Pilot valve operated boiler safety valve - has pilot operated when pressure is released from one side of safety valve

摘要

The safety valve for e.g. a boiler has a seat (4) and a connecting piston (6) connecting its upper chamber (7) with the pilot valve (8) by a pipe (9). Vessel pressure is applied to the space (52) of the pilot valve. If pressure increases the pilot valve member (63) closes against the spring (69) in the base of the valve. This isolates the chamber (7) in the safety valve from vessel pressure. Any further increase in pressure causes the piston (58) to move against the spring (67), opening the valve (60). This connects the space (54) which is at atmospheric pressure with the space (53) and hence the space(7) on the safety valve causing it to open.