Why your air compressor is overheating

The most common cause of an air compressor shutting down is overheating. As temperatures rise, air compressors are especially prone to overheating. This is partly due to an increase in the amount of water vapor in the air. Heat and moisture combined can spell trouble any piece of machinery. The reason for overheating could be the ambient temperature has exceeded the compressor’s maximum operating temperature, although this is actually not the most likely reason for an air compressor overheating. A dirty radiator, low oil level, or mechanical issues within your air compressor system could be the actual reason for excessive heat. The good news is that the most common reasons behind an air compressor overheating can be prevented with routine maintenance and daily monitoring.

Why do air compressors overheat and shut down?

The maximum operating temperature for most air-cooled rotary screw air compressors is 100℉ to 110℉. The ambient temperature of your mechanical room tends to rise quickly on warm days, especially if the room is not properly ventilated. The simple fix for this problem is a $10 thermometer and twice daily checks.

What if the temperature of the room is not the issue? Check the temperature of the discharge line. Normal operation temperature range in the discharge line is between 185℉ and 190℉. If the temperature exceeds that range, then there could be issues. Shutdowns occur in most machines at around 220℉, and many have an automatic shutdown feature built in at 220℉ to 230℉.

What causes an air compressor to overheat?

Our field service department tends to see an uptick in calls as temperatures and humidity levels rise. It’s not uncommon for at least one of the issues below to be contributing factor. If you don’t pay special attention to preventive maintenance before summer kicks off, any of these could be an issue.

Clogged coolers 

If the compressor operating temperature is too high, the coolers (or radiators) could be dirty.  Dirt accumulates inside of cooler, whether it be dust from the shop floor or pollen (for those who may have ventilation from outside). You can check for dirt by placing a drop light behind the cooler to see if any of the openings are impacted. The quick fix is to blow the cooler out in reverse direction of the air path to get your machine up and operational.

If it’s beyond that point, the fix may involve removing the cooler to have it properly steam cleaned. During routine maintenance, our service technicians clean the cooler. It’s best to address this at least quarterly. Clogged coolers also allow moisture to accumulate in the air lines. This is bad news. The formation of condensate tends to wreak havoc on air compressors when it has no place to go.

Air compressor condensate treatment and removal system
1: Air Compressor 2: Air receiver with drain 3: Refrigerated dryer with drain 4: Compressed air filter 5: Condensate treatment 6: Air-main charging valve 7: Compressed air network

Clogged or broken air dryer drain

An air dryer reduces the amount of moisture in compressed air. Refrigerant air dryers cool the air so it becomes saturated with moisture, and that moisture forms condensate. The condensate should drain away while the compressed air is reheated and discharged. If the air dryer seems like it isn’t doing its job, remember that a high inlet temperature prevents the formation of condensation where it should took place. Although a clogged or broken dryer drain is the most common culprit.

Condensate separators overflowing

Condensate is a by-product of air compressor operation containing water and trace amounts of oil. The separators filter oil from water created during air compressor operation so the moisture can be disposed of safely and legally. You must change coalescing filters and separators when they are dirty or they won’t work properly. Our technicians change condensate separators during routine maintenance to prevent this from happening. That said, it is a good idea to check your condensate separators regularly if the room temperature exceeds 75℉. Air contains more moisture as the temperature rises, so this issue tends to arise quickly in the summer.

Low compressor oil levels quickly lead to overheating

Compressors pass trace amounts of oil during operation. If the oil level is too low, the machine will not have proper flow through the cooler. Thus, it could easily overheat. Check your air compressor oil at least once per week to make sure that it is at the proper level. The manufacturer’s manual has instructions for proper oil check procedures. Our technicians top off the oil level during preventive maintenance visits, which typically take place every 3-6 months.

Excessive heat reduces the viscosity of the oil, which impairs proper lubrication.  Oil can absorb a great deal of heat, so the smell of burnt oil indicates that the oil quality is poor and not doing its job anymore. Often times, your compressor may sound more creaky than usual. You should drain and change air compressor oil at least once per year.  Generally, reciprocating compressor should have their oil changed every 500 to 1,000 hours.  Rotary screw compressors recommend changing the oil every 2,000 to 8,000 hours of operation, depending on the manufacturer’s recommendation.

Clogged inlet filter 

Excessive dirt in the inlet filter can also cause the machine to work too hard which in the summer heat could put it over the temperature limit when combined with any of the other items above. Be sure to change your inlet filter cleaner every six months (and especially before warm weather arrives.)

How to prevent an air compressor from overheating

Once- or twice-yearly routine maintenance work may not be adequate to prevent air compressor shutdown. Preventive maintenance protects your air compressor against wear and tear so it has a longer operating life, but it cannot address the day-to-day fluctuations in operating conditions. Predictive maintenance and remote monitoring help guard against unplanned downtime. Installing humidity and temperature sensors at critical points can alert staff when operating conditions fall outside of ideal parameters. Maintenance staff respond to alerts so that crew members identify and resolve potential issues before they trigger a shutdown.

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