The other day I was making popcorn for my family. I do that every once in a while when we plan to watch a movie together.
I always like to heat the cooking oil for a few minutes to make it nice and hot before I toss in the corn.
But this time, I got distracted…
I came back to a kitchen filled with blue smoke… I turned off the heat and threw away the burned oil.
But the sauce pan was covered with a red-brownish layer of burned oil.
While I was frantically cleaning the pan (before my wife would discover what I did 😉 I was thinking… this is the exact same thing I have seen so many times, in air compressors!
In air compressors that run at high temperatures for a long time, the oil will decompose and leave a brownish-red residue on all surfaces inside the compressors.
This deposit is called ‘varnish’ or ‘lacquer’. And it covers everything… the screw element, oil stop valve, check valve, you name it.
While some red deposit on your screws or inside some hose isn’t a really big problem, this varnish will also cover the inside of your oil cooler.
The result? Its cooling capacity will decrease and your compressor will run even hotter!
The only way to remove the varnish is to chemically clean it, which is quite expensive. So replacing the cooler (and other parts) is often the cheapest solution.
Now I know that your compressor has a high temperature alarm and a shutdown alarm. And yes, you can run your compressor just below the shutdown temperature. But that doesn’t mean it’s good for your compressor.
If you can’t lower the temperature by installing extra ducting or ventilation, your only solution is to change your oil more frequently.
I would suggest that if your compressor oil lasts for 4000 hours normally, and your compressor runs above 105 degrees Celsius (380 Fahrenheit), to change it every 2000 hours.
Or, if you have many or very big compressors, take an oil sample every 1000 hours and have it analyzed.
You will save money in the long run!