I. Criteria for Determination: Whether It Qualifies as Special Equipment
According to the “Catalog of Special Equipment” (Announcement No. 3 of 2019 issued by the State Administration for Market Regulation), a pressure vessel is a sealed device that contains gases or liquids and is designed to withstand a specified pressure. The key to determining whether it falls under regulatory oversight lies in whether its operating parameters meet the scope of application stipulated in TSG 21—2016, the “Safety Technical Supervision Regulations for Stationary Pressure Vessels.”
II. Analysis of Typical Operating Conditions of Mobile Air Compressors
Common mobile air compressors are typically positive‑displacement compressors, and their air receivers (buffer tanks) usually have pressure‑bearing functions. If the receiver has a volume of ≥25 L and an operating pressure of ≥ 0.1MPa (gauge pressure), and the medium is a gas, then it meets the basic definition of a pressure vessel under TSG 21.
III. Regulatory Highlights: The Complete Machine Versus Key Components
It should be noted that the complete mobile air compressor is not classified as special equipment; however, if its accompanying air receiver satisfies the aforementioned conditions, then the receiver itself is a pressure vessel and must be designed, manufactured, subject to supervisory inspection, and registered for use in accordance with the requirements of TSG 21.
IV. Practical Recommendations
- Verify the air receiver’s volume, design pressure, and medium type as indicated on the equipment nameplate and in the factory documentation;
- Confirm the presence of the special equipment manufacturing license (TS) mark;
- The user unit shall, in accordance with the law, complete the registration for use and fulfill its responsibilities for periodic inspections and routine maintenance.