H type safety joint, which is installed on the position required for subsurface drill stem and can bear in fishing operation all kinds of loads for pulling or pressing and used to transmit torque, is a subsurface safety equipment. In down hole operation, when necessay, the safety joint can be easy to discharge off so as to take out the drill stem above it. It is easy to connect the safety joint to ensure a continuous fishing operation when running in hole again.
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