Importance

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Abstract

A control system for power tongs comprises two tongs torque limiters, one of which limits tongs torque to a very low (hand-tight) level; the other limits torque at full make-up to, for example, 2000 ft.-lbs. The hand-tight torque limiter is manually or automatically disabled after the hand-tight level is reached. The system enables the operator to verify that the threads are properly engaged before applying full torque to the connection. The tongs have a very high reduction ratio, so that torque rises very slowly and can be more accurately controlled. The high torque limiter includes a normally closed shunt valve in series with an adjustable choke, the latter of which enables one to maintain a substantial, adjustable, residual torque on the pipe even after the shunt valve opens.

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First Claim