Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Lockout Tagout and Voltage Testing

  1. #1
    Join Date
    May 2018
    Location
    Boston
    Posts
    2

    Lockout Tagout and Voltage Testing

    To safely change the blade on a hardwired table saw, we require that the employee lockout the electrical disconnect switch.

    Question: Does OSHA requires that an additional test be performed to verify that there is no voltage? If so, can you please share the OSHA reference (actual paragraph that requires this please).

    Very much appreciated!

  2. #2
    Join Date
    Aug 2009
    Location
    Tacoma, Wa
    Posts
    519
    Try google and search for Lock out tagout --for more info

    Here is a link to a power point that discusses what you are asking

    https://www.osha.gov/dte/grant_mater...0-11/LOTO.pptx
    Shoulld be a good start

    I would have posted a direct answer but don't havce access to my referance stuff right now

    Good Luck!! And Welcome to the Forum!!
    Last edited by RichB; 05-03-18 at 10:51 AM. Reason: add comment
    RichB N7NEC

  3. #3
    Join Date
    Sep 2003
    Location
    Connecticut
    Posts
    249
    Quote Originally Posted by OSHA_70E_Questions View Post
    To safely change the blade on a hardwired table saw, we require that the employee lockout the electrical disconnect switch.

    Question: Does OSHA requires that an additional test be performed to verify that there is no voltage? If so, can you please share the OSHA reference (actual paragraph that requires this please).
    Sorta. Let's walk through it:

    1. Changing the blade would be considered maintenance and operations, not construction, alteration or repair, so we know Part 1910 applies, not 1926.

    2. The employee wouldn't be exposed to any current-carrying conductors, so Subpart S is out.

    3. 1910.147(a)(i)(1) says "This standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy, could harm employees."

    So 1910.147 is the section we need to look at.

    1910.147(c)(4)(i) says, "Procedures shall be developed, documented and utilized for the control of potentially hazardous energy when employees are engaged in the activities covered by this section," so, in reading further, we see that a written procedure for the control of hazardous energy is necessary.

    1910.147(c)(4)(ii)(D) requires that the plan spell out "Specific requirements for testing a machine or equipment to determine and verify the effectiveness of lockout devices, tagout devices, and other energy control measures."

    OSHA provides sample Energy Control Programs in 1910.147, Appendix A. Step 7 of the sample they give says, "Ensure that the equipment is disconnected from the energy source(s) by first checking that no personnel are exposed, then verify the isolation of the equipment by operating the push button or other normal operating control(s) or by testing to make certain the equipment will not operate."

    So yes, you have to test for the absence of voltage, but the test is to simply try to turn on the saw. In other words, if you open and LOTO the upstream CB feeding the hardwired saw, then try to turn on the saw, the fact that the saw doesn't start means it's safe to change the blade.

    On the other hand, if you get into the guts of the saw and start mucking around with possibly current-carrying conductors, maybe you need to glove up and test the conductors.

    Hope that helps.

  4. #4
    Join Date
    Sep 2013
    Location
    Brisbane, Australia
    Posts
    54
    Quote Originally Posted by wtucker View Post
    Sorta. Let's walk through it:

    .....
    OSHA provides sample Energy Control Programs in 1910.147, Appendix A. Step 7 of the sample they give says, "Ensure that the equipment is disconnected from the energy source(s) by first checking that no personnel are exposed, then verify the isolation of the equipment by operating the push button or other normal operating control(s) or by testing to make certain the equipment will not operate."

    So yes, you have to test for the absence of voltage, but the test is to simply try to turn on the saw. In other words, if you open and LOTO the upstream CB feeding the hardwired saw, then try to turn on the saw, the fact that the saw doesn't start means it's safe to change the blade....
    Great analysis from a compliance perspective (which was a direct response to the question). However, from a practical perspective, some people might take issue with the underlined bits above.

  5. #5
    Join Date
    Dec 2011
    Location
    Ocala, Florida, USA
    Posts
    2,760
    Quote Originally Posted by cdevine View Post
    Great analysis from a compliance perspective (which was a direct response to the question). However, from a practical perspective, some people might take issue with the underlined bits above.
    Why would some people take issue with this? It was my first thought.


    I know what I don't know, and I know where to go to find it!

