External DP for HX TUBES

Gilbert · **Posted:** Fri Jul 22, 2011 7:49 am

I have seen heat exchanger TUBE are designed with external pressure of full vacuum, but the shell side internal design pressure is higher (i.e. 20 barg). Does the tubes ext DP of FV is correct?

Javed Nasir · **Posted:** Fri Jul 22, 2011 8:46 am

Gilbert,

What is tube side design pressure?

Gilbert · **Posted:** Fri Jul 22, 2011 6:12 pm

tube DP is 25barg.

Javed Nasir · **Posted:** Sat Jul 23, 2011 8:36 am

Gilbert,
Following are the possibilities as far as tube side design conditions are concerned.

1- In operating conditions: Tubes shall be subjected to 5 Barg internal pressure.
2- There is no pressure in the tube side, tubes shall be designed against 20 barg as external pressure.
3- When exchanger is not in the operation. There is vaccume created in tube side and there is no vaccume in the shell side, you tubes shall be designed against full vaccume. This is the case that mentioned in your post.

So to design only on full caccume, I would say it is not correct.

Gilbert · **Posted:** Sat Jul 23, 2011 10:43 am

Yes you are correct, thanks a lot for clarifying...the datasheet looks less engineered..

sanjeev_shukla70 · **Joined:** Wed Apr 18, 2007 2:05 pm **Posts:** 260

Unless your datasheet specifically indicates that FV in the tube is the case when no pressure on shell side, I would consider 21 barg (FV+20 barg) for tube external pressure.

In addition FV as indicated in datasheet for tubeside are process design conditions and usual way of indicating design conditions. All possible combinations are to be considered for mechanical design, same case as of tubesheet where datasheet do not provide all combination to mechanical engineer.

Regards

External DP for HX TUBES

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