11. The Christmas tree is not only lovely, but may be an anxiety-relief valve . 12. Investigation showed that the relief valve actuated and vented gas for several hours. 13. Examples of normally-open valves are purge-gas supply valves or emergency-relief valves . 14. For these systems often so called " differential " relief valves are used. 15. Pilot-operated relief valves are a specialized type of pressure safety valve. 16. "He'll have a relief valve like a tight end or a running back. 17. A spring-loaded safety relief valve is usually installed on all oil and gas separators. 18. Hence the use of pressure relief valves and vent valves. 19. Gas-loaded relief valves are controlled by the nitrogen pressure loaded into the relief valve . 20. An over-pressure relief valve on the first stage is necessary to protect the hose.
