Compressor heat is an important subject to think about in the hot days of summer.  If the heat of compression created by your equipment isn’t properly dealt with overheating will occur—and that will affect the quality of your compressed air, and the life of your expensive compressed air equipment.  But problems can occur all year round if your compressor room ventilation is not properly designed and maintained.

A simple test can be used to help determine if you have a heat problem.  Touch the discharge pipe of your air compressor.  If it feels uncomfortably hot, you likely have a cooling problem.

Typical air compressors are quite noisy machines, although recent design changes have reduced this considerably. This noise usually leads facility designers to segregate the air compressor to a far corner of a plant, away from the main production.  Often, especially in climates where freezing temperatures are common, the compressors are placed in a special room for security and to reduce ambient noise.

Placing compressed air equipment in an enclosed area presents a problem.  Almost all of the energy input to an air compressor comes out as heat, for example, a fully loaded 100 hp compressor will produce 75 kW of hot air (or water in the case of liquid cooling).  This amount of heat is about 4 times that is required to heat a 2,400 sq-ft home in a cool climate.  To get rid of the heat, for air-cooled compressors, some sort of room ventilation is required.

Very often, no exhaust ducts are placed on the compressor, allowing hot air discharge into and overheat the room, even when there is a ventilation fan drawing in outside air.  The hot air will often exit the compressor, but will “short circuit” in a loop, returning back to the inlet of the compressor package ventilation.  This leads to overheating problems.

The excess heat will negatively affect the life of the compressor lubrication and electrical components within the compressor.  Excess heat will also overload the air dryer with excess moisture, causing poor air quality leading to free water contamination of the system.

Some things tips about compressor heat:

• Monitor your compressor room and compressor discharge temperatures; discharge levels over 100° F spell trouble
• Design your air cooled compressors so that the heat is ducted away from the compressor ventilation intake to prevent short circuits, sometimes the ducts need to be insulated to prevent radiation losses to within the room
• Pull in the coolest and cleanest air possible for cooling requirements, but not below freezing; compressor heat can be used to temper cold outside air
• Never allow compressor heat to be directed at air dryers
• Ensure compressor coolers are kept clean and free of dust. If filters are installed, make sure that these don’t excessively restrict the flow of ventilation air
• If ambient conditions are normally hot due to climactic conditions, you may need to consider secondary cooling to prevent air dryer failure
• If your discharge temperatures are constantly higher than 100° F you may need to oversize your air dryer—contact the manufacturer for advice
• Realize that compressor energy can be used to supplement things like building heat, process heat, and boiler feedwater heat; some manufacturers have heat recovery units that can be an optional part of a compressor installation, and
• If your compressors are constantly running hot, make sure the lubricant is changed more often than typically specified to prevent failure.