Friction Factor of Stainless Steel Sliding Plate

[onrush]

Dear Gentlemen!

As you know well, friction factor 0.3 is generally used for pipe stress analysis when the support slides between carbon and carbon plate and 0.1 between teflon and steel.

However, what friction factor can be used when the support slides between stainless steel and stainless steel plate?

 

[DSB123]

onrush,
Not too sure about the 0.3 friction factor. Fine when it's newly installed but after a little time the friction factor can increase to more than double the value you quote. Also the friction factor between teflon and steel is dependant upon the load. At the optimim loading then the friction factor can be as low as 0.05 but if the loading is not there then higher friction factors than 0.1 are relevant. For example, Carbon steel to carbon steel can be as high as 0.8 if the maintenance is not kept up. We use a value of 0.5 as a norm.

For SS to SS you need to consider the environment it is located at. Will the surfaces degrade and gaul??

Hope this helps.

 

[stanier]

There is no one answer to your question. What you should do is sensitivity analyses. Do the pipe stress analysis using a number of friction factors. If you identify a support as critical then you may need to change to a roller or sway brace.ie something that doesnt need the level of maintenance of a sliding support. Soemething that is more reliable.

That is the purpose of a computerised approach. It allows you to look at a number of scenarios and determine which elements are critical. This is the analysis. The design engineering comes in when you select a solution.

Remeber that the pipe stress package will only give you primary stresses. You need also to consider secondary stressses. That is where experience comes in.

When you have done the analysis find an experienced engineer, technician, fitter, maintenance superzvisor and explain what you have found in the analysis and ask their advice.

If you ask a dumb question you are embarasssed for five minutes. If you dont ask the question you will be ingorant the rest of your life.

 

[richay]

With regards to the sensitivity analysis, you can vary the coefficient of friction at the load case level, so you can do this in a single run. You can do this by changing the friction multiplier on the "Load Case Options" tab of the Load Case Editor.

Richard Ay
COADE, Inc.