OPTIMAL DESIGN OF OIL TANKS ACCORDING TO ECONOMIC CRITERIA WITH CONSIDERATION OF RELIABILITY

Abstract

Problem statement. According to state regulations, the main method of ensuring the reliability of steel vertical above-ground tanks for long-term storage of oil and petroleum products is the limit states method. This method ensures the reliability of tanks under the conditions and modes of operation envisaged by the relevant standards. However, issues relating to the reliability of tanks whose service life exceeds the normative one, as well as the economic efficiency of project decisions, require further scientific study. In this article, in accordance with the normative documents regulating the oil tanks design, the general method of oil storage tanks optimal design according to the criterion of minimum total expected costs while ensuring the required reliability level during a specified operation period is considered. Within the framework of this methodology, a model of optimal tanks design is formulated and an algorithm for its numerical realization is proposed. The results of numerical experiments using this model are given. The dependence of the rational values of the structural elements thickness for the tank with a volume of 5 000 cubic meters on the required level of reliability is investigated. The purpose of the article is to develop a method of making economically justified design decisions that ensure the required reliability level of oil tanks during a specified operation period, taking into account the current design standards. Conclusions. This article proposes an optimal oil tank design model formulated in terms of a non-linear mathematical programming problem with integer variables. With this model, rational design decisions can be made based on the criterion of the minimum total expected costs while ensuring the required reliability level during a specified operation period. The components of this model are the calculation models for assessing the reliability of the tanks, the parameters of which are determined based on the available results of statistical data processing from field surveys of similar objects. A special “greedy” algorithm was developed for the numerical realization of the proposed optimal design model. The obtained results show, in particular, that ensuring the oil tanks reliability is mainly related to ensuring the strength of the two lower wall belts and the tightness of the bottom. At the same time, the strength of the 1st belt has a key role. All this is in good agreement with the available data of field surveys and statistics of oil tanks capital repairs, which confirms the reliability of the obtained results.