| 摘要 |
A power tong system (10) is used to make up and break out threaded pipe connections. Rotary power tongs (15) are connected to an integral backup tong (25) through an extendable hydraulic cylinder and rod (30, 31). A brake (19) is secured to the rotary tong (15) to selectively hold the pipe stationary relative to the rotary tong. When rotation of the pipe by the rotary tong (15) ceases, the brake (19) is applied, and the cylinder and rod (30, 31) are actuated to angularly displace to power tong (15) and the backup tong (25) to apply a torque force to the pipe connection disposed between the power tong (15) and the backup tong (25). A resulting torque force is obtained that is greater than the maximum torque that can be exerted by the rotary tong (15) acting alone. The system may also be deployed to apply and hold precise torque forces on the pipe connections. When used to obtain a makeup torque below the maximum rated rotary tong output, the rotary tong (15) is regulated to limit its torque output. When the limited torque is reached, the brake (19) is applied and the cylinder and rod (30, 31) are actuated to apply a smooth, closely controlled increase in torque to the connection. The final torque level may be held constant for a desired length of time. In both the high and low torque applications, the brake (19) prevents the rotary tong (15) from being turned backwardly by the increased torque force applied by actuation of the rod and cylinder assembly (30, 31). Operation of the system may be manually or automatically controlled.
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