Hydraulic safety valve, with non-return valve in consumer line

摘要

The spring loaded slide of an additional valve is loaded by the primary pressuriser so as to connect the line (28) to the tank (36) off this pressure, using a pressuriser load spring adjusted so the slide reacts at lower pressure than the primary control piston. The valve is composed of the safety valve piston (72) which rides freely relative the slide (42) and reacts to a lower pressure than either slide or controller. The free travel between slide and piston is set so the piston entrains the slide after a pre-set path. Thus both slide and piston (42,72) are equipped with entraining sectors (76,74) for the piston to take the slide with it, slide and piston loaded by separate concentric coiled springs (76,86). The cone valve slide (42) is milled out (68) to vary the valve section and also waisted (64) between cone valve and milled recesses (68). The effective diameter of the slide on the consumer side should equal or slightly undershoot the slide section facing the controller.