Editing Maintenance (section)

===Preventive maintenance===
[[File:C-130J Hercules cleaning.jpg|thumb|[[Lockheed Martin C-130J Super Hercules|C-130J Hercules]] preventive cleaning at Keesler Air Force Base, Mississippi after a period of operation over the [[Gulf of Mexico]] (salt and moisture which lead to active corrosion require regular cleaning)]]
'''Preventive maintenance''' ('''PM''') is "a routine for periodically inspecting" with the goal of "noticing small problems and fixing them before major ones develop."<ref name="PMckList.NYT">{{cite news  |newspaper=[[The New York Times]]
   |url=https://www.nytimes.com/1985/02/17/realestate/preventive-maintenance-a-checklist.html
   |title=Preventive Maintenance: A Checklist
   |author=Micharl Decourcy Hinds |date=February 17, 1985}}</ref> Ideally, "nothing breaks down."<ref name="PM.PC-NYT">{{cite web  
 |website=[[The New York Times]]
 |url=https://www.nytimes.com/1984/08/14/science/personal-computers-preventive-maintenance-for-an-aging-computer.html
   |title=Personal computers preventive maintenance for an aging computer
   |author=Erik Sandberg-Diment |date=August 14, 1984}}</ref>

The main goal behind PM is for the equipment to make it from one planned service to the next planned service without any failures caused by fatigue, extreme fluctuation in temperature(such as heat waves<ref>{{Cite web |title=6 Tips to Keep Your Machine Cool in Summer {{!}} Al Marwan |url=https://almarwan.com/news/1126/Al-Marwan-Blog-8-6-Quick-Tips-to-Keep-Your-Machine-Cool-this-Summer |access-date=2024-06-20 |website=Al Marwan Heavy Machinery |language=en}}</ref>) during seasonal changes, neglect, or normal wear (preventable items), which Planned Maintenance and Condition Based Maintenance help to achieve by replacing worn components before they actually fail. Maintenance activities include partial or complete overhauls at specified periods, oil changes, lubrication, minor adjustments, and so on. In addition, workers can record equipment deterioration so they know to replace or repair worn parts before they cause system failure.

The New York Times gave an example of "machinery that is not lubricated on schedule" that functions "until a bearing burns out." Preventive maintenance contracts are generally a fixed cost, whereas improper maintenance introduces a variable cost: replacement of major equipment.<ref name="PMckList.NYT" />

'''Main objective of PM are:'''

# Enhance capital equipment productive life.
# Reduce critical equipment breakdown.
# Minimize production loss due to equipment failures.

'''Preventive maintenance''' or '''preventative<ref name="TaTive.NYT">{{cite news  |newspaper=[[The New York Times]]
   |url=https://www.nytimes.com/2010/04/18/magazine/18FOB-onlanguage-t.html
   |title=Wellness
   |quote=Complaints about preventative go back to the late 18th century ... ("Oxford English Dictionary dates preventive to 1626 and preventative to 1655) ..preventive has won"
   |date=April 18, 2010
   |author=Ben Zimmer}}</ref> maintenance''' ('''PM''') has the following meanings:

* The care and servicing by personnel for the purpose of maintaining equipment in satisfactory operating condition by providing for systematic inspection, [[Fault detection and isolation|detection]], and correction of incipient failures either before they occur or before they develop into major defects.
* The work carried out on equipment in order to avoid its breakdown or malfunction. It is a regular and routine action taken on equipment in order to prevent its breakdown.<ref>{{cite book
   |author1=O. A. Bamiro  |author2=D. Nzediegwu  |author3=K. A. Oladejo  |author4=A. Rahaman  |author5=A. Adebayo
   |date=2011  |title=Mastery of Technology for Junior School Certificate Examination
   |location=Ibadan  |publisher=Evans Brothers (Nigeria Publishers) Limited}}</ref>
* Maintenance, including tests, measurements, adjustments, parts replacement, and cleaning, performed specifically to prevent faults from occurring.

