Spare parts inventories assist maintenance staff to keep equipment in operating condition. Thus the inventory level of spares has a direct bearing on machine availability, a factor that is increasingly important in capital-intensive industries. This paper presents a risk based approach for spare parts inventory optimization. At the outset, the paper highlights the unique features of maintenance inventories, such as spare parts inventories, compared to other inventories such as work-in-progress or finished product inventories. After a brief mention of the principles on which many of the current inventory management models are based and their limitations, the paper presents a risk-based methodology to spares inventory management. ‘Risk’ in the current context is the risk in monetary terms that arises when a component (spare) is not available on demand. It is the expected value of loss, i.e., the product of the likelihood of unavailability of the spare from the inventory and an estimate of the consequence(s) of that unavailability. Given a budgetary constraint and the risk profile of a number of spares, the model gives an optimal inventory of spares. By basing the inventory on the risk profile of spares, the model includes factors that are not normally considered in various other models. The ultimate aim of the methodology is to have an optimal level of spares inventory such that machine availability, to the extent it is dependent on the level of spares inventory, is maximized subject to constraints. The methodology is expected to benefit both, operational and financial managers.
A Proactive Event-driven Decision Model for Joint Equipment Predictive Maintenance and Spare Parts Inventory Optimization
