Risk Assessment To The River Tranversing Oil Pipeline Of Great Or Middle Type

The technic of risk assessment in foreign countries rises from 70s last century, while 90s in our country. It is a systemic process that a certain probability and probable degree are assessed according to the safety, health,zoology .finance and etc of a special period. And now it is applied in many scientific fields, then widely in oil-gas pipline transportation.The risk factors of river tranversing oil pipeline is analysed in this paper. Based on related literrature, the types of fault is classified which affects the systemic safety. According to American risk assessment theory, the risks to the oil pipeline of long distance includes four species: erosion, demage caued by the third side, design fault and operation fault. For river tranversing pipeline which loads under whorl liberation, inner fluctuation, flood impact and etc, the fatigue breach and steady loss and intension breach must be considered besides those four factors. Therefore, the total fault tree is established based on this, hi order to carry out the risk assessment to the river tranversing pipeline, the exponent grading method is cited which is widely used currently. Apply this method, the value of relative social and management is acculated, while the judge method to the exponent grade is also established. At the same time, the corresponding value is adjusted so that they can be united with the risk assessment of non-river tranversing pipeline , and this provide decision makers more supplement and a quantity index. Thus the transition from safe management to riskful one is realized. The example testifies its validity.As some practical condition can't be identified as a certain exact grade in the process of exponent grading to the river tranversing oil pipeline, for example, each operater may have his unique character , and they can make different express on the fuzzy cell when the operating mistake is involved in.The final result is that various affection is lead in. So, in order to eliminate the affection that personal's subjective idea impact on the impersonality, we can apply the colligate fuzzy judging method to the assessment on the base of estabishment of the fault tree model and the fuzzy mathematics. Then the example of exponent grading is also cited in this calculation so that its validity is proved.The method that applying the exponent grading to the risk assessment of the river tranversing oil pipeline is simple and can be easily popularized. So far as we all know, it is a comparable mature assessment method, but the calculation precision is too low and the proportion that man-made impact occupied is too high. Like exponent grade method, fuzzy colligate judge also involves subjective impact of the evaluator in to a certain degree, but the later takes account the colligate affection in, simutanuously, the opinion from each side can be fetched in, including related technic workers, operators, managers, experts and etc. As the result, fuzzy judge possess certain subjective and scientific character.