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Saturday, August 31, 2013

Steel Reinforcing Bar Upsetting Machine, High Pressure Piston Pump Siezure and Subsequent Modifications

Last week we finished rebuilding and redesigning a high pressure piston pump on a rebar upsetting machine that had seized a taper roller thrust bearing, This was due to insufficient lubrication and cooling of the bearing. 
We removed and replaced the damaged top taper roller bearing with a quality NSK bearing and modified the bearing housing so that some of the pump's return oil will always supply the bearing.
 Extreme heat caused major discolouration of the bearing and shaft. We estimate that temperatures at the bearing reached nearly 300 degrees Celsius and that the heat soak probably caused the shaft to reach around 200 degrees Celsius
As this bearing is mounted above the oil level it was probably running dry and most likely that is why it failed. Another probable cause of failure is the poorly designed preload system for this bearing.
In addition the original design returned high pressure relief valve oil to the tank via the bearing housing but this oil was also returned to the bearing housing below the bearing so it may only have received a splash of oil when very high pressure activated the relief valve.
We also added a 10 Micron Return Oil Filter to the hydraulic power pack because there was only a simple oil suction strainer originally installed. This means that the new bearing will have clean filtered oil supplied to it and the pump.

Mobile Hose Fixers and Hydraulics Gold Coast.