Your Most Expensive Utility
In industry, compressed air is widely used for a variety of applications, from powering actuators and valves, to generating vacuums.
However, compressed air is the most expensive utility in industry. Therefore, the generation and use of it requires careful management to ensure costs are controlled.
Why is compressed air so expensive?
Simply put, compressed air is expensive because of the amount of electricity used by an air compressor. Typically, only 15% of power used by an air compressor results in compressed air; the remaining 85% of power is lost mainly as heat and noise.
So how do we manage compressed air?
The first action is to set a high-level checklist.
Is compressed air even necessary?
For air powered tools and devices, the answer is yes. But be wary of using it to clean places where a simple brush would do!
It’s important to be as efficient as possible. Up to 30% of the compressed air generated is actually lost through leaks in the system. Therefore, it’s vital to carry out regular leak detection.
Be aware that most leaks are inaudible. So, the best solution is to conduct an ultrasonic leak detection. It sounds obvious but – remember to fix the leaks after detecting them! Leak detection and necessary repairs should be carried out every three months.
Sequence multiple compressors
Once leaks have been repaired, it’s important to look at how compressed air is generated.
If a site has multiple compressors, they must be sequenced properly. For example: using a fixed speed compressor for base load and a variable speed compressor to follow the site loading. If there is only one compressor, variable speed units are more efficient.
Turn set point down
Once the leaks have been fixed, it’s a good idea to turn the set point down on the compressors. Remember, some of the pressure generated at the compressors will have been just servicing the leaks. But once the leaks are fixed, you can reduce the set point. Try 0.5 bar at a time.
Inlet and Outlet Air
The final step is to look at the compressors and observe the ambient air flow in and out of the units. Remember, cool air is denser than warm air (warm air rises), so be sure to duct cooler (external) air into the compressors. Cooler air requires less energy to compress than warm air.
The warm air coming out of the compressors should be put to good use. Can this be ducted into the site for space heating in the winter? It should be ducted outside in the summer.
A final check is to look at the filters on the compressors. Are they clean? Filters should be cleaned regularly for maximum efficiency.
So, here we’ve covered a very basic checklist for your system. Keep on top of these and you are well on the way to well-managed compressed air generation and use.
By Dan Smith C.Eng. MEI.
Dan Smith is Head of Energy Services for ClearVUE Systems. Dan provides extensive specialist knowledge gained from over 30 years of energy engineering, energy services and energy management experience in many different sectors all over the world, from China to Zambia.