Welding Procedure Qualification (WPS/PQR) — The Cornerstone of the Quality System

In engineering fields where the safety of human life and property is critical, such as pressure equipment, shipbuilding, bridges, and nuclear power, welding quality can never be guaranteed solely by a welder’s skill, intuition, or experience. Instead, it must be based on a rigorous and traceable welding procedure qualification system. The Welding Procedure Qualification Record (PQR) and Welding Procedure Specification (WPS) are the two most important technical documents within this system.

According to authoritative standards such as ASME BPVC Section IX, ISO 15614, and NB/T 47014, any welding procedure intended for production welding must be qualified in advance through a PQR. The fundamental purpose of procedure qualification is to verify, through the welding of test coupons, non-destructive testing (NDT), and destructive testing, that the proposed welding parameters are capable of producing welded joints that comply with the applicable standards. A complete PQR should provide detailed records of critical variables, including the base-metal grade and dimensions, welding process, filler-metal classification, shielding-gas composition, preheat and interpass temperatures, heat input, and post-weld heat treatment (PWHT) requirements.

Taking the welding of pressure piping as an example, the qualification range is a set of rules that welding engineers must strictly follow. For instance, when the base-metal group changes, when the welding process is changed from SMAW (Shielded Metal Arc Welding) to GTAW (Gas Tungsten Arc Welding), or when the heat input exceeds the qualified range by more than ±10%, requalification may generally be required, depending on the applicable code. Although these restrictions may appear cumbersome, they are fundamentally intended to prevent critical defects such as lack of fusion, slag inclusions, and cold cracking caused by uncontrolled welding procedures.

The WPS converts the test results and qualified parameters established by the PQR into practical work instructions that can be implemented on the shop floor. A qualified WPS must not only specify electrical parameters such as welding current, voltage, and travel speed, but also define quantitative requirements for joint preparation, including groove geometry—such as V-groove, U-groove, or double-V groove—as well as root-face dimensions, root gap, and back-gouging methods. During welding operations, the welding engineer or qualified welding inspector must brief the welding operators on the requirements of the WPS and conduct inspections to ensure that the actual process parameters remain within the specified limits.

It is also worth noting that with the development of digital technologies, blockchain- and big-data-based welding procedure management systems are emerging. By recording PQR/WPS data on a blockchain-based platform, companies can achieve full life-cycle traceability of procedure revisions and help prevent unauthorized modification of qualified parameters. At the same time, the use of numerical simulation software to predict welding residual stresses and distortion allows engineers to optimize welding procedures before qualification testing, thereby significantly reducing the cost associated with trial and error.

For manufacturing companies, a comprehensive welding procedure qualification system is not merely a “ticket to entry” for meeting regulatory and tender requirements; it is also an essential means of improving product consistency and strengthening brand credibility. In an increasingly competitive global manufacturing environment, companies that can manage welding procedure data more efficiently and systematically will be better positioned to gain a competitive advantage in the high-end manufacturing market.