Here are a few guidelines on how to keep your air compressor working optimally. Even if you own a cheap air compressor, keeping it lubricated, free of water accumulation and with proper air filtering you’ll be able to extend it’s working life and obtain a trustworthy tool for years to come.
Your air compressor is basically an engine, and as such it requires constant lubrication to prevent excessive friction from damaging the moving parts and ultimately seizing the piston/s.
Regularly check the oil level, some compressors will have a dipstick on the oil cap, others will have an oil level gauge like this one:
The oil gauge on an inexpensive air compressor showing the level is OK.
These are just as easy to read, the red dot represents the “OK” mark (I don’t know why they paint it red, should’ve been green) – Ideally you want to keep the oil level within the center of the dot, but as long as the level is within the dot, you are OK.
On these it’s also easier to judge the state of the oil by looking at it with a flashlight, you can often see whether it’s getting milky (water) or darker (regular wear) without having to remove a sample from the crankcase.
Oil is regularly lost through the exhaust and the breather hole on the crankcase. Oil also ages and because of this, you should replace the oil after a certain amount of duty hours. The actual time depends on many factors and it’s best if you obtain the manual for your particular compressor for a clear indication on when to replace the oil.
Non detergent lubricants are preferred, make sure you respect the viscosity the manufacturer suggests for your particular compressor.
It’s also important not to overfill them with oil as you can cause several issues, if the oil level is too high the oil can get whipped and it will foam up, losing some of it’s properties but most importantly it will gain volume, further increasing your problems.
So keep checking with your dipstick/gauge as you refill with oil and make sure your unit is perfectly level to the ground when you do this.
To remove the old oil there’s going to be a bolt at the bottom side or the bottom of the crankcase in all air compressors, all you need is a wrench. Make sure you remove the oil when it’s warm and to speed up the process even further, also remove the filling cap so you don’t draw a vacuum.
As the compressor’s intake happens to be our breathable atmosphere, humidity in the air is sucked in on every cycle. It doesn’t help that the compressor head heats up during it’s this compression cycle. As water will condensate and accumulate in the tank/s, it’s imperative to purge the tank/s at least once a week.
A common type of release valve found on most small to medium sized compressors.
Purging is easy, locate the release valve at the bottom of the tank and open it, once relatively little water comes out, close it. You don’t have to empty the tank/s every time you purge, but it is recommended you do so if you plan to store the compressor for a long period of time. If you feel the purge valve doesn’t seem to open all the way, close it and open it again; there could be some sludge blocking it.
For extended periods of storage, drain the entire tank and remove the purge valve entirely, leave it open so the water can drip and dry on it’s own. Make sure to place the purge valve cap in a secured location so you don’t lose it!
If you don’t purge, the water will rust the tank’s envelope and ultimately a puncture will occur. The tanks are naturally coated with oil from the compressor, but it can’t always protect the steel from rusting. The more that water sits in there, the worse it’ll get in time.
To automate this task there are several solutions on the market, but some are rather expensive. These are basically solenoid valves with a timer, some work by venting after a compression cycle (that is, when the tank is filled up, a bit of pressure is released to remove the accumulated water). These solutions are often implemented in big compressor setups. More commonly are timed interval purge valves that will open once a designated period of time, usually you set them to once a week.
If you were to roll your own, the hardest part would be finding a solenoid valve that is rated for your maximum operating pressure and that also couples to the existing fitting on the tank. The circuit would be a simple timer. I would personally implement it using a micro-controller so I can have the long timer (let’s say 1-7 days) and then a one-shot output for the relay that would ultimately drive the solenoid valve. By using a uC you are open to many possibilities such as a warning alarm before the purge cycle to alert anyone around the tank.
The quality of the air entering the compressor is important, for one to protect the compressor head but also to reduce impurities in the air source, if you are going to be spray painting then you’d already have a filtering system in place, but reducing the amount of pollutants will help extend the life of those filters. It’s also worth mentioning that some air filters will have a silencer built in, to reduce the noise of your compressor; so that’s worth checking out!
If you are going to stick with the original foam filter on your cheap air compressor, you can spray a bit of filter oil to improve it’s performance, the way you apply it is by spraying some on the foam and then squeezing the foam so it penetrates throughout. You only need enough so the dust will stick to the oil and become suspended on the foam, you don’t want to use enough oil that it drips because this will clog the foam and also introduce excessive oil into the air stream.
A cheap alternative to the plastic foam filters is an automotive oil filter, these can work with plain air just fine and they have a very convenient thread size, all you need is a male adapter since both ends would be female. You could check out the air filters for scooters and small motorcycles, but they may not have the same thread size. You definitely don’t want to use a smaller thread size as this will constrict the intake flow and increase the noise as well.
With these simple guidelines your air compressor will run properly for a very long time, take -your- time and follow them thoroughly!