Collets are finger-like devices that are used to make the hammer-pipe connection in the pipe ramming method of pipe installation. The device is used to lock tool components by adjusting the tubing string or downhole tool.
The collect forms a collar around the tool to be held and exerts a clamping force when tightened. Pipe ramming is a trenchless method of pipe installation that uses a pneumatic hammer to drive the pipe into the ground.
Trenchlesspedia Explains Collets
The hammer in a pipe ramming system is fitted on the rail system to the rear end of the pipe. The collets facilitate the connection and distribute the impact force generated by the hammer to the casing edge. The pipe, collet and hammer system is held in place by tensioned chains attached to the rear end of the pipe. The collets lock the nose end of the tool in the pipe and are designed for quick and efficient installation and removal.
They also provide secure locking of the tool nose to the casing so that the need to reduce casing flare or need for a support cradle is eliminated and time is saved.