| 摘要 |
<p>In a subsurface positive displacement pump used in the petroleum industry for pumping crudes characterised by a high degree of suspended solid particles, a ball check valve comprises a valve ball 12 and a valve seat assembly wherein the valve seat assembly comprises a hollow cylindrical body 16 defining an orifice 26 through which pumped fluid passes, the hollow cylindrical body being provided with a recess 28 on the surface facing the valve ball in the region defining the orifice wherein an insert 30 which forms the actual valve seat for the ball valve is secured in the recess. The insert is formed of a material having a hardness greater than the hardness of the material from which the cylindrical body is formed and the material from which the valve ball is formed is characterised by a high resiliency, a modulus of elasticity of between 0.1 x 10<6> psi to 15x10<6> psi and a hardness greater than that of the hollow cylindrical body. <IMAGE></p> |
