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Thread: LOTO molded case breaker

  1. #21
    Join Date
    Apr 2009
    Location
    Williamsburg, VA
    Posts
    4,179
    Quote Originally Posted by cornbread View Post
    Looking for opinion on using a molded case breaker for a lockout? My question concerns an operator throwing a disconnect with a molded case breaker to shut off the machine to clear a jam. Typically if we are doing any electrical work we check to make sure the power has been removed, but since we are not doing any electrical work do we still need to check to make sure the breaker opened or can the operator try to start the machine and if it does not start they are safe to clear the jam? I'm old school and I would want the power checked before I stuck my hands in? How do other folks accomplish this? Looking forward the replies!
    The way we did (past tense) it was lock out the eqpt breaker, and try to start the equipment. If those were done and the eqpt didnt start, we were good to go. LO of any valves to do piping work was done hand in hand with electrical lockouts, if say a pump had to be pulled and rebuilt.

    Using interlocks to secure equipment was not allowed. For example, the ash bin screw was the last piece of equipment in the chain of the entire ash system, the 7-10 hearth furnace, the biosolids feed system, the centrifuges, and the feed pumps (WWTP dewatering system). You could not lock out the ash screw to work on any of the former 20 or so pieces of equipment and rely on the interlocks to keep that equipment from starting. An operator could shut down that ash bin screw to stop the whole system, but for maintenance purposes, it wasnt allowed.
    Electricians do it until it Hertz!

  2. #22
    Join Date
    Apr 2008
    Posts
    355
    Appreciate the replies... I see there are several ways to skin this cat. On new installations we are settling on using a disconnect / plug combo, the operators would throw the disconnect on the plug and then they can unplug the motor and lock it out.. visual verification that the motor has been disconnected. Note, the plug is interlocked so it can not be pulled unless the disconnect is in the off position.

  3. #23
    Join Date
    Jul 2006
    Location
    San Francisco, CA, USA
    Posts
    6,774
    It's really all about assessing the risks and establishing a procedure that everyone agrees on. In several places that I have worked, ALL LO/TO procedures that involved electrical power required that an electrician perform, and verify, the lock-out. It's a PITA though to be quite honest.

    This is one of those situations where the whole "safety relay" systems enforced in the rest of the world would play a part in making life easier, and safer. In order to attain a Safety Certification on any machine, there is a thorough vetting of the entire procedure after an assessment is performed by a licensed professional.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  4. #24
    Join Date
    Feb 2004
    Posts
    6

    Permanent LED Voltage Indicators

    "Typically if we are doing any electrical work we check to make sure the power has been removed, but since we are not doing any electrical work do we still need to check to make sure the breaker opened or can the operator try to start the machine and if it does not start they are safe to clear the jam?"

    How about permanently mounted led voltage indicators from Graceport on the outside of the panel? These are designed to validate zero voltage for LOTO without opening the panel.
    I have also installed some of these inside panels as a voltage reminder for Techs so they don’t accidentally leave a disconnect on when doing diagnostics.

  5. #25
    Join Date
    Apr 2008
    Posts
    355
    We looked at the Graceport LED's and opted away as we fear they will start to use them for electrical lock outs and I don't think the Graceport meets NFPA 70E of verify .. test .. verify? Perhaps I'm wrong, that would be an easy solution.

  6. #26
    Join Date
    Jun 2003
    Location
    Portland, ME
    Posts
    1,190
    IMO, Graceport indicators have no business being part of verifying absence of energy.

    They can be used as guidance, but because there is no way to verify functionality then they can't be relied on for life safety.

    The method I've always seen for mechanical lockout (assuming no stored energy) was lock-tag-try:

    Ensure that the isolation mechanism cannot be operated after being locked. Then attempt to start the machine from any other controls to ensure failure to operate.

    Absence of voltage was only used when contact with energized parts was a risk.

  7. #27
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    17,969
    Attempting to start is only a valid test if there are no other safety lockouts (particularly self resetting) in the control system that might be disabling the machine.
    The corresponding test (run, lockout, try to run) may not be possible if there was originally a problem with the machine that required it to be shut down.

    Sent from my XT1585 using Tapatalk

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