Panel & Paint
We don’t think anyone is going to argue with the statement “every panel beater relies on his compressor”. Whether it’s for cleaning, spray painting, or driving tools and other equipment, the compressor is an integral part of every panel beater’s business.
Most air compressors used today are of a simple basic design, using a reciprocating piston, similar to that used in an internal combustion engine, but instead of providing power, is itself powered by an electric motor to compress air which it then stores in a tank until an air device is used.
The benefits of the tank are that the air is released at a constant pressure, and it can be “topped up” without interfering with the flow of air being used.
All that is pretty much basic stuff and the fact is that the basic design of compressors hasn’t changed much over the years.
Except, that is, for the advent of rotary vane compressors.
I recently came across an interesting piece from US company Mattei, which has been making air compressors since 1919.
Says Mattei:” The traditional way of supplying air throughout auto repair and body shops was with piston compressors. These machines are typically less expensive to purchase up-front than other compressors, which led to their status as the ‘industry standard.’ Waiting for an air compressor to “kick-in” was an understood practice, as pistons had to work up to a pressure, shut off, then build that pressure back up again once the pressure in the tanks went down.
“However, as manufacturers sought to lower costs, they made the size of the piston pumps smaller and less robust. While manufacturers may have assumed these changes would have little impact on the machine, in reality, they significantly altered the product.
“Today’s pistons have pumps running at a much higher speed,” Mattei quotes a customer, “and these compressors are not designed to run as hard or as fast as how they’re being used.
“Because of this, we’re commonly seeing the valves and pumps fail much earlier. The crankshafts are also breaking because the pumps are so overworked.”
And we all know how noisy piston compressors are; you can’t install them in the same room where people are working.
However, rotary vane compressors are much quieter-running. At the same time, says Mattei, not only can vanes operate intermittently to meet the needs of auto repair shops, they can also run flat-out, non-stop to readily meet the demands of high output collision repair shops. Other advantages cited by Mattei include: Energy efficiency: over the service life of an air compressor, 83 percent of total air compressor costs are related to energy usage. In comparison, purchase price only reflects 11 percent of the total cost of ownership and maintenance only represents six percent. Mattei says the advanced design of rotary vane compressors creates a near-perfect airtight seal in the rotor stator unit, which enhances volumetric efficiency and reduces the amount of energy required to deliver the air. This means vane compressors can achieve mechanical efficiencies of up to 90 percent.
Duty cycle: the duty cycle of a compressor is the maximum recommended percentage of time it should be compressing air before unloading or shutting down to prevent overheating, component wear, and oil carbonisation and breakdown. When sized properly, a typical piston compressor has a duty cycle of 50 percent and no more han 70 percent to ensure the pump runs cool and to prevent valve problems and premature wear to the compressor pump.
In contrast, says Mattei, a rotary vane compressor can run at 100 percent of its rated capacity for hours on end without any harm or damage to the vane airend. A properly sized rotary vane compressor often affords the user the ability to select a compressor one size smaller than a piston style compressor. This saves both on purchase price and on electricity consumption.
Operating temperatures: heat = wasted energy, and high discharge temperatures can also create moisture levels that can affectt spray booths and pneumatic equipment. Rotary compressors average between 76 deg.C and 83 deg.C, whereas piston units can run as high as 204 deg.C. And rotary compressors have an air-cooled aftercooler which removes 65 percent of the condensable moisture.
Air quality: Mattei says rotary vane compressors integrate high-efficiency filtration to ensure as little as 1 – 3 ppm of oil carryover enters the air system to prevent contamination of equipment or processes. Traditional piston compressors can pass 25 ppm or more, particularly if they run unloaded for periods of time.
Life expectancy: rotary vane compressors are designed to operate for up to 100,000 hours, while Mattei says it is not uncommon for the systems to exceed this.
More info: www.matteicomp.com