What is the Significance of first 2 hanger load cases. how can we describe H (hanger load) used with load cases?

L1 W (HGR)

L2 W+P1+T1 (HGR)

L3 W+P1+T+H (OPE)

For Hanger Selection you need to know the Load and displacement at that point.

In first case: You will get loads

In second case : you will get displacement

So, it will select appropriate spring size based on above datas

"Don't" fool with the first two load cases!

In my opinion you often have to "fool" them (in other words, change them) to get the appropriate hanger selected. Especially when you have WNC cases or D cases in the calculation.

CAESAR II - User’s Guide Notes on CAESAR II Load Case,
Chapter Error Checking, Static Load Cases, and Analysis, page 6-27:

Recommended Load Cases for Hanger Selection

If spring hangers are to be designed by the program, two additional load cases must first be analyzed in order to obtain the data required to select a variable support. The two basic requirements for sizing hangers are the deadweight carried by the hanger (hot load) and the range of vertical travel to be accommodated.
The first load case (traditionally called “Restrained Weight”) consists of only deadweight (W). For this analysis CAESAR II includes a rigid restraint in the vertical direction at every location where a hanger is to be sized. The load on the restraint from this analysis is the deadweight that must be carried by the support in the hot condition.
For the second load case, the hanger is replaced with an upward force equal to the calculated hot load, and an operating load case is run. This load case (traditionally called “Free Thermal”) includes the deadweight and thermal effects, the first pressure set (if defined), and any displacements, (W+D1+T1+P1). The vertical displacements of the hanger locations, along with the previously calculated deadweights are then passed on to the hanger selection routine.

Once the hangers are sized, the added forces are removed and replaced with the selected supports along with their pre-loads (cold loads), designated by load component H.

Note that load component H may appear in the load cases for hanger design if the user has predefined any springs- in this case it would represent the pre-defined operating loads.

CAESAR II then continues with the load case recommendations as defined above.
A typical set of recommended load cases for a single operating load case spring hanger design appears as follows:

Case # 1 W ....WEIGHT FOR HANGER LOADS
Case # 2 W+D1+T1+P1 ....OPERATING FOR HANGER TRAVEL
Case # 3 W+D1+T1+P1+H (OPE) ...OPERATING (HGRS. INCLUDED)
Case # 4 W+P1+H (SUS) ....SUSTAINED LOAD CASE
Case # 5 L3-L4 (EXP) ....EXPANSION LOAD CASE

@Mariog & AY, but why is it a usually recommended practice to copy the operating load/hot load from the output and manually input it in the input for Hanger selection?
pardon my "question" if it seems too trivial, just need to be sure i know why !

I wouldn't say that practice is "recommended". However, if you have a number of hangers in series, and there is a riser at one end of the line, there may be a variation in hanger stiffness and/or pre-load. If you want to "manually adjust/balance" out the loads, then you would start tweaking the individual hanger spreadsheets.

This is adjusting the input, not the "hanger design load cases". If you adjust the "hanger design load cases" incorrectly, your hanger design is wrong, which means everything else is wrong.

Details of the hanger design methodology can be found in the Technical Reference Manual.

Thanks MARIOG to clear the concept of Hanger load cases.

Indeed you may want to do this once you issued the spring hanger specification. In this way you will avoid changes of spring loads for minor adjusting of the piping.

Regards,

I have a new question on the old topic. What if your piping system has cold spring (or cut short piping). Should the hanger load case that is being used to calculate the movement include the CS??? When you ask CAESAR II to recommend load cases it does not include that in the hanger load cases.

The cold spring will not change the travel requirement for the hanger so it should not be included in the hanger travel calculation.

I am working on a project for our client and it involves an existing boiler blowdown piping system. The system has some existing hangers and we are installing some new hangers and rigid supports. The original system was designed and installed in the late 1950’s. It has several spots in the piping where cold spring (cut short piping) is in the system and some of the cut short is fairly significant (7.25”) which happens to match the displacement of the nozzles (7.25"). I am having CEASAR size the new hangers alongside the existing hangers.

There are a couple of points where CAESAR II is selecting constant support hangers. The movement at these spots are being calculated in the hanger load case that includes weight (W) + displacements (D1) + temperature (T1) + pressure (P1) + hanger loads (H) but it does not include any cut short (CS) piping. Because of this and since it is near the location of some piping that has cold spring installed the vertical movement is large compared (16” to 17”) compared to existing hangers that were designed for vertical movement of 6.5” to 7”.

Our client is questioning the hanger design but I cannot come up with a good reason why I have a much larger movement.