Offshore Discarded Platform Piles Removal Wire Saw Development And Its Dynamics Research

With the swift and violent development of the offshore oil industry, discardedoil gas platforms become more and more, how to remove those platform in asafer, more efficient, more environmentally compatible way becomes a questionthat each country Offshore Engineering Company is increasingly interested in.Itshistory is not very long that wire saw was applied in the field of removingdiscarded platform piles,but its advantage in this field is being increasinglyrecognized by people.Our country has fall behind the other country in the field oftechnology.To develop a wire saw that can safely, stably, efficiently cut discardedplatform pile is a urgent key technology.The study is funded by CNOOC technology development project(itemnumbers: C/KJFH001-2005), it bases on diamond wire saw cutting pipelinetechnological which belongs to special topic "Seabed pipeline restorationtechnologies" of the national "863" project important special items "Bohai bigoilfields exploration and exploitation key technologies" (item numbers:2002AA6020212-1).Its purpose is to develop a diamond wire saw that can cutdiscarded platform piles, research on its key technologies, improve its intelligentlevel of operation, implement technical storage for our country offshoreindustry ,and then lay the foundation for competition in the international market.Present situation and five routine cutting procedures of offshore discardedplatform piles removal at home and abroad are summarized and compared, ofwhich diamond wire saw development history and its latest application in pilesremoval field are particularly summarized.According to technical requirements of discarded platform piles removal wiresaw,referring to the design experience of foreign, and basing on domestictechnical condition, the whole scheme of discarded platform piles removal wiresaw is presented, including mechanical structure, hydraulic system, sensor systemand control system. Basing on sufficient demonstration, all structure of themachine base body and the measurement and control system are designed, anddiscarded platform piles removal wire saw engineering sample machine isdeveloped. Minimal clamp foce calculation of clamp device is researched in thesis.Model is simplified to special strained condition of wire saw working,force ofclamp position is analysed theoretically, and form-close of clamp device isproved.Basing on the analyse for wire saw once clamp or substep clamp in staticcondition,their minimal clamp foce multiple-objective optimization calculationmodels are presented. On the base of interacting analyse of clamp jaw with pilesin working, minimal clamp foce multiple-objective optimization calculationmodel of dynamic conditon is presented. Minimal clamp foce of three conditionsare calculated according to practicable working condition,and three results arecompared, which provide theoretical basis for structure optimization design andhydraulic system parameter selection.Dynamic equation of string bead wire cut motion is established with graphtheoretic modelling according to the structure of cut frame.Interaction of drivingsheave with string bead wire is analysed,driving torque computational proceduresare presented when sheave smooth and erratic turn. Causes of string bead wiretransverse vibration are analysed, transverse vibration dynamics equation isobtained, cut technology of minishing string bead wire transverse vibration ispresented by combining theoretical solution with test.Impact property is analysedwhen string bead wire cuts monolayer pipeline pile, dynamic model of string beadwire axial impact is obtained, course of impact is simulated with finite elementtransient dynamics analytical method, simulation results are analysed.Workingsituation and piles cross section that string bead wire cut monolayer pipe pile andcombined pipe pile are compared, the relation of cutting efficiency with stringbead spacing is gained by test.Existing flexible body tension detect devices at home and abroad areanalysed, contraposing practicable work characteristics of discarded platformpiles removal wire saw, a tension detect device with tension and detection functionis developed.Principle and method of pressure transducer in tension detect deviceare discussed. For dynamic off-center character of tension sheave having effect ontension measurement,a theoretical correction fomula is presented and proved bytest.Discarded platform piles removal wire saw testing platform isestablished.Cut performance test is carried out on it,test show that wire saw can fulfil 48" pile diameter cut task, hydraulic system, sensor system and controlsystem can stably operate. Cut technological parameters of wire saw are measured,interaction of parameters is analysed, best match of cutting speed and feed rate isgained when wire saw cut pile in different stage, experimental formulas of radialcutting force and tangential cutting force are established.Cutting tests provideparameters selection base for wire saw actual work.