Research Of Winch Bearing Pads Failure Under Additional Loads

Turbine service jack-up unit played an important role in marine engineering and lifting device with double-drum friction winches, legs, the body of vessel consisted of the lifting system. In the role of lifting device, the system completed dropping pile , lifting vessel and other action with friction winches providing tractive force. Safety and stable operation of lifting system was the base of offshore projects success. Because of the uncertain marine environment, the integrated operation system malfunctioned frequently especially the friction winches. This paper proposed and built vessel-pile-soil-water mathematical model of integration working system based on interaction mechanism between the marine environment and structure and "Haiyang 38" turbine service vessel external environment load with vessel failure, analyzed of the additional loads in winching operations,further study the mechanism relationship between winch additional loads and bearing pads failure adopted numerical simulation method.First of all, the additional loads in jack-up installation vessel working included two phase additional load at the interface and pile - soil interaction additional load at the interface. Based on the analysis of the load on the marine environment, study on the numerical simulation of the marine environment and establish integrated lifting system of winch lifting system interaction with the external environment, for study the relationship between additional loads and bearing pads failure, studying load transfer mechanism including lifting system additional loads and winch head rope loads.Secondly, kinematic viscosity, surface tension of the liquid and other factors influenced gas-liquid interface additional load, analyzed of winch additional loads in lifting operation adopting fluid simulation the method, the results showed that the hull, legs affected by large additional loads including hydrodynamic loads and other environmental loads, in addition got additional loads variation.Thirdly, soil cohesion and modulus of elasticity and other factors influenced pile - soil interaction interface additional loads, analyzed of winch additional loads in lifting operation adopting explicit dynamics simulation method and got additional loads variation in pressing piles and pile pulling process.The variation showd that low speed pressing pile helps to reduce the impact of additional load and keep stable.In pile pulling process, additional loads variation showed linear relationship with soil cohesion and legs buried depth and additional loads variation showed non-linear relationship with elastic modulus of the soil. With the increase of the elastic modulus of the soil, there wae maximum additional loads .Finally, based on the winch head rope loads transfer mechanism,the mechanism relationship between rope tension, amplitude and frequency of vibration force and winch bearing pads stress response was found. Based on the integrated lifting system additional loads transfer mechanism, winch head rope load variation in winch lifting operation process was found. According to the winch head rope loads transfer mechanism and head rope loads variation, analyzed of the mechanism relationship between winch lifting operation additional loads and winch bearing pads failure, the results showed that winch tension excessive due to the additional loads,as a result winch mode changed. In the role of random vibration, winch bearing pads harmonic stress increases, as a result bearing pads total stress was more larger than the allowable stress, bearing pads failure. Based on the bearing pads failure mechanism,optimized the winch winch structural. By tension releasing device using elastic elements of linear stiffness,relieved winch head rope tension effectively.