I. Basis for Determination: TSG 21, “Safety Technical Supervision and Inspection Regulations for Stationary Pressure Vessels”
According to the current “Catalogue of Special Equipment” and TSG 21-2016 “Safety Technical Supervision Regulations for Stationary Pressure Vessels,” an item qualifies as special equipment only if it simultaneously meets all three of the following conditions:Work stress ≥ 0.1 MPa (Gauge pressure),Volume ≥ 30 L,The medium is a gas, a liquefied gas, or a liquid whose maximum working temperature is equal to or higher than its standard boiling point..
II. Qualitative Analysis of Compressed Air Storage Tanks
Compressed air, as a typical gaseous medium, if the storage tank’s design pressure is ≥0.1 MPa and its volume is ≥ 30 L In that case, it meets the definition of a “pressure vessel” under TSG 21, falls within the scope of special equipment regulation, and must undergo registration for use, periodic inspection, and be operated and maintained by certified personnel.
III. Exceptions
- Work stress< 0.1 MPa (For example, atmospheric pressure buffer tanks) are not subject to these provisions;
- Miniature storage tanks with a volume of less than 30 liters do not qualify as statutory pressure vessels, even if their operating pressure meets the relevant standards.
- Simple air receivers used solely for temporary pressure stabilization and lacking a sealed, pressurized structure are generally not considered regulated equipment.
IV. Compliance Reminders
The user organization shall verify the equipment’s nameplate parameters and, in accordance with Appendix A of TSG 21, confirm its category and class. Compressed air storage tanks classified as special equipment must not be used for purposes other than those for which they were designed, operated beyond their rated pressure, or have their safety accessories removed without authorization.