[2026 New Regulation Warning] Micro-opening safety valves are strictly prohibited for use with gaseous media (TSG 92-2026)

According to the explicit requirements of the new regulations (Article D4.1 of TSG 92): When the working medium of pressure equipment is gas, steam, liquefied gas, or a liquid whose maximum operating temperature is ≥ its standard boiling point, full-opening safety valves must be used; it is strictly prohibited to use partially opening safety valves as a substitute!     A brief summary is as follows:

This post was last edited by The one on 2026-7-23 14:12. In light of the new regulations that have been implemented, companies should carry out the following inspections: 1. Conduct a thorough inspection of all safety valves in use; if micro-opening safety valves are still being used in gas or steam pipelines, they must be replaced immediately. 2. Ensure that the set pressure, nominal pressure, and discharge capacity of the newly selected full-opening safety valve fully match the operating conditions of the equipment. 3. The new regulations introduce risk-based inspection: regular inspections are required at least once a year, and this interval can be extended up to 5 years based on a risk assessment; however, inspections must be carried out immediately in the event of abnormalities such as leaks or frequent malfunctions.

The last edit to this post was made by The one on 2026-7-23 at 14:13. As of July 1, 2026, the \"Safety Technical Regulations for Safety Accessories of Pressure-Type Special Equipment\" (TSG 92-2026) came into effect. TSG 92 states that \"(1) When the working medium is gas, steam, liquefied gas, or a liquid whose maximum operating temperature is equal to or higher than its standard boiling point, a full-open safety valve should be used.\"； When the working medium is a liquid, a slightly opening type safety valve can be selected ； ” Should: As a legal term, “should” implies a mandatory obligation and is essentially no different from “must”; it is used to regulate legal obligations. Yes: one has the authority to do so, or one can choose not to do so.

TSG 92 mentions “regular self-inspections” and “regular calibrations”; if “improper selection” is detected and cannot be addressed in a timely manner, the safety valve should be taken out of use.

In China, safety valves are classified according to their opening height into fully open safety valves (with an opening height of four times or more the diameter of the flow channel), slightly open safety valves (with an opening height ranging from one-tenth to one-twentieth of the diameter of the flow channel), and moderately open safety valves (with an opening height between those of the fully open and slightly open types) (see Figure 1).

Full-open safety valves and slightly-open safety valves are classified based on their opening height, which relates to the flow area, curtain area, and discharge area. Flow area: It refers to the minimum cross-sectional area of the flow path from the inlet end of the valve to the sealing surface of the closing element, and it is used to calculate the theoretical flow rate in the absence of any resistance effects. (See Figure 2) Curtain area: The area of the cylindrical or conical passage formed between the sealing surfaces when the valve disc rises above the valve seat. (See Figure 2) Discharge area: The minimum cross-sectional area of the flow channel when the valve discharges fluid. For fully open safety valves, the discharge area is equal to the area of the flow channel; for slightly open safety valves, the discharge area is equal to the area of the curtain.

The derivation that the opening height of a fully open safety valve is greater than or equal to one-quarter of the flow channel diameter is as follows:

The discharge area determines the actual discharge capacity of the safety valve. Essentially, a safety valve is an automatic valve that discharges a specified amount of fluid using the force of the fluid itself, without any external force, in order to prevent pressure from exceeding the designated safe level. Once the pressure returns to normal, the valve closes again to prevent further flow of the medium.

In fact, as long as a safety valve meets the four basic requirements: ① accurate opening, ② stable discharge, ③ timely reseating, and ④ reliable sealing, it can perform its function of overpressure protection, whether it is a full-opening safety valve, a slightly-opening safety valve, or a medium-opening safety valve. This aligns with the saying, \"It doesn’t matter whether it’s a black cat or a white cat – as long as it can catch mice, it’s a good cat.\" If, during the design and selection process, even for compressible media, it is proven that a micro-operated safety valve meets the above four basic requirements under such conditions, and it is also verified that its discharge capacity is sufficient, then it can reliably and stably fulfill the function of overpressure protection.

The ASME codes classify safety valves as shown in Figure 3 below. There is one type of safety valve known as a safety relief valve, which can be used with both compressible and incompressible media. Performance and discharge capacity are tested using both types of media. When selecting such valves for calculation purposes, different rated discharge coefficient values are chosen depending on the type of medium involved.