Improvement And Research Of Hydrodynamic Mechanical Seal On Centrifugal Pump

Domestic and foreign petrochemical enterprises generally use the centrifugal pump to transport hydrocarbons.Due to the high saturation vapor pressure,flammable and explosive properties of propane and other light hydrocarbons,the leakage of propane pump seal is frequent,and the maintenance frequency is higher,and the service life is shorter and shorter.If the seal is invalid,the leakage of propane will not only cause safety problems,but also cause environmental pollution,resulting in huge economic losses.After many times,the effect of mechanical seal is still not ideal.In this paper,the process characteristics of B-512 pump are studied firstly,and the cause of the failure of contact type mechanical seal is analyzed,and the working principle and application characteristics of the non contact type mechanical seal are studied.Through the analysis and calculation,it can be seen that friction will cause the vaporization of liquid propane in the original seal.At the same time,due to the high saturation vapor pressure of propane,the liquid film pressure on the seal face gradually decreases from outside diameter to inside diameter,which also leads to the vaporization of propane.The phase transition of liquid membrane results in the unstable state of the end face fluid in the vapor and liquid phase.The face appears blast vibration phenomena,the wear of the end face is serious,which leads to the early failure of seal.Through the calculation,the original seal area ratio and other parameters are also to be optimized.Therefore,due to the sealing mechanism of the contact type mechanical seal and the natural characteristics of the light hydrocarbon medium such as propane,the original seal can not achieve the goal of zero leakage and even zero escape.According to the actual situation,the new series mechanical seal is designed.Based on the characteristics of non contact mechanical seal,the related structural parameters are calculated and the corresponding mechanical seal auxiliary system is designed to achieve the sealing requirements of propane pump.A three dimensional model of end face fluid is established.In order to verify the performance of the new mechanical seal,the flow field of the end face is calculated by FLUENT.The opening force,liquid film stiffness,end face friction force,friction power consumption,leakage and other parameters of the new mechanical seal are calculated.The influence of different working conditions on the sealing performance is analyzed.The new mechanical seal and the original seal are compared.Analysis shows that the new series mechanical seal makes up for deficiencies in the original.The upstream pumping mechanical seal and dry gas seal can run for a long time.The analysis shows that the leakage of new mechanical seal is small,the liquid film stiffness is large,and the friction power consumption is low,it is helpful to improve the working efficiency of propane pump.After the main seal failure,the dry gas seal can be used as a backup seal.The new seal does not require high reliability of the auxiliary system and it has a long life.This paper has guiding significance to the design of mechanical seal for light hydrocarbon pump.