| 摘要 |
<p>A valve system (10) includes an opening piston (54) and a closing piston (86) that preferably utilize any suitable means to control erosion such as, for example only, carbide inserts that define the various inlets and outlets of the opening and closing piston. Pressure from the casing bore above a selected value causes opening piston (54) to shift and permit fluid flow past the valve stem (76) of the closing piston (86) and into the filling port (74) of the packer. When pressure inside the inflatable packer produces a force on the closing piston (86) above a selected amount, the closing piston shifts to the closed position whereby fluid flow into or out of the packer is prevented. Once pressure is bled off the casing bore, the return spring (56) of the opening piston (54) pushes the piston back to seal off the port (38).</p> |
