All the Ways Heat Gets into Your Compressed Air System (And How To Get Rid of It)
Kaishan USA | October 16, 2024| Uncategorized
Removing heat from the air flow is critical in applications like robotic surgery, which demand clean, high-quality air.
Heat is the sworn enemy of an air compressor. It will shorten the life of the oil and the compressor itself. It will increase all your costs, including electricity bills and maintenance expenses. It can even result in poor air quality, including pass-through of oil and water.
Air that is too hot will damage end-use tools and equipment, degrading lubricants and seal materials. In addition, the water vapor in hot air will cause corrosion and scale buildup and may even result in freezing in colder climates.
And it’s hard to remove when it gets there. That’s why we take heat removal and cooling so seriously.
How Will You Know You Have a Problem?
You’ll know you have an issue with heat when your compressor has some or all of the following problems:
- It has a hard time starting, or it stalls during startup.
- It takes a long time to reach peak operation.
- It is making strange noises, like creaking or grinding.
- There is an odor, usually as if something is burning.
- It is tripping breakers.
There are three main ways heat gets into a rotary screw air compressor: it comes in from the outside, it’s generated by the compressor as part of the normal heat of compression, or it’s created when you have a problem of some sort with your system.
We’ll tackle these topics separately and show you how to cool things down. We’ll start with heat coming in from the outside.
Heat Comes in From the Outside
Heat often comes into your compressor from the outside air, especially during summer. Drawing 100F-plus into your compressor gets you off to a bad start. And it doesn’t get any better if that air intake is right at the parking lot where tractor-trailers spew diesel fumes into the air.
In addition, using air from inside many factories may not be much better. It simply complicates matters with airborne dust and dirt.
And the equipment room may be too small, or it may not have adequate ventilation. And it might have other equipment, like chillers or boilers, that put even more heat into the air.
Crowded equipment rooms with heat-producing electronics are probably not the best locations for rotary screw air compressors.
How You Can Cool It Off
For anything above a 25-HP compressor, it’s probably wise to supply your compressor with clean, fresh, outside air drawn in through a forced-air and duct system. As mentioned, you’ll want to avoid placing that intake at the truck parking near your loading dock.
And then there’s heat the compressor generates itself as part of normal operations.
Heat Generated by the Compressor Itself
Your compressor generates heat as a part of normal operations. It’s called the heat of compression, and it occurs naturally as the air molecules are jammed closer together.
The higher the ratio between the discharge and suction pressure, the more heat you generate. Plus, the faster your compressor operates, the more heat it produces.
You may have worsened the situation by locating your compressors in a separate enclosure. That may be good for noise levels, system location and distribution efficiency. And a well-planned enclosure will permit you to control the path the air takes around your air compressor system.
But a poorly thought-out enclosure is more likely to build up heat. It will trap heat inside and make it more likely that exhaust air will be drawn back into the system, escalating the heating issues.
Following the basic laws of thermodynamics, the energy of compression is transferred into the air. The ambient air that entered your system at 70F will reach 175F-200F in an oil-lubricated screw compressor, according to Air Compressor Guide.
You must get that heat out!
How You Can Cool It Off
With forced air cooling, an axial fan or centrifugal fan blows ambient air to cool the compressor.
All Kaishan rotary screw air compressors have forced air cooling, including our KRSD direct-drive rotary screw air compressors, which employ an axial fan.
All Kaishan rotary screw air compressors have forced air cooling. Our Kaishan KRSB belt-drive and KRSD direct-drive rotary screw air compressors employ an axial fan, while our KRSP and KRSP2 premium rotary screw air compressors use a centrifugal fan.
Additionally, oil-flooded rotary screw air compressors use a fine mist of oil to keep the compressor’s airend from overheating. The cool oil is injected into the compressor to keep the discharge temperature down. (To see a video showing how our oil-flooded unit uses oil for cooling, visit our KRSP2 page).
Oil-free units, however, do not use oil as a cooling agent (although gear oil floods the jackets in the airend to help cool the discharge air and keep the housing temperatures lower). The goal, of course, is to ensure clean, pure air for sensitive applications like food and beverage, healthcare, medical, electronics and semiconductor applications.
But that makes airend cooling even more of a challenge for oil-free units. The ambient air that enters your system at 70F? It will reach 350F in an oil-free rotary screw air compressor. As a result, Kaishan goes the extra mile, equipping its KROF two-stage oil-free rotary screw air compressor with oversized coolers and high-temperature, stainless-steel pre-coolers.
We equip our KROF two-stage oil-free rotary screw air compressor with oversized coolers to remove heat.
