Design And Process Research Of Extrusion Molding Mold For Marine Flexible Pipe Lining

Deep water composite flexible pipeline is an important equipment in the development of deep-water oil and gas resources and mineral deposits.At present,it is widely used in deep-sea development,but many key manufacturing technologies are monopolized by foreign manufacturers.The inner liner is one of the key components of deepwater flexible pipeline,which is used to seal the oil and gas medium in the transmission channel.With the increase of the depth of the subsea oil and gas field,the temperature of the oil and gas medium increases,the content of H2 S and CO2 increases,and the tightness of the common materials to the extreme transportation medium is greatly reduced.PVDF material has good high temperature resistance,corrosion resistance,oxidation resistance,good barrier and permeability to oil and gas media,and is an ideal material for the lining of deep-sea flexible pipelines.However,PVDF material is difficult to form and is prone to uneven wall thickness.Therefore,in view of the difficulty in the extrusion molding of PVDF lining of deep-sea flexible pipeline,this paper uses the numerical simulation method to establish the finite element calculation model of PVDF material extrusion molding,simulate and analyze the PVDF extrusion molding process,and analyze the influence of extrusion molding process parameters on the wall thickness uniformity of PVDF lining.The main research contents and conclusions are as follows:(1)In order to verify the validity of the numerical model,based on the existing melt flow theory,the melt flow law in the annular channel with taper was deduced.The extrusion mold was designed according to a certain proportion,the final runner size parameters were determined according to the requirements of the experimental equipment,the appropriate mold materials were determined,and the final manufacturing was completed.(2)PVDF will produce corrosive gas at high temperature,which will corrode equipment and cause harm to human body.It has high requirements on equipment and experimental environment,so it is difficult to directly use PVDF experiment to verify the effectiveness of the numerical model.Therefore,taking the extrusion molding of HDPE inner liner as an example,the validity of the finite element calculation model is verified by experiments,and then the model is applied to the simulation analysis of the extrusion molding process of PVDF inner liner.The experimental results show that the simulation results are consistent with the experimental results,which verifies the effectiveness of the numerical simulation method.The rheological properties of PVDF were studied experimentally,and the rheological constitutive model of PVDF was established.The material model was applied to the numerical simulation of PVDF extrusion.(3)The effects of extrusion process on the wall thickness uniformity and melt morphology of PVDF under gravity field were studied.The effects of temperature and screw speed on the melt pressure in the runner,the melt morphology in the free section and the melt wall thickness uniformity at the traction end were simulated and analyzed.The effects of traction speed on the melt morphology in the free section and the melt wall thickness uniformity at the traction end were analyzed.Finally,the cooling numerical model of PVDF inner liner is established,and the influence of cooling process parameters on cooling deformation is preliminarily analyzed.It provides a theoretical reference for production practice.