How to perform ball valve seal pressure test

Ball valve seal pressure test operation process

1. Preparation before pressure test
(1) Check the valve status: Make sure the ball valve is in the half-open or fully open position, and remove internal impurities;
(2) Install the pressure test equipment: Connect the pressure pump, pressure gauge (accuracy ≥1.6 level) and sealing fixture to ensure no leakage;
(3) Medium selection: Select water (clean water or rust-proof water) or air (dry and oil-free) according to the purpose of the valve.
2. Pressure test steps
(1) Low-pressure seal test:
- Slowly pressurize to 0.6MPa±5% (API 598 standard), and maintain pressure for ≥15 seconds;
- Check whether there is leakage at the valve seat and valve body connection (micro-drip is allowed ≤3 drops/minute).
(2) High-pressure shell test:
- Pressurize to 1.5 times the nominal pressure or design pressure (GB/T 13927 standard), and maintain pressure for ≥60 seconds;
- Check whether the pressure-bearing parts such as the valve body and welds are deformed or leaking (leakage is strictly prohibited). 3. Safety Precautions
- Personnel must avoid the front of the valve during pressure testing;
- Protective covers must be used during overpressure testing;
- Do not disassemble or adjust the valve while it is under pressure.

Interpretation of Ball Valve Seal Pressure Test Standards

1. International Standards
- API 598: Specifies a low-pressure seal test pressure of 0.6 MPa and a high-pressure shell test pressure of 1.5 times the nominal pressure. Applicable to the petrochemical industry;
- ISO 5208: Similar to API 598, but with stricter permissible leakage (≤ 1 drop/minute).
2. Domestic Standards
- GB/T 13927: Requires a shell test pressure of ≥ 1.5 times the design pressure and a seal test pressure of 1.1 times the design pressure. Applicable to general industrial valves;
- JB/T 9092: Emphasizes extending the pressure holding time to 120 seconds (for valves DN ≥ 100 mm). 3. Acceptance Criteria
- Shell Test: Any visible leakage or pressure drop >5% is considered unacceptable.
- Seal Test: Any dripping exceeding the standard or persistent bubble formation during the seal test is considered unacceptable.

Solutions to Common Problems

1. Leakage Treatment
- If leakage occurs during the low-pressure seal test, inspect the valve seat for damage or residual impurities.
- If leakage occurs during the high-pressure test, it may be due to a casting defect in the valve body, requiring valve replacement.
2. Analysis of Abnormal Pressure
- If pressure cannot be stabilized: Check the pump unit and piping for leaks or if the valve is not fully closed.
- If pressure indication deviates: Calibrate the instrument or replace with a higher-precision device.