Scholarly Survey of Steel-On-Steel Friction?

[StevenHPerry]

Has anyone happened across any worthwhile articles on friction that would be applicable to pipe supports?

Mr. Breen seems to indicate there was one in this years old thread:

http://www.eng-tips.com/viewthread.cfm?qid=38508&page=1

I know the rules of thumbs, I know some entities have decreed friction to be such-and-such, but nowhere have I seen it established in a factual manner.

Let's also skip handbook data presented with footnotes stating the values are only applicable in a complete vacuum with polished surfaces.

- 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.

 

[BigInch]

Is one really needed?

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[StevenHPerry]

The opinions on the subject vary from 0 to infinite.

The "friction isn't real" folks don't seem any more likely to budge than the "friction is infinite, if only temporarily" crowd.

The poor piping engineer is stuck in the middle trying to quantitatively satisfy piping load requirements on equipment.

Seems to me that objective fact would help the situation.



- 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.

 

[BigInch]

I'm just bearly on that opinion scale.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[DSB123]

Hi Steve,
This is an "olde" gripe with me. Everyone who uses Caesar II seems to use 0.3 for steel on steel. Where this value is from I am not sure but I feel it is very optimistic. ICI specify the minimum friction coefficient for pipe supports to be 0.5 for steel on steel. They did a lot of testing years ago and discovered that friction factors for steel on steel could be as high as 0.8 if the supports are located outside in a pipe service trench. Pipe supports alweys tend to "crud-up" which must increase the initial friction factor. How values of 0.3 can be applied to designs is beyond me but I will use whatever the Company mandate is even though I do not beleive these low values for piping systems that have been in place for some years. Steel to steel causes corrosion between the places which again increases the friction factor.

As you say it would be preferable to have "standard" values for steel on steel friction factors but I do not know of any such reference. Standard text books state 0.25-0.8 which is not very helpful.

 

[BigInch]

Guilty. 0.3 Top plate larger than bottom plate by the amount of expected movement with a good helping of grease, support not in contact with soil. After using it for 30 years, I don't see any reason to change it now.

Graphite and teflon ... similar rule of thumb numbers IMO have been proven many years ago.

If you treat them bad enough the friction coefficient might even be higher than 1, but why would you do that. Maintenance is supposed to be part of the equation for continued reliable operations. Its not a fire and forget system. Its hard, if not totally uneconomical, to design for operation by Dumb and Dumber.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[DSB123]

BigInch,
I have never seen significant maintenance of steel to steel pipe supports. Years ago yes maintenance was performed regularly but nowadays the bean counters cut maintenance budgets thereby giving rise to reactive maintenance not proactive maintenance. Hence the need for higher friction factors. I agree a fully greased support would have friction factors as low as 0.3 but not all supports are greased especially on high level piperacks.

 

[BigInch]

The end zone of what you are suggesting is a fixed anchor f = 1

So, now we design for bean counter maintenance procedures. Ha.
Then why bother with slide plates at all? Bean counters will now require friction factors = 1.0 We just eliminate slide plates and see how they like thick walled vessels and concrete columns 8 ft square.

How do you propose to calibrate your new friction factors anyway?
rusty red = 0.5
rusty red & brown = 0.75
rusty red & brown = 0.95
spongy black = 1.0, but no resistance possible due to the lack fo solidity, override f = 0


Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[LSThill]

DR. L.C. Peng. P.E. "PIPE STRESS ENGINEERING"
6.6 SIGNIFICANCE OF SUPPORT FRICTION
6.6.1 Effects of Support Friction
Page support friction, 26, 17 2-7 3
See also gas pipelines
uses of, 329-30

 

[DSB123]

So LSThill,
Exactly where in the Peng book does it cover/recommend Friction Coefficients. All of the references you quote are non-specific and certainly do not mention the range of Friction Factors. If you cannot contribute except for providing references which do not provide specific assistance then please refrain from posting!!