New Mechanical Seal System Of High Temperature Oil Pump In Atmospheric And Vacuum Pressure Unit

Single surface contact mechanical seals are commonly used with PLAN23/32+62(steam quenching)auxiliary flushing scheme on 22 high temperature oil pumps in atmospheric and vacuum distillation units in Dushanzi Petrochemical Company of Petro China.High temperature oil pump medium has high temperature,high density,low spontaneous ignition point,easy coking and high pollution.It is easy to cause fire or even explosion after mechanical seal failure.Therefore,it is necessary to improve the single-end bellows contact mechanical seal in order to improve production efficiency and safety factor.Firstly,this paper reviews the literature on the use of mechanical seals for high temperature pumps at home and abroad,and conducts field investigations.It deeply analyses the specific problems of mechanical seals for high temperature pumps,which are widely used at present,and finds out the specific breakthrough point for their improvement.Secondly,aiming at the problems of mechanical seals used in high temperature pumps,the double-end mechanical seals are proposed to replace the original seals,in which the main seals are liquid film lubricated non-contact mechanical seals,and the main parameters are calculated.Thirdly,the performance of non-contact mechanical seals with liquid film lubrication is numerically simulated,and the variation rules of pressure distribution,leakage and opening force of liquid film are obtained.Then the flow field and temperature field of the model are numerically solved by using Reynolds equation,energy equation and heat conduction equation with finite element software.The flow field and temperature field including sealing chamber,sealing assembly,rotating shaft temperature field and oil sealing field are obtained.According to the calculation results,the influence of oil seal flushing quantity on the cooling effect of series mechanical seals under operating conditions is plotted.By adjusting the flow rate of flushing inlet,the temperature and speed of three typical sealing components(series contact seal,single end seal and series non-contact seal),the advantages and disadvantages of the three kinds of seals are analyzed.Based on the actual requirements of the pump group equipped with sealing system in oil refining and chemical enterprises,and the analysis of flow field and temperature field,a set of auxiliary sealing system suitable for high temperature pump group is designed.The system can further improve the safety and energy-saving effect of the new sealing system.Through the above calculation and analysis,the following conclusions can be drawn:the arrangement of double-end liquid film seals for high-temperature pumps greatly weakens the influence of high-temperature process media on the outer seal;the radial flow of liquid film seals can take away the heat generated at the end face in time,so its high-temperature resistance is obviously better than that of contact mechanical seals;The series arrangement combined with circulating cooling of sealing oil can make the sealing components operate in relatively low temperature(compared with high temperature process medium),and improve the safety and reliability of the sealing.The scheme of mechanical seal pump group auxiliary system for high temperature pump combines the advantages of single pump seal auxiliary system and pump group oil seal supplementary system.It has certain applicability for high temperature pump group mechanical seal of refinery unit.