Shoes or clamps for pipe support. 4

[StoneCold]

I have what appears to be a simple question. In our chemical facility we have a lot of piping. The two methods of installation are either clamped to unistrut or pipe hangers. We don't have any lines larger than 4". However we recently aquired a building with steam, chilled water and cooling water in it. All of the piping in the building is sitting on shoes. Why choose shoes over pipe clamps or hangers? The piping in the building might be a little over the top because they have several expansion loops for a 15# steam line. That seems a little excessive to me.
Book reference on how to figure when to use what type of hanger?

Regards
StoneCold

 

[RossABQ]

If there are thermal movements you need a support system that will allow the movement; unistrut doesn't accomodate much if any.. It needs to be a support SYSTEM, all working together.

 

[pennpiper]

Point number one, no matter what kinds of facility or what kind of pipe or what the commodity, any piping subject to tempuratures above or below ambient will expand or contract. An operating piping system is a "living" thing and this includes that 15# steam system. Point number two, no matter what kind of piping system it is it needs anchors and guides.

Expansion (or contraction) in a piping system is normally handled in only three ways. These three ways or methods are; "Configuration", "Loops" and "Expansion Joints." All three of these need anchors.

"Configuration" is where you do not attach to any equipment that would be damaged by piping induced forces. You are able to design the piping system very loose with long runs and natural "L" or "Z" shaped changes in direction. An example of this would be in piping for offsite (or tankage) areas where the piping is supported on sleepers (low concrete or steel supports). You have anchors installed at the center point of long runs and you let the system "Float" with the expansion taken at the change of direction.

"Loops" are normally used in the pipeway of an onsite process unit where part of the system will attach to force sensitive equipment and you need to control movement. A "Loop," sized properly to take the calculated expansion is located at the center point between two anchor points.

"Expansion Joints" (there are a number of types) are also used in onsite process units especially where space does not allow for expansion loops. Pipe anchors are required to make an expansion joint work. The location of the anchors is based on proper design and stress analysis.

All piping systems, including the expansion and the anchors will impart a lot of weight and force. The important thing to remember is that the pipe support system needs to be designed to properly accomodate the total piping system including the weight, the expansion and the resulting anchor forces.

A support systems made up of " unistrut and pipe hangers" is not properly designed. Unistrut is adaquate for electrical conduit that has little or no expansion . Pipe hangers, by there design do not allow for the proper anchoring or guiding of a "living" piping system.

With this in mind it sounds like the "recently aquired building" may have been designed properly.

 

[BigInch]

There's not much that an axially growing pipe, laterally restrained from buckling, can't take out.

Figure about 200 lbs for each ºF change in temperature and for each square inch of steel in a pipe's cross-section, so for a 6" std wall pipe that's about 1000 lbs/ºF of temperature change. A 100 Fº temperature change on that 6" can theoretically give you as much as 100,000 lbs to contend with. Most times pipe is not totally laterally restrained and the pipe will bow when the load reaches the pipe's critical buckling load, but if the pipe is well retrained, the pump's going to move.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[StoneCold]

Ok so my piping attachments might be crap. They still work and have for the last 20 years. So we could use some improvements. That's why I am asking. It sounds like both biginch and penpiper reccomend going with shoes and an anchor point most of the time. Ok. So what books should I read to learn more about the practical application of shoes and anchor points? I am sure that I am not getting money for software to work this out so the solutions have to be old school. Suggestions?

Thanks
StoneCold

 

[Montemayor]

My hat is off to pennpiper for one of the really great, constructive responses. This post (with a little editing) would make a great FAQ on this Forum.

BigInch's contribution gives pennpiper's post added value and is an incentive to read the first carefully and to retain the valuable advice given there.

Stone:
What these two guys have stated is the basics that I started out with over 40 years ago. It works and it works because it is based on pure practical plant engineering. I had the advantage of owning a Tube Turns Hard Cover book titled "Piping Engineering". In it you find the same information given above and the methods on how to support and anchor piping. My second edition is dated 1971. There may still be some copies out there. Maybe this thread will activate some ideas or information on where this resource (& others) can be obtained. Let's hope so.

 

[NozzleTwister]

I've seen posts that the old Tube Turns 'Piping Engineering' is still available. See link below to Coade's Caesar II BB where you'll find the info on ordering.

http://www.coade.com/ubbthreads/ubbthreads.php?ubb=showthreaded&Number=6667

Good Luck,

NozzleTwister
Houston, Texas

 

[UKCats]

I find a lot of good used technical books on abebooks.com

 

[BigInch]

StoneCold,

Yes, agreed your plant will most likely continue to work for another 20 years, as long as you don't make major changes, like adding 12" pipe to those unistruts.

For low pipe stresses, flexibility is the key. Every added anchor or guide adds line stresses and forces to the attached equipment, so use anchors and guides judiciously and only when necessary to protect your equipment by directing expansions away from your equipment.

Many typical pipe configurations can be analyzed using a few simple structural beam and frame formulations and adding the results together.

Another very practical way to see what will happen to a particular pipe configuration is to make a model of it out of some baling wire or a solid 12 ga. copper electrical wire. Bend the wire to scale. To mimic expansive growth effects, hold it at anchor and guide points and push in directions opposite to growth (adding axial compression to pipe segments). You will see where the pipe will tend to flex to reduce the induced stresses.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[lilliput1]

You can get a slide rule from Ricwill that would give you length of elbows or loops that would alow the piping to move with the expansion without exceeding the allowable stress.

 

[11echo]

I have to ask, aren't these steam lines & cold water lines insulated? If so you'd need shoes for that reason alone! As stated above, piping system grow OR contract for temperature changes and controlling this movement is easily done when the piping is installed on shoes. It can be done on piping system that don't have shoes, but anchors and guide for this type of system are more complicated and harder to install. My $0.02 anyway.

PS ...Look at the "Navco Piping Datalog" book!!

 

[dcasto]

Even when running a pipestress analysis program, you'll still need some intuition on what to do to make the model produce acceptable results (stress' less than allowable). StoneCold, I'll bet your existing piping would be fine if analyzed and you have a good start in how to apply the info pennpiper states. With this encouragement a little basic recommendation. When you set up the supports, get rid of anchor points in your model and in your initial plan. Then add guides where expansion is in 1 axis, like BigInch states. I let a junior engineer fight CEASAR for two weeks before I gave him the points above. He solved the piping in 2 days.