Heat is not the friend of any compressor. Overheating can shut down your compressor, cause excessive water and oil to pass downstream, can kill air dryers, and prematurely age system components.
For this reason, it is a good maintenance step to monitor the temperature at various points in the system. This can help you flag problems and prevent them from occurring in the future when you can least handle them.
There are many low-cost infrared guns now available, and even some inexpensive thermal cameras to help you check your compressors. The photograph at right shows a thermal image of a small 25 hp air cooled compressor; this picture helped detect a cooling system short circuit, where the hot discharge air was being drawn back into the cooling air intake of the compressor.
This is a commonly seen problem (well, if you have an IR camera). This condition caused excessive discharge air temperatures and dryer failure — which was a disaster for this customer because wet, oily and rusty compressed air came into contact with their food products.
Here are some tips on temperature measurement:
- Monitor intake cooling air to ensure normal temperatures; temperatures should be well below 100° F
- Measure compressed air discharge temperatures; most air dryers are rated for only 100° F intake temperatures … if the air is hotter, then the dryer capacity may be exceeded. You will need to take special steps to address this problem.
- Measure temperatures on the inlet and outlet of refrigerated dryers. You should measure a temperature differential, if not, then the dryer is likely not working. Log the temperatures so you know what is normal.
- Measure the temperatures on the intake and output of any compressor coolers. Keep track of this temperature so you know what is normal. As coolers age, the cooling efficiency degrades.
- Take thermal pictures of the internal electrical circuits. Bad electrical contacts can easily be seen.
- Check out motor temperatures; overheated motors and bearings can indicate a problem. Log these so you know what is normal.