Kelly Air Force Base
Large transport aircraft such as the C-5A are flown into Kelly AFB for overhaul maintenance. As a part of this maintenance process, the entire aircraft paint system is removed and the aircraft is repainted. For the past two decades, the paint has been removed with wet chemical strippers such as methylene chloride and large amounts of rinse waters. Methylene chloride has been identified as an EPA 17 ITP chemical. Many alternative approaches have been evaluated and several have been selected as feasible. Kelly AFB selected a dry abrasive process using plastic beads to replace methylene chloride.
A facility large enough to enclose a C-5A was constructed at a cost of approximately $16 million. This is the largest Plastic Media Blasting (PNM) facility in the world. Inside the facility, a completely closed loop blasting system was installed. The system consists of holding pots and a recirculating system for the media, a dense particle separation system, a pressure system, and a series of blast nozzles. The entire system was constructed in duplicate on both sides of the facility. The media is blasted against the aircraft to remove paint, allowing the paint and the media to fall on the floor, are swept into troughs in the floor and redelivered back to system where it is cleaned and ready for reuse. The media continues to be reused in the system until its broken into very small dust like particles and is no longer usable for blasting. The system automatically segregates the dust from the good media into a collection system for removal from the process.
The first aircraft was processed through this facility in June 1992. At the time of this report, approximately 30 aircraft have been completely processes in this facility. Blast nozzle operations have seen continued development for both nozzle design and blasting techniques by the operators.
The process is dry and no VOC's are emitted. It eliminates the use of methylene chloride, does not require the use of rinse waters, and reduce waste generation by more that 50%.
Details of Reductions
Additional Information :
The time required to strip an airplane was reduced from 14 days to 7 days. Water usage was reduced by 20 million gallons/yr Methylone Chloride usage was reduced by approximately $48,000/yr and hazardous waste disposal was reduced by approximately $118,000/yr.