Reliability-based maintenance strategies for heat exchangers subject to fouling

Fouling in heat exchangers is an unavoidable by-product of the hear transfer process. The decision regarding periodic maintenance (cleaning) of the exchangers subject to fouling is generally based on thermal and economic behavior of the process. In this paper, a reliability-based maintenance strategy is discussed by incorporating the risk and scatter 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 preheat train. The variation in the dimensionless cost Gamma with reduced time t(p)/(t(p) + t(down)) is presented for different values of unit cost parameters gamma(1), gamma(2), and gamma(3) representing additional fuel cost, antifoulant cost, and miscellaneous costs, respectively. Furthermore, the optimal cleaning cycle of the heat exchanger recently investigated by Casado (1990) is demonstrated to be a special case of the results presented in the paper.