Dear Members,

We are doing a stress analysis for a piping with the following design parameters,

Design Temp 135 Deg C (T1)
Max. Ambient Temp 45 Deg C
Min. Ambient Temp 3 Deg C (T2)
Design Pressure 1380 kpa
Pipe Dia 8”, Pump Discharge Nozzle Size 3”

The load cases we considered are as follows,
L1 = W+P1+T1 (Ope)
L2 = W+P1+T2 (Ope)
L3 = W+P1 (Sus)
L4 = L1-L3 (Exp)
L5 = L2-L3 (Exp)
L6 = L1-L2 (Exp) 135-3 = 132 Deg C or L4+L5 (Exp) (135-45) + (45-3) = 132 Deg C (Max. Stress Range)

The above load cases are satisfied for stresses on the piping. Hope so.

The doubt is for restraints (at the pump nozzle connections, equipment connections and limit stop & guide loads) what are the load cases I need to refer. That is, should I have to refer the load cases L1, L2 & L3. If so, the restraint temperature range for L1 load case will be (135 – 45) = 90 Deg C and L2 load case will be (45 – 3) = 42 Deg C and L3 is the sustatined case. For the above the cases the pump nozzle load is within the allowable, but if I consider the load case below the pump nozzle load is more than the allowable.

If the above is acceptable, then what about the restraint value of max. temperature range of 135-3 Deg C = 132 Deg C. Should I have to create a new load case of L7 = L1+L2-L3 (Ope) (i.e. W+P1+T1+W+P1+T2-W-P1 = W+P1+T1+T2) for checking the allowable nozzle load and restraints. Is it is acceptable?

An alternative option to find the restraint load for max temp range is inputting the ambient temperature as 3 deg C in the special execution parameter and finding the max temp range for restraints as

L1 = W+P1+T1 (Ope) where T1=135 Deg C and Ambinet as 3 Deg C = 135-3 = 132 Deg C.

Is the above load cases are acceptable. Please clarify, if I am wrong.

`Dear Mr.Richard Ay,

I am waiting for your reply...

Patience is a virtue.

Here's how I look at it...
The ambient temperature is the pipe temperature at the time the piping system is assembled. Hopefully this is also the temperature of the pipe when it is cut to length otherwise you will have a variety of cuts short or cuts long when you assemble things. Set your CAESAR II ambient temperature to this value.
With this starting point established, all other "operating" states can be evaluated. Of course you have an operating temperature for the line (135C) that you will check. But those other temperatures (45C & 3C) should also be considered if the pipe wall goes to that temperature. I imagine though that at these "ambient" temperatures, the line may be empty so fluid weight (and pressure) may also change for these analyses.
As far as I know, the pump has to meet these allowable limits even if the impeller is not spinning; that those "ambient" loads must also pass.