Pressure Thrust In Expansion Joints

Dear All,

How CAESAR II is calculating the Force due to Pressure thrust in expansion Joints:

As per ASME B31.3 Appendix X X301.2.2:
Main anchors shall be designed to withstand the forces and moments listed in X301.2.2(b), and pressure thrust, defined as the product of the effective thrust area of the bellows and the maximum pressure to which the joint will be subjected in operation.

It mean:

F = A x P
a: effective area
P: Maximum operation pressure

1- But the value of the force in anchor calculated by CAESAR II is very different (10 times lower than F = A x P). any advise about this???

2- The equation above is for metallic expansion joints, is there other Equation for rubber expansion joints??

Regards,

Abdelkader,

1. The value of force at the anchor is different because the anchor is not the only restraint in your system. You probably have other restraints that are sharing the load. For example, assuming that you are using untied expansion joints and assuming that you have modeled the equipment (I presume you did), then the load will probably go to the equipment's anchor at the bottom. The bottom line is that the external and internal forces acting on the system are balanced (i.e. in equilibrium).

2. The equation is the same for any type of expansion joint (regardless of material), because it is independent of material. It is a purely mechanical principle; that Force = Pressure x Area.

Please check 1 above and tell me if that is what happened.

AbdulRahman,

Thanks for your answer I tested it with adding anchors just before and after the expansion joints and I got the same value as F = A x P.

As you said the force is balanced with the equipment nozzle in the first case

Regars