Verification Testing of Gate Valves Per API Specification 6A

Southwest Research Institute (SwRI) has for many years provided expertise and state-of-the-art facilities for testing and evaluating mechanical and environmental effects on oil industry equipment.

SwRI recently completed the design and installation of a unique computer-controlled, fully automated valve test facility to evaluate production gate valves as recommended in API Specification 6A, Appendix F, PR2 level. The facility can accommodate up to 4-in, 15,000-psi valves and actuators.

Test set-up with test valve installed

Test valves are installed in a hydraulic loop with high pressure, pneumatically operated valves that direct pressure to each side of the test valve, according to the test specification. The computer system and customized software automatically control the required testing parameters.

Simple machine intelligence has been built into the computer software. If a leak beyond the preset limit is detected, the program initiates a trouble-shooting routine to locate the source of the problem. If it appears that the leakage occurs from a seal seating problem, the computer cycles the valve several times and restarts the test. If the leakage persists, the test is shut down until an operator locates and corrects the problem.

An environmental chamber is an integral part of the test loop. Installed during the temperature extreme test phases, the insulated chamber contains heating elements and cooling coils that enable high and low temperature limits to be maintained.

Appendix F for Specification 6A requires precise measurement of leaks across the gate and seat of the test valve. SwRI developed a sensitive electronic leak detection unit that uses a precision low pressure transducer to measure the change in the fluid head caused by leaks. The software establishes a baseline level before control valves are opened, and then measures the differential change for the required hold period.

Sour gas testing of valve stem packing

Data Collection

Computer-based control system

Data collection by the computer includes pressures (upstream and downstream), temperatures (on valve surface), and leakage rates. All data are automatically written to a hard disk and backed up on a floppy disk, and hard copies of the test parameters are printed during every phase of the test. Test valve pressures and actuator operating pressures are recorded in real time on a strip chart as additional data backup, and an active CRT displays parameters during the test for quick reference.

Full-Scale Sour Gas Testing Capabilities

SwRI maintains a sour gas testing facility for gate valves and other oil field components. This facility contains isolated test cells with safety features that include explosion-proof wiring, H₂S and methane sensors, and an automatic air purge system. SwRI has the equipment and experience to provide custom gas mixtures for the test requirement.

Reporting

Reports contain summaries of measured test parameters that include valve and actuator pressures, temperatures, and leak rates. Also provided are narrative descriptions of test operation and procedures, along with photographic records of the laboratory set-up and tested equipment.

Scheduling

Current fees and facility availability schedules for API 6A testing and for special full-scale H₂S testing are available on request. Inquiries are invited.

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