In our Stress Analysis - Hanger Report, the horizontal movement of the spring is 19mm, suspecting the horizontal movement is more. I preferred to go for an option of “Large Rotation Rods – Spring Hangers” as per Caesar-II – Application Guide, Chapter-3 Restraints.

As briefed in the application guide, I modeled the large rotation rod by including the following input,

From Spring Hanger Report (Piping Technology Catalog),

Spring Rate is 1051 N/cm
Cold Load is 10530 N
Hot Load is 12098 N
Load Variation is 13%
Vertical Movement is -15mm
Horizontal Movement is 19 mm

In the restraint input spreadsheet (at the spring hanger node),
Len is 2391mm
Stiff is 1051 N/cm
Fi is 10530 N.

Based on the above input the updated Spring Hanger Report is as follows, the changed values are shown in bold

Spring Rate is 1051 N/cm
Cold Load is 10882 N
Hot Load is 12098 N
Load Variation is 10%
Vertical Movement is -11.57 mm
Horizontal Movement is 20 mm

To make a conclusion, as explained in application guide “The user must, however, make sure that the spring stays within the design limits. (This is not difficult to do. The maximum computed load on the spring is compared to the manufacturer’s load limits)”.

So, referring to the above, as per Restrain summary, the following loads at spring (Flex +YROD Prog Design VSH) is,

Operating Case (Fy) = -23844 N
Sustained Case (Fy) = -20916 N, which is more than the Spring design load limits as mentioned below,

As per Spring Report (Piping Tech. Catalog),

Minimum allowed single spring load is 9341.267 N and
Maximum allowed single spring load is 16013.6 N.

So, from my point of view, the program selected spring may not be sufficient to withstand the force due to horizontal movement. Please clarify it.

Also please provide the solution for this, if my above conclusion is right. I request Mr. Richard Ay to also provide the solution for the same, it’s been past one month there is no reply from Richard Ay.

I believe your conclusions are correct. You need to manually pick a different spring - and then predefine this data in the input at this location.

Can you explain why you have support selected with a hot load of 12098 N while the resraint report shows an operating load of 23844 N?

Dear Richard Ay,

As said by you, "You need to manually pick a different spring - and then predefine this data in the input at this location." Can you some how explain in detail to proceed further.

After you decide which spring will work (from following the procedures in the Vendor's catalog), you take the spring rate and cold load and define these fields at the bottom of the "hanger dialog" (in the piping input).

Hi Mr. Dave

As I explained earlier the steps for considering the large rotating rod case as per Caesar-II manual. After analyzing the spring support, for the YRod restraint input, the analyzed spring rate and cold load is added. Based on the above input, again the analysis must be done for YRod restraint, in which the new operating load is increased from 12098N to 23844N which is more than the vendor design load limit (16013.6N), but the hot load considered for the selection of spring support after including the YRod restraint remains 12098N.

Mr. Dave please clarify it.

Your response does not provide any clue as to why the hanger's hot load is 12098 N while the restraint report shows an operating load of 23844 N?
Do you have both the hanger AND the +YRod in your model?
Does your operating deflection (in Y) change when this load doubles?
What is your +YRod length?
Please review your model more closely.

Hi Mr. Dave,

Do you have both the hanger AND the +YRod in your model?

Yes.

Does your operating deflection (in Y) change when this load doubles?

Yes, the vertical and the horizontal movement changed from -15mm and 19mm to -11.57 and 20mm. (as already mentioned in earlier thread)

What is your +YRod length?

Length is 2391mm.

Please review your model more closely.
Mr. Dave can you tell some more specifically what you are point out.

Thanks in advance.

My guess that you added the flexible rod model with preload to account for the change in hanger load caused by horizontal growth. If you add the rod model then remove the hanger. Use one or the other, not both.

A hanger that's 2391 mm long need to swing less than a half degree to accommodate the 19mm horizontal growth. There is insignificant change in the spring load with this added horizontal growth.

Hi Dave,

Your guess is right, i modeled both spring hanger and flexible rod at once. As suggested by you, i modeled only one at a time, but i am not able to get a clear solution / idea of the concept in Caesar software using the large rotation rod concept..

If it should be modeled as per your earlier reply, then it must have clearly indicated in the Caesar Application guide.......

Also, the procedure for considering large rotation rod is only available in Caesar 4.4 Version. Later versions such as Caesar 4.5, 5.1 does not include that in Application guide!!!!!!. Why it is so, is that option have become obsolete.

Hi Dave,

Why there is no response from your part. Am i asked any irrelevent question. My main query is "why the procedure for considering large rotation rod is only available in Caesar 4.4 Version. Later versions such as Caesar 4.5, 5.1 does not include that in Application guide!!!!!!. Why it is so, is that option have become obsolete."

Hope for your reply.....

I do not give high priority to questions about CAESAR II Version 4.4.
I speculate that this detailed capability of CAESAR II - to account for change in load due to horizontal displacement of the hanger node - exceeds the basic design limits imposed on the engineer. As I understand things, you should not have your hangers deflect more than 4 degrees. If you meet this (B31.3?) requirement you will not have much change in load.