Lockout Tagout and Voltage Testing

[OSHA_70E_Questions]

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!

 

[RichB]

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_materials/fy11/sh-22300-11/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!!

 

[wtucker]

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.

 

[cdevine]

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.

 

[Strathead]

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.

 

[Jraef]

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.

 

[cdevine]

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

 

[Strathead]

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.

 

[cdevine]

...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.

 

[wtucker]

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.

 

[petersonra]

My understanding.

All OSHA requires is lockout the CB, test the on/off switch to make sure it does not start and go about changing the blade.

You can do more if you want, but OSHA does not require it.

The guy doing the blade change would need to be trained on how to perform the lockout and the blade change. Then, and only then, could he be authorized to do so.

 

[ramsy]

I sorta think you guys are over-thinking this....

The legally required disconnect within sight is appliance cord & plug.

Pull out cord & plug before changing blades. No LOTO needed if plug is withn sight.

 

[wtucker]

The legally required disconnect within sight is appliance cord & plug.

The saw's hardwired.

 

[just the cowboy]

Both sides of the fence

Both sides of the fence

The saw's hardwired.

I have seen this from both sides of the fence. I was on the LOTO design team for a world wide manufacture.

Having worked in a plant with hundreds of machines that were locked out for clearing jams every 5 minutes, we would of went out of business having an electrician check before reaching into a machine.
We did the throw disconnect and listen for clack, LOTO, test with on button, press off button after testing with on button, clear jam. reset and run machine. If an electrician was needed every time nothing would of ever got done.

On a machine that maintenance was being done to, we did test to ensure voltage was removed.

For the OP's question. I don't trust anything with dust ( sawdust, paper dust, ....) I have seen them start on there own due to dust conducting across buttons or switch's. I believe they still make disconnects with windows so they could SEE the blades are open, that is the only way I would feel safe with my hands on a saw blade.