I find normally vertical displacements in spring location in sustained case.

The displacements are in the range from 1 to 20mm even.

Sustained is Weight + Pressure case

Spring is a restraint, in practical at site, there is no displacement at the spring location in cold condition.

Because of displacement in spring location, the nearby restraints are showing those taking less load, actually at site it will take more load.

What is the way to overcome this?

Spring is activated on Sustained case. Simply because it's not locked by pin as Hydro test case.

If you'd like to see the result that spring is acting like a rigid, go to load case option and change hanger stiffness to Rigid at SUS case. But I suppose it's not correct analysis.

Or we can set the hanger as cold balanced. Cold balanced spring displacement should be zero at sustained case.

Krish,

Sorry but I disagree with your statement. By default the spring is designed to balance the system in the hot (OPE) condition. The spring will be unbalanced in all other conditions, and will therefore likely have displacements. It is a misconception that springs have zero displacement in the SUS case.

I found some standard request to keep spring vertical movement within plus/minus 1 mm at sustain case.

Please light me up, why to be 1mm.

Failure to do so indicates the spring, while loaded with pipe, will not suddenly un-spring or spring further when unlocked.

This indicates an unsafe condition for the operator pulling the pin, and further risks damage to the system. And further yet, attempting to pull the spring out of service becomes an even bigger chore.

That doesn't seem realistic. The pipe is going to be empty when the stops are pulled, so it will be pulling with some excess force just from the missing mass that it is designed to carry. And, as Dave noted, it's size to be balanced in the operating position. If the spring is designed to move up, then by design it will also be pulling with extra force when the stops are pulled and the system is cold. Both of these factors can result in the spring moving to a new equilibrium position depending on how far away and how flexible the pipe is to the adjacent supports.

Ahh, try to combine balancing in operating temperature with alignment on compressors.

One thing that I ever wonder was how people try to avoid sensitive subjects.


It will be no progress if we do not challenge.

There are two approaches: hot vs cold.

Improper site installation clould result unbalance of the spring supports after removing the pin.

It may out of topic, but we would have to check nozzle alignment before the rotating equiment has been installed, if we used spring near nozzle.

I'm in power plant area, so luckily there are lmitied rotating machine that I have to consider, and there are standard to do that. But at the design stage, engineer must consider that and prepare it.