Rigid Support Displacement Criteria - CAESAR II - Help

CAESAR II Users Guide

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English
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CAESAR II
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CAESAR II Version
12

Specifies the minimum amount of travel for hanger design. This is a cost saving feature that replaces unnecessary springs with rigid rods.

Typical units (depending on your unit system):

  • in

  • mm

  • cm

The hanger design algorithm operates by first running a restrained weight case. The load to be supported by the hanger in the operating condition is determined from this case. After the hanger design load is known, the software runs an operating case with the hot hanger load installed. This analysis determines the travel at the hanger location. If this determined hanger travel is less than the Rigid Support Displacement Criteria, then a rigid Y-support is selected instead of a spring for the location.

The software does not apply the criteria if you leave the Rigid Support Displacement Criteria box blank or zero.

A typical value is 0.1 in.

You should insert a single directional restraint instead of a rigid rod in some cases. Rigid rods are double-acting restraints. In some cases, these can develop large hold down forces that do not really exist because the support has lifted off, or because the rigid rod has bowed slightly. When this condition develops, you should rerun the hanger design inserting single directional restraints where rigid rods were put in by CAESAR II.

Do not replace hangers with rigid rods in very stiff parts of the piping system. These parts are usually associated with rotating equipment or vessel nozzles that need to be protected.