| 摘要 |
A system is disclosed for monitoring/testing operation of the servo operation of a pneumatically assisted spring loaded relief and/or safety valve 1 without loss of supplementary valve member closure loading at 3A. This comprises shut off valves FIVA & B, 3 way cock TBB (to which a pump can be fixed), a number of pressure gauges for monitoring operation and a relay valve R35P to which the loading on upper chamber 3A is fed back to assist the biasing force acting in the closing direction of the relay. To ensure valve operation when signalled, but pilot activation fails to remove valve member supplementary loading, such pressure is fed back to the control diaphragm of the regulator supplying servo valve lift assisting pressure thus augmenting it's output pressure by a like amount. These pressures, lift inhibiting, and lift assisting, are equal and self cancelling, each applied to it's opposing actuator chamber. Valve lift assisting servo pressure is controlled by the preset spring loading of it's regulator. The pressure gauges, suitably located, demonstrate pressure changes during simulated servo cycle operations. The system also includes pilot valves 5A and 5B. <IMAGE>
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