new to compressors.


Old 06-12-05, 04:07 AM
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new to compressors.

Hi ,I have recently bought a compressor and have a few queries.

It is a rolson 50 litre 2 hp, i sprayed a shed with it last week but was not really sure what i was doing , i plugged it in and just sprayed.

question 1: what are the 2 gauges for? both seem to show the same pressure.
question 2:how do i check if the shut of valve is working without blowing myself up?

question3:the oil seems a greyish color, is this normal ? can i use a good quality motor oil in it? do all compressor sumps contain a certain amount of water in the oil?

Excuse my ignorance and any advice appreciated.
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Old 06-12-05, 07:48 AM
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Did you see GregH's "sticky" about compressors?

At least on mine one gauge is the pressure I've set the shut-off to
The other is the actual pressure in the tank
If they are both moving together it means I haven't set the shut off
Not sure if yours is like that

Most compressors take a straight non-detergent 30 (or 20) weight oil
As far as I know there should be no water in there at all
Old 06-12-05, 09:36 AM
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slickshift pretty much said it.

Question 1. One guage will indicate tank pressure and the other will show the regulated pressure.
If you turn the handle or knob counterclockwise it should lower the pressure on one of the guages.
You would then adjust it to the pressure you need.
I don't know what type of sprayer you have. If it's a syphon type gun you would need to thin the paint to the right consistancy then start with a setting of about 45 psi then fine tune for a proper spray.

2. You know the pressure switch is working when the compressor shuts off at around 100 psi and restarts at around 80 psi. (Some are preset to slightly higher than this but not too much higher)

3. It would be normall for the compressor oil to be grey if it hasn't been changed for a long time.
For the longest life, 30 weight non-detergent oil should be used.
Because the oil is so dirty you could for now put some 10w-30 motor oil in it to flush out the dirt . Run it for about an hour then do a couple of changes with the non-detergent.

Another maintenance item would be to open the tap on the bottom of the tank to drain the water from it.

Any more just ask.
Old 06-12-05, 10:45 AM
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Many thanks Greg and Slick. I left the compressor on to see what would happen, right enough at 100 she cut off, and restarted again about 80...all ok there.

As i bought the machine 2nd hand i think the air filter is missing, there is a drilled orifice at the side of the cylinder head? is this the filter location?

One more question , the whole on /off thing has me confused......i have read articles that say leave compressor on for 2 mins and let it rest for 4...that kind of thing. the first day i used it i used it continuously for about half an hour with no problem. Is there any rule of thumb for this?

many thanks guys.
Old 06-12-05, 05:22 PM
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Before I could afford a big compressor I used a sears 1hp 12 gal making it do jobs it was never intended for. I over used it frequently for 10 yrs before I got a 6hp 60 gal. I still have the little compresor and it still works fine although I seldom use it now. I think you should be fine. I'm not sure about gregh's suggestion of non- detergent oil. I have always used detergent oil. They also sell oil just for compressors - it just cost a little more.
Old 06-12-05, 09:44 PM
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As far as the on-off thing goes you might be referring to duty cycle.
If you have a belt drive unit with a cast iron head then most of these are near 100% duty cycle and you don't have to worry about it.

Not sure about the air filter.
Some compressor pumps have the air intake right on top of the heead and use a small piece of foam as the filter.

Is what you refer to as an orifice, located at the side of the head near the top?
Do you feel a small amount of air leaking from the orifice while the unit is running? If so then this will be where the pressure bleeds from the head in order to not have pressure against the pistons when it goes to restart.
It is less expensive for mfr's to do this than to provide the much better way of using a pressure switch with a bleeder connection to take the pressure off the head for restart

The suggestion to use detergent type oil was to only do this once to help clean the crankcase.
Detergent oil tends to foam in compressors and will eventually gum up the reed valves because of the scrubbing action of this oil.
Non-detergent oil is the same stuff that is sold as air compressor oil but is cheaper.
Just make sure you use 30 weight.

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