The Research And Application Of Atmospheric Storage Tank Risk Assessment Based On RBI

With the continuous development of petrochemical industry,the number of atmospheric storage tanks used to store a large number of flammable and toxic materials also increases,which not only increases the risk of personnel and equipment,but also increases the cost of enterprise safety inspection and maintenance.Risk Based Inspection(RBI)technology is widely used in the field of petrochemical industry.This technology can assess the risk of atmospheric storage tanks,so as to formulate corresponding inspection plans according to the risk level and reduce it.RBI risk assessment technology mainly includes two aspects: one is to determine the failure mode and calculate the failure probability of tank bottom and tank shell respectively according to API 581 specification;Second,according to the nature and quantity of storage media to calculate the financial-based consequences of failure and area-based failure of consequences.There are two calculation methods of corrosion rate of tank bottom plate suggested in API581 specification.The one cannot be applied in large scale due to high cost.Although the other is convenient,the assessment coefficients are not well targeted and accurate for a particular tank.Therefore,this paper explored a mathematical model for calculating the corrosion rate of storage tank floor based on the Weibull extreme value distribution.And this model used ultrasonic thickness measurement data of atmospheric storage tank floor,to supplement the shortcomings of the two calculation methods of corrosion rate of storage tank floor mentioned in the specification.The calculation results were compared with the magnetic flux leakage(MFL)scanning detection of tank floor respectively.The comparison error between this model and MFL scanning detection is less than 10%.The results show that the Weibull extreme value distribution model based on the ultrasonic thickness measurement data can predict the corrosion rate of tank bottom,which provides more choices for the calculation of tank bottom corrosion rate in RBI technology.Because of the API 581 only standard to calculate the storage tank individual risk,but the individual risk should also be affected by a whole tank farm.Therefore,on the basis of twodimensional risk matrix add the Z axis(the tank farm risk prevention level),building threedimensional risk matrix to increase the storage tank comprehensive risk assessment.Due to the natural fuzziness of risk,the fluctuation of risk resistance can’t be taken into account by using the previous assessment methods.This paper presents a tank farm risk prevention level assessment method based on the structure entropy weight method and cloud model.The method not only provides the assessment index weights combined subjectively and objectively but also consider the fuzziness of the risk prevention level boundary.This method can consider the relative difference between the risk prevention level’s fuzziness of different experts.In the process of atmospheric storage tank risk assessment,the calculation process is very complicated,and it needs to manage a large amount of data,so the digital assessment software is of great significance.In this paper,the Py QT5 graphic editing toolkit in Python is used,and the atmospheric storage tank risk assessment software is written according to API 581 specification.The software is divided into "storage tank risk calculation module" and "storage tank information management module".Database files can be shared between the two modules to realize the interconnection between the data of the computing module and the management module,so as to help enterprises more conveniently manage the risks of atmospheric storage tanks,or reasonably adjust the calculation coefficients in the computing module according to a large number of storage tank risk data.Not only that,but also added in the calculation module to calculate the corrosion rate of the bottom plate and calculate the risk prevention level.The added risk prevention level can realize the two-dimensional risk assessment of atmospheric storage tank to three-dimensional risk assessment,more comprehensive consideration of the tank farm safety status on the tank risk level.