Abstract: As an important device in the installation,drilling and completion stages of underwater dry oil production equipment,the steel cylinder plays the role of isolating the external seawater,creating a dry installation and drilling and completion environment,and facilitating underwater construction operations. Based on the risk characteristics of cylinder positioning operations,the structural entropy weight method is used to analyze the dangerous and harmful factors of the cylinder positioning operations,and the weight of each factor index is calculated to obtain a total ranking of the weights. The pre-hazard analysis method is used to analyze the five dangerous and harmful factors with high weight values,namely atmospheric pressure,stress release,vertical attitude center height,hoisting wire rope state,and steel cylinder vertical fixed center-of-gravity position. The prevention and mitigation measures to reduce the safety risk of underwater dry operations are put forward to ensure the safe production of enterprises,reduce casualties and property losses.

Key words: steel cylinder positioning, structural entropy law, pre-hazard analysis