Compressors pressurize air for testing of space shuttle components

Quincy, IL--In the pneumatics arena, high pressures are not unusual. Nor are large volumes. But both together call for special accommodations.

That was the case in the recent design of air compressors for a U.S. government facility that tests space shuttle components. The facility, which uses 32 miles of eight-inch-diameter pipe, needed the air inside the pipes pressurized to 4,000 psi. The reason: The facility tests equipment in conditions that simulate reentry into the atmosphere.

Engineers from Gardner Denver Machinery (Quincy, IL), could meet those needs only by custom designing a package of compressors that totaled more than 7000 hp. Their package includes six 600 hp rotary screw compressors that pressurize the air volume from atmospheric (14.7 psi) to 125 psi and six 700 hp reciprocating "Boosters," which take the air from 125 psi to 4,000 psi.

The key to the system is the use of the split compression system, says John Miller, a product specialist, rotary screw compressors, Gardner Denver Machinery. By employing rotary screw compressors to take the air from atmospheric to 125 psi, the company's engineers say they vastly simplified the custom-designed reciprocating units. All of the reciprocating units use a three-stage design, which Miller says is not unusual for high pressure applications. But without the rotary screw compressors, he says that a more elaborate design would have been needed for the reciprocating compressors. "Using the rotary screw compressors probably eliminated two additional stages of air compression from those reciprocators," Miller says. "That's why we went with a split series of packages. It allowed us to stay with three-stage reciprocating design. Anything more would have been far more costly."

Most important, however, the design enables Gardner Denver to meet the application's needs, which Miller says are the most unusual that he's seen. "The huge air volume and high pressures of this application are far out of the norm," notes Miller. "In ordinary industrial application's this just isn't done."