1> Pressure
1. Nominal pressure PN
The nominal pressure PN is the rated pressure for continuous operation in a dynamic pressure system, used to ensure that different components are properly matched in terms of their specifications.
2. Maximum working pressure Pmax
The maximum working pressure is the highest actual pressure value, including pressure peaks, and applies to continuous operating conditions.
3. Test Pressure and Medium
Pressure testing is a fundamental test procedure for valves and fittings (refer to JB/T 902-1999 and GB/T 26480-2011), encompassing shell testing, upper-seal testing, low-pressure sealing testing, and high-pressure sealing testing.
① The shell test pressure for valves shall be 1.5 times the maximum working pressure, and the test medium shall be liquid. If the contract specifies a high-pressure gas shell test, such test shall be conducted after the liquid pressure test at 1.5 times the maximum working pressure, with the test pressure set at 1.1 times the maximum working pressure, for safety reasons.
② The test pressure for the valve’s high-pressure sealing and upper-seal tests shall be 1.1 times the maximum working pressure.
③ The low-pressure sealing test and the low-pressure upper-seal test shall be conducted using nitrogen at a pressure of 0.4 to 0.7 MPa.
④ The test pressure for the joint shall be 1.5 times the maximum working pressure.
⑤ The test pressure for the safety relief valve leakage test is 0.9 times the set pressure.

II> Valve Leakage Requirements
1. Duration of maintaining the test pressure (JB/T 9092-1999): 15 seconds for nominal diameters ≤ DN50 mm, and 60 seconds for nominal diameters DN65–150 mm.
2. For shell testing and upper-seal testing, no visible leakage is permitted. If the test medium is a liquid, no obvious visible droplets shall be observed; if the test medium is a gas, no bubbles shall escape, and no structural damage shall occur during the test.
3. The maximum allowable leakage rates for the sealing test are as follows: