This is a common question asked by customers in the compressed air industry. To answer this, we need to understand where the heat is being generated.
When air is being compressed the heat value becomes greater than the volume can contain. This is called the heat of compression. Because of this compressed air must be cooled, or the heat must be moved to another location.
We will limit ourselves to a fluid injected rotary screw compressor for this discussion. This is the most common type of compressor used today.
During the compressor cycle, lubricant is injected into the compression chamber. One of the functions of the lubricant is to remove the heat of compression. Compressed air mixed with the lubricant is discharged to a fluid separator. The recovered fluid flows through a heat exchanger where the heat of compression is removed. The fluid is then filtered and injected into the compression chamber.
What issues cause overheating?
Fouled Heat Exchanger
A common cause of air compressor overheating is a fouled heat exchanger. Most compressor packages use air to air exchangers. A fan will be used to move air through a heat exchanger and remove the heat from the lubricant. If the heat exchanger is fouled with air borne contaminates, the cooling capacity will be reduced. Cleaning the surface of the exchanger may be all that’s needed.
Fluid Shortage
Confirm the fluid level is correct. A shortage of fluid will reduce the amount of heat removed from the compression chamber. Most air compressors utilize a sight glass to indicate the fluid level. Check the service manual for the correct fluid level.
Worn/Contaminated Lubricant
The lubricant in your air compressor can be a critical factor. Only use lubricant that meets the manufacturers specification. Lubricants have a limited nominal life expectancy which is affected by the operating environment. Worn and contaminated lubricant has a reduced heat carrying capacity. Note that lubricants must be tested periodically to prevent damage to the compressor package components.
High Ambient Temperature
High ambient temperature will cause over heating issues. Air compressors are typically designed to operate in a 100F ambient temperature. Heat rejection rates will be less at temperatures greater than 100F. Heat transfer rates are affected by the temperature difference.
Ducting
Many compressor packages utilize ducting to direct air to other areas. This ducting may also contain louvers to compensate for seasonal temperatures. These require inspection and maintenance to function properly.
Worn Components
Worn components in the package can cause overheating. These are more complicated to determine and should be referred to an experienced repair facility.
What can the customer do to minimize overheating issues and their cost?
Having a daily inspection program is an economical way to prevent air compressor shutdowns. Metropolitan Air Compressor can assist you in developing a program to achieve this. A maintenance agreement with Metropolitan Air Compressor Is also a great way to prevent air compressor shutdowns.