Abstract: A fluid pressure reduction system includes at least two streams. A working stream includes valves with associated pressure sensors for modulating output pressure. A control system monitors pressure via a sensor and actuates a slam shut valve in the event of a fault. In the event that another stream is at fault the arrangement allows the slam shut valve to be opened. In the faulty stream only, pressure again rises, the slam shut is again shut and cannot be reopened until manually reset following fault clearance. Independent control in each stream assists in system integrity. All streams can close and reopen once. The second closure determines the faulty stream.

Abstract: A fluid pressure reduction system includes two streams, each stream having pressure regulators 19 & 20, 32 & 33. Isolation slam shuts 16 and 30 are provided in respective streams. A sequence tester 40 allows a sequence of test operations to be effected such that the slam shuts can be opened and closed and the working pressure settings to the regulators can be changed to check system integrity. These tests can be effected without interrupting the supply of gas through the system. It is also possible to carry out the sequence from another location.