| 摘要 |
A testing apparatus for a valve (10) of a type controlled by a piston (15) in a cylinder (14), the piston being moved between a first position in which the valve is open and a second position in which the valve is closed, comprises means to supply gas at a first higher pressure to one side of the piston to maintain the valve in the first position. Means are provided to reduce the gas pressure on the one side of the piston from the first, higher pressure to a lower pressure, and to then seal the one side of the piston so that gas may not pass to or from that side of the piston. Means are also provided to then pass gas at a second higher pressure to the opposite side of the piston to urge the piston to move from the first position to a third position intermediate the first, and second positions.
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