I have a few questions about Rubber Expansion Joint modelling in CAESAR II. There are 5 inline cooling water pumps connected with piping circuit of size 20". Pump Nozzle size is 12". Temperature is 150 F. The nozzle allowable loads are very low , so expansion joints are inevitable.
Now the questions are:

1. What are stiffness values of rubber expansion joint, as project is at initial stage and no vendor data is available. I think that CAESAR II expansion bellow database (Flexonic) only deals with metallic joint.

2. Are Tie-rod or Limit rod required ?. Pressure is 175 psig. But my main concern is nozzle allowable loads.

3. If yes, then what is best way to model Tie-Rod or Limit rod is CAESAR II ?

4. The actual issue lies with pump suction piping. Pump discharge loads are okay. Can i install bellow ONLY at suction piping ? Is it a recommended ?

Regards,
Ali Raza Bashir
Piping Stress Engineer

In response to your questions above:

1) Correct, the data supplied with CAESAR II is for metallic bellows. You should contact a probable vendor and ask for some ball-park stiffnesses.

2) Again I would contact the specific vendor you may deal with to discuss this.

3) There are examples of tie-rods in the Applications Guide. In short, you can go with the simple model with uses a rigid rod in the center of the joint. (Granted this is not physically possible, but it works numerically.)

4) This is an operational question. I would discuss this one with your pump vendor to obtain buy-in.

Thanks Richard for your valuable comments.
1.Yes, i am planning to download catalog of different expansion bellow vendors. For same size and type, I will compare stiffness of different vendors and will go for an averaged sort of value.
2. Its an only engineering project. I have to issue only the datasheet of bellow. Vendor selection and coordination is entirely the client responsibility.
3. As per your advice, i will go for Simple method.
4. Still indecisive.

Regards,
Ali