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May 2012 Aerator Update

May 2012 Aerator Update

As promised I have a bit more information on using Thordon SXL in aerators for you to look at:

Here is a photo of a Thordon SXL bearing from an aerator at Taumaranui after 12 months use. This is on a very dirty pond bordered by pine trees, so a lot of floating debris including the pine needles are present.They are getting 12 months of service from the bearings and then rotating the housing 180° to get another 12 months. The staff running the plant thinks it’s wonderful because they don’t have to grease the machines.

We recommended they use a 2205 stainless shaft sleeve as this will wear better than 316 or 304, which they did do. Also they have got the sleeve diameter at 65mm on a 50mm shaft with a collar to run against the bearing to take any lateral thrust. As you can see below the 2205 shaft sleeve has been well polished.

As you can see in the picture below they have widened the water-lube hole out to about 20mm and provided a dam around it using an epoxy filler to create the barrier. So long as the hole is kept clear, the bearing will be well lubricated and cool to the touch when running.On the bottom side of the bearing is a similar arrangement with a hole, but the hole is plugged, so when the bearing housing is rotated at 12 months use, the plug is removed and put in what then becomes the bottom hole.

At the gearbox end he has done a split housing so it can be unbolted and the bearing rotated in the housing and then clamped up again.

We had another engineer come in the shop today from the Waikato – Hamilton region and he is going to do his next one with a much bigger shaft sleeve diameter – 90mm or 3-1/2”. 

If he sticks to imperial an size, then we have imperial sized bearings that are machined ready to fit. If he chooses a 3-1/2” bearing for example, then the standard housing ID size will be 4-1/4”, so you would machine the housing to 
that. For more information about what sized Housing ID and shaft size to use please call me (Vic) on 09 443 5886.

The advantage of the bigger shaft sleeve diameter is:

  • Less pressure because the bearing has more surface area
  • Higher surface speed of the shaft sleeve and thus more “lift” from the hydrodynamic effect.
  • The bearings will last longer.

With the hydrodynamic effect I tend to think of a boat going from hull speed to planning speed and it’s this effect that lifts the shaft off the bearing so it is riding on a film of water between the shaft and bearing.

He is also going to support the motor and gearbox as the torque arm doesn't give any support in this regard and this will reduce the pressure on the bearing further. 



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