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  • 1.  Regarding unplanned downtime calculation for system and subsystem

    Posted 07-08-2020 12:47 PM
    Hi Guys,

    I would like to get all of you valuable comments on the below query:

    Query:

    Lets assume my Plant as a system is having 10 sub-equipment.

    If a failure of a total plant (for e.g. Power Failure) will be an unplanned downtime for my Plant with some Corrective Maintenance Downtime.

    So my question is when I consider my sub-equipment for availability calculation (individual equipment wise calculation) should I consider the same failure's downtime as an unplanned downtime/corrective maintenance downtime for the equipment as well.

    Regards



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    Deepak

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  • 2.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-09-2020 08:49 AM
    Hi Deepak,

    I am not CMRP but am working towards it however I will give my opinion on the matter.

    I believe you want to know if you had a whole plant loss of power would you include this unavailability in your sub-equipment availability (asset) calculations?

    I would not include this. Maintenance and reliability best practices state availability is the probability that an asset is capable of performing its intended function.... It later states that availability is a function of reliability and maintainability of the asset. It is for this reason I personally would only consider asset availability not the whole plant failure in your calculations.

    Another way to think is that availability is calculated by (MTBF)/(MTBF/MTTR). If MTBF is the operating time over number of failures then it would not include the whole plant loss of power as it could not be operated. 

    You also would be looking to address the availability of an asset with which the fault lies elsewhere hence giving false work to address.

    Final point is that if you include total power failure on every single asset then in turn it becomes irrelevant because you will reduce every single assets availability percentage and not achieve anything than a lower availability and OEE etc..

    In short; my own personal opinion is to not include it for availability metrics but do consider it other tools i.e. FMEA, RCA, etc. again I hope someone else will share their thoughts as I am not actually CMRP and would like to hear feedback and thoughts.

    Kind regards

    Keiron.

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    Keiron Arndell
    Cheshire
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    Original Message


  • 3.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-11-2020 06:41 AM
    Dear Keiron,

    I also had the same thought. The impact of total plant failure shall not be considered in the asset availability calculations. 
    As the definition of Availability in ISO 14224 clearly states that "ability to be in a state to perform as required. If we think requirement of the assest is in question only when plant is in running state. This is another justification i felt on the matter.
    But what you had mentioned with equation really supports my concern.
    Thanks a lot, and all the best for your CMRP preparations.

    Regards
    Deepak


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    Deepak Dili Vasumathi RELIABILITY ENGINEER
    Reliability Engineer
    Kuwait Oil Company
    ERANAKULAM
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    Original Message


  • 4.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-12-2020 04:54 AM
    Deepak,
    Sub system will not be taken in to account.
    Regards,
    Mugundan

    ---------------------------------
    Mugundan Devanathan
    dmugundan@gmail.com
    United Arab Emirates
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    Original Message


  • 5.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-12-2020 12:47 PM
    I Would not include it if you are calculating the reliability of a specific equipment, or sub system.  However, if you calculate individual equipment/ system reliability ONLY, it shows a distorted reality, therefore I believe you always have to calculate the TOTAL reliability as well, otherwise you will miss improvement opportunities.  TOTAL reliability should include all losses (8760 hrs, full quality and speed), most  argue to not include market downtime which may make sense since no one can predict it.  The quest to achieve improved TOTAL reliability must be a partnership between operations, maintenance and engineering (also materials if they don't report to mtce.)

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    Torbjorn Idhammar
    President & CEO
    IDCON, Inc.
    http://www.idcon.com
    Raleigh NC
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    Original Message


  • 6.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-18-2020 02:07 AM
    Dear Torbjorn,

    I agree with the concept of Total reliability, but given this scenario any improvements on the equipment wont have any impact on the failure happened as this is concerned with the total plant which is outside the boundary of the equipment.  This duration is like a delay time for the equipment. 
    But, while analyzing the plant reliability this scenario perfectly fits in and any opportunity for improvement can be studied.

    Regards
    Deepak

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    Deepak Dili Vasumathi RELIABILITY ENGINEER
    Reliability Engineer
    Kuwait Oil Company
    ERANAKULAM
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    Original Message


  • 7.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-17-2020 11:55 AM
    In my experience, Common failures like Power Failure affects the Plant/Unit and is considered at the Plant/Unit level Calculations. In my view, that would not be considered at Individual Equipment level. 

    You've also mentioned about some Corrective Maintenance Downtime, that I suppose is on Equipment. In case an Equipment is damaged in/associated to the common event (can think of rotary equipment failure during coast down or choke up of static equipment) and requires Corrective Maintenance, you need to think.

    I'd tend to include that individual downtime (Corrective Maintenance Event) at the Equipment level (in my view, they'd be exceptions and also likely in major equipment only)...    

    Hope this helps...
    Regards

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    Sundar Naranammalpuram P.
    Navi Mumbai
    Maharashtra
    India
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    Original Message


  • 8.  RE: Regarding unplanned downtime calculation for system and subsystem

    Posted 07-18-2020 02:11 AM
    Dear Sundar,

    Actually Corrective Maintenance is done on the substation which is external to the equipment boundary. If any failure had found on the equipment due to this equipment, then I strongly agree with you that it should be included in the equipment reliability calculations. 
    But if equipment is unaffected, then I think adding this downtime due to common event on equipment can result in erratic availability and reliability numbers.

    Regards
    Deepak

    ------------------------------
    Deepak Dili Vasumathi RELIABILITY ENGINEER
    Reliability Engineer
    Kuwait Oil Company
    ERANAKULAM
    ------------------------------

    Original Message