The Role of Welding Procedure Specifications in Quality Control

April 10, 2025

In the world of industrial fabrication, quality is not optional, it is a requirement. When it comes to welding, one of the most important tools for maintaining consistency and safety is the Welding Procedure Specification (WPS). At F&L United, WPS documents are a cornerstone of our approach to quality control in pipe fabrication and specialty welding projects.

Whether we are fabricating piping systems for the pharmaceutical industry or supporting high-pressure applications in petrochemical plants, each weld must meet strict mechanical, chemical, and procedural requirements. The WPS is how we define those requirements clearly and repeatably across projects, crews, and even job sites.

This blog takes a closer look at the critical role of Welding Procedure Specifications in fabrication, how they support regulatory compliance, and why they are essential for operational success.

What is a Welding Procedure Specification?

A Welding Procedure Specification is a formal, written document that provides detailed instructions for producing a weld according to established standards. It includes variables such as:

  • Welding process (e.g., GTAW, SMAW, FCAW, GMAW)
  • Type of material
  • Joint design
  • Position of the weld
  • Type and size of filler metal
  • Preheat and interpass temperatures
  • Travel speed and voltage
  • Post-weld heat treatment (PWHT)

This document serves as a guide for welders to follow, giving them the information needed to produce consistent welds that meet the mechanical and performance requirements of a given application.

Why Welding Procedure Specifications Matter

At first glance, a WPS might seem like just another layer of paperwork, but it directly influences weld quality, safety, and compliance. Below are several reasons why WPS documents matter so much in fabrication.

1. Promoting Consistency Across Welders and Shifts

Welding crews are often made up of individuals with varied backgrounds and experience levels. The WPS removes ambiguity by standardizing every key parameter of the weld. It removes guesswork and allows fabricators to produce the same results, regardless of who is holding the torch.

This kind of consistency is especially important for projects involving long runs of piping or repetitive welding on multiple spools, where variations can compromise integrity or introduce stress concentrations.

2. Supporting Quality Control and Inspection

Inspectors and quality personnel rely on the WPS to validate that the welds have been performed correctly. It serves as the basis for Procedure Qualification Records (PQR) and Welder Performance Qualifications (WPQ). If a weld is found to be defective, the WPS can help determine whether the proper procedure was followed or if a deviation occurred.

Welds produced under an approved WPS can also be more easily tested using non-destructive testing (NDT) methods like ultrasonic or radiographic testing. These evaluations depend on having consistent welding variables to detect anomalies.

3. Meeting Industry and Regulatory Standards

A Welding Procedure Specification is required by many governing codes and standards, including:

These codes often require that WPS documents be backed by procedure qualification tests that validate their mechanical properties, such as tensile strength and impact toughness.

According to the U.S. Occupational Safety and Health Administration (OSHA), incorrect welding procedures and lack of control can lead to a wide range of safety risks, including exposure to fumes, burns, and mechanical failure. A clear, qualified WPS mitigates these risks by aligning shop-floor activities with safe and recognized practices.

How F&L United Develops Welding Procedure Specifications

Developing a WPS at F&L United is not just a documentation exercise. It is a hands-on, practical process that involves engineers, welders, and quality control personnel. Here is how we do it:

1. Identify the Application Requirements

Every project begins with a clear understanding of material compatibility, pressure and temperature expectations, and the end-use environment. For instance, high-purity piping in pharmaceutical facilities may have different welding needs than structural supports in power plants.

2. Select the Welding Process and Materials

We evaluate whether the project is best suited for TIG, MIG, flux-core, or stick welding based on the materials and joint configurations. The filler metal is matched carefully to the base metal to prevent issues like cracking or galvanic corrosion.

3. Develop the Procedure and Conduct Qualification Tests

Once the procedure is drafted, we conduct test welds and perform destructive and non-destructive tests in accordance with applicable codes. These results are documented in a Procedure Qualification Record (PQR), which supports the WPS and validates its effectiveness.

4. Qualify the Welders

No WPS is complete without qualified welders. We provide training and qualification tests to make sure each welder can meet the required performance criteria under the conditions outlined in the WPS.

5. Monitor and Audit on the Job

Throughout the project, quality inspectors verify that the welders are following the WPS. We track variables like heat input, preheat temperatures, and interpass cleaning to maintain control over the final outcome.

The Cost of Cutting Corners

A poorly defined or unqualified WPS can lead to major issues, including:

  • Weld failure in service
  • Costly repairs and rework
  • Failed inspections
  • Legal and regulatory penalties
  • Reputational damage

In worst-case scenarios, the absence of a qualified WPS has led to catastrophic failures in pressure vessels and pipelines. The National Board of Boiler and Pressure Vessel Inspectors documents such incidents and reinforces the importance of documented, code-compliant welding procedures.

At F&L United, we recognize that the cost of non-compliance is far greater than the cost of doing things right the first time. Our WPS library is continuously updated, audited, and expanded to reflect current codes and project demands.

Adapting to Project-Specific Needs

While WPS documents are standardized, they are not static. Each one can be tailored to meet the specific needs of a project. For instance, welding a duplex stainless steel pipe for chemical processing requires different parameters than carbon steel pipe used for fire protection systems.

We often work with clients during the planning phase to develop project-specific WPS documents that reflect custom joint designs, restricted weld positions, or environmental conditions such as cold-weather welding.

Final Thoughts

Welding Procedure Specifications play a pivotal role in achieving reliable, repeatable, and code-compliant welds in industrial fabrication. They form the bridge between engineering intent and execution in the field. More than just a checklist, the WPS is a critical document that supports safety, quality, and traceability.

At F&L United, every weld begins with a WPS that has been tested, validated, and field-proven. Our commitment to welding excellence is reflected in our ability to meet the highest standards—across industries, materials, and applications.

If you are planning a pipe fabrication project or specialty welding turnaround, get in touch with our team to learn how a comprehensive WPS can help deliver high-quality results from the first arc to final inspection.