A new impeller-to-sump seal was developed for a line of hermetically sealed centrifugal compressor units. Tests, using an actual compressor unit, were made to simulate steady operating conditions. Both new seal configurations and the original seal were tested. A new seal configuration resulted in a 25:1 reduction in refrigerant leakage. The seal met all other technical and economic requirements dictated by the application. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Boston, Massachusetts, October 5–7, 1976