Other terms and abbreviations related to PM are:

* scheduled maintenance<ref name="Downtime.mil">{{cite web
   |title=CPOL: System Maintenance and Downtime Announcements
   |url=http://cpol.army.mil/announcements
   |archive-url=https://web.archive.org/web/20081002072445/http://cpol.army.mil/announcements/
   |url-status=dead
   |archive-date=October 2, 2008
   |access-date=March 21, 2019
   |quote=... out of service from 6:00–7:00am Eastern for regularly scheduled maintenance.}}</ref>
* planned maintenance,<ref name="Upgrade.gov">{{cite web
   |title=Dodge City Radar Planned Maintenance  |website=weather.gov (National Weather Service)
   |url=https://www.weather.gov/ddc/DodgeCityRadarUpgrade
   |quote=... will be down for approximately five days}}</ref> which may include scheduled downtime for equipment replacement
* planned preventive maintenance (PPM) is another name for PM<ref name="WhatPPM" />
*{{Visible anchor|breakdown maintenance}}:<ref name="WhatPPM">{{cite web
  |title=The development of a cost benefit analysis method for monitoring the condition of batch
  |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/p010185.pdf |archive-url=https://web.archive.org/web/20190322072113/https://apps.dtic.mil/dtic/tr/fulltext/u2/p010185.pdf |url-status=live |archive-date=March 22, 2019 }}</ref> fixing things only when they break. This is also known as "a reactive maintenance strategy"<ref>{{cite web
   |url=https://www.bidwells.co.uk/insights-and-research/blog-what-is-ppm-maintenance
   |title=What is PPM Maintenance?}}</ref> and may involve "consequential damage."<ref>e.g. from leaks that could have been prevented</ref>

====Planned maintenance====
{{redirect|Routine maintenance|the album by Aaron West and the Roaring Twenties|Routine Maintenance (album)}}
Planned preventive maintenance (PPM), more commonly referred to as simply '''planned maintenance''' ('''PM''') or '''scheduled maintenance''', is any variety of scheduled [[Corrective maintenance|maintenance]] to an object or item of equipment. Specifically, planned maintenance is a scheduled service visit carried out by a competent and suitable agent, to ensure that an item of equipment is operating correctly and to therefore avoid any unscheduled breakdown and downtime.<ref>{{cite book | last1 = Wood | first1 = Brian | title = Building care | publisher = Wiley-Blackwell | year = 2003 | url = https://books.google.com/books?id=xi6e4KhRoPwC | access-date = 2011-04-22 | isbn = 978-0-632-06049-8}}</ref>

The key factor as to when and why this work is being done is timing, and involves a service, resource or facility being unavailable.<ref name="Downtime.mil" /><ref name="Upgrade.gov" /> By contrast, condition-based maintenance is not directly based on equipment age.

Planned maintenance is preplanned, and can be date-based, based on equipment running hours, or on distance travelled.

Parts that have scheduled maintenance at fixed intervals, usually due to wearout or a fixed [[shelf life]], are sometimes known as time-change interval, or TCI items.

==== Predictive maintenance ====
{{main|Predictive maintenance}}
'''Predictive maintenance''' techniques are designed to help determine the condition of in-service equipment in order to estimate when maintenance should be performed. This approach promises [[Cost saving|cost savings]] over routine or time-based [[preventive maintenance]], because tasks are performed only when warranted. Thus, it is regarded as condition-based maintenance carried out as suggested by estimations of the degradation state of an item. The main promise of predictive maintenance is to allow convenient scheduling of [[corrective maintenance]], and to prevent unexpected equipment failures.<ref name="DPenn.PdM" /> 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.<ref name="simap">{{Citation| last1 = Garcia | first1 = Mari Cruz| last2 = Sanz-Bobi | first2 = Miguel A.| last3 = Del Pico | first3 = Javier| title = SIMAP: Intelligent System for Predictive Maintenance: Application to the health condition monitoring of a windturbine gearbox| journal = Computers in Industry| volume = 57| issue = 6| pages = 552–568| date = August 2006| doi = 10.1016/j.compind.2006.02.011 }}</ref> 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.<ref>{{Citation| last1 = Kaiser | first1 = Kevin A.| last2 = Gebraeel | first2 = Nagi Z.| title = Predictive Maintenance Management Using Sensor-Based Degradation Models| journal =  IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans| volume = 39| issue = 4| pages = 840–849| date = 12 May 2009| doi = 10.1109/TSMCA.2009.2016429 | s2cid = 5975976| hdl = 1853/56106| hdl-access = free}}</ref>

'''Predictive replacement''' is the replacement of an item that is still functioning properly.<ref name="BatRep.NYT">{{cite news 
   |newspaper=[[The New York Times]]
   |url=https://www.nytimes.com/aponline/2019/03/22/science/ap-us-sci-space-station.html
   |title=Spacewalking Astronauts Swap Out Space Station's Batteries
   |date=March 22, 2019  |access-date=March 22, 2019}}</ref> Usually it is a tax-benefit based {{citation needed|date=March 2019}} replacement policy whereby expensive equipment or batches of individually inexpensive supply items are removed  and donated on a predicted/fixed [[shelf life]] schedule. These items are given to tax-exempt institutions.<ref>such as universities and local schools, which write government-acceptable receipts</ref>{{citation needed|date=March 2019}}

==== Condition-based maintenance ====
'''Condition-based maintenance''' ('''CBM'''), shortly described, is maintenance [[Maintenance, repair and operations|when need arises]]. Albeit chronologically much older, It is considered one section or practice inside the broader and newer predictive maintenance field, where new AI technologies and connectivity abilities are put to action and where the acronym CBM is more often used to describe 'condition Based Monitoring' rather than the maintenance itself. CBM maintenance is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating.

