Study On The Influence Of Temperature And Internal Pressure On Bolt Force And Sealing Of Pipe Flange Connection System

Flange connection systems are one of the most widely used connection methods in industrial equipment,and bolt force is an important factor in maintaining the tight connection of a flange connection system.The magnitude and distribution of the bolt force are affected by changes in temperature and internal pressure,which further affect the sealing performance of the flanged connection system.The relationship between temperature,internal pressure,and bolt force is studied by theoretical analysis and FEM simulation.The influence of temperature and internal pressure on the stress distribution of a gasket is analyzed.The tightness class of the pipe flange connection system is evaluated.The main contents of this paper are as follows:(1)Study on the influence of temperature on bolt force.The difference between axial thermal deformation and thermal expansion was analyzed,and the calculation formula for bolt force and temperature was deduced.It was found that the bolt force changed linearly with temperature and was related to the thermal expansion coefficient of the bolt.(2)Study the variation law of internal pressure and bolt force.The variation law of internal pressure and bolt force and the influence of internal pressure on the surface reduction force of the gasket are studied.The results show that the internal pressure is positively correlated with the bolt force and negatively correlated with the gasket surface reduction force.(3)Simulation and comparison of the relationship between temperature,internal pressure,and bolt force.The FEM models of NPS 3 and NPS 24 pipe flange bolted connection systems were established,and the effects of temperature and internal pressure on the bolt forces of different pipe diameter flange connection systems with different bolt materials were analyzed.The results show that the theoretical analysis and FEM simulation have good consistency.(4)The stress distribution of a gasket under different temperatures and internal pressures.The stress distribution characteristics of a gasket under different temperatures,different internal pressures,and different bolt materials are studied.The results show that the stress on the inner and outer sides of the gasket changes linearly.The stress of the gasket decreases unevenly along the radial direction with the decrease in temperature and increases irregularly with the increase in temperature.The influence of internal pressure on the stress distribution of gaskets connected with different bolt materials and different temperatures is approximately the same.(5)Study on the sealing grade of the pipe flange connection system.The influence of temperature and internal pressure on the tightness parameters of the pipe flange connection system was studied using the PVRC tightness classification theory,and the distribution of tightness parameters of the gasket sealing surface under different temperatures and different internal pressures was obtained.The leakage model of the pipe flange connection system is established,and the mass leakage rate of the model under different temperatures and different internal pressures is analyzed.At the same time,compared with the common sealing grade,the sealing grade of the pipe flange connection system is obtained.