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Was that a failure or ‘just a repair’?

01.01.2014  |  Bloch, H. P.,  Hydrocarbon Processing Staff, 

Keywords: [Miantenamce] [MTBF] [MTBR] [reliability] [bearings lubrication oil] [seals] [downtime]

Purists among reliability professionals are sometimes concerned about the accuracy of the measurement of the mean-time-between-failure (MTBF) of an asset. There are many ways to conduct this failure frequency rate assessment. Fig. 1 represents a multi-site major refining company. This figure demonstrates that the corporate reliability engineers are making reasonably accurate affiliate-to-affiliate comparisons. However, some petrochemical and refining companies make a distinction between repairs and failures. As one engineer wrote, “I have a philosophical question around the classification of repairs vs. failures when tracking rotating equipment reliability. As I see it, there are basically two structures or philosophies: asset or component.”

  Fig. 1. Repair frequency and MTBF
  tracked by a major corporation with
  over 15,000 process pumps.

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Tom McGuinness

The purpose of all this is to maximize plant profitability. Profitability is determined by two factors, revenues and operating costs. MTBF and MTTR both need to be tracked at least at the "whole machine" level. RAM modeling then allows us to use this data to predict and optimize overall throughput of the plant. By tracking at the "whole machine" level, we can then identify and rank the bad actors in terms of relative impact on profitability. Tracking at the component level is important if we want to improve overall MTBF and MTTR of each whole machine. This could be done by assigning a code number for the root cause of each downing event.

Cristián Schmid

Very interesting and helpful information. Thanks!

Abdulrahman Alghamdi

Very helpful thank you Article

Jason Micas

The intent of tracking MTBR is so that you have some measure of weather or not you are improving. So long as you do it consistantly (and don't cheat the system) you will still see if you are improveing. Personally, I have always counted a repair if you have to do LOTO to do the work. This would imply that you have to take the pump out of service and it is not available to operate. The reason you want high reliability is so you can produce more product, have less operational distractions and safety. I have always prefered to fill seal reservoirs (Plan 53) with the pump off- I do not count this as a failure because with a pressurized refill cart I can fill it while it is running but sometimes it is easier to just turn the pump off- same goes for bearing oil changes.

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