Valve Testing After Repair: Hydrostatic, Seat Leakage, and Function Tests

After maintenance or repair, valves must be tested before returning to service to confirm pressure integrity and sealing performance. The test scope depends on the nature of the repair and the applicable valve standard.

Shell (Hydrostatic) Test

The shell test verifies body and bonnet pressure integrity. Test pressure is typically 1.5 times the rated working pressure at 38 °C (100 °F) per API 598 or ISO 5208. Pressure is held for the minimum duration specified in the standard with no visible leakage permitted.

Gate and globe: test at 1.5 × rated pressure for 60 seconds minimumBall and butterfly: body test per API 598 or manufacturer specificationPressure test medium: water (preferred), kerosene, or test gas for dry applicationsRemove entrapped air before pressurizing to prevent inaccurate results

Seat Leakage Test

Seat leakage tests use water or gas at rated pressure differential across the closed valve. Acceptance criteria per API 598 Table 3 specify maximum leakage by valve type, size, and test medium. Metal-seated valves allow higher leakage than soft-seated valves.

Operational Function Test

Exercising the valve through full open-close cycles confirms smooth operation, correct packing adjustment, actuator coupling, and limit switch calibration. For control valves, stroke the valve from 4 to 20 mA and verify actual position response.

Documentation

Issue a test report with date, test pressures, durations, and resultsSign off by authorized inspector or QA representativeReturn failed valves to workshop for reworkStamp or tag valve to indicate test completion date and next due date