METALON BEARINGS DESIGN DATA & PARAMETERS

PRESSURE-VELOCITY-TIME
In order to determine the feasibility of using an METALON bearing in a specific application, the factors of pressure, velocity and time should be considered. The basic concern with most non-metallic including METALON is the risk of heat build-up, and the ability of the assembly to dissipate of this heat. The pressure on a bearing is the load applied divided by the loaded area. By convention, the loaded area is calculated as the bearing length multiplied by the shaft diameter. This is not entirely accurate, but it is convenient. Velocity when applied to a
bearing configuration refers to peripheral velocity (and not rpm) in either feet per minute or meters per second. It is impossible to separate pressure and velocity when dealing with a bearing application because both are potential sources of frictional heat. They must be considered together. Our studies have indicated that it is not possible
to publish absolute dry PV (pressure-velocity) figures for the METALON grades. We must consider the specific combination of pressure and velocity and relate this to the time factor (duty cycle) as this too influences the probability of heat accumulation. If the assembly operates over a short duty cycle, it has time to cool down between operations and therefore may be able to accept higher pressure and velocity figures than a similar assembly running continuously. Obviously lubrication has a major influence on PV-T limits, and therefore grooves are provided for dry, grease lubricated, oil bath and water bath conditions. He PV-T graphs were developed using a bath of oil or water. If the system can be designed to incorporate a forced flow of lubricant instead of a bath, much of the frictional heat will be dissipated by the flow of lubricant. Once the bearing is operating under hydrodynamic conditions, no additional frictional heat is develop as the speed is increased, other than a slight increase in frictional drag of the lubricant. This increase is so low that it does not affect the bearing operation. Velocity can be increased significantly (compared to a bath-type system) as long as there is sufficient flow of cool lubricant to dissipate the frictional heat generated. 

PV-T CHART

1) Average bearing temp. in comparison with the contact surface temp. which can be considerably higher.
2) The correction factor must be take into account when long-time static loadings at average bearing temp.
    above  23^oC are concerned.
3) The given pv-limits refer to properly designed plastics-metal combinations with good heat dissipation
     possibilities that  operate continuously at an ambiant temp. of about 23^oC. The then established average
     bearing temp. correspond with the allowable values give in Table 1.  It's obvious that in case of an intermittent
     service higher pv-values can be allowed where on the contrary lower  pv-limits must be take into account when
     an operation at ambiant temp. above 23^oC is concerned Plastic-plastics combinations can also be used.
     However their load capacity (pv-limit) is, due to their poor heatdissipating possibilities, lower than for a
     plastic - metal combination.
4) The practical speed limit for dry operating sliding parts in  ERTALON, ERTACETAL & ERTALYTE is about
    2 m/ sec. Above this limit, they can hardly withstand the loads.
5) Much higher pv-values can still be allowed when bearings are concerned by which a hydrodynamic lubricant
    film is established or which are continuously & abundantly water-cooled.

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