Maintenance, industrial and production

Maintenance, industrial and production

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. 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. See Systems engineering

It has been estimated that up to 50% of all life-cycle equipment costs are attributable to operation and maintenance. Equipment buyers are now requiring better information on time to failure and repair. Suppliers have responded by including such things as failure mode and effects analysis, statistical information on failure times, cost-effective maintenance procedures, and better customer training with their products. Additionally, many companies emphasize design enhancements to improve maintainability, such as built-in diagnostics, greater standardization and modularity, and improved component accessibility. See Engineering design

Maintenance activities can be classified into several broad categories, depending on whether they respond to failures that have occurred or whether they attempt to prevent failures. The simplest and least sophisticated maintenance strategy still used by many companies is reactive maintenance or breakdown maintenance. Equipment is operated until it fails, then repaired or replaced. No effort is expended on activities that monitor the ongoing “health” of the equipment, and maintenance is focused on quick repairs that return the equipment to production as soon as possible. A slightly more sophisticated maintenance strategy is preventive maintenance, also known as calendar-based maintenance. This system involves detailed, planned maintenance activities on a periodic basis, usually monthly, quarterly, semiannually, or annually. As in reactive maintenance, preventive maintenance does not monitor information on equipment status. Rather, it attempts to avoid unplanned failures through planned repairs or replacements. Predictive maintenance is based on an ongoing (continuous or periodic) assessment of the actual operating condition of equipment. The equipment is monitored while in operation, and repair or replacement is scheduled only when measurements indicate that it is required. Predictive maintenance programs seek to control maintenance activities to avoid both unplanned equipment outages and unnecessary maintenance and overhauls.

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