Maintenance, repair and operations
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Maintenance, repair and operations  (MRO) involves fixing any sort of mechanical, plumbing, or electrical device should it become out of order or broken (known as repair, unscheduled, casualty or corrective maintenance). In the aircraft maintenance market sector, maintenance, repair and overhaul (MRO) services also include inspection, rebuilding, alteration and the supply of spare parts, accessories, raw materials, adhesives, sealants, coatings and consumables for aircraft manufacturing and MRO.
In all sectors, effective MRO involves performing routine actions which keep devices, equipment, machinery, building infrastructure and supporting utilities in working order (known as scheduled maintenance) and prevent trouble from arising (preventive maintenance).
The marine transportation, offshore structures, industrial plant/equipment and commercial facilities market sectors depend on scheduled or preventive paint maintenance programmes to maintain and restore coatings applied to steel, and also concrete and masonry assets in environments subject to attack from erosion, corrosion and environmental pollution.
MRO can be categorised by whether the product remains the property of the customer (i.e. a service is being offered), or whether the product is bought by the reprocessing organisation and sold to any customer wishing to make the purchase (Guadette, 2002). In the former case it may be a backshop operation within a larger organization or smaller operation.
The former of these represents a closed loop supply chain and usually has the scope of maintenance, repair, or overhaul. The latter of the categorisations is an open loop supply chain and is typified by refurbishment and remanufacture. The main characteristic of the closed loop system is that the demand for a product is matched with the supply of a used product. Neglecting asset write-offs and exceptional activities the total population of the product between the customer and the service provider remains constant.
- Any activity – such as tests, measurements, replacements, adjustments, and repairs — intended to retain or restore a functional unit in or to a specified state in which the unit can perform its required functions.
- For material – all action taken to retain material in a serviceable condition or to restore it to serviceability. It includes inspection, testing, servicing, classification as to serviceability, repair, rebuilding, and reclamation.
- For material – all supply and repair action taken to keep a force in condition to carry out its mission.
- For material – the routine recurring work required to keep a facility (plant, building, structure, ground facility, utility system, or other real property) in such condition that it may be continuously used, at its original or designed capacity and efficiency for its intended purpose.
Manufacturers and industrial-supply companies often refer to MRO as opposed to original equipment manufacturer (OEM). OEM includes any activity related to the direct manufacture of goods, where MRO refers to any maintenance, repair or overhaul activity to keep a manufacturing plant or facility running. Maintenance is strictly connected to the stage of ideation, in which the concept of maintainability must be included. In this scenario, maintainability is considered as the ability of an item, under stated conditions of use, to be retained in or restored to a state in which it can perform its required functions, using prescribed procedures and resources. Overhaul extends to the concept of improving performance over and above original design specification.
Generally speaking, there are two types of maintenance in use:
- Preventive or scheduled maintenance, where equipment or facilities are inspected, maintained and protected before break down or other problems occur.
- Corrective maintenance where equipment is repaired or replaced after wear, malfunction or break down.
Architectural conservation is another type of maintenance involving the preservation, rehabilitation, restoration or reconstruction of historical structures made from stone, brick, glass, metal, and wood with MRO materials which match the original constituent materials where possible, or with suitable polymer technologies.
Preventive maintenance is maintenance performed with the intent of avoiding failures, safety violations, unnecessary production costs and losses, and to conserve original materials of fabrication. The effectiveness of a preventive maintenance schedule depends on the RCM analysis which it was based on, and the ground rules used for cost efficacy.
Corrective maintenance of equipment after equipment break down or malfunction is often most expensive – not only can worn equipment damage other parts and cause multiple damage, but consequential repair/replacement costs and loss of revenues due to down time during overhaul can be significant. Rebuilding and resurfacing of equipment and infrastructure damaged by erosion and corrosion as part of corrective or preventive maintenance programmes involves conventional processes such as welding and metal flame-spraying, as well as engineered solutions with thermoset polymeric materials.
More recently, advances in sensing and computing technology have given rise to 'predictive maintenance'. This maintenance strategy uses sensors to monitor key parameters within a machine or system, and uses this data in conjunction with analysed historical trends to continuously evaluate the system health and predict a breakdown before it happens.  This strategy allows maintenance to be performed more efficiently, since more up-to-date data is obtained about how close the product is to failure. 
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- Auto maintenance
- Design for repair
- Do it yourself
- Logistics center
- MRO Software
- Product Lifecycle Management
- Reliability engineering
- Scheduled maintenance
- Total productive maintenance
- No to be confused with
- "Defense Logistics Agency". www.dla.mil. Retrieved 5 August 2016.
- United States Code of Federal Regulations Title 14, Part 43 - Maintenance, Preventive Maintenance, Rebuilding, and Alteration
- "All actions which have the objective of retaining or restoring an item in or to a state in which it can perform its required function. The actions include the combination of all technical and corresponding administrative, managerial, and supervision actions.""European Federation of National Maintenance Societies". www.efnms.org. Retrieved 5 August 2016.
- Marine Painting Manual Paperback (softcover reprint of original 1st ed. 1989 edition), A. M. Berendsen, Springer, 2013, ISBN 978-90-481-8244-2
- ISO 20340 - Performance requirements for protective paint systems for offshore and related structures
- ISO 12944 – Corrosion protection of steel structures by protective paint systems
- Federal Standard 1037C and from MIL-STD-188 and from the Department of Defense Dictionary of Military and Associated Terms
- North Atlantic Treaty Organization, Nato Standardization Agency AAP-6 - Glossary of terms and definitions, p 158.
- "Commercial Electrical Contractor and Domestic Electrician Leeds". 247 Electrical Services Leeds. Retrieved 2017-01-26.
- Materials for Conservation: Organic Consolidants, Adhesives and Coatings by C.V. Horie, Butterworth-Heinemann, 2nd ed., 2010, ISBN 978-0-75-066905-4
- "RCM Reliability Centered Maintenance Analysis". www.mtain.com. Retrieved 5 August 2016.
- Industrial Polymer Applications: Essential Chemistry and Technology, Royal Society of Chemistry, UK, 1st edition, 2016, ISBN 978-1782628149
- Garcia, Mari Cruz; Sanz-Bobi, Miguel A.; Del Pico, Javier (August 2006), "SIMAP: Intelligent System for Predictive Maintenance: Application to the health condition monitoring of a windturbine gearbox", Computers in Industry, 57 (6): 552–568, doi:10.1016/j.compind.2006.02.011
- Kaiser, Kevin A.; Gebraeel, Nagi Z. (12 May 2009), "Predictive Maintenance Management Using Sensor-Based Degradation Models", IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans, IEEE, 39 (4): 840–849, doi:10.1109/TSMCA.2009.2016429