| 摘要 |
<p>A jacking mechanism for jacking a well casing or other well pipe vertically, and including a hydraulic control system in which a reversible variable displacement pump acts in one condition to deliver pressure fluid in parallel with another pump to the lower end of a jacking cylinder to actuate the piston thereof upwardly, with fluid discharging from the upper end of the cylinder to the variable displacement pump and being metered therethrough to regulate the rate of upward movement of the piston. In a second condition of the apparatus, flow through the variable displacement pump is reversed to lower the piston, and a variable restriction valve regulates discharge of fluid from the lower end of the cylinder to act with the variable displacement pump in regulating downward movement of the piston and supported pipe. In a third condition of the apparatus, the variable displacement pump discharges fluid to the lower end of the cylinder in a relation exerting an upward force of increased power on the piston and suspended pipe.</p> |
