Slide Bearing Plates
Slide bearing plates are a very cost-effective way of providing for movement of mechanical systems.
Piping Technology & Products, Inc. supplies slide bearing plates for a variety of applications including support of piping, heavy equipment such as pressure vessels, and structural steel members. The plates provide a low coefficient of friction which can be attached to a supporting structure. This combination provides support while simultaneously allowing an object to move (slide) along the supporting surface.
Slide Plates: The “Sandwich” Concept
Like other leading designers in our field, Piping technology & Products, Inc. uses the “sandwich concept when applying slide plates to our customers’ system. Figure 1 shows a “sandwich” composed of two identical slide plates, one on top and another on the bottom. Each slide plate is composed of two components: a metal backing plate (which is the bun of the “sandwich”) and a low coefficient of friction material which is bonded to the metal backing plate.
In a typical application a slide bearing plate is welded to a structural steel member which is strong enough to provide the required support, but whose coefficient of friction is too high. Figure 2 shows an application in which a slide bearing plate is welded on top of one steel beam supporting another beam. When the top beam moves (due to thermal expansion, for example) it slide across the surface of the bearing plate without contacting the supporting beam. To return to our “sandwich” metaphor, the top half of the “sandwich” is bonded to the sliding beam, and the bottom half to the supporting beam.
Materials
One combination of materials that we often use is that of PTFE, 25% Glass Filled bonded to stainless steel. Both materials resist oxidation and have long lives even in stressful environments. For large slide plates, galvanized steel can be used in place of stainless to reduce the cost. PTFE, 25% Glass Filled provides a low coefficient of friction for most combinations of temperature and load. Figure 3 shows the recommended conditions for 3/32” PTFE, 25% Glass Filled. Note that a 500 psi load would be at the limit at 400 degrees F.
When the slide bearing plate must function at higher temperatures, graphite can be used instead of PTFE, 25% Glass Filled. The ideal temperature range of graphite is around 1,100 degrees F. For combinations of temperature and load beyond the capabilities of graphite, special designs must be considered.