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Restrained Mechanical Joint vs. Regular Mechanical Joint

Restrained Mechanical Joint vs. Regular Mechanical Joint

Restrained Mechanical Joint vs. Regular Mechanical Joint

I am new to the water world. Is the only difference between a restrained mechanical joint and a regular mechanical joint the addition of a grip ring such as a mega lug that has set screws that screw down onto the pipe. Also does a concrete kicker make a regular mechanical joint a restrained mechanical joint.

Any information would be helpful. thanks, Civil G

RE: Restrained Mechanical Joint vs. Regular Mechanical Joint

A restrained joint is a special type of push-on or mechanical joint that is designed to provide longitudinal restraint. Restrained joint systems function in a
manner similar to thrust blocks, insofar as the reaction of the entire restrained unit of piping with soil balances the thrust force.

The mechanical joint uses the basic principle of the stuffing box and gland developed nearly 100 years ago and does not provide longitudinal restraint.


RE: Restrained Mechanical Joint vs. Regular Mechanical Joint

The theory behind a thrust block is that the longitudinal forces in the pipeline are transferred to the concrete thrust block. The thrust block typically has a larger surface area at the back to transfer those forces to the soil. A restrained joint on the other hand transfers those longitudinal forces into friction along the length of the pipeline. So there has to be sufficient length of pipeline resisting those forces for the restrained joint to work properly. You can't just put a restrained joint on a fitting and not consider how much of the pipeline has to have joints restrained. It is all dependent on the size of pipe, depth of bury, trench backfill and bedding conditions, type of fitting (i.e. deadend, valve or bend) and the test or operating pressure in the pipeline.

I have seen many instances where a thrust block was installed that wasn't big enough or where a restrained joint was used, but none of the joints on either side were restrained. In all the cases the joint failed either at the joint itself or at an adjacent joint in the pipe. It is very important to consider all factors when using either of these systems.

RE: Restrained Mechanical Joint vs. Regular Mechanical Joint

If you are new to the water world, start your career off on the right foot. That would mean that you will rarely if ever use thrust blocks.


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