By Vince Carucci
Previous articles in this series discussed machinery allowable load bases and temperature considerations. This article discusses piping support and restraint considerations for machinery piping systems.
Piping must be designed and installed such that there is essentially zero forces and moments applied to the machinery nozzles when the system is not operating and is at ambient temperature. In order to accomplish this, sufficient pipe supports must be installed near the machine to carry the weight load. In addition, close flange alignment tolerances must be specified in the system design specification and adhered to during piping installation.
Designing the pipe supports to be adequate while the system is not operating is not enough. These supports must also function when the piping system is operating and at temperature. Therefore, spring supports must be used at locations where support is needed and the net vertical force (thermal force minus weight force) on the pipe is upward. Springs are needed in these cases in order for the supports to be effective when the system is operating. When performing or reviewing computer flexibility analyses, care must be taken that all the fixed supports that are modeled are really effective when the system is operating.
It is common to install restraints or anchors in machinery piping systems. These items are used to direct piping system thermal movements away from the machinery nozzles into other parts of the system that are better able to absorb them. This approach reduces the piping loads that are applied on the machinery nozzles.
Much of the work we do at Carmagen is to review piping systems that have been designed by others to determine their acceptability. Here are a few items we look out for in machinery piping systems:
We'll have a few more things to say about this topic in later articles in this series.