Key Technologies Study On Deepwater Subsea Pipe Multifunctional Operating Machinery

Submarine pipelines are the lifelines of offshore oil and gas fields.Subsea pipelines’ maintenance and installation widely adopt driverless mechanical connection technology and largely depend on the pipeline operating equipment.European and American countries rank high in the study of submarine pipeline maintenance technique and equipment,while the study of China is still in the initial stage.With the exploitation of deep water oil and gas fields in China,the theory and engineering study on the deep water subsea pipeline connection technique and equipment has a greater practical significance for breaking the foreign technical barriers and guaranteeing the safe operation of deep water oil and gas fields.Before mechanical connectors connecting the subsea pipelines,some preprocessing operations on the pipelines need to be finished.Currently,the pretreatments of the pipeline need to be finished by the cooperation of many sets of machines.Implementation of such operations may involve multiple lifting operations for relevant tools.Moreover,manipulation of such tools by using ROVs in deep water environments may face difficulties in secondary positioning.These difficulties may eventually reduce operation efficiency and increase operation costs.In order to solve the above problems,a new kind of deep water subsea pipeline multi-function operating machinery which integrates the abilities of pipeline cutting,chamfering,welding crown removing and anti-corrosion coating grinding is proposed in this thesis.Many key techniques,including multi-operation device integration,milling technology of achieving large cutting depth,operation stability and control technology of chamfering depth error,et al,are analyzed and studied.On the basis of the processes and technical requirements of the deep water connection,the design scheme of the deep water subsea pipeline multi-function operating machinery is determined.According to the requirements of large milling depth and multifunction,waved edge drilling and milling cutter,composite drilling milling and countersink and dovetail type end milling cutter are used to realize pipeline cutting,welding crown removing and chamfering.Anti-corrosion coating is removed by grinding plate.A system of two-arm holding self-centering pipeline clamping device is proposed to fit the requirements that multifunctional pipeline operating machinery need to keep the stability and reliability when grip the pipeline with different diameter and ensure concentricity between the cutter head and the pipeline during the operation.The circumferential rotation of cutter plate is achieved by the opening cutter plate’s synchronous drive which is driven by two small gears.The axial caterpillar action is achieved by the combination of the alternating clamps by using double sets of clamping devices and axial hydraulic cylinder.The principles are particularly described;the virtual prototype is designed;and the working processes of the machinery are projected.The mathematical models of waved edge milling cutter’s chip thickness are established based on the theory of end mill radial deflection.The influence of the milling cutter’s edge sine wave amplitude and the feed rate of each tooth on the formation of chip are studied.On this basis,a special waved edge drilling and milling cutter for cutting deep water pipeline is developed,the influence law of cutting parameters on milling force and tool’s wear and the optimal cutting parameters are obtained through the cutting experiment.The equivalent shear milling force convolution models of waved edge end milling cutter are established,and the dynamic forces value during milling deep water subsea pipeline are predicted.According to the characteristics of the clamping device griping the pipeline and the hardness solution of the driving force caused by the hyperstatic problem,the simplified mechanics model of the machine when clamping pipe is established,the mechanical conditions on stable operation of the machine are analyzed,the criteria for the stable operation of the machine is obtained.Based on the criterion,the mechanical model of machine during clamping pipe and rising are established.The correctness of the criterion is verified by dynamics simulation.According to the problem that the rotation center of cutter head and the pipeline are not concentric,which increases the probability of tool damage when chamfering,a method to measure the deviation of the pipeline center relative to the cutter head rotation center is put forward.The calculation model of the tool’s locus error is established,and the control strategy of tool’s locus error is determined,and the on-line control of the depth of cut is realized.Considering the demand of double hydraulic cylinders synchronization during creeping operation,the mathematical model of control system is established based on the control strategy of master-slave synchronization.The PI control parameters are acquired through system simulation research and analysis.Engineering prototype and onshore testing system are developed.Anti-corrosion coating removing test,deep water pipeline cutting test,chamfering test and axial creeping test are carried out.The schematic design of the machine and the stability of the working performance,the cutting performance and cutting parameters of the waved edge cutter,the criteria for the stabilization operation and the error control strategy of control system are validated by the tests.The design theory of the machinery and the error control strategy of control system are verified,which meet the requirements of the connection of the subsea pipelines.And the results validate the feasibility and effectiveness of the research results in this thesis.The study of this paper provides a theoretical basis for the subsea operation and the development of the engineering prototype,and can provide referential experience for the study of other deep water equipment.