Hello Dear Friends

I am analyzing for first time a system which includes hot taps, so that existing line won´t be taken out of operation by the time of tie-in the new line. I am trying to understand the behaviour of the entire system taking into account three scenarios:
1) Existing line cold, new line hot
2) Existing line hot, new line hot
3) Existing line cold, new line cold

Firstly I was told to note and write down initial displacements from existing line at its operating temperature.

Then I create a CAESAR II file (1) including both of the existing and new line, placing an anchor in a point near the hot tap; this file was with the new line at operating (OPE T1) and maximun (OPE T2)temperature and existing line to 70F.and Run it.

Secondly, I copied this file into a new one (2) but now, I deleted anchor and inserted initial displacements(all 6 degrees) with opposite sign to simulate the drawback of the existing line. I change new line temperature to 70F and kept existing line to 70F as well and run it.

Then I was told to combine Tope stress from CAESAR II file (2) with Tope stress from CAESAR II file (1) with ABS summation method (NOT SCALAR NOT AlGEBRAIC) and told I can note EXP stresses at critical nodes in order to add its absolute values, getting in this way the CODE STRESS RANGE.

Questions:
1) Why to place an anchor near the hot tap having the existing line to 70F? I mean, if I let the existing line to have 70F, won´t this line get back?

2) When talking about Tope stresses, should I read these values from stress extended report for OPE load case or for EXP load case?

For CAESAR II file (1), I have the following load cases:

1 OPE W+T1+P1 T1= 180F ; T2= 212F
2 OPE W+T2+P1
3 SUS W+P1
4 EXP L1-L3
5 EXP L2-L3

For CAESAR II file (2), I have the following load cases:

1 OPE W+T1+P1 T1= 70F
2 SUS W+P1
3 EXP L1-L2

My confunsion is how to apply the ABS method to the Tope stresses.
This is the first time I do a similar analysis.

Please any answer will be very appreciated..
Thanks

Sor, just to have some comments, my opinion is that you will never have 1st scenario (existing line cold, new line hot) so you may want to adjust your basic thinking of the situation.

Sory, I'm always in a hurry, if no one will answer I will try to answer later.

Regards,

Read this newsletter article, beginning on Page 13. This should help.

I read that article years ago, and that's pretty much exactly what I've been doing. Note that operating cases are now (optionally) code cases by appendix P. By the way, Richard, is ME News archived someplace available to us? I have a dozen or so random issues that I've been keeping for years, but it would be great to be able to look at them all.

See the link:

http://www.coade.com/Mechanical%20Engineering%20News%20Index.shtml

Regards,