I have observed , especially for big bore piping connected to compressors etc., the springs near the compressor nozzles do not share much load as compared to the hot load they are set for. More load is shared by compressor or pump nozzle. This is irrespective of whether hanger stiffness is set as 'rigid' or 'as designed' for WNC case.
Whether someone will be able to explain this behaviour ?
Regards,
Sunil

In above message I mean that these observations are for WNC case only.
Regards,
Sunil

Did you release the nozzle (restraint) for the hanger design?

I will check with releasing nozzle restraint (anchor). But I feel I have already checked it that way. Most of the times we set the spring operating load by trial and error to bring the nozzle loads within limits. Hence I feel my observations are valid with operating load set as per my requirement. In the process I have definitely released the anchor.
Will recheck.
Regards,
Sunil

I must confess I'm confused by your use of "share much load" with regard to your springs.

Something that you must realize is that the spring can only change its load with displacement. A nearby anchor, such as a pump nozzle, is going to minimize that displacement.

Let me give and example and we'll see if we can approach an understanding. Say you have a top discharge compressor nozzle with a pipe that goes up vertically to an elbow. From the Elbow, the lines runs horizontal. At the top of the elbow, you've coded a spring.

Now, through "trial and error" you've sized the spring load such that there is a minimal load on the compressor nozzle. All it great. Since it's compressor piping, we've coded the pipe as "empty" since the vapor doesn't weigh much. Let's say that you determined that the installed spring load is 1000lbs and the spring rate is 150 lbs/in.

Now you run a hydro case, so the pipe is full of water. All the extra weight has to be supported somehow. If you keep the spring "as designed", it is going to carry 1000lbs. no more, no less. So, all of your extra water weight is carried by the compressor because the anchor point of the nozzle will not allow the pipe to move down and displace the spring. If you removed the compressor anchor and ran a liquid full case, the pipe would continue to sag until the spring was stretched enough that the load increased to balance the added water weight (or the spring bottoms out).

Now, lets look at the other possibility - for the hydro case, you've coded the spring as "rigid", so it should just be like any normal Y support and share the extra load with the nozzle. Now, I'm no coder, but I usually see in this case that when you have an anchor/support down low and another directly in line above it, Caesar wants to show most of the load down on the lower support. In fact, I've seen it happen where my "rigid" spring carries less load than the original design setting (it may only show 500lbs instead of the 1000 lbs that we set). Why this happens is probably has more to do with the limitations of the equations of the model vs. any real world event. In reality, the millwright is going to adjust the spring (hopefully with the travel stop still in place, if he's competent) to get the flanges and bolt holes lined up for the bolt up procedure and I doubt there's a good way to account for that in the model, other than to remove the compressor anchor for a hydrotest case and plan for the full load to be on your rigid spring (and, subsequently, the support steel above it).

Hopefully some of that rambling relates to your questions. Let me know if I'm getting close.

Dear Edwin,
You are on right track.
Richard,
Releasing the anchor does not change the scenario much.
I feel that Anchor being stiffer support takes more load as compared to spring which becomes rigid in WNC case
Thanks,
Sunil