Scientists find better solvent for cleaning oxygen lines

  • Published
  • By Timothy Anderl
  • Air Force Research Laboratory Materials and Manufacturing Directorate
WRIGHT-PATTERSON AIR FORCE BASE, Ohio (AFPN) --  Air Force Research Laboratory scientists and engineers recently teamed with Aeronautical Systems Center experts here to identify a suitable replacement for Freon, a solvent that was banned for ozone depleting tendencies.

Experts from AFRL's materials and manufacturing directorate nonmetallic materials division revealed that a solvent, dubbed AK 225G, offers equivalent cleaning to the banned solvent. Freon was widely used to clean liquid- and gaseous-oxygen systems in Air Force aircraft and ground-service equipment.

The new solvent is currently being incorporated into the Air Force technical order for oxygen line cleaning, which will be published by April, said Ed Snyder, from the directorate's fluid and lubricants group.

When the banned solvent was discontinued, users began searching for an environmentally friendly substitute that would perform at least as well as the previous solvent, Mr. Snyder said.

Experts evaluated seven solvents advocated as replacements during testing at the directorate, at NASA’s White Sands Testing Facility, the Phoenix Chemical Laboratory in Chicago, and at Edwards Air Force Base, Calif. Using the banned solvent as the baseline, engineers conducted several tests to determine the candidate solvents' ability to clean oxygen-system components.

Experts used two types of testing procedures: liquid oxygen mechanical-impact ignition resistance and autogenous-ignition temperature. The tests focused on the compatibility of the seven candidate solvents with liquid and gaseous oxygen, which is critical to the safety of working with the solvents, Mr. Snyder said.

Other important properties that were tested were: system materials compatibility, immersion cleaning ability and wipe cleaning ability. Along with the properties tested, the candidate solvent needed to be environmentally friendly and possess nontoxicity at levels that were acceptable for user exposure.

Those tests confirmed the superiority of AK 225G as the most effective of the commercially available solvents tested, Mr. Snyder said.

Since AK 225G is still an ozone depleting substance, its production is scheduled to be banned by 2020, according to existing international treaties.

"However, developing this interim solution to a very serious problem will provide additional time to develop a truly nonozone depleting, effective, safe wipe solvent for oxygen systems, while still maintaining compliance with existing international treaties," Mr. Snyder said. (Courtesy of Air Force Materiel Command News Service)