With the rapid development of the petroleum refining and chemical industry, the working conditions of the production process are continuously improved, especially the requirements for leakage and safety of mechanical seals for high temperature media pumps are becoming more and more strict.

Double-end mechanical seals have been widely used in actual production. According to the definition of API 682, double-end mechanical seals without pressure and double-end mechanical seals with pressure are considered for choosing barrier fluids (also known as seal oils, buffers, seal fluids, flushing media). The barrier fluid is generally oil or water that does not react with the medium, and contaminated low viscosity oil or water. Avoid using volatile liquid as barrier fluid. Commonly used are soft water, ethylene glycol, ethylene glycol and water, engine oil, white oil and so on.