Analysis Of Trajectory Deflections Of Mounting Point For Polar Crane In Nuclear Power Plant

As a special overhead crane to replace the reactor fuel or maintain the heavy equipment in nuclear power plant(NPP),the polar crane should locate the load in a high degree of accuracy due to the special working circumstance.Because the working environment of the polar crane is closure and the operation is smooth,the key factors that affect the locating accuracy are the layout and the reeving way of the rope-pulley system,which is very common in engineering.At present,significant achievements have been achieved in anti-swing of the load for general cranes by many domestic and foreign scholars.However,the rope-pulley system is oversimplified and the model established is not applicable for cranes with high precision locating requirements.According to the specific structure characters,this paper analyzed the load trajectory of the rope-pulley system,which are summarized as follows(1)Considering the specific layout and reeving way of the rope-pulley system,an equilibrium path method of quasi-static for analyzing the trajectory deflections of the polar crane in nuclear power plant was proposed.The equilibrium path equation of the hook block as well as the compatibility conditions of the rope length were given in the mothed.Properties and formulations of the variables involved in these equations were discussed in detail.A numerical method was derived to solve the common tangent between spatial pulleys,which was conforming to the rope reeving.When calculating the rope tensions,the changes of the tension directions caused by the movement of the pulley and the influence of the tension transmission at two ends of the pulley were taking into account.New pulley efficiency coefficient was obtained through synthetically considering the Stiffness resistance of rope and the frictional resistance of pulley shaft.Then the recurrence relation of tensions at both ends of the pulley was given.The rope lengths wound by the drum and left in the system were computed.Moreover,the influence mechanisms of the guide pulley and the equalizer was discussed.Finally,the kinematic analysis of the hanging point on the hook block verified the reasonable of the method,whose result can be as a valuable reference for the design of the rope-pulley system of polar crane in NPP.(2)For some pulley-rope system,both ends of the rope are all connected to drum.The rope drives the pulleys from both ends while the system hoisting.Then the rotation directions of the pulleys are unknown in advance,which causes that impossible to determine the tensions relationship at both ends of the pulley.As to this problem,taking the kinematic velocity parameters of the hook block and the change rate of the rope tensions as generalized velocity of the system,the paper chose hoisting height as the describe parameter and obtained the velocities of the inlet and outlet points on pulley by performing on the coordinate equation of common tangent point with respect to the hoisting height.Further more,the change rate of tension direction was obtained.Then the highly nonlinear equations were converted into ordinary differential equations by performing on the governing equation of the equilibrium path.A general method to analyses the trajectory of mount point of the rope-pulley system was proposed,and the method of constraint stabilization was used to prevent the occurrence of default in numerical solution.The effectiveness of the model was verified by numerical examples,and compared with the former nonlinear equation,the first order differential model significantly accelerated the computational efficiency.(3)In order to accurately analyze the mounting point deflection and improve the locating accuracy,the paper established the rigid body dynamic equations of the hook block by taking hoisting speed as the known parameter.Based on the velocities of the inlet/oulet points on spatial pulleys,the acceleration expressions of the inlet/oulet points were further deduced,and then the two order differential form of the compatibility conditions of the rope length can be written out.According to the D'Alembert principle in the height direction,the rope tension can be solved as the hoisting acceleration was known,and then two order differential equations of the hook group acceleration and drum's parameters were obtained.The results comparing the dynamic results with the quasi-static results shown that the mounting point was swinging around the equilibrium path,and the correctness of the result is verified.The analysis results have certain reference value for the operation and control of the polar crane.