B31.1 and use of 'flexible' support 4

[JRoss1]

Long time user, first time poster.

I have a system designed (and registered) to B31.1.

I've been trying to find a way to create a +y support (or as close to it as possible) from an above cantilever. It would be supporting an elbow between two 90 degree flexible metal hoses (both in the horizontal plane).

I have an idea of using a ‘wire rope’ or chain that would hang down from the cantilever. This would attach at the elbow and allow each of the flexible metal hoses to move, support the elbow vertically (+y) but not restrict upward movement, and allow the elbow to have minor displacements in the horizontal plane.

I do not have experience using anything like this and I also am not familiar with what code allows.

Does anyone in the community have experience or expertise with this?

Thanks,
-Jordan

 

[StevenHPerry]

"Resilient" I think may be a better term. A spring hanger. Anvil, Bergen, Lisega, PTP, Rilco to name only a few in alphabetical order.

And watch out for pressure thrust.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[JRoss1]

If I was going to get more specific, it is 6" carbon steel, design pressure 80psig, and it is a 'U' with two 90 degree elbows requiring support (also 90 degree elbows at the inlet and outlet).

Can I achieve horizontal displacement (let's say 2" radially, cantilever is 12" above elbow) from a spring hanger? My experience has used them only for vertical displacements.

I'm not familiar with "Resilient." I haven't been able to find that term used anywhere.

I appreciate the help,
Jordan

 

[StevenHPerry]

http://www.techstreet.com/cgi-bin/detail?doc_no=mss|sp_58_2009;product_id=1653687

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[JRoss1]

It sends me to "Spring Hanger" which only considers vertical movement. I require something for horizontal movement.

 

[JRoss1]

Maybe simple question would be:

Is there any reason, by code or otherwise, that I could not support the elbows by a chain (material incompliance with B31.1/MSS SP-58) which allowables are acceptable?

 

[StevenHPerry]

Spring hangers will "swing". MSS and manufacturer's individually will caution against "excessive" swing angles. A common rule of thumb is 1" of swing for every 1' of elevation. It is resilient in that it provides a supporting force even afer the supporting object has moved from its original position.

A chain or rope support is not resilient because it only provides a supporting force when it is taught. Since you say you want to allow vertical up movement, the weight of the pipe must be taken elsewhere.

From my quick read, you have a U bend with flex hose on either end, 6" and 80psig, suspended by what amounts to a chain fall or wire. Are your hoses designed to take 2000# of tension? And is a few inches all the movement you're really going to see?

For your short form question, read B31.1's support section. It's only 3 pages long.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[JRoss1]

I understand what you're saying about resilient. I don’t believe I will have the luxury of 2’ or that the elbows will only move 2”.

I’ve attached a quick sketch to explain. The sketch would be a ‘bird’s eye’ view.

If I analyze my existing piping to support the entire weight of the U and the requirement of the hanger was to only prevent sagging of the U-elbows and reduce the applied torsion onto the existing piping. The only displacement the U should see is if the object on either end of the piping displaces.

I re-read B31.1 support section.

I do really appreciate this dialogue and the help you’ve already provided me with. Does this change anything from your recommendation? It is very difficult to explain over these forums – especially as this is my first attempt and I did try and simplify it in the beginning (which has led to confusion).

 

[StevenHPerry]

So you saw that chain is allowed.

But your sketch actually makes it worse in my mind. There's no stability. I'm envisioning one of these things.

80psig in your 5/8" OD garden hose is one thing, but in a 6" line is quite another.

Good luck!

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[Duwe6]

Use 'ears' - lugs with clevis holes in them - welded to your ells. Use spring cans attached at the top of a rods about 4-ft long, centered above the ells. Attach these rods to your ells with a clevis. Flexible in all 3 axes.

 

[CRG]

It looks like you need guides on the 6" approach to the expansion loop. How far upstream/downstream are anchors located on the 6" steel pipe? If the rest of the piping system is designed properly, I do not see why you need spring cans to support the elbows.

 

[JRoss1]

StevenHPerry,
Thanks again for your help.


Duwe6,
I like the idea and I do have experience with the components as hangers. I don't know if it is the best idea but it seems like it will work.


CRG,
Supports are very close. There is a guide on the lower end 1-2ft away and there is an anchor 1-2ft away at the top. The anchor at the top has the ability after a seismic event to displace. The reason for the supports on the elbows is to maintain the sloped design of the piping throughout, reduce 'sagging' of the elbows to extend life, and reduce torsion/forces on the piping.

 

[CRG]

JRoss1, take a look at the following link and see if it gives you a better understanding of how these types of loops are installed:

http://www.metraflex.com/loop_configs.php

I am not sure what the purpose of your center hose that you had in your sketch?

 

[JRoss1]

This would be the typical design we would like to go with but the anchor that displaces is capable of 2" radially and/or -/+1" vertical.

There is also a requirement for the loads at the anchor to be extremely small after maximum displacement. This led to the custom design shown with the centre hose.