Who can tell me why the hot loads & vertical movements in Hanger Table are different from the OPE load case output?

The "hot load" is the weight of that portion of the piping system that the hanger must carry (determined without the spring in the system). The "vertical movement" is the displacement at the hanger location in the "Free Thermal" condition (hot load applied up, but still no spring in the system). Using these two values, a spring is selected and then inserted into the system.

At this point, your real load cases are analyzed, with the selected springs in the system. You will rarely obtain the same loads or travel in your real load cases, since the hangers were selected without their effects on the system.

One option you have to alter the typical hanger design to permit CAESAR II to iterate during the hanger design, using the selected hangers to improve the hanger design. To turn this on, in the Static Load Case Editor, go to the "Load Case Options" tab. Scroll this to the right until you find the column for Hanger Design. For the "free thermal hanger" cases, change the option from "Ignore" to "As Designed". (Read the "help text" on this option before you use it.)

Yes, as you mentioned, I selected "include hanger stiffness during hanger OPE travel cases" option, but some (not all) displacements in the EXP output table still don't match with the vertial movements in the hanger table.

I donnot know why. And which displacements should be used for hanger design?

The Expansion case displacements aren't real displacements that you can run out and measure - these values are a displacement range.

For hanger design you should use the values in the hanger table, checked against the results of your OPE cases.

Richard Can you please explain . The final selection is based on hanger table or the restraint summary which is close but not exactly same as hanger table.

Regards
Lee

The spring as designed by CAESAR II (and reported in the hanger table) should be sufficient to handle the loads and travel from all of your load cases.

Dear sir ,

I still face the same problem while I select "AS DESIGNED" in "OPERATING FOR HANGER TRAVEL " case.

I found the vertical displacement is -1.41mm in hanger table but it shows -1.7 mm in restraints summary (The case is W+T2+P1+H ).

I try to change the "AS DESIGNED" to "IGNORE" and get the same value -1.7mm
both in hanger table and restraints summary (case W+T2+P1+H).In most case , the travel in hanger table can be corresponded to the restraints report summary while "IGNORE" is selected.

1.What's the reason that it shows different valuses while the setting is "AS DESIGNED" ?
2.What's the different between the "Field installed load" and "Actual installed load" ?

Regards,

hi ccckkk and others,here below is my consider:


you have two temperature cases, I guess you have not select the multiple hanger option, so CII select the hanger as per the first temperature case, and apply the selected hanger to all the useful cases.


When you apply the "as designed" option, CII will apply the hanger stiffness in the "Free Thermal Case". Richard Ay has mentioned, i.e. "permit CAESAR II to iterate during the hanger design".



"Actual Installed (cold) Load" is the case "WNC (Pipe+Insl+Refrty) +H", i.e. in this case only consider the all weight except the fluid weight, and hanger stiffness.
"Field Installed Load" is the case "W (Pipe+Insl+Refrty+Fluid) +H". What it differ from "theory install load" are displacement and hanger stiffness are considered.

Hi llljq, Thanks for your kindly reply.

I try to do a test file as below ,
There is only one Temperature case =250 degree C
and there is one spring hanger with spring rate=1000 N/CM predefined.
The load case is like :
Hanger stiffness
1.W (HGR) Rigid
2.W+T1+P1 (HGR) Ignore
3.W+T1+P1+H (OPE) AS DESIGNED
4.W+P1+H (SUS) AS DESIGNED
5.L3-L4 (EXP) ------
The hanger table
MVT HOT COLD SPRING RATE
20 1 4.784 1842. 2320. 0. 1000. 7.507
The restraint summary
20 FY=-1842 DY=4.784

When I change the hanger stiffness to "AS DESIGNED" IN CASE 2
The hanger table
20 1 4.754 1842. 2317. 0. 1000. 7.507
The restraint summary
20 FY=-1553 DY=4.766

Can anybody teach me what's reason resulted in above case while I change "IGNORE" TO "AS DESIGNED"

REGARDS,

Hi ccckkkk
Just press F1 on that box, it will show what it means.
For caesar to select spring from it's database, it required two parameter
1) Weight at that point
2) operating movement at that point.
Based on about two data caesar choose spring.

If in case 2 you select "IGNORE" caesar will calculate movement at that point without considering any spring constant there.

If in case 2 you select "As Design" caesar will calculate movement at that point with considering spring constant there.

Since selection criteria change it will set bit different load & displacement at that point.

Since you made predefine stiffness it remain same in both the cases.


Regarding restrain summery ;; what I think is that when we select "ignore"
caesar consider theoretical installed load is ZERO elevation load.

When select case 2 " As design" it do not consider theoretical installed not in ZERO elevation it fix some other point as zero elevation & make calculation accordingly for restrain summery.




Regards

Habib

Hi Habib , thanks for you kindly reply.
Sorry for my poor experience , I still have some questions:
1.If I predefine the hanger stiffness (ex: 1000 N/CM) , the case 2
needed to be changed "AS DESIGNED" , doesn't it?
2.If I change case 2 from "IGNORE" to "AS DESIGNED" , It needed to
follow the hanger table and inform to the vendor , doesn't it?
3.If question 2 is yes , how do I really explain to our client that
the hanger table (hot load=1842N)can't match the restraint summary (FY=-1553N)

Thanks,

Hi ccckkkk

I suggest still you follow case 2 "Ignore"
Yes in any case you have to follow vendor table.
If you like you can fully define spring. Specify stiffness & theoretical cold load. In that situation case 1 & case 2 are no more required.
If you are doing manual selection always cross check with vendor table.

Regards

Habib

Hi Habib, I'm appreciated your kindly help.
If I already predefined the hanger stiffness only , but the case 2
is still "ignore" selected ; how should I jutisfy this hanger table and
restraint summary is calculated based on the existing stiffness ?

Regards,

Hi ccckkkk

You cross check restrain summery load change it will match (displacement change* spring stiffness)


Regards

Habib