| 摘要 |
An overpressure device for applying pressure from a first hydraulic fluid to a second hydraulic fluid comprises: (a) a housing in which is located a piston (b) an opening in the housing for the entry of the first hydraulic fluid to one side of the piston (c) a second opening in the housing for the entry of the second hydraulic fluid to a chamber on the other side of the piston whereby the pressure of the first hydraulic fluid is exerted on the second hydraulic fluid, and (d) an additional means of exerting pressure on the piston so that pressure exerted on the second hydraulic fluid is greater than that of the first hydraulic fluid alone. The overpressure device is particularly suitable for use in applying pressure to the sealing system of the ball valve described in European patent application No. 82302173 when used to control the flow of fluid, e.g. crude oil in a pipeline. The overpressure device enables the pressure in the pipeline to provide a portion of the pressure required to pressurize the sealing system. |
