Typical example are the atmospheric pressure tower pump and decompression tower pump in atmospheric pressure distillation unit、The slurry pump in the catalytic unit etc. Their common feature is temperatures up to 360 to 370℃，The medium contains the impurities，higher viscosity。It is one of the difficult problems of the machine pump maintenance work in the oil refinery。The working environment for changing the mechanical seal is often flushed with an injection type(Refers to the single-end surface mechanical seal)。What fluid is used to rinse it out? Some companies use light diesel oil to rinse fluids，Although easily available in oil refineries，Other performance is also better，However, mix with the heavy oil，It is not worthwhile economically。More importantly, it is easy to cause the pump evacuation.Light diesel oil is a component ranging from 170 to 360℃,At 270 to 300℃, more than 50% of the components are vaporized,More than 90% of the components were vaporized at around 350℃.apparently,Light diesel oil is not suitable for the above heat oil pump.Using the raw oil (wax oil) of the catalytic unit as the rinse fluid overcomes the above disadvantages,That is, to reduce the production costs,And avoid the pump evacuation,To reduce the viscosity of the wax oil,The temperature can be controlled at about 100℃,Normal pressure tower pump and pressure relief tower pump, using single end surface sealing can also use wax oil as flushing fluid.