Hi everybody

I'm working on the case with 2 OP tempreture.T1=-75C , T2=65C. Both of them pressure are same.
Max ambient T=55C , Mi ambient T=22C.
I made this load case:

I)

Amb T=55
1) L1=W+HP HYD -
2) L2=W+T1+P1 OPE -
3) L3=W+P1 SUS -
4) L4=W+T1+P1+U1 OPE -
5) L5=W+T1+P1+U2 OPE -
6) L6=L2-L3 EXP ALGEBRIC
7) L7=L4-L2 OCC ALGEBRIC
8) L8=L5-L2 OCC ALGEBRIC
9) L9=L7+L3 OCC SCALER
10)L10=L8+L3 OCC SCALER

II)

Amb T=22
1) L1=W+HP HYD -
2) L2=W+T2+P1 OPE -
3) L3=W+P1 SUS -
4) L4=W+T2+P1+U1 OPE -
5) L5=W+T2+P1+U2 OPE -
6) L6=L2-L3 EXP ALGEBRIC
7) L7=L4-L2 OCC ALGEBRIC
8) L8=L5-L2 OCC ALGEBRIC
9) L9=L7+L3 OCC SCALER
10)L10=L8+L3 OCC SCALER

Is this method correct?
If not Can any leave a correct loeadcase?

By not including T1 and T2 in the same analysis you will not be presented with the extreme displacement range: (W+T1+P1)-(W+T2+P1). Note: I am not showing valid CAESAR II combinations here.

Hi Mohammad,

I think the true intent of the code is not satisfied with the load cases given by you. In my opinion the load cases given in (I) are not required at all. You can fix the installation temperature = 22 Deg C and run two operating cases T1 and T2 in the same analysis.

Amb T=22
1) L1=W+HP HYD -
2) L2=W+T1+P1 OPE -
3) L3=W+T2+P1 OPE
4) L4=W+T1+P1+U1 OPE -
5) L5=W+T1+P1+U2 OPE -
6) L6=W+T2+P1+U1 OPE -
7) L7=W+T2+P1+U2 OPE -
8) L8=W+P1 SUS -
9) L9=L2-L8 EXP ALGEBRIC
10) L10=L3-L8 EXP ALGEBRIC
11) L11=L4-L2 OCC ALGEBRIC
12) L12=L5-L2 OCC ALGEBRIC
13) L13=L6-L3 OCC ALGEBRIC
14) L14=L7-L3 OCC ALGEBRIC
15) L15=L8+L11 OCC SCALER
16) L16=L8+L12 OCC SCALER
17) L17=L8+L13 OCC SCALER
18) L18=L8+L14 OCC SCALER

Your expansion stress range load case as per the code requirements is from 22 Deg C to 75 Deg C which is not covered in the both the sets of load cases given by you. By fixing the installation temperature at 22 Deg C, L9 given above covers the entire range from 22 Deg C to 75 Deg C.

Whenever we have the minimum ambient and the maximum ambient temperatures, it is alwayse conservative to choose minimum ambient as installation temperature for hot lines and maximum ambient as installation temperature for cold lines.

Thank SRI & Dave

but i think I shoud made L2-L3 for the extreme displacement range.

Is it correct?

That is the maximum expansion case.
Yes you can do this case, it correct.

Dear Mohammad,

I missed to notice the -ve sign on 75 Deg C temperature limit. I apologize for that. You are right L2-L3 represents the maximum displacement stress range.
But still I think you will be having a problem with restraint loads. ASME B31.3 319.3.1(b) makes it mandatory to compute the values for reactions as algebraic difference between the value at maximum(or min) temperature for the thermal ccle under analysis and the value at the temperature expected during installation. However I have the correct maximum ambient and minimum ambient for the site location, and cannot decide the true installation temperature, as I do not know when the piping is going to be fabricated and erected.