When taking an oil sample using a vampire- or thief-type vacuum pump, try bending or crimping the sample hose before extracting from point of entry. This stops the sudden suck back of air and the oil in the hose from dragging any airborne contaminants back into your clean sample. (Mark Speirs, BHP Billiton)

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"We prefilter our wind turbine gearbox oil to ISO 17/15/12. We heat the oil with band heaters on the drum and pass it three times through a three-micron filter cart. This is very time consuming. Our post filtration sampling tests show that once in a while, we fail to meet the contamination standard with this procedure. Does anyone offer a service to filter drums of oil to this ISO contamination standard so that we can get our mechanics out of the shop and up the wind turbine towers?"

Your local distributor is in business to make a buck. I suggest making arrangements with the local agent to pre-filter and guarantee cleanliness to your standard for a fee. Keep in mind that the drum itself is very dirty, and the seams (top and bottom) release trapped particles as the drum is moved and vibrated.

A better option is to receive the drum and dedicate a small side stream filter to prefilter the oil once you have it in stores. This will cost you less in the long run, and will put you in better control of the end results.

You also mention that sometimes the filtration you conduct does not meet your specification. It would be a good idea to verify that the filter element in the filter unit is rated to perform the job you require and is changed systematically to prevent filter dumping.

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