| 摘要 |
<p>A mud saver valve is described that features an outer housing that retains upper and lower valve pistons therewithin. The pistons coordinate to provide a check valve so that fluid, such as drilling mud, is permitted to flow in one direction while under pump pressure and works as a relief valve in the event of excessive wellbore pressure when the pump is turned off. Both pistons are provided with apertured plates that selectively define fluid passages through the valve. In the described embodiment, the valve also includes a frangible vent cap that is self-securing and easily replaceable. The cap permits venting of excessive downhole pressures.</p> |
