|Magor Mold relies on rotary vane-style compressors from Mattei. |
Many manufacturing companies don’t place aircompressor design high on their lists of operational concerns, but they should.
The design of a compressor plays a significant role in its efficiency and reliability when working in today’s 24/7 manufacturing environments.
An inefficient, inadequate, unreliable or failed compressed-air system can take down millions of dollars of automated equipment and can waste precious production time as well as putting customer relationships at risk.
Hans Hermann, purchasing manager at Magor Mold, in San Dimas, Calif., said his shop used to be able to trace equipment failures to problems with its compressed-air systems. But that has changed since the shop moved away from piston-driven compressors to rotary-vane compressors.
As a designer and builder of injection molds, Magor Molds depends on compressed-air systems to be consistent and reliable. It has machines that require high volumes of air 24/7 and does a lot of lights-out manufacturing.
“Any equipment failure we experience usually occurs because of compressed-air problems,” said Hermann. “We may have been planning on running the equipment lights-out overnight. But when one of the technicians comes in to set up a new job, he has to re-start and finish the job from the night before. So we’d be behind as much as a day, and that was a big expense.”
The shop now uses rotary-vane model compressors from Mattei Compressors (www.matteicomp.com).
According to Hermann, rotary vane-style compressors are more efficient than the shop’s old pistonstyle ones because piston-style compressors cycle too often based on the predesignated pressures that are set and typically have to run at higher pressures to be able to deliver the pressure the shop needs. For example: He said that piston compressors go up to a pressure, shut off, let their tanks go down, and the compressor starts again to fill the tanks. So if a shop wants to keep its pressure at 120 psi, a piston compressor has to run from 130 to 150 psi to maintain the delivery of the desired pressure.
“Rotary-style compressors deliver compressed air on demand and can run constantly at 125 psi, so a shop doesn’t need regulated air. Every 2 psi lower equates to a 1 percent savings in power consumption,” said Hermann.
Magor Mold uses a 30-hp Mattei compressor purchased in 2002. As the company has expanded and added machinery, Hermann said he saw that there were issues with production timing when the compressor required service.
He contacted Lans Co. (www.lanscompany.com) of Glendora, Calif., a provider of compressed-air systems, seeking a backup compressor to minimize downtime for when his shop’s compressor needed maintenance. The shop purchased another 30-hp Mattei, so now when the primary compressor needs service, Hermann switches to the auxiliary one and doesn’t miss a beat.
Cost of power
For some shops, the cost of electric power to drive compressors is not a major issue, and in fact, an excessive use of power is a significant cost that is often swept under the rug. Older models of compressors, for example, can cause spikes in electrical power loads during peak usage periods, resulting in demand profiles that could cost many thousands of dollars per year.
“In some shops, it may be a 20-hp or 30-hp compressor, but in any event, it is essential and can cause a lot of expense,” said Stuart Silverman, president of Lans.
“In Mattei compressors, we install a ‘part winding start’ at no extra charge. This allows the motor to ramp up to speed, which lowers the usage spike during peak periods. By making the peak smaller, we can lower a sizable electric bill. And those savings are more than enough to justify the cost of a high-efficiency air compressor. For shops running 60-hp compressors, that’s a savings of about $1,000 per month,” he explained
According to Silverman, oil and water are shop air’s worst enemies, which is why shops such as Magor Mold must be very conscientious about keeping those elements out their compressor systems. If they didn’t, the pneumatics of their machines would foul and deteriorate quickly unless preventative measures were taken.
Magor Mold runs all its air through a tank that collects moisture, and the moisture is drained daily. It also routes air through an air dryer.
Mattei compressors have extremely little oil carryover, said Silverman. However, Magor Mold still runs its air through an oil-removal filter.
Silverman attributes many in-plant air-system problems to leaks and negligent maintenance. He attests to many an operation where punctured hoses and improper repair have not only caused system inefficiencies, but have led to the purchase of additional, unnecessary compressors.
A 0.125-in.-diameter hole in a hose can cost as much air as put out by a 10-hp compressor, indicated Silverman.
However, the main enemy of all air compressors is heat, and overall, inadequate maintenance creates heat problems.
“If you run them dirty or run the oil low or don’t change the oil often enough, compressors will run hot. Leaks will make them run harder, which means hotter. And if the air filter is clogged or belts are out of adjustment, the system will run slower, and, again, hotter. The outcome to all this is inefficient systems, high maintenance costs, premature failures and unscheduled downtime,” warned Silverman.