Tube sheet thickness vs. tube thickness

[starfarooq]

One of the heat exchangers at our plant is near to completion of its service life and now we want to retube its U-Bundle. Its a high pressure tube bundle with channel head as a integral part of it. Now for longer service life we want to change the material of the tubes from existing CS to SS. Since the required tube thickness in case of SS is less than the CS tubes (which are installed as per original design), one of the vendors have showed his reservation about the thickness of the tube sheet. According to him, with the reduced tube thickness, the ID of the tubes will enlarge which will result in weaker tube sheet (In other words, if we consider the tube wall as part of tube sheet after expansion, the holes diameter in the tube sheet will enlarge, thereby reducing its strength.) So the conclusion is that we cannot use the tube sheet with less thickness of tubes. I invite the valuable comments from the forum members.

 

[boo1]

consider the thermal different

 

[SnTMan]

starfarooq, if the tubesheet were orginally designed per TEMA, no account would have been taken of either the tube wall thickness or material, so from that you could say, "makes no difference".

Part UHX rules do account for both tube wall thickness and material properties, so you could say "makes a difference".

I suspect in your particular case the change in tube will not make any difference, however if I were you I would not trust my suspicions.

Do the calculations both per TEMA and Part UHX (if possible) and see what they tell you. If still in doubt other types of analysis may be in order.

Regards,

Mike

 

[starfarooq]

I have checked the data sheet of the original tube bundle, it says as follows:

CODE:
Design: Stoomvezen
Construction: TEMA R

Does Stoomvezen takes tube thickness into account when calculating tubesheet thickness?