| Safety valve is an overpressure protection device installed on pressure vessel.Seat ring and disc are the key components to ensure good sealing performance of the safety valve,the seal forms generally is metal to metal seal.However,due to the influence of incorrosion,crack,wear of the safety valve sealing surface in engineering practice,valve sealing failure will happen,resulting in the safety valve leakage quantity to exceed state standard.Therefore,calibration and maintenance of safety valve are particularly important.In view of sealing surface repair,the new safety valve grinding equipment was designed and developed.Simulated movement of the disc by using matlab in order to selecte reasonably grinding processing parameter;Studied the relationship between surface roughness and sealing performance,that's why using surface roughness express quality in the experiment.Based on the the new grinding mechanism as experiment equipment,making a standard process route of the disc grinding processing and increasing effectively the grinding efficiency and surface quality.In the paper,the main studies and achievements include as follows:Firstly,established safety valve seat grinding and disc grinding mechanism model by using solidworks software,the key components including stent,grinding head and arm were carried on mechanical design,and expounded the movement characteristics of key components.Next,on the premise of all abrasive disc nearly distribution,combining method of mechanics with kinematics,analysis of pressure distribution and friction torque in contact area was considered in grinding process,it was concluded that the eccentric distance,abrasive tool rotation speed were the main process parameters affecting the disc rotation speed.The motion equation of diamond grits from grinding tool was deduced and using matlab simulate the motion trajectory of disc abrasive grinding,found that the speed ratio and eccentricity,rotating speed of grinding tool,the initial position of the workpiece were the main factors influencing the particle trajectory shape.Then,safety valve closed grinding theory was conducted.Based on gaussian distribution function,the paper was intended to build mathematic model of the micro surface roughness.It was concluded that the metal surface fluctuation degree was more and more significant with the increase of surface roughness.Formation process of roughness was discussed under different grinding media and the relative motion of the valve seat and valve disc.Researched the influence of the surface roughness and the working pressure on the leakage of safety valve closure by the leakage test,provided certain theoretical basis why quality was evaluated by the surface roughness and selection standard of the grinding pressure and grinding media in the subsequent experiment.Finally,optimized disc process parameters in coarse grinding and fine grinding,made a new process route of lapping repair.With different fineness sand paper as grinding medium,studied the influence of the grinding pressure,grinding time and grinding speed by using SAS method during disc coarse grinding and fine grinding process on the material removal rate and the surface roughness and surface microstructure.Considering the efficiency and the quality of grinding,optimized the process parameters.The result shows that grinding pressure 15 N,grinding speed 30 rpm,milling time 10 min are the best process parameters combination in the process of coarse grinding,the material removal rate can achieve 27.5 ?m/min and the surface roughness is 0.213 ?m.Grinding pressure 15 N,grinding speed 20 rpm,milling time 4 min are the best process parameters combination in the process of fine grinding,the material removal rate can obtain 2.15 ?m/min,the surface roughness is 0.102 ?m.In this paper,grinding maintenance equipment development has important engineering application value for continuous automation,research of grinding process on safety valve provides theoretical significance to improve the quality of workpiece surface. |
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