By Hank Hogan
Stennis Space Center, Miss. – Just before the eye of Hurricane Katrina passed overhead, Daniel Gurneck faced a contamination-control nightmare. Gurneck, cleanroom shop foreman at NASA’s Stennis Space Center, was told by a family temporarily sheltered in the facility that rainwater was coming in from beneath double doors leading to a 1,500-square-foot, Class 10,000 (ISO Class 7) cleanroom. The roof had given way. Shortly thereafter, a tornado sucked an emergency exit door open, exposing the cleanroom to the Mississippi Gulf Coast elements.
“There was water dripping from the ceiling through the lights,” says Gurneck as he recalls the scene. “Leaves had blown in.”
In addition, the power was gone and with it went the ability to maintain positive air pressure as well as temperature and humidity control. Two weeks passed before Gurneck and his crew were allowed back. It was another week before the cleanroom was up and running.
“We had to get down on our hands and knees and scrub and scrub and mop and wipe and scrub,” says Gurneck.
The rocket propulsion test facilities at NASA’s Stennis Space Center. The cleanroom supports activities for testing on these stands. Photo courtesy of NASA.
The clean up involved several steps. The first was a DI water scrub of the floor. That was followed by a wipe-down of surfaces using the Freon replacement AK225G, which Gurneck says was to remove non-volatile residue. The clean-up crew replaced the HEPA filters on the cleanroom’s flow benches and recertified them. Those parts that were completely assembled were opened up and visually inspected under a particle-highlighting black, or ultraviolet, light.
However, engine parts and pumps that were in the process of assembly at the time of the cleanroom breach failed upon testing due to the weeks of heat and high humidity. These had to be flushed. As a final step, Gurneck and his team inspected the entire cleanroom under a black light.
For Gurneck, the lesson is that environmental control has to be maintained in the event of an emergency. Doors that blow open or roofs that leak can be closed or sealed, but there must be back-up power to maintain humidity and temperature control.
Ultimately, after four days, contamination control was restored. Gurneck and his crew could then go back to assembling engines, pumps and associated equipment in a clean manufacturing process involving particulate- and organic-residue-free components.
Michael O’Halloran, director of technology at the cleanroom construction firm CH2M Hill IDC, isn’t surprised that humidity caused so much trouble. “That can be a major problem in a cleanroom because it could allow the start of bacterial growth,” he says.
If mold and bacteria grow on the containment side of a cleanroom, they can shed for weeks, months, or even years. Such particulate generation can continue long after the bacteria and mold have been killed, particularly if the biological contaminants are downstream of filters.
Like Gurneck, O’Halloran says the lesson in this is that there must be sufficient back-up power to meet minimum needs for as long as necessary. He advocates that such contingency planning include not only the cleanroom but also its supply chain. In that category he includes electricity, water, air, gases like liquid nitrogen, and other supplies.
O’Halloran notes that it’s hard to scale up a nitrogen tank to account for a truck that skids off the road after a facility is complete. However, that’s not the case during the design phase. “When you start the design, it’s relatively easy to make the nitrogen tank bigger,” he says.
Such considerations play a part when anticipating how to deal with a hurricane, earthquake, volcano or other natural disaster. The cost of handling these contingencies may seem large but, as O’Halloran says, that has to be balanced against the cost of a cleanroom being down for days or longer.