At Alcoa's Michigan Casting Center, automotive engine block castings are manufactured and tested prior to shipment. An inspection process called a flour-penetrant inspection (FPI) is required for every casting to ensure that it is free of hairline fractures.

FPIs require a darkroom environment, which is difficult to achieve because the castings enter the room by conveyor. A light-tight seal around the conveyor is critical; if too much light enters the room, it can take up to five minutes for workers to re-acclimate to the darkness, hindering productivity.

Alcoa's Jeff Foster was charged with finding a way to seal the conveyor opening while maintaining a high-speed operation. Initially, standard overhead doors and sectional doors were considered; however, they could not provide the necessary speed or were prohibitively expensive.

Eventually Alcoa chose barrier curtains that rollup quickly to pro-vide an exceptional seal around the conveyor. Furthermore, their operation could be automated to meet Alcoa's productivity requirements. Compared to other high-speed doors, they were priced lower.

Foster installed the curtains at four conveyor openings. The curtains open and close at the rate of 32 inches per second, so castings can quickly enter the FPI area. Horizontal stabilizer bars in each curtain maintain a light-tight seal under positive or negative pressure, while a unique bottom-edge design conforms to the floor for a tight bottom seal. According to Foster, he has been pleased with the curtains' performance and how it has helped productivity.