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Posted On: 03/07/2006

Rotary screw compressors redefine best-in-class

PlantServices.com

Competition among air compressor manufacturers is strong and spirited, with each vendor vying to satisfy a growing niche in the balance of size, type, efficiency, performance, reliability, service – and cost. When Michigan City, Ind.-based Sullair (www.sullair.com) decided to revamp its workhorse 40 hp to 60 hp rotary screw line, it made sure it covered the bases with an extensive survey of customer needs.

“Our benchmarking survey found seven key areas of concern to compressor buyers: energy efficiency; air quality; environmental considerations; form, fit and finish; serviceability; controls and life-cycle cost,” says Jeff Elmore, manager, engineering, product development and air systems management, Sullair.

The company set out to design the new line to be measurably better than the competition in each of these areas. The 3000 (40 hp), 3700 (50 hp) and 4500 (60 hp) are now available.

“As 75% of the life-cycle cost of an air compressor is energy, we made sure the 3700 is as energy-efficient as possible. We were able to achieve significant improvements over our previous design, and now it’s best in class.” The design includes Epact motors as standard, with NEMA Premium motors optional (standard with variable-speed drive). “The NEMA Premium motors are 1% to 1.5% more efficient, and typically would pay back in 18 months at 6 cents per kilowatt-hour,” he says.

Along with minimizing energy consumption, Sullair paid considerable attention to environmental impact. The floor of the housing is a sealed containment pan that can hold 100% of the fluids in the unit, the coreless oil filter has no metal in it so it can be easily incinerated or crushed, and the standard Sullube synthetic lubricant is biodegradable. “In most jurisdictions, condensate can go directly down the drain,” Elmore says.

“Extremely efficient” separation keeps lubrication carryover at less than 1 ppm, which also reduces make-up fluid consumption. The standard lubricant offers an 8,000 hour change interval and supports a comprehensive five-year warranty. A food-grade lubricant is available, and opting for a factory fill of 24KT silicone lubricant extends the air-end warranty to 10 years.

The units operate at 68 dba, 10 dba quieter than the previous generation. “Compressors are not being put in the back room anymore,” says Elmore. “They’re on the floor, closer to the point of use, and should be aesthetically pleasing. These are the quietest compressors on the market, and they look good, too.”

At 34.5 in. by 62 in., the 61.5-in. high machines fit through a standard 36-in. door and have “a smaller footprint than any other competitive 40 hp, 50 hp or 60 hp compressor on the market,” Elmore says.

Twelve features have been engineered to make routine service clean, simple and safe. Highlights include:

• The fluid level sight glass is visible without opening a door.
• Routine service is designed to be performed from one side.
• The fluid filter housing is inverted to minimize spills.
• The cooler slides out on rails for cleaning.
• The separator element chamber lid has no tubing to disconnect.

Units come with the company’s WS controls, which are simple to navigate but offer critical operating information including status, temperature, pressure, and load/unload setpoints, both on the display and via serial communication to a local or remote PC. It also tracks historical information such as operating hours, fault logs and service due. As many as 16 machines can be sequenced with the standard controls.

The ultimate objective, of course, is clean, dry compressed air at the lowest life-cycle cost. Elmore says, “When you add up the energy efficiency, speed of service, make-up fluid savings, etc., the 3700 Series’ 10-year cost is best-in-class.”