This concept is applicable to mission-critical systems that incorporate [[active redundancy]] and [[fault reporting]]. It is also applicable to non-mission critical systems that lack redundancy and fault reporting.

Condition-based maintenance was introduced to try to maintain the correct equipment at the right time. CBM is based on using real-time data to prioritize and optimize maintenance resources. Observing the state of the system is known as [[condition monitoring]]. Such a system will determine the equipment's health, and act only when maintenance is actually necessary. Developments in recent years have allowed extensive instrumentation of equipment, and together with better tools for analyzing condition data, the maintenance personnel of today is more than ever able to decide what is the right time to perform maintenance on some piece of equipment. Ideally, condition-based maintenance will allow the maintenance personnel to do only the right things, minimizing spare parts cost, system downtime and time spent on maintenance.

=====Challenges=====
Despite its usefulness of equipment, there are several challenges to the use of CBM. First and most important of all, the initial cost of CBM can be high. It requires improved instrumentation of the equipment. Often the cost of sufficient instruments can be quite large, especially on equipment that is already installed.  Wireless systems have reduced the initial cost.  Therefore, it is important for the installer to decide the importance of the investment before adding CBM to all equipment. A result of this cost is that the first generation of CBM in the [[Petroleum industry|oil]] and gas industry has only focused on vibration in heavy rotating equipment.

Secondly, introducing CBM will invoke a major change in how maintenance is performed, and potentially to the whole maintenance organization in a company. Organizational changes are in general difficult.

Also, the technical side of it is not always as simple. Even if some types of equipment can easily be observed by measuring simple values such as vibration (displacement, velocity or acceleration), temperature or pressure, it is not trivial to turn this measured data into actionable knowledge about the health of the equipment.

=====Value potential=====
As systems get more costly, and instrumentation and information systems tend to become cheaper and more reliable, CBM becomes an important tool for running a plant or factory in an optimal manner. Better operations will lead to lower production cost and lower use of resources. And lower use of resources may be one of the most important differentiators in a future where environmental issues become more important by the day.

Another scenario where value can be created is by monitoring the health of a car motor. Rather than changing parts at predefined intervals, the car itself can tell you when something needs to be changed based on cheap and simple instrumentation.

It is Department of Defense policy that condition-based maintenance (CBM) be ''"implemented to improve maintenance agility and responsiveness, increase operational availability, and reduce life cycle total ownership costs".<ref>[https://web.archive.org/web/20140701070946/http://www.acq.osd.mil/log/mpp/cbm%2B/cbm_policy_memorandum.pdf CBM Policy Memorandum].</ref>''

=====Advantages and disadvantages=====
CBM has some advantages over planned maintenance:

* Improved system reliability
* Decreased maintenance costs
* Decreased number of maintenance operations causes a reduction of [[human error]] influences

Its disadvantages are:

* High installation costs, for minor equipment items often more than the value of the equipment
* Unpredictable maintenance periods cause costs to be divided unequally.
* Increased number of parts (the CBM installation itself) that need maintenance and checking.

Today, due to its costs, CBM is not used for less important parts of machinery despite obvious advantages. However it can be found everywhere where increased safety is required, and in future will be applied even more widely.<ref>{{cite journal | title=An enhanced diagnostic scheme for bearing condition monitoring | journal=IEEE Transactions on Instrumentation and Measurement| year=2010 | last1=Liu |author2=Wang, Golnaraghi | volume=59 | issue=2 | pages=309–321 | first1=Jie | doi=10.1109/tim.2009.2023814| bibcode=2010ITIM...59..309L| s2cid=1892843}}</ref><ref>{{cite journal | title=A review on machinery diagnostics and prognostics implementing condition-based maintenance| journal=Mechanical Systems and Signal Processing| year=2006 | last1=Jardine |author2=Lin, Banjevic | volume=20 | issue=7 | pages=1483–1510 | first1=A.K.S. | doi=10.1016/j.ymssp.2005.09.012| bibcode=2006MSSP...20.1483J}}</ref>