At present, the total length of submarine pipelines laid in China's sea areas has exceeded 3,000 km. Due to various reasons, successive damages to the submarine pipelines have occurred. In order to get rid of the dependence on foreign technology, to achieve rapid repair of submarine pipelines relying on domestic technology and equipment, the formation of submarine pipeline maintenance technology and special equipment with independent property rights is an urgent requirement for the development of China's offshore oil industry. The research work of this thesis was carried out in combination with the subproject of "underwater special-purpose work implement equipment" in the "863" plan. Its purpose is to develop a set of different diameters for 6" to 24", 60 meters to shallow submarine single layer or double layer. Oil and gas transmission pipeline underwater maintenance cutting equipment - underwater diamond rope saw engineering prototype. Therefore, based on the review of the development status of underwater cutting tools and commonly used underwater cutting methods at home and abroad, this paper proposes the design idea of using submarine diamond wire saws to cut submarine oil and gas pipelines, and determines underwater diamond rope saws. The overall plan of the machine, and analyzed and designed the main moving parts, introduced the working principle and technical characteristics of the control and detection system. Based on the analysis of the characteristics of the wire saw and the processing performance of X52 grade pipeline steel, the grinding mechanism of the diamond bead rope was described in conjunction with the single-layer cutting test of the seabed oil and gas pipeline. A uniform design test method was used to establish the mathematical model of wire saw grinding force. The effect of process parameters on grinding force was analyzed theoretically, and it was pointed out that during the process of flexible and intermittent grinding of diamond Wire Sawing Machine, it is suitable to adjust the process parameters and control the grinding force ratio within 0.88 to 2.05 to maintain good Sharpness and cutting performance; reasonable cutting process parameters can be used to control the cutting surface roughness R_a of the steel pipe can reach 3.2μm, and no waviness and cold hardening occurs. This paper also studied the wear mechanism and durability of the wire saw. Scanning electron microscopy was used to observe the wear state of beaded diamond abrasive grains and carcass, and combined with the macro wear test of the beads, the wear characteristics of diamond single crystals and carcass were determined. Through the experiment, the durability of the wire saw (wear rate) was investigated theoretically, and the empirical formulas of the wear rate, feed rate, and line speed were established.
The analysis indicated that the wear rate of the wire saw was kept at an optimal level. The condition is that the linear velocity should be kept as constant as possible. According to the position of the cross section of the cutting line of the wire saw, it is suitable to adjust the feed rate to achieve the highest cutting efficiency. Combining the statistical analysis of diamond abrasive grains under different cutting conditions, the correctness of the conclusion was verified, and finally the durability of the selected diamond wire saw was evaluated. The above research provides relevant theoretical basis for the development, improvement and improvement of engineering prototypes for underwater diamond wire sawing machines. Specially developed submarine diamond wire sawing machine engineering prototype for submarine oil and gas pipeline cutting operations, its main advantage is that it can adapt to the working environment of the seabed, can cut metal materials and non-metallic materials in one operation, and to the operator and the environment No harm will be generated. It will be able to play a more effective role in the maintenance of submarine oil and gas pipelines in the future, and broaden new fields for the application of diamond wire saw technology in China.