Study On Long-distance Pipeline Reliability Of Hot-water Heating System

To meet the demand of the urban residents and the requirements of the energy-saving and emission reduction for environment,transporting the heat of thermal power plants around the city to heat customer become the best option under the combined weights of the growing demand of heating year by year and the tighter environmental regulations.Many cities build the long-distance pipeline project of hot-water heating system one after another.On account of the feature of he long-distance pipeline project which include the large thermal loading and temperature difference of heat medium and high pressure,if it break down,the adverse impact of social and economic loss will be very serious.However,there are no specific design method and requirements about the longdistance pipeline when we look into the present Chinese criteria.And the reliability evaluation method of the existing district heating system can not completely be suitable for the reliability evaluation of the long-distance pipeline.Thus,the study of the reliability of the long-distance pipeline of the hot-water heating system is not only the practical needs of the engineering construction,but also the need of completing the reliability evaluation of the district heating system.This paper mainly establish the reliability evaluation index system of the long-distance pipeline and study the design method of the long-distance pipeline based on the reliability.According to the construction features of the long-distance pipeline and the influence of faults on the heat consumer,the reliability evaluation index system including the deterministic indicators and the probability indicators first be established.The deterministic indicators include the allowable pipe range,pipe diameter and valve interval.The probability indicators include the connectivity of the construction and the index of heat supply reliability.And the multi-pipe system of the long-distance pipeline belonging to voting model has been defined.The index of heat supply reliability of the long-distance pipeline has been established.The derivation and discussion of the flow coefficient of the multi-pipe fault conditions and the quantitative analysis of the flow coefficient of the fault conditions have been finished.Secondly,by using the reliability evaluation index system of the long-distance pipeline,the reliability of the two-pipe three-pipe and four-pipe have been calculated respectively.And the connectivity and the rate of heat-input of three types of fault flow parameter of pipe network have been analyzing respectively.On the basis,the suitability of the pipe forms have been synthetically analyzing combining the intensity index of pipe reliability.And the variation trend of the rate of heat-input have been observed by using image method with the features of the rate of heat-input changes having been calculated by using sensitivity analysis method.Finally,a design based on reliability can be done to the long-distance pipeline,according to the established reliability evaluation index system of the longdistance pipeline.a decision flow of the reliability of the long-distance pipeline which is used to examine the reserve capacity and heat supply capacity of the long-distance pipeline including existing and designing scheme have been given.And a design flow of the long-distance pipeline based on reliability have be proposed.On the basis of reliability limits,the pipe diameter,pipe range and pitch limits of isolating valve can be calculated.The indexs established in this paper should be all used to evaluate.And the study provide references for the reliability evaluation and the design of the long-distance pipeline of hot-water heating system.