maximum shear load -pipe shoe and support 1

[Journeyman1972]

What's the maximum shear load before a teflon slide plate is needed between a pipe shoe and the supporting steel

 

[BigInch]

Teflon coated plates are usually reserved for vessel (horizontal heat exchangers) use. In any case, the allowable load depends on the loads (usually axial) that either the pipe or vessel delivering the load to the support can take, or the load that the support can resist. A shear load from a slide plate would normally translate to a lateral load on the support, so unless the support has good lateral bracing, it won't be very high, and even if you do use a teflon plate, the support may still not have adequate resistance. Supports without lateral bracing of some kind are rather weak and will usually deflect to accomodate the support movement whether the support has a teflon or steel2steel slide plate. Rather than use teflon coated plates everywhere, you might be better off designing supports with higher lateral resistance capability, unless its a one off thing.



BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[PhilEduard]

Journeyman1972

Using teflon slide plates on pipe shoe evolves normally from pipe stress analysis. A system for example, consists of piping and equipment as pumps, vessels, etc., and of course you have pipe supports. Pipe supports are of different in nature say it could slide, it could be totally anchorded or hanged by spring for a reason, etc. Where pipe are supported via imposing a pipe shoe over a steel plate, a friction factor of 0.3 in most case are being used by stress analyst and this is a generally used figure for a carbon steel-to-carbon steel friction. What it means in the analysis is that a resistance in that support point is a vertical load equivalent to 0.3 x the vertical load at that point. And so the higher the vertical load at that point, the higher is the total load if it is imposed on a steel plate to steel plate support. Example a vertical load at that point of 1000 lbs when hang (no friction resistance) will be then .3 x 1000= 300 lbs + 1000 = 1300 lbs. Back to the general layout, piping generate load/forces and imagine a condition relative to this support and the equipment nozzle flange - an additional vertical load at that support is reflected back to the flange nozzle and you are maybe aware of the fact that theses nozzles has qualifying loads and moments requirment from the manufacturers. And, it is a situation where you need to use a teflon or polyethylene slide plate (a friction factor of .05 to .1 approx.) to lower the effect into the nozzle load. This is more obvious where you have big diameters of piping with heavy flanges. Otherwise if steeel to steel slide plate is not going to create trouble to the nozzle allowable, it is more practical to use it. Also if there is really a need to limit your load in the lateral direction (specially where seismic acceleration load are high - these loads are again a multipler in the lateral directions instead of vertical direction), then again you could consider teflon slide plates other than increasing the number of guides in your pipeline.

Hope this helps.

Phil