Abstract: Mechanical seal is composed of at least one pair of end faces perpendicular to the rotation axis, which keep contacting closely with each other and slide relatively under the action of fluid pressure, elastic force (or magnetic force) of compensation mechanism and the cooperation of auxiliary seal to prevent fluid leakage. Mechanical seals are widely used in metallurgical and petrochemical pumps because of their good sealing performance and low bearing wear. The failure analysis of mechanical seals can comprehensively and accurately find out the main failure modes and performance effects of seals before and after operation, study the causes and mechanisms of failures, and analyze and summarize effective measures to control the occurrence of failures or reduce the frequency of failures in combination with the control methods currently adopted in work, so as to eventually prolong the service life of mechanical seals.

Key words: mechanical seal, welded metal bellow, leakage