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Really Esoteric Downtime/OEE Question

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  • October 31, 2019 at 5:06 pm #243252

    AlonzoMosley
    Participant

    Trying to build some discipline around calculating “Availability”.

    Using the formula

    Availability = Operating Time / Planned Production Time, where

    • Operating Time = Planned Production Time – Downtime Loss, and
    • Planned Production Time = Plant Operating Time – Planned Shutdown Times

    (in other words, Availability = (Plant Operating Time – Planned Shutdowns – Downtime Loss) / (Plant Operating Time – Planned Shutdowns)

    I have always learnt that “Planned Shutdown Time” includes scheduled, routine breaks. And that Downtime Loss includes anything that stops planned production.

    So here’s where I need a reality check:

    • My operations run 24 / 7. Operators stagger breaks, as their units continue to run. (There are planned shuts every few weeks in certain units, but…)
    • My maintenance team works 7AM-11AM and 12N-3:30PM. (11AM-12N is a plantwide scheduled maintenance lunch time)

    Because Maintenance is on break, but the asset is not on break, I would presume that does not count in my “Planned Shut Down” calculation – after all, if I pay double-time and pay a meal allowance, they can work during lunch. Ditto after hours – I can call someone in (in four-hour increments at double-time, but still).

    So my “Planned Production Time” is 24 hours. Full stop.

    If a machine breaks down at 10:45, Maintenance rushes to do the LOTO before lunch, and then after lunch has it up and running by 12:15… there are some who argue that’s only 30 minutes of Downtime Loss (because of the Planned Shut Down from 11A to 12N), and some who argue it’s 90 minutes of Downtime Loss because it’s lost production time…

    (See if you can guess if OEE has been weaponised to beat up on Maintenance!)

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    November 1, 2019 at 7:27 pm #243281

    Chris Seider
    ★ 20 Years ★
    Participant

    Planned shutdown times should ONLY include times where no one was employed to run the line.  Routine maintenance and operator maintenance are still losses.

     

    All calendar time should be included except for unscheduled run time for lack of orders or normal unscheduled time that isn’t manned.

     

    Your scenario would have 24 hours in the denominator for availability.

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    November 4, 2019 at 8:54 am #243325

    Rhb
    Participant

    Keep in mind that OEE is Overall EQUIPMENT Effectiveness.  So, don’t make it too complicated.  Any delays during a planned/manned production period that degrades throughput counts against availability.

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    November 4, 2019 at 10:27 am #243328

    Gary Ennis
    Participant

    Also, OEE is just a number to gauge where you are with your processes.  Following the logic Chris expressed it should be real and not manipulated to look good.  It is to help guide you as where you should be looking for issues to solve.

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    November 4, 2019 at 10:59 am #243329

    AlonzoMosley
    Participant

    That’s what I thought, Chris. Just wanted to confirm. There are some loud and pushy people trying to use OEE as a cudgel, and some louder and pushier people trying to avoid any and all accountability. Ain’t life grand!

    Part of why I’m rusty on this is, I do try to avoid using OEE because it can frequently be a political tool – when it should be, like you say, a gauge. Plus, if you’re not careful, it becomes rolled up averages of rolled up averages, and thus meaningless. (Here, for example, I only want to focus on Asset Availability, not necessarily the whole calculation.).

    Thanks for the replies.

     

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    November 4, 2019 at 11:52 am #243330

    Chris Seider
    ★ 20 Years ★
    Participant

    OEE is a great tool but not easy to “measure” if loss capturing isn’t credible.

    I’ve helped many clients improve 10% output on poorly performing lines by finding either 1) easy to tackle significant loss buckets or 2) just providing instant feedback (even if just hourly) of how production is occurring so management and supervision has a chance to react.

     

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