this would need to be calculated. There is far too much involved to design
it all here.
There are many serious issues.
Each issue would have to be addressed in turn
the stress distribution would be much different,
-the edge rotation of each plate would be different than the edge rotation
of a single thicker plate.
- this could be mitigated by a sufficient v groove weld on the edge , but
again the depth and strength of the weld would have to be calculated.
the deflection of individual plates , especially at the centre would be
different than the deflection of a single tubesheet, and more signficantly
each slightly different from the other. The inner sheet will see higher
temperatures than the outer (slightly but enough to make a difference) and
pressure on the inner would be transferred as deflection of the inner plate
onto the outer plate.
While the distribution is axisymmetric, it is not radially or longitdinally
uniform and this is where the difficulty arises.
I understand your dilemna, and with considerable effort its likely possible
with the proper design alterations. I am sure Chris will agree FEA of the
tubesheet is the only secure method of analysing this.
TEMA and none of the canned programs have any routines for layered
tubesheets because the elemental interations are too complex are far better
suited to FEA.
We have done layered vessels and sandwiched tubesheets and they do not act
the same. Since it is for yourselves , it may be worth the effort and risk,
but if the tubesheet has to be 30mm it is at substantial pressure and would
require registration.It would not be valid to assume they act as a single
unit. This would not be accepted by the Local PRESS VESS ASME authorized
inspector in accepting the design.. It is easy with a simple model to
demonstrate they do not act as one unit. another example is an interesting
paper on the web somewhere about the scuffing effect of adjacent components
in a heat exchanger able to slip relative to each other.
Unless you are intimately familiar (or engage someone who is) with all the
details and the detailed calculations of heat exchanger design (and what
they mean) it is almost certain you will ruin two good pieces of plate.
al
-----Original Message-----
From: GET Mithapur [mailto:getuser@tatachemicals.com]
Sent: Wednesday, July 21, 2004 4:34 AM
To: 'pipingdesign@yahoogroups.com'
Subject: [PipingDesign] Heat Exchanger Tube Sheet
Dear All,
This question is not purely related to piping, but let me allow to ask......
We have 16mm Tk Titanium plates in stock. Now, We have to fabricate one heat
exchanger for our use.
As per calculation, required thickness of the Tube sheet is 30mm.
The type of Heat Exchanger is rectangle and tube sheet size is 1600 mm X
1225 mm Tk.
As titanium is a very costly material and 16mm Tk. Is already available
with us, CAN WE USE 2 x 16 mm plates instead of one 30 mm Tk tube sheet?
Please advice....
The application is to cool CO2 Gas...
Your prompt reply anticipated.
Regards
Yahoo! Groups Links Received on Wed Jul 21 11:48:00 2004
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