Maintenance Policy Choice Depending on the Breakdown Character

by • 25.05.2014 • Maintenance management, Theory based on practical experienceComments (0)1727

This post is also available in: Russian

     Before reading we recommend you to become acquainted with publication: Maintenance Policies

     Please, imagine the following situation: The production line start-up was completed. A responsible project manager has got from you the last signature on the Acceptance and Handover report, confirming the successful start-up completion. Let’s assume that you were so lucky to get all operating documents from him before departure. So, he wished you “Good luck” and left. At the same time, after the manager departure all contractors, adjusters and other companies, who has been installing and setting-up all this facilities and trying to hide all weak points, disappeared within very short period.

     What should be done first to make your equipment maintenance and repair system working like a dream? What would you do first?

     If you have found time to think about this issue – it is already good. And as soon as you have thought about it the equipment starts failing. It doesn’t matter that the most part of this breakdowns – are the Design bugs. It doesn’t matter that another part is connected with operator mistakes. Absolutely none takes care that it is impossible understand the origin of to the third part of breakdowns at all. But law is the law: The Production Line must run 24 hours and 7 days a week.

     What will you discover, when in the interim of the next in turn all-hands job (or during it) you find time to look through the “Procedures and Regulations” for FTM performance?

     Example: Monthly inspection of tightening the fastener on the cyclone lid by means of torque indicating wrench is required in accordance with the “Procedures and Regulations”. That very cyclone, where you have already welded a reinforced metal sheet onto a worn out wall.

     Another example: Bearings lubrication on the roller table should be carried out 2 times a month. But while attempting to find a pressure lubricator, you are making sure that it is not available at 220 bearings. And three of these 220 bearings have already failed. Moreover, a control card of your maintenance free frequency converter which cost covers a fourth part of your Maintenance budget for spare parts tools and accessories has suddenly burnt out.

     I can give you an infinite variety of such examples. Any plant engineer been involved into industrial enterprise start-up process from the beginning has faced with similar situations.

     However the question we asked in the beginning of the given article is still left without answer. A lot of chaotic thoughts come into my mind: «Shall we choose the maintenance policy first? Shall we use a Proactive approach? What recommendations were given by the equipment manufacture? 5S? TPM? ».

     Well… Each engineer has its own experience connected with the maintenance and repair process beginning. Generally, more skilled plant engineers have the equipment structure already prepared in form of some informative data base by the moment of start-up. It doesn’t matter what software tool is used for this purpose, either the state-of-the-art automated control system for Maintenance, or Excel file. This data base is necessary in the function of Maintenance processes development “chronicles” or the Production Enterprise “clinical history”. It reflects all data on failures and breakdowns, Maintenance performance results and etc.

     What is the purpose of this data base? There are a lot of reasons for its creation. One of them is need in analysis performance and DD and PD development. Unfortunately we have not always enough time for “drawing Japanese Ishikava’s fish” or “pulling out” answers on 5 “Why?” questions from breakdown mechanic. In this case we recommend you to use standard tool for choosing the Maintenance policy depending on the equipment breakdown character.

     Thus, without going into particulars, let’s divide all possible breakdowns into three types:

  1. Breakdowns preceded by failure. The failure developing period is sufficiently long, so as to have time for repair works planning before scheduled equipment outage for preventive maintenance and to avoid emergency shutdown. Failure is detected either by instrumental way, or by simple inspection;

     Example: a leakage occurred in the stuffing-box seal of one pump. Soon the leakage intensifies and in one moment the pump is unable to maintain the required pressure. It results in the pump breakdown.

       2.     Breakdowns without failure developing period (the equipment sudden breakdown). In this case it does not seem possible to identify the equipment state deterioration before the breakdown. A traceable failure developing period is absent.

Example: the lamp on the control board burnt out. It was replaced with another one. Then it burnt out again in approximately four months. It was replaced again. After replacement the lamp burnt out in three days. It was replaced one more time. For this once its life lasted one month and etc. Thus you see that it is impossible to trace the failure periodicity.

       3.     Breakdowns with traceable failure developing period.

Example: Te same lamp, but it burns out with definite periodicity, approximately every 60 thousands switching on-off or each 3 months.

In principle that’s it. Now, let’s look at the diagram and discuss it.

  • I Type failure. – It is recommended to use the maintenance policy called Condition Based Maintenance (CBM) or “Maintenance for technical state reasons”, which comprises the following: creation of inspection check-lists, planning the equipment visual inspections and diagnostics with definite periodicity. Repair is planned in response to failure detection.
  • II Type failure. – It is recommended to use the maintenance policy called Breakdown Maintenance (BDM) or “Maintenance in response to actual breakdown”. Specifically it is planned and scheduled emergency repair, which includes emphasis on losses reduction from this type of failures, units preparation for modular repair, personnel training, and etc.
  • III Type failure. – It is definitely the Fixed Time Maintenance (FTM) (Preventive job on planned lamp replacement). In this case we just establish the regulations both for age repair and for planned (calendar) repair. Planed unit replacement is carried out upon the event occurrence independently on the technical state.

The approach described above is rather useful when the breakdown origin is difficult to detect or failures and breakdowns quantity exceeds the resource limits available for their detailed analysis and DD and PD development.

 The author of the resource Fedor Belov

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