Abstract: Medium pressure boiler feed pump is the auxiliary boiler water supply equipment of 60 t/a methanol plant of certain company. In the process of domestic substitution of fittings, the domestic substitution of mechanical seals used in the pump has repeatedly failed due to leakage. This paper finds out the causes and mechanism of the leakage by analyzing the leakage passages which may occur in the operation of mechanical seals one by one. Then it compares and checks the structure and main technical parameters between the mechanical seal substitution and the original BURGMANN (Germany) mechanical seals. The paper chases down the essential causes for the leakage failure of the domestic substitution of the mechanical seals. Then it puts forward some suggestions for improvement.

Key words: mechanical seal, leakage, spring pressure, face pressure, domestic substitution