Tips July - September 2002

Suggestions for Reducing Equipment Loading

Piping imposes loads on equipment nozzles. These loads may exceed the allowables given by the manufacturer or codes such as API 610.

The following guidelines may be helpful in reducing these piping loads on nozzles connected to equipment.

1. If the dead loads exceed the allowable,

  • Ensure the piping system is adequately supported,
  • Remove unneeded supports; they may be the cause of the problem.

2. If the thermal loads exceed the allowable,

  • Check the design and operating temperatures. Consult the process engineer to obtain correct or reasonable values for different operating conditions.

3. Try modifying the piping support system and layout

  • Add expansion loops if apt,
  • Use expansion joints or other flexible joints,
  • Consider spring mounted pumps,
  • Modify the layout of piping by rerouting,
  • Use guides or anchors at strategic locations,
  • Use reinforcing pads on vessel nozzles.

Rod Hanger - Notes

A rod hanger in CAEPIPE functions as a limit stop, that is, it functions as a non-linear one-way restraint. It is rigid in -Y direction and fully flexible in +Y direction (in a Y-vertical system). The rod hanger offers no resistance in +Y direction.

Rod hanger results are included in the hanger report which reports results for the first operating case (W+P1+T1). In the hanger report, a rod hanger's spring rate may be shown either as Rigid or zero. The zero spring rate often confuses users. It simply means that there is liftoff at the hanger location for the first operating case. One can confirm this by studying the output Y displacement at the support in the first operating case (which will be 0 or positive).

Liftoff (i.e., zero spring rate and a zero or positive operating condition displacement) indicates the support may not be needed and could be removed.

Read Ron Haupt's "The Problem with Piping "Lift-off" tip of the month in our Piping Articles section.