1398 50 CFM (1400 LITERS/MINUTE 1 x 104 mm Hg (0.1 MICRONS) THE YOUNGEST, BUT LARGEST MEMBER of the Welch family of ... Welch. Duo-Seal Vacuum Pumps are - manufactured in wide variety of capac. - ities and ultimate vacuum character. ... Built by Wyle to North American Aviation specs, it is designed to test Apollo and other electronic gear under humidity, temperature, altitude and 100anbsp;...