Reducing risks in spare parts service contracts with a long downtime constraint

This article investigates spare parts service contracts for capital goods. We consider a single-item, single-location inventory system that serves one customer with multiple machines. During the contract execution phase, the true demand rate is observed. It can differ from the estimated demand rate because of two factors: increased demand variation in finite horizon settings and a shift in the mean utilization of the machines by the user during the contract. When the true demand rate is higher than the estimated demand rate, the Original Equipment Manufacturer (OEM) is faced with higher-than-expected costs for the execution of the contract, and the asset user is generally faced with a higher number of extreme long downtime events. Therefore, we introduce the flexible-time contract, which ends after a predetermined number of demands. Using a Markov decision process, we prove that a state-dependent base stock policy is optimal under a flexible-time contract. Using simulation, we compare the flexible-time contract with the standard fixed-time contract. Our results show that the flexible-time contract reduces the costs for the OEM by up to 35% and prevents not meeting the agreed-on service level. We obtain similar results in a multi-item setting.

本文探讨了资本商品的备件服务合同。我们考虑了一个单件、单地点的库存系统，为拥有多台机器的单个客户提供服务。在合同执行阶段，观察到实际需求率。由于两个因素，实际需求率可能与估计需求率不同：有限范围设定中的需求波动增加以及用户在合同期间对机器平均利用率的调整。当实际需求率高于估计需求率时，原始设备制造商（OEM）面临超出预期的合同执行成本，而资产使用者通常面临更多极端长时间停机事件。因此，我们引入了弹性时间合同，该合同在达到预定的需求次数后结束。通过马尔可夫决策过程，我们证明在弹性时间合同下，状态依赖的基库存策略是最优的。通过仿真，我们比较了弹性时间合同与标准固定时间合同。我们的结果表明，弹性时间合同将OEM的成本降低高达35%，并防止未达到约定的服务水平。在多物品设置中，我们获得了类似的结果。