Research On Risk Assessment Method Of Wuhan Metering Station Based On RBI

Wuhan metering station,the substation of national oil and gas large flow metering station,undertakes the metrological verification of 300-400 natural gas flowmeters each year.With the densely surrounding population which caused by the geographical position,the suburb Wuhan,once the metering station happen accident,it will not only affect the normal distribution of natural gas of the lag of the flowmeter verification work,but also lead to serious casualties,major economic losses and bad social impact.At present,the Risk Based Inspection(RBI)method is often used to assess the station's failure risk at home and abroad to ensure the safety of the station.However,compared with the conventional natural gas station,Wuhan metering station has the characteristics of multi pipelines and devices,frequent personnel operation and the dropping possibility of equipment due to the addition of the verification process.Therefore,the conventional RBI method can not be fully applied to the Wuhan metering station.It is necessary to analyze the characteristics of the risk accident through the detailed investigation of the situation of the Wuhan metering station.This paper has carried out the following aspects of research:(1)The Wuhan metering station conducted three survey and data collection,detailed analysis of the production process and operation flow metering station.Combined with PHMSA database and SY/T 6714-2008 standard,the main failure accidents of Wuhan metering station are classified into two categories,namely,mechanical damage accidents and equipment drop accidents.(2)Based on the characteristics of multi pipelines and equipment,divide the failure probability into the mechanical damage and the equipment drop taking into account the possibility of equipment dropping.About the mechanical damage accidents,considering the actual situation of pipeline and equipment in Wuhan metering station,improve and correct of equipment correction coefficient and management correction coefficient.In order to complete the semi quantitative calculation of falling probability of equipment,first,extract the factors of affecting the failure.Then,determine the weight distribution of the influencing factors using analytic hierarchy process(AHP).Last,set up the quantitative score table of each link.(3)Based on the SY/T 6714 standard and failure result of conventional natural gas station,set up the event tree of the equipment or pipeline mechanical damage and the equipment dropping.And the leakage of natural gas,pipeline or instrument loss and casualties were used as the measure of failure consequence.In view of the existing natural gas station risk assessment methods can not calculate the impact of equipment drop,based on the effect of mechanical damage of pipeline or equipment,the calculation model is established on the basis of the free fall theory of heavy objects.Combined with the specific distribution position of pipeline equipment,the quality and volume of heavy loads,and the transportation route,the failure consequence of the equipment falling accident of metering station was calculated quantitatively.(4)Considering the Wuhan metering station bordering on the Wuhan branch station,the consequence of the failure accident may expand.From the geographical location,the connection pipeline and the common system,obtain two kinds of possible chain reaction accident:gas channeling accident in venting system,pipeline failure accident of connection pipeline.Aiming at the gas channeling accident,starting from the condition of the accident,based on the domino effect principle,combining the station position and the venting flow,the main failure equipment is obtained.And according to the original value of the station assets equipment,the probability and the consequence of the accident are obtained.(5)Based on the failure probability classification standard of the Norske Veritas which has mature system and high international reputation,combining with the operation situation of Wuhan metering station,the failure probability of pipeline and equipment is divided into five grades:A,B,C,D and E.Considering relevant laws and regulations,combined with the actual assets of Wuhan metering station,the failure consequence of pipelines and equipment is divided into five grades,which are negligible,considered,serious,very serious and disastrous.According to analyze the risk analysis methods such as risk matrix and ALARP principle,use the 5x5 risk matrix as the risk classification scheme of Wuhan Metering station.(6)Based on the quantitative risk assessment method and the risk acceptance criterion of Wuhan metering Station,the risk evaluation of 146 pipelines and 5 equipment was carried out,and the results show that the highest failure probability of Wuhan metering station is 6.4 e 10-6,and the minimum failure probability is 4.5 e 10-8.Comprehensive failure probability,failure consequences and acceptable criteria,Wuhan Metering Station has 6 pipelines,4 equipment at a higher risk grade,the rest of the pipelines and equipment are in the low risk grade,so the overall safety performance of Wuhan metering station is high.Based on the risk assessment results,the following two suggestions are put forward:Before June 15,2018,the safety quality inspection of the pipelines and equipment with grade two is carried out.Before June 15,2020,Safety quality inspection of pipelines and equipment at risk level.