Method for testing for fluid leaks
Blowout preventers, fluid pressure systems and portions thereof may be tested for leaks by calculating an Apparent Compressibility Factor which is determined during initial pressurization of the system to the test pressure. The equivalent decay rate is calculated by measuring the amount of intensifying fluid required to be added to maintain the system at the test pressure level. The equivalent decay rate in psi per minute is then compared to the acceptable decay rate for the pressure level of the test to determine if the system passed the test.
1. A method of pressure testing a fluid handling system for leaks at a specified test pressure compressing;
a) pressurizing the system to the test pressure by introducing pressure intensifying fluid under pressure into the system,
b) measuring the system pressure at time intervals during the pressurizing of the system,
c) determining an apparent compressibility factor of the system by calculating an amount of intensifying fluid required to raise the pressure of the system one psi,
d) measuring for a finite time period an amount of added intensifying fluid required to maintain the system at the specified test pressure,
e) determining an equivalent decay rate, based in part on the determined apparent compressibility factor, and
f) comparing the equivalent decay rate to an acceptable decay rate to determine if the system passes the pressure test.
2. The method according to claim 1 wherein the apparent compressibility factor is determined by the following formula
Va/PSIA =ACF
wherein ACF is the apparent compressibility factor, VA is an incremental volume change of intensifying fluid added as the pressure is increased to or near the test pressure and, PSIA is an incremental pressure change of the intensification pressure as the system is initially pressurized to the test pressure.
3. The method according to claim 2 wherein the equivalent decay rate is determined by the formula Pd=VI/ACF where Pd equals the equivalent decay rate, VI equals a volume loss rate for a given time period which is equal to the amount of added intensifying fluid required to maintain the test pressure for a given time period, and ACF is the previously calculated apparent compressibility factor.
4. The method of claim 1 wherein the fluid handling system is a blowout preventer for an oil/gas well.