This is B.suresh kumar working as stress engineer in SST INDIA (p) Ltd. i am in confusion with following topic.

After pipe stress analysis, suppose at one location on piping calculated load acting on the constant spring support is 500kg. If I use constant spring support which is designed for taking load of 1500 kg at that location, what happens?

Like that if I use constant spring supports designed for 3 times higher than calculated load at three different locations on piping, suggest me what happens.

Actually this kind of practical problem I am facing at one plant , where plant officials telling that all constant spring supports are not confirming to the calculated (displacements & loads). When I visually inspected individual constant spring support almost 60% of supports showing 30Degs upwards movement (deflection). That plant started 18 years ago. I think they are over designed like above mentioned. I used their hanger report in the analysis; I found that piping is moving upwards by around 3 to 4 meters upwards in W+P condition only. When I checked previous hanger report with CAESAR selected supports, I found large difference in calculated loads like above mentioned. Example suppose load of 500 kg (Caesar selected) is acting on constant support at one location on pipe, at that location they used constant spring support designed to take load of 1200 kg.



So please suggest me what I have to do.

Quick solution: Send rocks and rope to site. They can hang them in supports.

If the pipe material is in creep range you have one &^%(*&% serious problem. Anything from replace all pipes to replace hangers only.

Hangers must be on top block. 3 times over design will be like rigid rod. I assume you could try to model the line using CNodes with displacements, bottomed out spring or similar. All theoretical. If springs were designed that bad how was the erection? I do not think you can establish were was the neutral position of the pipe in cold condition. If you do not know where the pipe was, you do not know how much it moved. Also you do not know what cold pull they managed to put in.

I have seen quite a few engineering calculations and technical specifications from your part of the world. Very confucing because of mixed use of units. Just double check that your unit cenvertions are correct.

"please suggest me what i have to do" "after pipe stress analysis, suppose at one location on piping caliculated load acting on the constant spring support is 500kg . If i use constant spring support which is designed for taking load of 1500 kg at that location , what happens."

Why in the world use more force than is required???? If you need 500 Kg then use 500 kg it seems simple enough to me.

Hi Suresh,

First of all check for unit consistency in your model. secondly in your part of the world you have advantage of knowing all units so use it correctly.

simple and plane enough that you can not use constant spring support over designed three times of its calculated value. As this plant is 18 year old look for latest revision of hanger design report. You must do two things, first, visit the site again and mark all hanger location and movement and then model it in CAESAR to design new spring, second, model present hanger node movement using C node and check for system behavior.

I guest with this exercise you should be able to find out real problem. So star with finding latest revision :-)

Hi rajeev,

thak you for your suggestion, i am not able to undestand(you must do two things, first, visit the site again and mark all hanger location and movement and then model it in CAESAR to design new sping, second, model present hanger node movement using C node and check for system behaviour)

please suggest me ,

B.Suresh Kumar