RELIABILITY-BASED MAINTENANCE STRATEGIES FOR HEAT-EXCHANGERS SUBJECT TO FOULING

Fouling in heat exchangers is an unavoidable by-product of the hear tr ansfer process. The decision regarding periodic maintenance (cleaning) of the exchangers subject to fouling is generally based on thermal an d economic behavior of the process. In this paper, a reliability-based maintenance strategy is discussed by incorporating the risk and scatt er parameters of the linear random fouling growth model. In addition, the dimensionless cost-objective function is formulated by considering various cost elements for a heat exchanger used in a crude oil prehea t train. The variation in the dimensionless cost Gamma with reduced ti me t(p)/(t(p) + t(down)) is presented for different values of unit cos t parameters gamma(1), gamma(2), and gamma(3) representing additional fuel cost, antifoulant cost, and miscellaneous costs, respectively. Fu rthermore, the optimal cleaning cycle of the heat exchanger recently i nvestigated by Casado (1990) is demonstrated to be a special case of t he results presented in the paper.