Study On Sealing Compound Technology Of CIPP Lined Hose

With the continuous development of urban construction,the scale of underground pipe network is expanding.Due to the long laying time,some pipelines have reached the service life one after another,coupled with environmental changes,resulting in different degrees of structural and functional defects of the pipeline,which will not only reduce the service life of the pipeline,but also lead to various problems,harm to the city safety,so it is urgent to maintain and repair the underground pipe network.Cured in place pipe（CIPP）in trenchless repair is gradually widely used because of its advantages of low cost,short cycle,good construction safety and small traffic impact.However,due to the late start of this technology in China,although the equipment and materials used in the repair project have been localized,there is a lack of basic research,and the quality control is based on experience,which limits the development of this technology in China.This paper studies the welding technology of lined hose,the core material of CIPP for drainage pipeline,in order to provide support for the mechanized and continuous production of lined hose for Trenchless in-situ repair in China.（1）Through the research on the modification and composite mode of the material,the sealing material of the lined hose is developed,and the "specificity" of the sealing material is determined.The three factors affecting heat sealing welding（hot air temperature,welding speed and hot air volume）are studied,and the optimal combination process parameters of joint welding are determined.The results show that under the conditions of heat sealing temperature of 300 ℃,welding speed of 1.80m/min and hot air volume of 20m³/h,the strength at the weld of LLDPE hose is the highest,with tensile strength of 275 MPa and peel strength of 286N/m.The thermal surface before and after heat seal separation is tested by TG-FTIR,DSC,SEM and other instruments.It is analyzed that the heat seal welding process is divided into four stages: sealing film heating melting,interface convection,entanglement and cooling crystallization,among which the heating melting and entanglement stages are the key to determine the quality of hot air welding.The optimum parameters of welding process are determined by orthogonal experiment: hot air temperature is 300℃,welding speed is 1.80m/min,hot air volume is 20m³/h,and the peel strength at the joint is 185N/m.（2）The welding mechanism of TPU（thermoplastic polyurethane elastomer）hose is studied.The sealing performance,apparent morphology and melting state of the joint are tested by universal electronic tensile machine,TG-FTIR,DSC,SEM and other instruments.The results show that the welding process of TPU hose can also be divided into four stages,and the heating melting and entanglement stages are the key links;The results of orthogonal experiment show that when the hot air volume is 20m³/h and the welding speed is 2.16m/min,the peel strength is the largest,which is 2106N/m.（3）Through the finite element simulation analysis of ANSYS and the calculation of thermal mechanical coupling element,the distribution of temperature field and the value of residual stress produced by thermal process are obtained.The results show that the longitudinal residual stress caused by residual heat during welding is 1.28×10^-3MPa,the simulation result of transverse residual stress is 8×10^-5MPa,the total residual deformation is 0.0015 mm.（4）Through the research on the optimization of production equipment,the feeding device,hose forming and shipping device and hose inner and outer welding device were upgraded to improve the production capacity.Reduce the height of the front end of the feeding device to form a bottom-up slope to reduce the feeding resistance;Increase the limit function of the hose forming transfer device to ensure the alignment and splicing state of the hose and reduce the workload of manual butt joint;Optimize the hot air welding device,change the relay control to PLC control,and control the temperature control accuracy within±1℃,so as to ensure the stability of the welding process;The pneumatic lifting device is used to control the traction part at the front end of the welding equipment to solve the problem that the two ends of the pressing roller are not parallel due to the manual adjustment of the gap between the power roller and the driven roller.The optimized process production line is used to prepare DN1000 lined hose with wall thickness of 20 mm.The finished hose is of good quality.The optimized process production line can complete the preparation of medium diameter lined hose.