Hello friends,

I'm trying to quantify the effects of temperature changes on process piping and I would appreciate some feedback.

I have a simple 1-1/2'' sanitary line that goes from a flow panel in a building to another in a second building, passing outside in the process. The two points are approximately 50 m appart and the routing goes from floor level to approximately 5 m in height to connect both buildings. Here's a view of the layout :



I wanted to evaluate the impacts of the temperature change of having an empty outdoor routing exposed to -40C suddenly filled with hot CIP solution. In reality, the outdoor portion will be insulated and heat traced to avoid freezing but I want to study the worst-case scenario below.

The indoor extremities are at a pleasant 20C while the middle outdoor portion is at -40C. I'm using TEMPERATURE 1 for this varying ambient temperature along the piping.

TEMPERATURE 2 is my design temperature, which I set to a ceiling value of 100C. This temperature is applied for all the routing.

My load cases are the following (besides alt sus):
L1 (HYDRO) : WW + HP
L2 (OPE1) : W + T1 + P1
L4 (OPE2) : W + T2 + P1
L6 (SUS) : W + P1
L7 (EXP1) : L2 - L6
L8 (EXP2) : L4 - L6

CAESAR II is however recommending me another load case :
L9 (EXP3) : L2 - L4

My plan was to look at OPE1, OPE2, EXP1 and EXP2 to have an idea of the flexibility and associated stress of both temperatures sets.

I have some doubts understanding what EXP3 represents exactly. It seems to be a what I'm looking for as it calculates the displacement stress range between T1 and T2, which is a wider delta than T2 with the default CAESAR II ambient.

As I suspected, the preliminary results seem to indicate this. The L9 case is more critical than L8 by a small margin. I think it should be a representation of the expansion stress between the two temperatures states.

Is my reasoning correct ?
Is there another approach I should look into ?

Thanks for the feedback

CAESAR II doesn't know what your temperature values mean. To CAESAR II, you have two operating temperatures: T1 and T2. For a complete set of load cases, the software will assume that the system could cycle between T1 and T2, hence the EXP3 load case. If this cycle is not possible, delete that load case. (So your conclusion is indeed correct.)

Thanks Richard!