Analysis using Hanger

Hi i am new to CAESAR

In my model i have one spring hanger vertical at one node.

When i view my results , it shows in load case analyzed

1) (HGR) CASE NOT ACTIVE
2) (HGR) CASE NOT ACTIVE

whats the meaning of this "(HGR) CASE NOT ACTIVE"

Regards

It means hanger load cases are not viewable in the report. If you want it to be viewable, go to Load Case Options in Static Load Case Editor, and under Output Status column, change it to "keep".

Nald

Thank you very much.

Regards

Engr_mech,

The reason the "hanger design" cases are disabled by default is because these results don't reflect your actual piping system, and therefore these results shouldn't be used for anything. These load cases are used by c2 to design the spring hanger. For details on how this is done please refer to Chapter 6 of the Technical Reference Guide.

Thanks Sir

With hanger report output window

1) Actual installed load = 0 , why is that.?

2) Also it is showing load variation =15% , why is that.?

3)max table displacement range = 7.5 in , why is that?

Regards

1) Because you have to request that this computation be performed. This switch is on the "Hanger Run Control" dialog back in the input.

2) Because a hanger can only balance the system in one single position. For any other position (load case) the hanger is not balanced. This value gives the extent of that unbalance.

3) Extra (soemwhat useless) information. This is the maximum displacement for the largest hanger in the table.

Thanks Richard Ay You are always helpful for newcomers like me.

1) what the principal difference between sustained load case and installed load case?

2)In spring hanger output window, how can "theoretical installed load" be higher than "hot load"? I think "hot load" value should always be higher than "Theoretical installed load"?

Regards

Dear Mech Engineer,

(1) Installed load case and sutained load case remain same.

(2) for spring latest refer anvil catalogue page no 131 formula.

just understand the basic concept " how spring works ?"

still if you have any doubt, please let me know

I think we cannot compare these two values i.e hot load with theoretical installed load in Hanger Report output . They are separate entities

Hot load - showing loads due to temperatures.

theoretical installed load- due to flanges + weight of pipe + bends etc

is it true....

Have you been through the section on hanger design in the Technical Reference Manual? Everything is explained there.

Richard Ay, I have query regarding the defaut load cases for hanger. As per Technical Reference Manual:
"For the restrained weight run, rigid “Y” restraints are placed at each hanger location, and any anchors to be freed are properly released.
Immediately after the restrained weight case, an operating analysis is performed. The “Y” restraints are removed from the hanger locations and the hot loads just calculated are inserted. Any anchors that were freed for the “restrained weight” analysis are fixed"

For those instructions provided for the two hanger load cases, are these automatically done by CAESAR II?

Well for my opinion these are the recommended load cases issued by by CAESAR II, L1 for restrained weight case , L2 for operating for hanger travel , and in my humble opinion they are automatically done by CAESAR II.

Richard Ay , kindly confirm

Regards

Yes these are automatically setup by CAESAR II.

Thanks for guiding Sir .

@Richard Ay,

i have gone through technical discussion on hanger sizing algorithm

there it is written in restrained weight run case "This case usually includes weight, pressure and concentrated loads. Hanger hot loads are calculated in the restrained weight case".


why this is called " hot load " , as it is nothing to do with temperature .

why is it, please clarify

Regards

The loads calculated here (in the "restrained" weight case) are the loads which "balance" the deadweight of the system.
These loads will be the target loads on the springs in their HOT position (as we are more interested in balancing the system in the operating position).
So, you are correct, these loads are not established with temperature effects but they will be used as the targeted "hot" load in hanger sizing.

In technical reference manual it is written with regard to hanger discussion that

"The actual installed load may differ from the theoretical installed load by (K)(d), where (K) is the spring stiffness and (d) is the displacement of the pipe in the installed condition"

But usually my both values come same .

1)Then whats the difference between "Theoretical installed load" & "actual installed load".??

2)Do CAESAR provide the facility to show total weight of the geometry (without fluid content)???

Regards

In your case there is no vertical displacement of the system at the hanger location after pulling the pin upon initial installation which results to same theoretical and actual cold load. But in case of the system will displace under the load this will lead to extension or compression of your spring which result to new load and this new load is the actual cold load.
Did you provide additional load case for calculating Actual cold load?
How did you set the load case?

1. Theoretical cold load is the load to which the spring should be preset prior to installation, this is done in the factory and the spring is pinned to keep at this value. Actual cold load is the load of the spring after pulling the pin.
2. The load case WNC stands for Weight No Content.

