Info > Technical Tip: Mechanical Joints

The mechanical joint, developed in the mid 1920's, is based upon the engineering principle of the stuffing box. It has four parts: a flange, cast integral with the socket or bell of the pipe; a rubber gasket fitting a recess in the socket; a gland or follower ring, to compress the gasket and the bolts and nuts for tightening the gland. An ordinary ratchet wrench is the only tool required to assemble the joint.

Technical tips are for informational purposes only.

There are several good practices to keep in mind when installing bolted gasketed joints. Pipe ends should be cleaned thoroughly to insure complete removal of dirt, scale and rust. Prior to assembly, rubber gaskets for all types of joint connections including mechanical joints, Dresser couplings, and push-on or stab joints should be lubricated with the recommended pipe lubricant. If lubricant is not available, the use of soapy water or even plain water is better than nothing. The pipe must be centrally located within the mechanical joint or coupling middle ring. Tighten opposite bolts and nuts evenly and in an alternating pattern to insure equal spacing of the follower gland from the mechanical joint bell or coupling middle ring. The recommended range of torques are shown in the table below.

* The torque loads may be applied with torque-measuring or torque-indicating wrenches, which may also be used to check the application of approximate torque loads applied by a man trained to give an average pull on a definite length of regular socket wrench.

IMPORTANT: All rubber gasketed joints are designed to seal at the manufacturer’s recommended range of water working pressure and are not intended to resist pipe movement into or out of the joint. Suitable restraint must be provided to insure that the pipe does not move out of the joint.

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