  6. #6
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,115
    Quote Originally Posted by Strathead View Post
    Why would some people take issue with this? It was my first thought.
    In THEORY, the breaker could have failed to actually open, but there could have been some OTHER condition that was preventing the saw from starting, then when that other condition changes, the saw CAN start. In most places I've worked (that had a written safety procedure), an Electrician was always required to apply a LO/TO procedure on electrically powered equipment (permanently wired), because he/she had to verify that the energy was removed.

    From that OSHA presentation linked above:
    Lockout/Tagout requires, in part, that a designated individual turns off and disconnects the machinery or equipment from its energy sources(s) before performing service or maintenance and that the authorized employee(s) either lock or tag the energy-isolating device(s) to prevent the release of hazardous energy and take steps to verify that the energy has been isolated effectively.
    Some folks choose to interpret those steps more loosely than others. I have certainly seen people do the "lock-out / attempt to start / tag out" routine as verification, but I was not employed at those places. Everyplace I've worked had a stricter interpretation, including a test - verify - test OF the electrical test. We had to open the switch / breaker, test the load side to make sure it was dead, verify our meter was working by touching the line side, then test the load side of the switch again after verifying, then close it up and apply the lock. Operators could UNLOCK without an electrician, just not lock out.
    Last edited by Jraef; 05-04-18 at 07:49 PM.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  7. #7
    Join Date
    Sep 2013
    Location
    Brisbane, Australia
    Posts
    54
    Quote Originally Posted by Jraef View Post
    In THEORY, the breaker could have failed to actually open, but there could have been some OTHER condition that was preventing the saw from starting, then when that other condition changes, the saw CAN start.
    Exactly Jraef. OTHER conditions may include:
    • Control circuit problem
    • No mains power
    • Jammed saw

    However, the thought of getting an electrician to verify the isolation on every lockout could be viewed as:

    • Time consuming hence very costly
    • Putting the electrician at risk more often than is necessary

    Possible solutions include:

    • Only using electricians to verify isolations on high consequence, high frequency lockouts and taking a risk on the others
    • Employing voltage indicator leds for use for non electrical isolations ie 90% of isolations

  8. #8
    Join Date
    Dec 2011
    Location
    Ocala, Florida, USA
    Posts
    2,760
    Quote Originally Posted by cdevine View Post
    Exactly Jraef. OTHER conditions may include:
    • Employing voltage indicator leds for use for non electrical isolations ie 90% of isolations
    I agree that I missed the nuance and Jraef had a reasoned answer that I accept. However, this has the same pitfalls. When trained to use a voltmeter properly , I was taught to check it on a known live source, then check the desired circuit, then check it on a known live circuit again. The point is that indicator LED's can also fail. turning off a disconnect that is right next to the saw and obviously the one that controls the saw, is a 99.9% assurance that the blade won't restart. It is all in the assurance level vs. cost that the employer wishes to designate.


    I know what I don't know, and I know where to go to find it!

  9. #9
    Join Date
    Sep 2013
    Location
    Brisbane, Australia
    Posts
    54
    Quote Originally Posted by Strathead View Post
    ...The point is that indicator LED's can also fail...
    Yes Strathead I agree which is why LED indicators that incorporate self testing facilities are normally used. Preferably, a safety rated indicator with automatic testing.

    The need to verify electrical isolations for the purpose of non-electrical work is sound and often mandated. However, how a company might approach verification may be different based on:

    • consequence ie finger cut or crushed head
    • isolation frequency ie weekly or every 5 years
    • safety culture/duty of care ie recognising why the try start method by itself may be misleading

    Given the above considerations there are many cases when it can be very cost effective to do more than just meet the code or send electricians to do a test each time.

  10. #10
    Join Date
    Sep 2003
    Location
    Connecticut
    Posts
    249
    I sorta think you guys are over-thinking this. The original problem was that the blade needed to be changed. There was no suggestion that the saw had malfunctioned in any way. If this were your own saw in your garage, you'd simply shut the darn thing off and change the blade. The extra (emphasize "extra") step here is to open the breaker.

    Let's not forget the stated purpose of 1910.147: "This standard covers the servicing and maintenance of machines and equipment in which the unexpected [emphasize "unexpected"] energization or start up of the machines or equipment, or release of stored energy, could harm employees." It's trying to protect the guy changing the blade from somebody turning it on while he's not looking. If the switch on the saw is off, it's going to be under the control of the person changing the blade, so the saw won't start even if the breaker is closed.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •