Dynamics analysis of cutting mechanism of underwater guillotine pipe saw

In order to cut off damaged offshore pipeline, an underwater guillotine pipe saw, which was composed of sine cutting mechanism, eccentric cam mechanism and spiral feed mechanism, was designed. According to its technique process of cutting pipe, dynamic model of the guillotine pipe saw were proposed, and its simulation analyses were finished. Analytical results showed that when there were optimized parameters: cutting velocity v=480 mm/s, feed velocity vj=15 mm/min, height of lifting the blade in return range ℯ=10 mm, the driving power of the guillotine pipe saw is enhanced by 2.52% due to hydrodynamic influence. Sea current has less influence on cutting work, whose reason was analyzed. Underwater experiments of the guillotine pipe saw were carried out in a port. The experimental results indicate that energy loss along hydraulic pressure pipes within 60 meters underwater was 21.7%, much more than hydrodynamic energy loss (3.3%), and error is 8.3% between test data and theory data. So the dynamic model is applicable for offshore pipeline service if the driving power of the guillotine pipe saw working in epicontinental sea is enhanced by 25% compared with working on land. What´s more, the proposed dynamic model can also be used for deepwater working with underwater hydraulic power supply.