Metal Bellows Mechanical Face Seals For High Performance Pump Applications

Abstract

Metal bellows seals have been steadily gaining wider acceptance in process and general industrial pump applications. This paper discusses design criteria and advantages of metal bellows seals, and attempts to define applications where the metal bellows seals offer operating advantages. The design principles of metal bellows seals to adjust hydraulic balance, or mechanical face contact force are explained. The mechanical face contact force, and not balance, is considered to be the important design criteria. The significance of welded metal bellows plate (diaphragm) shape is highlighted, and the optimum plate configuration for fatigue strength, manufacturability, and pressure capability is discussed. To further enhance the reliability of metal bellows seals, it is critical to control the seal face distortion and tribological behavior of the wear pair. The role of finite element analysis as a design tool to minimize face distortion and the microstructural control of the seal face materials to minimize face friction and wear are discussed.