By Ron Marshall
The words “bang for your buck” are frightening when it comes to compressed air, but there are definitely very good opportunities to save money by optimizing the way you operate. Compressed air is one of the most costly utilities used in industrial and commercial sites. Only about 10% of the energy input into a perfectly running air compressed air system comes out the other end as mechanical power to a tool or machine. In poorly controlled and leaky (imperfect real-world) systems, the power to work ratio is much worse.
Any air system can be made more efficient in three basic ways:
- Producing the compressed air more efficiently,
- Using less compressed air, and,
- Using the heat of compression for something useful
Here are some tips to help reduce the overall cost of your compressed air system:
- Lower Pressure—Use less power in producing compressed air by reducing the compressor discharge pressure. Every 2 psi reduction will typically reduce the full load power of an air compressor by 1%. For unregulated compressed air demands, the flow reduces by about 1% for every 1 psi pressure reduction.
- Better Control—The efficiency of the production of compressed air can be improved using more efficient compressor part load control modes, or in the case of multiple compressors, some sort of central controller. The best and most efficient control mode, where used appropriately, is variable speed mode. Savings can also be gained by running in load/unload, with appropriate storage capacity, instead of modulation mode. Often, control improvements can be made by the push of a button in properly setting up your compressors to coordinate properly and to turn off when not required. Have your service provider help you with this.
- Turn it off—Often air compressors are left running, feeding only leaks or very small non-production loads during nights and weekends. Big savings can be gained by turning the air system off during these hours. And if the total system can’t be turned off, definitely various machines can be isolated when they are not producing product by simply turning off the supply valves.
- Leakage and inappropriate use reduction—If you have a well-controlled system, fixing leaks and eliminating wasteful practices like open drainage, continuous blowing, cooling of motors and other uses will reduce the power required by the air compressors.
- Recover Your Heat—About 90% of the energy input to a compressor comes out as recoverable heat. If you have a use for the heat the compressor produces, by all means use it to displace some other energy source. The easiest heat recovery project, in colder areas of the world, is to supplement building heat. Most manufacturers can provide some sort of heat recovery option for your compressor that can produce hot water up to 90° C for boiler make up heating or process use.
- Train Your People—Awareness of the high cost of compressed air and what to do about it is key. Make sure your plant maintenance and production people know the ins and outs of your compressed air system and what to do if they spot a problem. And if a problem is reported, fix it!
- Measure Your System—Few people know how much their compressed air costs or even how much air the plant is using. Even rarer are the operators that have a handle on how efficient their system is and how much air they are wasting. At the very least, have your system monitored by a reputable compressed air auditor once every 5 years. At best have continuous monitoring of your key compressed air performance indicators like power, energy, flow, pressure, dew point and leakage levels running into your energy management system.
Filed Under: Pneumatic Tips