The application earned the BAE Systems-PPG Aerospace team a BAE Systems 2008 Bronze Chairman’s Award for productivity.

Technicians defrost the exact number of seal caps required, so waste is reduced, and finished racks look neater because capped fasteners are identical.

PRC seal caps are small caps molded from liquid PRC sealant that cures to form a flexible rubber shell. The cured caps are filled with more sealant, and then frozen to arrest curing. The seal caps are thawed and applied over fasteners to cure, affording high quality, less waste and better uniformity than traditional extruded application.

“The PPG seal caps cost more to purchase than the wet sealant we used previously, but this is more than covered by the advantages they bring in improving operator productivity and reducing cycle time,” said Tim Meakin, avionics racks department team leader at BAE Systems’ airframe engineering and manufacturing site in Samlesbury.

BAE Systems had used PPG Aerospace’s PR-1770 fuel tank sealant, which was manually extruded onto fasteners on six-sided avionics racks measuring about 18 by 18 by 6 inches. Dick Surtees, PPG Aerospace account manager at the Shildon, UK, Application Support Center, suggested using PRC seal caps during a sales call.

“With so many small fasteners located in such a tight area, it was a challenge for BAE Systems’ technicians to apply wet sealant,” Surtees said. “PRC seal caps are supplied in ready-to-use trays that are laid out at the work station, thawed, then easily applied over the fasteners. They also require less drying time than wet sealant.”

An existing seal cap size considered initially did not meet BAE Systems’ weight requirements, Surtees said.

“They liked the concept but the initial cap they tried increased weight. We produced prototypes for a smaller cap that exactly matched the profile of the fastener heads and adjusted the wet sealant fill. These were applied to test panels and compared against wet-sealed fasteners. The custom seal caps weighed the same, and the BAE Systems’ design department approved their use.”

The PRC seal caps used by BAE Systems are made of and filled with the same PR-1770 fuel tank sealant that had been used, so additional qualification was not needed.

Empty caps are made at the seal cap center of excellence at PPG Aerospace’s Application Support Center in Mississauga, Ontario, Canada; sent to Shildon for filling and freezing, then delivered to BAE Systems in Samlesbury.

PPG Aerospace is the aerospace products and services business of PPG Industries. PPG Aerospace, PRC-DeSoto is the producer and distributor of aerospace coatings, sealants and packaging and application systems. PPG Aerospace, Transparencies is the supplier of aircraft windshields, windows and canopies.

PPG Industries is a US-based supplier of protective and decorative coatings.

BAE Systems is the combination of British Aerospace (BAe) and Marconi Electronic Systems (MES).