The actions taken to preserve the operation of devices, particularly of electromechanical equipment, to ensure that the devices can perform their intended functions when needed. The field of maintenance science is an interdisciplinary research area that employs techniques from physics, engineering, and decision analysis to develop methods for the safe and reliable performance of devices and equipment. Traditionally, the focus of maintenance has been on equipment availability—the ratio of operating time less downtime to total available time. Modern maintenance practices focus on increasing equipment effectiveness, that is, making sure that the equipment is both available and capable of producing superior-quality products.