Reliability Analysis Of Spring Type Safety Valve Based On Environmental Conditions Model

Safety valve is an important safety accessory of pressure vessel and pressure equipment,which plays an important role in the process of protecting equipment.Its reliability is of great significance to the economic benefits and safety production of enterprises.The acquisition of accurate and effective failure data is the basic work for reliability analysis,design and improvement of safety valve.However,due to the limitation of environmental conditions and other factors,the available failure data,such as the data provided by the manufacturer or the general failure database of the industry,will be directly used in reliability analysis,which will have large errors.However,the failure data within the enterprise will take many years Accumulation and consumption of a large number of human and financial resources,too small sample size will lead to the contingency of the analysis results.Considering the above problems,the following research work has been carried out:(1)Taking the corrosion failure of spring safety valve as an example,the failure mechanism is analyzed,and the environmental conditions affecting the failure are determined.Based on the K-factor method,the model is constructed with temperature and relative humidity as covariates.The failure data in OREDA is used to fit model,and the unknown parameters in the model are solved with the least square method,so as to realize the safety considering the environmental conditions Correction calculation of total valve failure efficiency.(2)On the basis of obtaining the model of safety valve failure efficiency environmental condition,the goodness of fit between the model and failure data is ensured by means of error checking calculation and membership function construction,so as to realize the statistical verification of the model;and the single variable analysis and sensitivity analysis are carried out for the model to quantitatively determine the impact of each environmental condition on the change of failure efficiency,which can be regarded as failure Provide guidance for the collection of data environmental factors.(3)Considering the low applicability of "failure rate environmental condition" model for low temperature environment,the "low temperature failure rate regression" model is constructed by multiple regression,and is tested according to the steps of regression analysis;compared with the former model and recommended data,the results show that although the overall calculation effect is inferior to the former model,the calculation effect is better in the low temperature range;at the same time,it is proposed that the "low temperature failure rate regression" model is more effective in the low temperature range.the two models are combined in sections to reduce the error of failure rate calculation.(4)Taking the model calculation result as the input of equipment level failure rate of safety valve,fmeda is carried out on the emergency relief valve of wax oil hydrogenation unit in a certain area,and the safety failure fraction and diagnosis coverage rate are obtained.The failure probability of relief system,and compared with the calculation results before the correction,it is shown that the failure probability after the correction is smaller under the given environmental conditions,which is more suitable for the correction Practical use.The failure rate environment condition model proposed in this paper is an improvement of the failure database,which can provide a reference for the reliability analysis of safety valves under different environment conditions.The statistical test and the calculation of failure probability combined with fmeda technology verify the effectiveness and availability of the model,which has a good engineering practical significance.