There are many methods in safety assessment of the tank farm. Because the elements of the accident are always uncertainty, the traditional safety assessments have the limits by themselves. The fuzzy comprehensive evaluation is a way to fuzzy and quantifys the uncertainty of dangerous elements. This method is always used in safety assessment through the way of rating by experts and security level can be observed. And fuzzy comprehensive evaluation is already used in the safety assessment of a system, and it is a simple way to assess. The fault tree analysis is a method of analysis in quantization. It exists a problem in getting the date of basic events' probability, because of lacking enough statistical data. According to the fuzzy evaluation,the basic events' probability can be certain. Those data can be used in practical calculation. And this method is effective and useful in assessment.

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