| 摘要 |
A water pump located in a cased borehole has a lower inlet and an upper outlet which is coupled to a pipe means that extends to the surface. At the surface, the borehole is coupled to a water delivery pipe and the pipe means is coupled to a conduit having a sand dump valve. An opening is formed through the pipe means near the outlet of the pump. A packer is located between the inlet of the pump and said opening. A sandtrap is located in said opening for trapping sand flowing with water from the pump outlet through the opening and upward through the annulus between the pipe means and borehole wall. In order to remove the sand from the sandtrap, the sand dump valve is opened to allow sand trapped by the sandtrap to flow upward with water through said pipe means and to be discharged through said conduit means.
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