4 replies to this topic

[WilliamN]

Dear peers,

I know this is an old topic. so I searched our forum, unfortunately I didn't find a post of my question.

 

I am designing a new shell and tube exchanger with fixed tube sheets. The mean metal temperature difference between shell and tube is ~ 100 C. The temperature difference is indeed large.  Both shell and tube are stainless steel material.  I think an expansion joint is not needed so long both shell and tubes are same material regardless of the temperature difference. I would appreciate If you could share your comments on this subject .

 

William

 

[fallah]

William,

 

As far as I know, if there would be the tube to shell metal temperature difference of 50 C or more, then expansion joint or floating head is required in hot service...

[AlertO]

William

 

you should avoid using fixed tube sheet exchanger for your service as fallah mentioned. however, please be careful for using expansion joint, if your service is toxic or high pressure because it will be a source of weakness of the exchanger which can lead the leakage problem.

[Pilesar]

You probably need some flexibility in your exchanger. Even if your thermal expansion coefficients are the same for your shell and tube material, the actual expansion is a function of length and temperature change. Because the shell and tube temperatures change by different amounts, thermal stresses result which may be greater than the exchanger can be economically designed for without some means to dynamically relax the stress. The TEMA standards explain the calculations needed to check if your final design is suitable. You might also use the method described by Kopp and Sayre in their ASME paper. If you do not want to calculate the expansion joint, the exchanger manufacturer should perform these calculations based on the most adverse conditions you supply to them. Often the most adverse conditions are not the normal operating conditions, but perhaps occur during startup or shutdown or some upset condition.

[Gulley]

There is a tip in either www.gulleyassociates.com or the spreadsheet: Process Heat Transfer 1.04 by Art Montemayor. It has the title: Is an expansion joint required in the shell? It gives some guidelines.