Grease ...the story !

End of the month again and not a bad month generation-wise: 437 kWh clocked up which, for a month with only 28 days in it, isn't too bad. It makes the capacity factor for the month 87% whereas the corresponding month last year saw 100%.  Ah well, you can't have a bonanza February every year !

End of the month is greasing time and this morning, just after 8am, I gave the Powerspout its usual 2 squeezes of the grease gun which delivers a meagre 0.7 mls ( 0.4g) of grease.

In its first life, the shaft and bearing housing of a Powerspout did service in a Whirlpool washing machine.  In such an application, the bearings didn't get the same 24/7 operational use so there was no need to re-grease them. When they failed, that was the signal for the washing machine to go to the scrap heap. But, if it was a lucky washing machine, its bearing housing, shaft and motor might get salvaged for a second life in a Powerspout.

In this second life, re-greasing becomes essential, not only because of the continuous use but because of the damp environment the bearings find themselves in.  So a greasing point has been added to the bearing housing which connects with a grease nipple on the turbine casing.

The point of relating all this is that when grease is pumped in, it has to envelop the rotating shaft and to travel left and right along the shaft to reach the bearings at each end.  New grease contributes significant drag on the shaft which can be seen as a reduction in power output immediately after greasing. After a few hours, the effect disappears. 

Here is the record of power out to the grid immediately after my greasing at 8am this morning, showing a drop of about 5 w.

Another point arising from this arrangement of delivering grease centrally between the two bearings is that significant hydraulic pressure can be produced by a grease gun especially if it is operated forcefully.  The dust shields, whether metal or rubber, are not designed to have grease forced against them and could conceivably be deformed by the pressure achieved.  (This paragraph was amended 14/4/2016)

To prevent this, I operate the grease gun very slowly. Also, I have removed the inner dust shields of the two bearings so they are more open to let grease enter the ball race, pass through it and out the other side.  It is quite easy to remove the shield by gently bending inward the tabs of the shield where it locates in a groove in the outer race.

So that's Grease...the story !  I don't think it's likely to be shown in a cinema near you anytime soon !