SoFloReefer
New member
I think there have been bearing failures for two reasons. The first is likely from having the dry side improperly spaced so that the coupling magnets are too close. My guess would be that this is the main cause of failure. This will cause a much greater thrust force on the bearings. The other possibility is that the dry side is not properly aligned with the wet side. This would cause radial forces and vibration on the bearings that would likely be negligible otherwise.
When seeing how additional loading will effect the life of a ball bearing, look at the equation for bearing life L10=(C/P)^3, where C is the dynamic load rating and P is the load placed on the bearings (In the case of combined radial and thrust loads, the calculation for P is more complicated). L10 gives the number of revolutions, in millions of revolutions, that 90% of the bearings should complete before failure. If the bearing used on the MP-40 is indeed the DDR-1980; this bearing has a dynamic load rating of 2463 N (554 pounds).
So lets look at two examples: One where the load on the bearing is 50 pounds, and one where it is 20 pounds. Lets assume that the pump runs at an average of 1000 RPMs over its life:
(554/50)^3*1e6=1360e6 rev
(1360e6 rev)/(1000 RPM)/(60 min/hr)/(24 hr/day)/(365 day/yr)=2.6 years
so 90% should last this long. A few percent will fail significantly sooner, and around 50% will likely last 5x as long.
Second example, P=20 lbs
(554/20)^3*1e6=21253e6
(21253e6 rev)/(1000 RPM)/(60 min/hr)/(24 hr/day)/(365 day/yr)=40.4 years
The point being is that the change in thrust load will likely seriously impact the expected life of the bearings. Also, even with normal loads, a few percent will always fail prematurely.
What could be done to fix this? A different (read larger) bearing can be used with a greater dynamic load rating. Perhaps a thrust bearing could be incorporated into the design or the pumps could be designed to shut off if the two sides are too close together.
Anyways, I don't know enough about the design of the pump to come to any solid conclusions. What I do know is that I have an MP-10 and if I run it at full power it is loud and gets hot. I run it at 1/2-3/4 power and it is fine.
When seeing how additional loading will effect the life of a ball bearing, look at the equation for bearing life L10=(C/P)^3, where C is the dynamic load rating and P is the load placed on the bearings (In the case of combined radial and thrust loads, the calculation for P is more complicated). L10 gives the number of revolutions, in millions of revolutions, that 90% of the bearings should complete before failure. If the bearing used on the MP-40 is indeed the DDR-1980; this bearing has a dynamic load rating of 2463 N (554 pounds).
So lets look at two examples: One where the load on the bearing is 50 pounds, and one where it is 20 pounds. Lets assume that the pump runs at an average of 1000 RPMs over its life:
(554/50)^3*1e6=1360e6 rev
(1360e6 rev)/(1000 RPM)/(60 min/hr)/(24 hr/day)/(365 day/yr)=2.6 years
so 90% should last this long. A few percent will fail significantly sooner, and around 50% will likely last 5x as long.
Second example, P=20 lbs
(554/20)^3*1e6=21253e6
(21253e6 rev)/(1000 RPM)/(60 min/hr)/(24 hr/day)/(365 day/yr)=40.4 years
The point being is that the change in thrust load will likely seriously impact the expected life of the bearings. Also, even with normal loads, a few percent will always fail prematurely.
What could be done to fix this? A different (read larger) bearing can be used with a greater dynamic load rating. Perhaps a thrust bearing could be incorporated into the design or the pumps could be designed to shut off if the two sides are too close together.
Anyways, I don't know enough about the design of the pump to come to any solid conclusions. What I do know is that I have an MP-10 and if I run it at full power it is loud and gets hot. I run it at 1/2-3/4 power and it is fine.
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