Is there any firm criteria to select tube to tubesheet joint such as expanded only, seal welded, strenght welded, partial strength welded, expanded with grooves , and similarly other etc.

I am aware of the fact that these type of joint is based on the service tmeperature, and longitudinal stress in tubes in fixed tubesheet type of exchangers.

I am confused in most of the cases there may be upto 4 to 5 options availble to pass the joint strength.....but I have not come across an firm rule of thumb to follow in this regard to pin point the exact joint to be selected.

please share some information and help in this regard as how to choose the tube to tube sheet joint.

Hello Farid

The joint type is taken from ASME Section VIII, Division 1, Appendix A. If you look at that appendix, all the various tube to tubesheet joint types are discussed. If you are still confused, you can email me at: techsupport@cdoade.com. Just address it to Ray.

hi Ray,

Thanks but I do know the selection of tube to tubesheet joint in Pv-elite both as per Appendix A and UW-20.what actually I am asking is about the general critieria of tube to tube sheet joint selection based on service , temperature and pressure etc.
lets say for example we have a fixed tube sheet type of exchanger. i have the choice to go for full strength , partial strenght as per UW 20 and similarly for Appendix A expanded with two grooves.In all these three cases the joint strenght is satisfactory as per strenght calcualtions point of view. the confusion now is which one to follow here.....any firm rules of thumb...any other factors based on which joint is selected...I do have an idea that in high tmeperature applications expanded joint is not desirable but here the problem is I am not sure about the range of temperatures which should be followed as a guide line ...

There is no hard an fast rule. The sole purpose of the joint is to maintain the tube in place and prevent leakage. The tubes suffer from vibration during the course of their service, and this vibration can loosen them sufficiently to cause leakage. Transporting a unit can also loosen the tubes, especially if the unit is transported over a long distance on rough roads. Ideally, the tubes should be welded, however, this is a very expensive process when large numbers of tubes are involved.

Grooves are always a good idea, but the machining with a fly cutter is expensive. This is the next best thing to welding. If grooves are employed, the transporting and vibration problem is lessened. Every thing comes down to cost of production.

The mechanical expansion of tubes is extremely important. You always use a very experienced boiler maker (artisan) and you must not over expand the tubes. If you over expand the tubes, you cannot re-expand them when leakage is detected at the shop test, or, after transportation. That is why welding - even seal welding is the best solution.

Another thing where you have to be very careful, is not to expand the tubes for the full thickness of the tubesheet. This will cause tube failure (fatigue) when vibration is experienced in service.

To conclude, there is no hard an fast rule. You must balance cost against risk. If experience indicates (from past experience) that expanding only is satisfactory, then that is the way to go. But, remember, generally the fabricator has to give a service guarantee - that is the rub.

I am not a heat exchanger expert, but I have limited experience as I was an inspector for in South Africa form many years, and I draw on my limited experience.

Thanks a lot Ray for these valuable information.