The forced air and duct system then draws air from the coolers and vents it outside, preferably a suitable distance away from your air intake.
You can remove the heat from your compressor with fluid cooling, especially if you already have process cooling systems.
You can also use water as the cooling medium for the compressor airend. In a water-cooled compressor, the cooling water flows through either a shell and tube or brazed plate heat exchanger, where it cools the oil and/or the air. Unlike some competitive units, Kaishan separates the cooling water from the cooling oil circuit in our oil-free units, preventing the cooling water jackets in the airend from becoming contaminated with scale or rust buildup, which impedes the heat exchange rate and thus reduces the life of the airend and results in elevated operating temperatures.
But water cooling is not a fix-it-and-forget-it solution. Whether it’s a closed-loop (using a cooling tower) or open-loop system (tapping an external water source like a river or pond), you need filters and even water treatment to prevent clogging or fouling of the water. Lack of proper water treatment is a very common reason water-cooled heat exchangers fail prematurely.
The good news is that you can recover some of that heat and use it in other parts of your enterprise for space heating, preheating boiler water, water heating or even process heating (like drying).
In most cases, at least 70% to 80% of the energy used to compress the air becomes waste heat. And Compressed Air Best Practices says you can recover up to 90% of that heat loss.
For more information on configuring your compressed air system to maximize heat recovery, see our blog post, “Compressor Room Design.”
Finally, heat can be generated by some kind of equipment malfunction or maintenance issue.
Heat Created by an Equipment Problem
Heat can also build up in your compressor because of several different issues or malfunctions:
- Clogged air filters
- Drain traps blocked by dirt or debris
- Separators saturated with water
- Thermal valves stuck
- Clogged oil filter
- Low oil level
You can also have worn bearings, which present you with an unpleasant decision—either to replace the entire airend or to purchase a new compressor.
How You Can Cool It Off
You can address many heat-producing equipment malfunctions with good maintenance. We encourage all our customers to develop several different levels of maintenance:
- Regular cleaning and inspection of filters and drain traps, removing any obstructions or replacing clogged filters.
- Oil sampling, ensuring your oil has the remaining life to continue to keep the compressor properly lubricated, thus reducing operating temperature.
- Preventive maintenance, doing routine procedures like oil changes and filter replacements on a regular schedule.
- Predictive maintenance, closely monitoring data from sensors located throughout your compressed air system and taking action to deal with problems before they become serious.
Good maintenance, after all, is preferable to unplanned shutdowns, which can result in lost production time and ruined processes and materials. You may have to schedule a planned shutdown to address the issues in a comprehensive way. And while no one likes a planned shutdown, its much better than the unplanned kind.
For more information on preventive and predictive maintenance, see our blog post, “The Differences Between Air Compressor Preventive Maintenance and Predictive Maintenance. And Why You Should Care.”
Help Is Close at Hand
Following a consistent air compressor maintenance plan will ensure that you deliver high-quality compressed air, save money and prolong the life of your air compressor and the other components in your compressed air system. It may even extend the service life of the equipment you’re powering.
Unfortunately, many companies are finding that they no longer have the expertise in-house to deal with the complexities of today’s advanced equipment like air compression systems.
That’s why having a relationship with an air compressor maintenance professional is so important. We strongly advise companies to seek outside help when issues arise. You can avoid serious problems by bringing in a professional anytime your equipment begins building up heat that you can’t seem to dissipate. Or see a drop in performance you can’t explain.
Bring in a compressed air professional anytime your equipment begins building up heat that you can’t seem to dissipate. Or see a drop in performance you can’t explain.
We work with a nationwide network of independent distributors, who can provide on-site help and consultation as needed. These factory-trained air compression experts can service your air compressor system without a problem. And they have staff members who are skilled in advanced technology.
Key Takeaways
- Heat is the sworn enemy of an air compressor, shortening equipment life, increasing costs and causing poor air quality.
- Air that is too hot will damage end-use tools and equipment and degrade lubricants and seal materials.
- There are three main ways heat gets into a rotary screw air compressor: it comes in from the outside, it’s generated by the compressor as part of normal operations or it’s created when you have a problem of some sort with your system.
- Heat can get into a rotary screw air compressor by coming in from the outside, it can be generated by the compressor or it’s created when you have a problem.
- You may be able to address many heat-producing equipment malfunctions with good maintenance.
Let Us Help
Removing heat from your rotary screw air compressor is critical to the operation of your compressed air system and all the end uses that rely on that system. If you need help controlling heat or developing a maintenance program to address heat issues, get in touch with the experts at Kaishan. Contact us today.
