Rotary screw compressor - Optimization

[Carsten S]

Just bought a second-hand Balma Galaxy 4 screw-compressor. It was originally fitted with a little flimsy XPZ belt, so I ordered new pulleys and a belt at work.
Originally it was fitted with 90 mm on the motor, and 132 mm on the compressor. When i ordered the new parts I got a 118 mm pulley for the compressor, just for testing.
With the new pulley it takes 2 minuttes less to build up pressure, thats quite some difference! But more wants more.
With the new 118 mm pulley, the motor runs near FLA, according to the typeplate. (Running 10,6-10,7A, FLA is 10,9)
The motor is a 3 kW 230/400 volt, 2800 rpm, wired in Y, feeded with 3x400V, 16A breaker.

If i'm calculating correct, the compressor run at ~2130 rpm. - The typeplate on the compressor-block says max 8000 rpm, 15 bar.
Could I, if I need more air fit a 4 kW motor and gear it up, maybe 1:1 this is well lower than the max rpm? Do I need to adjust oilflow or something?

 

[normspanners]

I do not know that machine but IMO The oil flow should increase as the rpm increases automatically by the factor of the increased pump rpm. You may have to calc the extra drive required but as you have already fitted a beefier belt, and because you are increasing the wrap of the first pulley and the overall speed it may not be such a problem.

 

[Carsten S]

Thanks for your reply
There is no oilpump in a screw compressor. It has a 12L reciever with ~2,5L oil. The compressor puts the reciever under pressure first to build up lubrication.

 

[normspanners]

There is no oilpump in a screw compressor. It has a 12L reciever with ~2,5L oil. The compressor puts the reciever under pressure first to build up lubrication.

Yes maybe on yours there is no pump, some do , but sorry I meant compressor pump anyway, it was just IMO because some screw machines have variable speed motors that increase/decrease as the demand changes, therefore you would not know at what speed the pump was at, at anyone time? the oil feed must be automatic in some fashion? By the mere fact it is pumping more air so therefore more oil because of the differential in pressure?