One pass floating tubesheet H.E. with internal expansion joint

[FSKeng]

I need to design a one pass floating tubesheet heat exchanger. inorder to compensate diffrentail thermal expansion a thin-walled expansion joint is going to be used on the floating tubesheet(floating tubesheet is conected to the shell cover by this expansion joint)!!!
dose any body know of any rational methode for designing this kind of exchangers?
nothing is mentioned in UHX about design of this kind of exchangers!!!!

thank you very much

 

[SnTMan]

FSKeng, tubesheets are covered by part UHX and can be designed so.

The expansion joint is designed for internal pressure, external pressure and the calculated differential expansion each way at the location where it is installed. It will be designed to Appendix 26.

Expansion joints in this application typically do not have to provide resistance to the longitudinal pressure loads, as they are taken by the shell and bundle. However they should have a stay bar system for use during maintenance, when the shell cover is removed. During a hydro for example the full hydrostatic end force is applied to the expansion joint when the shell cover is removed.

In practice, you supply the expansion joint vendor with the joint movement required, usually both plus and minus, the diamter required, the pressures and temperatures, cycle life if required, materials if necessary and the vendor does the rest.

Sorry, I don't know of any reference books to suggest.

Regards,

Mike

 

[FSKeng]

hi mike

thank you for your comments, I still have a question.
with the expansion joints attached to the floating head the floating head is no longer free to move as a real floating head dose, I think the spring rate of expansion joint will have an important efect on the bending stresses in the tube sheet, (some how like a fixed tube sheet), as you said Appendix 26 is enough for design of expansion joints but what should be done for the tube sheet bending stresses especialy in the case of thermall loads !!!!

any help is appreciated

 

[SnTMan]

FSKeng, that is an aspect of the problem I had not considered before, and that part UHX seems not to address. Perhaps the Code commitee can further complicate tubesheet design by accounting for this in a future Edition

These designs have been in successful service by the hundreds or thousands prior to the introduction of Part UHX rules, leading me to believe the effect of joint stiffness is not important, and it was standard practice to disregard it when designing to TEMA rules in the past. As bellows joint spring rates are generally very low compared to the spring rates for the tubes, shell, etc. this practice would seem justified.

I suppose one could account for it by converting the additional load to an equivalent pressure to be added to the design pressure, carefully accounting for when it applies to shell side and tubeside pressures. I doubt that I would go to the trouble, as increased complexity of a calculation does not imply improved accuracy.

Regards,

Mike

 

[FSKeng]

Ok, thank you for sharing your valuable exparience, now I feel more confident about neglecting the effect of bellows.
but as a research topic I may follow this case.

Arash

 

[SnTMan]

FSKeng, glad to help, if your research turns up anything useful I hope you will share.

Regards,

Mike

 

[djack77494]

FSKeng,
My first suggestion is that you would obtain a better response to your query if you have it appropriately placed in the Heat Exchanger forum. Single tube pass S&T exchangers are manufactured by many fabricators. They can be dificult to assemble and they also tend to be an expensive way of getting area. Nonetheless, they have their place and can function well when properly applied.

Since expansion joints are by their very nature "flexible" I do not understand the concern with stresses that are imposed BY the expansion joints. In any case, I consider this to be an instance of "don't try to reinvent the wheel". If you have the software that you should have to design exchangers, it should provide you with an analysis of the stresses and pressure-bearing abilities of the various components.

 

[FSKeng]

mike: surly I would
djack77494: thank you for your coments