VALVE, INTENDED FOR INSTALLATION IN AN ERUPTION VALVE SHAFT OF AN UNDERWATER DRILL WATER.

摘要

In a shut-off valve intended to be lowered on a pipe string into a blow-out valve shaft in the outlet of a borehole, provided in known manner, with (i) a housing with a channel passing through it and a displaceable valve body which opens this channel in a first position and closes it in a second, (ii) a pressure-sensitive operating element connected to a pressure pipe for displacing the valve body to the first position and a closure element which displaces the valve body to the second position on reduction of the pressure in the pressure pipe, the improvement whereby the operating element is exposed to the hydrostatic pressure of the fluid surrounding the housing in order to compensate for the hydrostatic pressure of the fluid in the pressure pipe. More especially, the valve body is constructed as a pivotable ball with a passageway opening which can be brought into line with the channel in the housing. Overcomes problems which exist in known shut-off valves, inter alia the high pressure which must be exerted on the operating piston when the valve is held open to overcome the hydrostatic pressure of the medium surrounding the valve, and the fact that if a cable passing through the valve breaks above the valve, this cannot be shut because the cable cannot be withdrawn.