Compressed air is a vital utility used in countless ways to benefit everyday life. While those in manufacturing and industrial plants recognize the ‘plant workhorses’ importance as a source of process and instrument air, most people associate compressors with the small compressor in their garage used to inflate tires. They do not realize that compressed air is the energy of choice to power a great variety of applications. Probe’s Petrus Pretorius explains.
Sanders, grinders and paint guns in automotive service shops, presses and accessory equipment in dry cleaning stores and commercial laundries all depend on a reliable supply of compressed air. Theme parks depend on compressed air to run roller coasters, fountains, and animated characters. Construction and road crews use compressed air to power jackhammers and repair our roads.
Compressed air is, after all, a utility – just like water, gas and electricity.
In a practical sense, it is a medium that carries potential energy. However, it can be expensive to produce, and from a simple energy efficiency point of view compressed air may not appear advantageous at first. Considering that it takes about 8 Hp. of electrical energy to generate 1 Hp. output on an air motor, compressed air has an efficiency rating of only 12%. How is it then that compressed air is so widely used? What are its real advantages?
High output to weight ratio
Air driven tools such as drills, saws or jackhammers have high output to weight ratios. They use air motors, which are smaller and lighter than electric or hydraulic motors, providing superior ergonomics for the operator. In an assembly line application, it’s easy to see that efficiency and productivity increase with tool speed and usability while user fatigue is decreased or eliminated altogether.
Compressors such as the Fini K-MAX (7.5Kw – 22Kw) range and SCC Smart & Focus (5.5Kw – 250Kw) range have been designed to minimise energy costs without affecting performance, and are ideal for tough applications such as found in steel mills and foundries. Here they encounter high temperature, dirty environment and frequent overloading. While air tools still require periodic maintenance to keep them at peak efficiency, they are very forgiving under these conditions and are almost indestructible.
Air tools and pneumatic cylinders also have a “soft feature.” If a drill bit or grinder gets stuck in the material, air tools just stop working. When electric and hydraulic tools overload, they can damage not only the tool and/or work piece but may also seriously injure the operator.
Electric energy cannot be practically stored and must be used immediately. This causes problems when heavy users are brought on line for short periods of time or are temporarily overloaded causing demand spikes in the electrical system.
The result may be tripped fuses, and malfunctioning or destroyed equipment because of voltage drop. And since power companies have to produce and then transmit these bursts of electrical power, they often charge costly “peak demand charges”, which can significantly increase a facility’s power bill.
Compressed air on the other hand is easily stored in air receivers and readily available for brief peak demand periods. When a compressed air system is properly controlled, problems such as low system pressure or voltage drop in the facilities’ electrical system are eliminated and replaced by seamless operation in the plant system. The result is a smooth air and power system response at lower energy costs.
While there are inefficiencies in converting electricity into compressed air as well as line losses in the compressed air distribution, “efficiency” needs to be considered in terms of a whole process or product being produced.
Consider the alternatives to a blow-moulded gas tank or PET plastic bottle machine (moulding machines use air) using compressed air. Metal gas tanks are manufactured from cut pieces of sheet metal, which need to be heated, formed and then welded into the final product. Not only is the product more expensive to produce but the resulting (welded) seams are subject to leaks.
Another example is how efficiently inert gases such as Nitrogen can be produced with compressed air wherever it is needed. Using compressed air for new manufacturing techniques reduces product costs and increases product versatility and quality.
For more information on the ideal compressor for your application visit our Probe Industrial Technologies page here.