Application of RBM strategy in texaco coal gasification system

Risk-based maintenance (RBM) approach is helpful to develop a cost-effective maintenance plan to ensure benefit and safety with low maintenance cost. However, most maintenance is imperfect in process industry. The imperfect effect has not been considered in the maintenance planning step in the previous works on RBM strategy. As a result, they could hardly fit the reality. An improved RBM approach which integrates the Proportional Age Reduction (PAR) model was proposed in this work. The parameters of failure distribution and improvement factor were estimated by the Max Likelihood Estimation (MLE) approach. The economics risk of every subsystem was estimated and compared to the risk criterion. The best intervals of imperfect periodic preventive maintenance of key equipments were scheduled to keep the subsystem risk below the risk criterion. A case study of Texaco coal gasification system in a synthetic ammonia plant was presented as well. The result shows the imperfect maintenance effect leads to the reduction of the length of periodic preventive maintenance interval in order to satisfy the risk criterion.