@Nald

1)Ya i called the third load case for the hanger by going in hanger design control data in model option in input spreadsheet, and checked on "Calculate actual cold loads" , is that correct? my hanger output report is showing vertical movement of 0.75in. why then actual is same with theoretical installed load?

2)in which report weight will be shown after including WNC load case??


3) The initial load case of hanger design which is "restrained weight case" calculates dead weight . This case usually includes weight, pressure and concentrated loads . this is written in technical manual .
As there is no temperature involved , i was wondering why they have used term "hot load" for restrained weight case.????
Nald kindly guide

Regards.

1. Yes you are right..This is the displacement in the hot condition. In your case, after pulling the pin the system does not produce net load or your piping system is not flexible enough to displace the system. Since the system did not displaced at hanger location therefore the spring did not experience extension or compression from its theoretical cold load setting.
2. I'm not sure what specific report to show the weight of the system without its content. But I think you can use restraint report. May I ask you, What do you after this report? and what is the significance of this report in relation to your analysis?
3. As Explained by Sir Dave Diehl.

1. I had little confusion , it is written in technical manual under hanger design topic that "This case usually includes weight, pressure and concentrated loads. Hanger hot loads are calculated in the restrained weight case."

why temperature is not included above , as temperature constitute hot load(operating condition)??


2. I am considering WNC because i am interested to know how much my
pipe + fittings weight(without fluid weight) . Is there any other way in CAESAR to measure this (just wanted to avoid hand calculations , just curious how much my system weigh).?????

Richard Ay kindly teach me .

Regards

1) Please read the section on hanger design in Chapter 6 of the Technical Reference Manual. This explained there.

To summarize, the purpose of the spring hanger is to carry part of the "system weight", through all positions of the piping system. Temperature is not part of the weight, hence it is not included in the "restrained weight" case. Temperature affects hanger travel, so it is included in the "free thermal design case".


2) Go through "error checking" and look at the Center of Gravity report.

1) Under "Hanger design Load Data" , I enter "Allowable Load Variation" as 20% , and run analysis , output hanger report shows Load variation 16%.
My question is when i have specified it 20% , why output is showing 16%???


2) How CAESAR calculates "horizontal movement" value in hanger design output report . whats the formula for that?

Regards

The "allowable load variation" is the maximum permitted. You can have anything less than this limit.

The horizontal movement at the hanger location is determined the same as any other node - [K]{x} = {f}.

@ Sir Richard Ay

"Horizontal movement (inches)" as shown by hanger output report in CAESAR II is calculated by "CAESAR Algorithm" or shown in "Hanger vendor catalog"???

Regards

Dear Richard Ay,

May i know why the pressure effect or load is not considered in calculating the hot load of spring hanger?

Please clarify....

Weight, pressure and concentrated loads are considered in calculating hot loads.

The assumption in hanger design is that the hanger carries the "weight" of the associated piping. Pressure is not weight, hence it is not considered in the "load to be carried" by the hanger.

Dear Richard,

Thanks for your reply. The assumption may be good for a low pressure piping. For a medium or high pressure piping, the pressure load will have some effect on the weight load in designing the spring. Also i request you to clarify in some more detail..

@ Sir Richard Ay

"Horizontal movement (inches)" as shown by hanger output report in CAESAR II is calculated by "CAESAR Algorithm" or shown in "Hanger vendor catalog"???

Regards

Sillyman,

In a piping flexibility analysis pressure has no effect on the computed displacements of the piping system (unless you turn on Bourdon or have untied expansion joints), therefore pressure has no effect on the computed loads that act at the hanger location.


Engr_mech,

The displacements reported are those computed during the analysis.

ok thnx Sir Richard Ay.

But @Sir Richard Ay

CAESAR II "Hanger output report" , show only figure number e.g B-268 , but not shows Type number of spring hanger e.g A, B,C,D..Why?

Regards

Except for the designation for spring cans, "Types" A, B, C, D, etc. are packaging, not spring, isses. We itemize cans only because they have a different vertical clearance.

@ Dave Diehl,

Sir i have another confusion , In CAESAR II hanger design Output report, there is one entity "Maximum table displacement range (in)".

What is this?

Is this calculated by CAESAR Algorithm or seen through Hanger Catalog?

Regards

It's the maximum travel you can get from that manufacturer for all the springs we have in CAESAR II. Each manufacturer will have a single value.

That means this value is found in catalog, and not calculated by CAESAR II Algorithm , right....?

Regards

Yes. you get the same value for the same manufacturer, no matter the model.