Dear all,
The average pipe diameter/thickness are used when designing a piping system, the finally installed piping
system may have a little bit differences with theoretical design,such as pipe weight and valve weight because
of error,so using rigid hangers/supports is prefered,some companys limits the use of flexible hangers/supports under certain percentage.
if in a piping system, 80% are flexible, how to adjust all those flexible hangers/suppots in fields to aviod too much support or lack of support.

any comments, welcome.
Thank you!

Assuming you mean spring supports, most have something like a 20% load adjustment available, normally used to make adjustments during hook-up. I don't think specific instructions would help since it would be too dependent on the pipe system geometry.

A decent construction / installation contractor should be employed.

80% flexible supports seems high and may risk unforseen problems such as low frequency resonance. Try to use more hard supports.

Dear MoverZ,

Thank u for your comments, because of high temperature >550C and limited space ,it's hard to use more hard supports unless change layout which is not easy for limited space,yes, the piping system with >80% spring hangers/suppotrs may have low frequency.

yes, spring hanger and constant hanger have like a 20%adjustment available,
but how much do you know to adjust for a certain node? adjust and make the pipe to the displacements in sus case on that hanger node?or some other method.

thank you!

Competent installation contractors know how to do this. Incompetent installation contractors won't get it right anyway, even if you show them. MoverZ was correct - don't worry about it. Generally, the process is to adjust the spring hangers in the field until the installed position is correct. If you still can't accept "don't worry about it as an answer, your pipe support vendor will have guidelines, or you can surf their web sites for information.

Ordinarily springs or constants should never be field adjusted. Why? Well once you start "adjusting" the preset which was set by a calibrated hydraulic press in a shop setting you have lost all control of what your preload is. Why is this you ask? Because the scales are too coarse and seldom reliable enough to make a calibrated adjustment.

What happens if the pipe wall varies? Usually (not always) the variation is of no great significance I have however experienced some "heavy" pipe. But I did not crank away blindly in the field first I had some UT of the wall made calcd the new weight, made some runs and figured out what my springs had to go to.


Then I looked to see if they could or could not be adjusted adequately. Some could and some needed to be replaced with larger sizes. Adjustments were done at a local machine shop with a hydraulic press.

So think about what your doing before you just start cranking away and worry about things that you need to and not things that you don't have to worry about.

On such high temperature line I am not too keen to have site adjustments either. End result tends to be unknown and pipe will end up with creep damages. Local elctricity supplier's standard here is to use load cells in support points, measure pipe thicknesses spool by spool, take sample of insulation on a scale, calculate and set supports. Load hysteresis either under 4% or 2.5% (Used/new constant). Complex procedure.

If you have over 80% springs please check that every part of the line "knows" which way to expand. There must be FP, rods or something else to fix the direction of thermal expansion. If the expansion direction is controlled by springs only it will never work.

Thank you, CraigB ,John C. Luf and Jouko,

yes, a "floating" system which was supported by 100% spring hangers/supports usually is not acceptable, some rigid restraints or similar measures should be used to control the pipe position after exp. are similar to designer's expectation and make the system be more stable. one vertical rigid restraints (+Y) were used in every long vertical pipe, and some X or Z restraints are used on appropriate nodes if needed and possible.

Jouko, the procedure which you have mentioned is indeed a complex one, a detailed operate instruction is needed,and time may be a problem.

to all,
what's your opinion or any principles about the limitation of flexible hangers/supports under certain percentage.