ISO 9606, and ASME IX. These standards specify the qualification processes, documentation, and testing requirements that ensure welds meet both safety and performance criteria.

In this blog, we’ll explore what a WPS is and why it matters, its types, codes, the step-by-step process of writing a WPS, the advantages of having one as well as understand why hiring professionals to develop a WPS is essential.

What Is a WPS?

A WPS or Welding Procedure Specification is a comprehensive written document that defines how a welding operation should be performed to achieve consistent, code-compliant results. It includes vital information such as the welding process, base materials, filler metals, welding positions, preheat and post-weld heat treatments, as well as inspection and testing procedures.

In essence, a WPS acts as a recipe for welders. It outlines every step of the welding process that welders can follow to produce consistent welds throughout the project. Developed and tested through qualified procedures (known as Procedure Qualification Records or PQRs), a WPS ensures welds meet the required mechanical and structural properties for its intended application.

Why Do You Need a Welding Procedure Specification?

A WPS does more than just providing the right technique to follow; it guarantees safety, quality and compliance. Here’s how it supports key aspects of any welding operation:

Compliance with Regulatory Standards

The UK welding processes have to comply with standards of BS EN ISO 15614 and ASME IX. Failure to comply may pose a severe safety risk and lead to project postponements or legal consequences. A WPS will help bridge the gap between theory and practice and make sure all the welds are according to the national and international standards.

Quality Assurance

A clear WPS ensures that every weld is checked, tested and recorded according to the specifications of a project. It also helps to achieve uniform, defect free welds by setting a certain parameter, such as current, voltage, and travel speed. This documentation becomes valuable for audits and long-term traceability.

Consistency in Welding Operations

Standardising weld parameters through a WPS eliminates variability among different welders and projects. It ensures that, regardless of the personnel, all welds follow the same procedure and generate the same outcome, which is a crucial requirement in large scale and critical applications, such as pressure vessels or pipelines.

Knowledge Transfer and Training

A WPS serves as a training aid. It enables new welders to be trained on prequalified practices and helps to maintain a welding culture of safety and quality in a company. With the help of the WPS, even the newly trained operators can work in accordance with the industry standards.

Types of Welding Procedure Specifications

Welding Procedure Specifications are of three types. Depending on their purpose and level of qualification any of the following approach is selected for a project:

Preliminary Welding Procedure Specifications (pWPS)

A preliminary WPS acts as the initial draft of the welding procedure. It outlines proposed parameters, filler materials, and joint designs. The pWPS serves as a foundation for welding procedure qualification tests and is refined based on test outcomes. It’s an essential step in developing the final WPS.

Prequalified WPS

A Prequalified WPS is a procedure that has already undergone testing and approval under recognised codes, meaning it can be used without additional qualification tests. This type saves time and cost while maintaining compliance and reliability for common welding applications.

Standard WPS (SWPS)

A Standard Welding Procedure Specification is based on the recognised standards in the industry and can be used in various organisations or projects. These are processes that have been tested extensively, which makes them very useful in ensuring consistency during mass production or when repeating a welding procedure.

Understanding WPS Codes

WPS codes are alphanumeric identifiers that signify compliance with specific welding standards. For example, a WPS that is based on BS EN ISO 15614-1:2017 would be coded differently than one written in ASME Section IX. Such codes include the process (GTAW or SMAW), base material grouping, and qualification range. Using WPS codes engineers and inspectors can determine the parameters and regulatory environment of each procedure quickly.

How to Write a Welding Procedure Specification (WPS)

Creating robust welding process specifications involves a structured four-step process which is mentioned below:

1. Specify What You Need to Complete Your Weld

The process begins with listing all welding essentials for a given process, such as base materials, filler metals, shielding gases, preheat requirements, and tools. During this step the joint configuration, thickness, and positional requirements are also assessed. This stage forms the groundwork for both experimentation and qualification.

