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Oil in my air compressor?

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  • Oil in my air compressor?

    Now i changed the oil in my air compressor and put teflon tape on my fittings and everything i am supposed to.
    When i ran my compressor i checked everything. When i went to drain it oil came out. So i checked the oil in my air pump and it was full. then i ran it agin and more oil came out when i drained it.
    I f someone could tell me why this is happening and what to do to keep it from happening i would be very happy. Thank you.
    Does anyone actually read siglines?

  • #2
    Hi Shed:
    Be sure not to over fill it. Most compressor's only require a small amout of oil in the bottom of the crankcase. I don't know what kind of compressor you have so it's dificult to tell why your getting it in the tank. If the rings are worn badly they could pass oil. Be sure your intake filter is clean.


    • #3
      If the oil level is correct (not over full)then the rings and cylinder wall are probably worn allowing oil past the piston. If it still pumps air well, and it isn't blowing oil out the air supply fitting, you can probably get by by draining the oil out of the tank and checking the oil level often. Bernie is right, make sure the air intake filter is clean.

      [This message has been edited by Carl (edited 02-06-2004).]


      • #4
        I'm no compressor expert, but I kinda think thats normal to have some oil pass thru. A few years ago I bought a new Campbell Hausfeld compressor and filled it with the oil provided, to the exact level specified. First time I drained the tank there was oil mixed with the water that drained out. And that's always been the case. My thinking is that the compression stroke atomizes some of the oil which is then passed on into the tank, along with the air.


        • #5
          Piston rings are not perfect. There will always be some oil consumption in a ringed reciprocating piston pump. There doesn't have to be much oil get past the rings into the air flow per stroke for the consumption to accumulate to levels causing grave concern.

          A dime is a bit over 11/16" dia. Imagine a patch of oil the sixe of a dime x 0.0001" thick vaporized off the cylinder wall per stroke on a compressor running at 900 RPM for 50 hours per month. Do the math and the oil consumption is about 2 quarts.

          A little oil swirling in the surface of the blow-down water is normal.

          People are used to concepts like "doesn't burn a drop of oil" referrring to the engine in and older vehicle. Well that neat older engine does "burn" a little oil but the dilution products (gas, water, combustion fractions, etc) over an oil change interval is about equal to the oil consumed so the dipstick readings remains unchanged.

          If piston rings sealed perfectly you wouldn't need to change the oil at all.


          • #6
            I beg to differ Forrest. Modern multi weight oils contain co-polymer viscosity index improvers which are long chain molecules. These molecules are sheared apart and the oil gradually suffers permanent viscosity loss becoming thinner. This has nothing to do with contamination. It also gradually oxidises from the exposure to heat and oxygen which breaks down the chemical structure.

            Air compressors get quite hot in high duty cycle service and even if single weight oils are used there is always the contamination of the oil produced by wear products.

            [This message has been edited by Evan (edited 02-06-2004).]
            Free software for calculating bolt circles and similar: Click Here


            • #7
              I disagree Evan, not about oil breakdown in ICE's because it does under the influence of crankcase chemistry.

              The short oil change interval in ICE's is primarily necessitated by combustion product contamination more than viscosity change. Changes in viscosity over a limited range has little effect on an oil's ability to from a hydrodynamic film or as a boundary lubricant particulalry in a moderately loaded mechanism (except for the cam followers) like an ICE.

              Viscosity enhancers used in ICE applications do poop out over time. It should be noted that viscosity enhancers are selected by lubricant manufacturers more to obtain an engineered life ensuring a steady consumer market rather than maximizing the lubricant's service life to lower the frequency of oil change.

              Our problem is not lubricant life in an ICE but lubricant consumption in a compressor. My "burns no oil" illustration using a gas engine was for comparative reference only in regards to apparent oil consumption not to open a general discussion on another if related subject.

              My belabored point was that some oil carry through is to be expected.

              For what it's worth and another bend of the subject, 2190 TEP oil used in Navy steam turbine powerplants and reduction gears in the absense of casualty the same 1500 gallons of oil is used for the 5 to 7 years between overhauls with care and attention of the crew focussed on filtration and water separation, and samples taken for testing. There's sometimes a little make-up for leaks and losses.

              At the overhaul yard the oil is pumped out, sent to a portable processing plant, filtered, corrected for PH ec, additives added as needed and replaced in the powerplant.

              It's conceivable a well run ship could serve its full 40 year live with essentially the same oil as when it was commissioned.


              • #8
                The first thing I'd check is for a plugged air inlet filter.Any restiction would cause it to "suck" oil from the crankcase.


                • #9
                  Well when i drained it a put a dixie cup under it, and it put about 1/4 inch in the cup.
                  As apposed to water with a little oil. It was oil with a tiny bit of water.
                  Thank you for your feedback so far.
                  Does anyone actually read siglines?


                  • #10
                    Actually Shed a little oil in a compressor tank is a good thing,keeps the rust holes down to a minimum,rusty water is a bad sign thou.

                    I was recently told to use 20/30wt R&O hydraulic oil for my compressor pumps by my local Sullair dealer,he said on the newer compressors they rely more and more on splash lube and needle bearings instead of ball bearings,the anti-foam quality of the R&O pays off in the long term by insuring lube getting to the needles and bearings.

                    ICE are far more critical in tolerences than a compressor,in a compressor you can get away with a lot of ring wear,but not in the ICE

                    [This message has been edited by wierdscience (edited 02-06-2004).]
                    I just need one more tool,just one!


                    • #11
                      I don't care what everyone else says; oil in the tank is bad news. Especially if you use your compressor to paint stuff.

                      Checking the intake (filter) is a good start. Also check the crankcase vent. These get clogged with dirt and oil. If these are clean and it's not overfilled, the rings are bad. If it still makes good air, use it. Just don't paint anything with it!

                      By the way, I thought your tank was bad. If this is a new-old tank, maybe the oil was already there. (You said the compressor remained full of oil) ???


                      • #12
                        Uhh...geee isn't that what oil/water seperators are for?
                        I just need one more tool,just one!


                        • #13
                          Another possible source is oil vapors in the air. This could be a small part of the situation in a shop enviornment.

                          But in all likehood, if you are getting mostly oil and very little water then it has to be comming from the crankcase.

                          Paul A.
                          Paul A.

                          Make it fit.
                          You can't win and there is a penalty for trying!


                          • #14
                            Check to make sure that the intake filter is clean. Make sure you are using a reciprocating compressor oil NOT motor oil - DO NOT USE MOTOR OIL! Compressor oils are Non-detergent in nature, motor oils are highly detergent and will damage the compressor.

                            Darins recommendations from his Sulair dealer DO NOT apply to your small compressor. Darin would be wise to listen to them if he has a Sulair compressor because Sulair has strange gasket material that are attacked by most compressor oils and therefore require very expensive lubricants specifically formulated for them. (Only Sulair and Amsoil has this oil)


                            • #15
                              Forrest Addy, You is a man after me own heart, you know about 2190T oil. At least you know enough NOT to use it where it's NOT made to be used. DO NOT use 2190T in an ICE, no detergents for one, it has no high temperature resistance for the second reason and it is about 23 weight oil for another. And it is used for many years at a time because the filtration is so good and the quality is checked frequently enough to catch chemical changes long before damage occurs. The filter system has magnets as well as filter bags, even have some pieces of the bar magnets in my toolbox to hold drawings up where I can see them at the machine. Have done some of the machine work on a new filter set too, taper for the plug has to be VERY precise to prevent unfiltered oil getting around the filters and back into the system.