Rigid Hanger with Big Displacements

[nikolastrojman]

Hi all!

Does anybody of you guys have any experience with installation of rigid hangers on a line which has big thermal displacements and consequently swing angles bigger than > 4° which is accepted worldwide as a industry standard for rigid hangers?
We would of course avoid this problem normally by installing rigid supports, but unfortunately in this situation it wasn´t possible as existing steel structure (without proper reconstruction) can only accommodate for the use of rigid hanger

I want to be sure that nothing will happen to rigid hangers if we have swing angles of 7°/8°/9° depending on the location of the support.

Any suggestions for this situation and how to approach this issue?

 

[LittleInch]

One with rollers instead?

E.g.

https://www.alliedcorrosion.com/product/adjustable-roller-hanger/

picture / drawing always helps envisage what you mean / what the issues might be.

what does the supplier say? They will have seen this before.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

"We would of course avoid this problem normally by installing rigid supports, but unfortunately in this situation it wasn´t possible as existing steel structure (without proper reconstruction) can only accommodate for the use of rigid hanger "

Sometimes engineering is a series of poor compromises .... are you telling us that you CANNOT install supplementary steel or that you WILL NOT install supplementary steel to properly support the rod hanger ?

Did you perform a detailed stress analysis of the piping system of interest using a computer program such as CAESAR-II to evaluate various pipe support locations and loads ? ..... no ???? .... why not ????

Is this the first job you have had dealing with pipe support issues ?

MJCronin
Sr. Process Engineer

 

[0707]

Adjustable Roller Hanger as LittleInch says is a good solution, apparently. I have experienced in SS lines great thermal displacement in FCC unit with rigid hangers, again adjustable Roller Hanger seems to be a good solution. A piping flexibility study would be required

regards

luis

 

[nikolastrojman]

Hi!

Additional info about the problem we are facing...

Detailed piping stress analysis is performed using ROHR2 (instead of CAESAR II) to verify the piping routing design compliance with the design code and to calculate the support loads, displacements...in case of rigid hangers also the rotations....In normal operation (60-65°C) the max. rotation of the hangers is 6°, but we also want to verify the behavior of the hangers in case of line operating at design temperature (130°C) when we have rotations > 10°.

This information is provided to LISEGA to check and verify the rigid hanger design, whether it will work or not with the design temp.

Your proposal for the rolling hangers is interesting, we will check this option with the supplier.

Regarding the steel structure issue, at the moment, client´s and form our colleagues in the civil dpt. prevailing attitude is " WE CANNOT CHANGE EXISTING STEEL STRUCTURE". For me it is total bs, and I agree this is a poor compromise we said yes to.

 

[alchemon]

A variety of manufacturers make in line (aka in the pipe) expansion joints. You could consider using that here to help eliminate the thermal stress.

 

[saplanti]

This is very bed example of supporting structure IMO for the piping group. If you are obliged to use the existing structure, the only problem with existing (or new) supports is that they do not have adequate vertical rod/chain length for the lateral displacement. If you are able to drop the elevation of the supported piping you may have this distance. Otherwise I suggest to use the same/similar supports.

Please note that the hanger legs are the same length, they move sideway together with some lift with pipe. If the hanger rod/chain lengths are short the piping will feel the rise if it is always in contact with the bottom support. Therefore you need to lower the pipe elevation/ extend rod/chain length to reduce this impact.

 

[LittleInch]

A drawing or sketch of the different support towers would help, but are the straight line supports suspended from the Y shaped cable thing? And the further suspended below that?

Man that's a mess of a piping support system though. I guess your pipes are only slung underneath because they ran out of room?

You could also look at installing teflon plates betweeen the pipe support and the support hanger to reduce the amount of load?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

The piping stress model can include the whole rigid hanger and you can see the effect of large rotation on the pipe stress and the hanger load. If these pass code, then you can use the hanger.