Special Equipment Manufacturing License for Clad and Lined Pressure Vessels

Regulatory Framework and Licensing Architecture

The Special Equipment Manufacturing License (TS License) issued by the State Administration for Market Regulation (SAMR) of China represents the mandatory regulatory gateway for any organization intending to manufacture pressure vessels, pressure piping components, and their associated composite or lined products. Under the Special Equipment Safety Law of the People's Republic of China and its implementing regulations, no enterprise may legally produce pressure-bearing equipment without obtaining this license, which is classified into multiple levels based on the category, design pressure, design temperature, material grade, and intended service conditions of the equipment.

For enterprises engaged in the fabrication of clad-plate pressure vessels, weld-overlay lined vessels, or bimetallic piping components, the TS license is not merely a formality but a comprehensive demonstration of technical competence across multiple disciplines including design, material procurement, welding procedure qualification, non-destructive examination, and final quality assurance. The license is divided into categories such as Class I, Class II, and Class III pressure vessels, with each level imposing progressively stricter requirements on the scope of processes, material grades, and equipment capabilities that the manufacturer must demonstrate.

Scope Requirements for Cladding and Overlay Processes

A critical aspect of the TS license that often confuses engineers is the requirement to explicitly list cladding and overlay welding processes within the license scope detail. This means that a manufacturer cannot simply hold a general pressure vessel fabrication license and then arbitrarily apply weld overlay or cladding techniques to their products. Instead, the specific cladding or overlay processes must be documented, qualified, and approved as part of the license application.

The license scope must clearly define the material combinations permitted, such as austenitic stainless steel 304L/316L over carbon steel Q345R or low-alloy steel 15CrMo, or nickel-based alloy Inconel 625 over 316L. Each material combination requires its own welding procedure qualification record (PQR) performed in accordance with NB/T 47014, which specifies the essential variables including electrode type, current range, voltage, travel speed, preheat temperature, interpass temperature, and post-weld heat treatment parameters.

Practical Implications for Engineering Teams

In practice, the TS licensing process demands that engineering teams maintain meticulous documentation throughout the entire fabrication lifecycle. Every weld overlay joint on a pressure vessel must be traceable to a qualified welding procedure specification (WPS) that falls within the approved license scope. This includes not only the base metal and overlay material designations but also the joint geometry, the number of layers, the sequence of deposition, and the applicable acceptance criteria from NB/T 47013 or JB/T 4730.

Engineers must pay particular attention to the distinction between the structural strength of the base material and the corrosion resistance provided by the overlay layer. The TS license review panel examines whether the manufacturer has demonstrated understanding of metallurgical compatibility, thermal expansion mismatch, and the potential for interfacial cracking during service. For example, when overlaying Inconel 625 on a 15CrMoR vessel, the license holder must document how they control carbon migration at the interface, manage residual stresses, and ensure the overlay layer meets the required minimum thickness without excessive dilution.

Key Reflections and Recommendations

The TS licensing system, while administratively demanding, serves as a robust quality assurance framework that ultimately protects both the manufacturer and the end user. Engineers should view the licensing process not as a bureaucratic hurdle but as a structured methodology for validating their technical capabilities. I recommend that organizations maintain a living document that cross-references each approved WPS with the corresponding license scope entry, ensuring that no fabrication activity falls outside the authorized boundaries. Regular internal audits against the license conditions, combined with proactive engagement with the licensing authority on process extensions, will minimize production interruptions and maintain regulatory compliance throughout the organization's operational life.