The marine hydraulic cathead is the basic supporting component of the drilling rig,oil cylinder in-ternal leakage and loading efficiency are important factors that affect its safe and efficient operation.Aiming at the above two parameters,designed a testing device with an electronic scale.Used the pressure maintain-ing method to measure the internal leakage at 230mm in the middle of the oil cylinder,refered to the load value on the electronic scale to confirm whether the pressure maintaining was effective,and calculated the loading efficiency.The above method was applied to conduct experimental research on 8 hydraulic catheads in a certain sea area.The internal leakage test values of the oil cylinders of the 8 hydraulic catheads in this series were all lower than the standard value of 0.9MPa,and the internal leakage value was qualified.Partial analysis was conducted on the four hydraulic catheads whose loading efficiency did not meet the required 0.88,and found that the eccentricity of the piston joint and the untightening of the threads were the reasons.After replacing the eccentric piston joint and tightening it,repeated the test and all met the required values.The hydraulic cathead was produced and operated normally at sea after leaving the factory in 2020.In the future,hydraulic catheads will need to optimize cylinder sealing,increase the internal leakage standard appro-priately in exchange for greater load efficiency,add a guide device to the moving pulley to stabilize load ef-ficiency.The results indicate that using this method to test the internal leakage and loading efficiency of the hydraulic cathead is feasible and effective.This method can provide the reference for the same or similar ex-periments.
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