In case of steel (MS) to steel (MS) contact between the pipe and support respectively, the coefficient of friction generally taken is 0.3.In one of the projects the client is suggesting to use the value as 0.5 as the surrounding environment is not so clean and the piping is low grade MS with rough finish. In addition to the industry practice of using the value of 0.3 is there any backup to substantiate the value considered for specific cases with varying site conditions?

Moving this from "General COADE" to the "CAESAR II" forum.

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• Friction Solution Technique
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The important thing to note is that the coefficient of friction is not a constant value. The magnitude of this coefficient will change over time. If you have a system which is sensitive to friction, then I would recommend 3 perhaps 4 different runs, as follows:

• run with no friction (to ensure everything else is correct)
• run with most probably value of "mu"
• run with the lowest estimate of "mu"
• run with the highest estimate of "mu"

Then, you should take the worst possibilities from all these runs and make sure your system can handle it. Friction is not a trivial problem.

Hello,

The reason that different people use different values for steel on steel
friction is because the value varies so much in real life, based on the circumstances. the value of friction factor it depends upon number of factors one of these are the surface roughness (surrounding environment). For example, I took a look in Marks' Standard Handbook for
Mechanical Engineers in the chapter about friction, and found the following
coefficients of friction for steel on steel:
Static, "grease-free in a vacuum" - 0.78
Static, "grease-free in air" - 0.39
Static, "clean and coated with oleic acid" - 0.11
Static, "clean and coated with a solution of stearic acid" - 0.013

Dynamic coefficients for steel on steel seem to be based upon sliding
velocity:
Velocity (in/sec): 0.0001 0.001 0.01 0.1 1 10
100
Coefficient: 0.53 0.48 0.39 0.31 0.23 0.19
Now steel on steel " grease free in air " seems to be the most appropriate
condition which simulates the real site surface condition. Probably this is
the cause for this 0.3 value.
But allways remember it doesn't depends upon surface area because at micro level the actual contact surface area is one thousandth of the area seems with naked eye.

Cheers,

Saneh Gupta
Stress Analyst,
Fluor India, N.Delhi