188.8.131.52.2 Seat Leakage
(a) The hydraulic pressure shall be maintained at 1.5 times the component rated pressure for a period sufficient to establish the rate of leakage, but not less than 1 h nor more than 24 h. The test shall be started at the maximum stipulated fluid temperature for which the valve is designed. The fluid temperature shall be permitted to gradually decrease during the test to 20°C (68°F).
(b) The test shall be repeated using a pressure of 750 kPa (110 psi).
(c) Total leakage from output to input during either test shall not exceed the flow rate of the valve divided by one million.