Questions & AnswersCategory: Compressed Air Qualityscrew-air-compressor-oil-reduction
Reza asked 1 year ago

Dear sir  we have Berg compressor with the model of BSD37. the oil level of compressor is reduced by 2 liters in every 2000 hours air compressor operation.

Is such a phenomenon normal? How much does the standard amount of oil reduction in the BSD37 air compressor during 2000 hours operation ?

I would be grateful if you could answer our questions.

Yours faithfully,


1 Answers
Cas Staff answered 1 year ago


Great question!

A small amount of the compressor oil always ends up in the compressed air. This is called oil carry-over. For a well-maintained screw compressors running in good conditions, the oil carry-over is typically around 3-5 ppm or 3 mgr/m3 of air.

ppm means ‘parts per million’. In this case, 1 m3 (cubic meter) of air weights around 1 kg. And 1 mg is 1/1.000.000 of a kilogram. As you can see, 3 ppm equals 3 mgr/m3.

I looked up the info for this compressor and the normal oil carry over is 5 ppm, and the capacity is around 6 m3/min.

Here is the calculation to calculate the total oil consumption (carry-over) for 2000 running hours:

  • 5 ppm / mgr/m3 oil carry-over
  • 6 m3/min compressor capacity
  • 2000 running hours

Cubic meters of air produced in 2.000 running hours:

2000 * 60 * 6 = 720.000 m3

720.000 * 5 / 1.000 = 3.600 grams of oil.

At a density of 0.89 kg/liter, that’s around 4 liter!

The 2 liters in your questions sounds reasonable!

I wouldn’t worry to much about it, as long as you don’t have any problems with the oil in your compressed air – it all depends what you use your compressed air for.

If you need cleaner compressed air, use compressed air filters to upgrade the quality. If sized and installed correctly, they will have no problem with removing all that oil and making virtually oil-free compressed air.

Hope this helps 🙂

All the best,