30 YEARS OF VACUUM PUMP DESIGN AND MANUFACTURING KNOW-HOW The Welch aquot;Duo-Sealaquot; vacuum pump was developed to fill the need for a highly efficient, quiet, reliable pump for producing high vacuum. Thirty years of ... Catalog contains photos, descriptions, specifications and typical performance curves of all aquot;Duo-Sealaquot; vacuum pumps. Welch aquot;Duo-Sealaquot; ... They range in capacity from 21 to 1400 liters/minute and ultimates from 2 x 10 2 to 5 x 10 5 mm Hg (torr.).