From gyroscope production to molecular contamination
Forty-five years ago, Western Electric Company in Winston-Salem, NC, faced what seemed an insurmountable problem. The gyroscopes it supplied to the Nike missile program, each costing $20,000, were being rejected at a rate of 99 out of 100. Dust in the manufacturing area was identified as the culprit, so in 1954 the company set out to build a “dust-free” pro duction room, which was completed in early 1955.
Three members of that original design team believe they designed and built the first known cleanroom in the world. They believe this because Western Electric, which was part of the powerful Bell telephone system, had access to the latest technology worldwide, yet wasn`t able to uncover any information on cleanroom design.
“When we started our project in the early 1950s, the only thing we could find was clean benches. Western Electric couldn`t find anybody anywhere that had actually built a cleanroom,” says William Otis Ameen, the architect on the project. After an article was published in December 1955 describing the room`s design, Ameen says the company was flooded with letters from people all over the world wanting more information on the new “dust-free” room.
G.T. Nickell, a mechanical engineer at Air Conditioning Corp., had never heard of a dustfree room either when he was approached by Western Electric`s engineering director. Nevertheless, he said he could design and install the ventilation and air conditioning system for such a room in three months if the company built it inside a pre-existing facility, recalls Nickell, now chairman of the board of the renamed company, AC Corp. (Greensboro, NC).
“I knew that filtration technology was available, probably from the Manhattan project (the effort to develop the atomic bomb), and that Carrier Corp. held the patent for and manufactured the Cambridge absolute filter, which had a capability of removing 99.95 percent of 0.3 micron particles,” Nickell says. “The rest of it was common sense.”
Ameen and Nickell, together with mechanical engineer T.K. Atkinson, subsequently designed and built the 7,200-square-foot production facility, which included:
Seven areas within the facility, with the assembly room and bearing room the most critical for dust control.
Every surface material chosen for washability.
A refrigeration system that included blower, surface dehumidifier, two flat bank filter racks capable of supporting 30 20-inch by 20-inch fiberglass filters, and return air ducts extended to the floor level.
An absolute filtering unit capable of handling 19,500 cfm with maximum velocity of 200 feet per minute through the filter.
Relative humidity below 45 percent; temperature of 70 degrees Fahrenheit ± 1 degree; and positive room pressurization.
State-of-the-art techniques used for light-part degreasing, vapor cleaning and ultrasonic cleaning.
Pressurized pass-through window in the wall between the cleaning and main assembly areas.
Cracks and corners kept to a minimum; vinyl floor curved on a five-inch radius at the base to the wall to avoid dust collecting in corners; inside and outside wall corners rounded with two-inch radius for ease-of-cleaning.
Suspended ceiling system designed for easy surface wiping; lighting fixtures and other equipment flush mounted in the ceiling to prevent dust pockets.
Central vacuum system for cleaning the gyros fitted into a copper socket when not in use to limit dust.
Air supply outlets designed to blow air almost straight down, thereby minimizing the induction of room air into the supply air.
A framed gelatin floor mat at the room`s entrance where employees cleaned their shoes. (The mat was cleaned with kerosene.)
Dust-proof garments, caps and shoes for personnel.
Formica and stainless steel bench tops, supported on chrome pedestals and round bases.
The dust counting device was somewhat primitive, Nickell says. A microscope, through which an air sample could be observed, was used to count dust particles one micron and larger, a count that was extrapolated to an average dust count in particles per cubic feet. A typical reading in the cleaning room was 2,000 particles per cubic feet.
Within two weeks after production commenced in the cleanroom, the gyroscope rejection rate dropped to one out of a 100. Western Electric continued producing gyroscopes for many years and built numerous other cleanrooms throughout its system.
Construction of the company`s first dust-free room, however, preceded much of the current cleanroom industry terminology, Nickell points out. “The term `cleanroom` had not been applied to this type of facility, and the term `HEPA` was not known. The only dust-free work that had taken place up until this point had been under hoods that used good filtration,” he says.
The only major technology advancement since the 1955 Western Electric construction, discounting the improvements in dust counters, controls and filters (ULPA), is mass air displacement with laminar flow, Nickell says.
Editor`s Note: Although historians say the first cleanrooms may have originated earlier, Western Electric has shown clear evidence that it built one of the first — if not the first — cleanroom in 1954. If you can top Western Electric`s claim, or know of another early cleanroom or contamination control innovation, please contact the editor.