大型油轮在装卸过程中干舷高度变化大，加上潮水涨落和波浪的影响，船舶始终处于运动状态中，因此升降梯在机构上要保证有三个自由度的运动，在液压系统中通过特制的浮动阀达到浮动状态，使升降梯能够长期地跟随船舶作相应运动。 During the loading and unloading process of large tankers, the height of the freeboard varies greatly, plus the influence of tidal fluctuations and waves, and the ship is always in motion. Therefore, the lift must ensure three-degrees-of-freedom movement on the mechanism and pass through the hydraulic system. The floating valve reaches a floating state so that the lift can follow the ship for a long period of time.