2. Add Essential Information to the Preliminary WPS (pWPS)

Using the base information, a pWPS is drafted which contains a detailed plan outlining proposed welding parameters including current, voltage, travel speed, and joint design. This serves as the document that is verified during testing.

3. Welding Procedure Qualification Record (PQR)

Next comes testing the draft procedure in real conditions. The obtained weld test piece is subsequently tested through non-destructive (NDE) and destructive testing to ensure its integrity and mechanical properties. The information obtained in the course of the testing serves as an evidence that the process gives satisfactory results. The PQR officially supports the validity of the final WPS.

4. Create the Final WPS

Once the PQR confirms compliance with applicable standards, the final WPS gets formalised. It becomes the source that guides welders to create welds in a certain project. The final Welding Procedure Specification incorporates all of the validated parameters and serves as a technical reference to the fabrication and inspection team.

Advantages of WPS

A properly developed Welding Procedure Specification provides a broad range of benefits, such as:

• It ensures consistent welds are produced and reduces human error
• It guarantees compliance with industry standards and codes
• It clearly defines operational parameters which improves the safety aspect
• It improves efficiency by reducing rework and downtime
• It supports audits and quality control through traceability
• It helps in training new welders by standardising the process

Importance of Hiring Professionals for WPS Development

Only experienced welders possess sufficient knowledge of materials, welding processes, and codes that is necessary to draft an accurate Welding Procedure Specification. By outsourcing it to a professional welding company, you can be sure that you are investing in a WPS that will satisfy your project’s needs, and also comply with the regulatory standard.

Here are some factors that make hiring professionals a wise option for drafting Welding Procedure Specifications:

Knowledge About Codes & Their Applications

Professionals know the subtleties of BS EN ISO, ASME, and AWS codes. They are fully aware of what standards are applicable for a particular purpose and how they can be interpreted, be it for pressure vessels, pipelines or structural steelwork.

 

Variable Selection That Reflects Real-World Conditions

Professionals carefully define essential, supplementary and nonessential variables. They optimise ranges for parameters such as amperage, travel speed, and heat input, to balance flexibility and performance. This ensures that welders produce consistent quality welds without constant requalification.

Designing a WPS That Works in Practice

The professionals develop procedures that work accurately in the field. They consider material behaviours, environmental factors and positioning challenges, which results in practical and highly strong welds.

 

Special Considerations for Non-Standard Materials

Some materials such as duplex stainless steel, aluminium and nickel alloys need close control of heat input, interpass temperature and shielding. Metallurgical skill is employed by professionals to make sure that these materials retain their intended characteristics post welding.

Planning for Reusability and Future Flexibility

The procedures written by professionals provide the widest possible range of qualification, by covering a variety of thicknesses and joint configurations within the limits of the code. This saves time and money in future projects as it eliminates the need of opting for repetitive qualification.

 

Dealing with Client Specifications and Regulatory Requirements

Industrial clients often add their own strict specifications to standard codes. Professionals know how to interpret and integrate these requirements efficiently. Their experience with regulatory reviews ensures WPS documents meet every expectation and pass approval smoothly.

Conclusion

Welding Procedure Specifications are incredibly important for quality, compliance, and efficiency. They transform the art of welding into a science backed by regulatory precision. Whether working on critical structures or performance-intensive components, a WPS ensures every weld is sound, safe, and standardised.

Yet, the real difference lies in who writes your WPS. A professionally drafted and tested WPS not only meets but can anticipate future requirements, protecting projects, budgets, and reputations alike.

Trust Gammax Independent Inspection Services for Expert Drafted WPS

At Gammax Independent Inspection Services Ltd., we specialise in developing and qualifying Welding Procedure Specifications that conform to BS EN ISO 15614 and ASME IX codes. We maintain a library of current BSEN, ASME and ASTM standards that allow us to interpret various codes and standards. Visit us today to learn more or schedule a consultation.