{"id":201,"date":"2011-03-08T06:57:38","date_gmt":"2011-03-08T11:57:38","guid":{"rendered":"http:\/\/www.livingreliability.com\/en\/?p=201"},"modified":"2025-11-06T06:03:34","modified_gmt":"2025-11-06T11:03:34","slug":"pm","status":"publish","type":"post","link":"https:\/\/www.livingreliability.com\/en\/posts\/pm\/","title":{"rendered":"What is PM?"},"content":{"rendered":"

PM is a general term that encompasses all forms of pro-active maintenance including:<\/em><\/p>\n

    \n
  1. scheduled overhaul<\/em><\/li>\n
  2. scheduled inspections (CBM)<\/em><\/li>\n<\/ol>\n

    CBM is the prominent form of maintenance today. Although all scheduled activities are called “PM” (for example, in the CMMS or EAM), they are predominantly CBM activities (inspections) performed, often, at the same time as scheduled service<\/a> and minor adjustments. It is important to recognize that these inspection activities are indeed “CBM” in that they often provide recorded observations which may contain \u00a0predictive “intelligence”. (See Unconventional CBM Variables<\/a>.)<\/p>\n

    Even a repair (misleadingly labelled “corrective maintenance” in the CMMS) work order, following a failure often\u00a0turns out to be mostly preventive (PM). The failed <\/em>part is indeed replaced but the opportunity is taken also<\/em> to inspect (a kind of unscheduled\u00a0CBM activity) other parts of the system\/component. Some of them will be renewed preventively (suspensions) even though they may not yet have failed. These unplanned suspensions and failures, if recorded, constitute an opportunistic source of \u00a0valuable data for RA.<\/p>\n

    What is PM? It is simply “maintenance”. That is to say, all maintenance activities are preventive. The term “corrective maintenance” has been used in\u00a0CMMS software to mean a “repair” following a failure. Rather than “corrective maintenance” it is better to call this activity\u00a0simply “repair”. The reasoning is that maintenance in general (even preventive<\/em> maintenance) applies “corrective” (i.e. restorative) action. Why is such pedantry necessary in our routine speech? We should\u00a0use precise language in order to avoid biased (reliability) analysis. “Repair” should imply, unambiguously, that something has failed or potentially failed. When we use the word “Corrective” it could mean that an unfailed<\/em> item was\u00a0renewed or replaced. That item may have been far from an\u00a0unfailed condition. Extraction\u00a0of a sample of work orders based on the failure code “corrective” would therefore yield a mixture of failed and unfailed\u00a0instances of the failure mode of concern. Analysis of that sample could generate an erroneous conclusion and decision policy[1<\/a>]<\/sup>. \u00a0A more precise “analytic” word to use, for the renewal\u00a0an unfailed item, is “suspended”.<\/p>\n\n

      \n\t
    1. [1]<\/sup><\/strong>For the consequences on CBM performance of mislabeling suspensions as failures see http:\/\/www.livingreliability.com\/en\/posts\/defeating-cbm\/<\/a>↩<\/a><\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"

      PM is a general term that encompasses all forms of pro-active maintenance including: scheduled overhaul scheduled inspections (CBM) CBM is the prominent form of maintenance today. Although all scheduled activities are called “PM” (for example, in the CMMS or EAM), they are predominantly CBM activities (inspections) performed, often, at the same time as scheduled service […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,89],"tags":[55],"class_list":["post-201","post","type-post","status-publish","format-standard","hentry","category-rcm","category-theory-and-definitions","tag-terminology"],"_links":{"self":[{"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/posts\/201","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/comments?post=201"}],"version-history":[{"count":1,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/posts\/201\/revisions"}],"predecessor-version":[{"id":7669,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/posts\/201\/revisions\/7669"}],"wp:attachment":[{"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/media?parent=201"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/categories?post=201"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.livingreliability.com\/en\/wp-json\/wp\/v2\/tags?post=201"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}