Nuances of 1910.147 & 1910.333 deenergization verifications

[WarAxe]

1910.147(c)(4)(ii)(D) says...

"Specific requirements for testing a machine or equipment to determine and verify the effectiveness of lockout devices, tagout devices, and other energy control measures."​

...and its application to working on electrical conductors is 1910.333(b)(2)(iv) which says...

"Verification of deenergized condition. The requirements of this paragraph shall be met before any circuits or equipment can be considered and worked as deenergized.

​

(A) A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted.​

(B) A qualified person shall use test equipment to test the circuit elements and electrical parts of equipment to which employees will be exposed and shall verify that the circuit elements and equipment parts are deenergized. The test shall also determine if any energized condition exists as a result of inadvertently induced voltage or unrelated voltage backfeed even though specific parts of the circuit have been deenergized and presumed to be safe. [...]"​

A couple questions based on the above OSHA requirements:

1. 147 tells me that for a mechanical LOTO (e.g. clean/inspect of vent fan externals) that merely trying to operate controls is a sufficient verification as long as the fan works and the controls work. But what if the fan is suspected to be jammed? Or what if the control circuitry is suspected of intermittently shorting? Then that check is meaningless.
2. 333 tells me that for an electrical LOTO (e.g. 480 fuse replacement inside disconnect) that I must perform two separate checks. First, (A) says I need to operate controls as in 147 above -- but then I have the same questions as above. Second, (B) says I do a live-dead-live type check. I have had workers plea to me that the (B) check counts for the (A) check when the (A) check is 'unfeasible' such as in the examples given.

I have much more to share on this, but I don't want to "lead the witnesses" toward my way of thinking... especially if I'm wrong.

 

[cdevine]

My thoughts WarAxe...

​

1. 147 tells me that for a mechanical LOTO (e.g. clean/inspect of vent fan externals) that merely trying to operate controls is a sufficient verification as long as the fan works and the controls work. But what if the fan is suspected to be jammed? Or what if the control circuitry is suspected of intermittently shorting? Then that check is meaningless.

Largely agree. If you can't use the same technique under all circumstances then what good is it? There are two situations where it is partially useful. Firstly, In the case of the isolation point being remote from the motor and where the wrong isolation point is mistakenly turned off, a try start attempt that is successful could help in identifying the error. Secondly, the act of doing this test before the live dead live check and getting a successful dead result reduces a worker's exposure in the test below. All that being said, IMHO there are far quicker and reliable methods than the try start method for verification for mechanical works and it should be replaced in the legislation.

333 tells me that for an electrical LOTO (e.g. 480 fuse replacement inside disconnect) that I must perform two separate checks. First, (A) says I need to operate controls as in 147 above -- but then I have the same questions as above. Second, (B) says I do a live-dead-live type check. I have had workers plea to me that the (B) check counts for the (A) check when the (A) check is 'unfeasible' such as in the examples given.

Agree. The only thing I would add is that generally verification for mechanical works is more frequently required than verification for electrical works. Because of this a good method for verification for mechanical works is worth seeking out as it saves money and reduces worker exposure to potentially live circuits.

 

[WarAxe]

I'm really interested to see how others who have to follow OSHA are able to meet these specific requirements amidst real-world scenarios such as the examples/questions I posed.

 

[cdevine]

Could it be that "A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted." provides the flexibility to use other (potentially more reliable) methods of verification other than Try Start?

 

[don_resqcapt19]

This is one reason a number of facilities require a local lockout disconnect at each motor. That way there is no question that the power has been disconnected, however to be sure you would have to verify that the disconnect switch opened all of the conductors. With a knife blade disconnect, you can just open the cover, after putting on the correct PPE, to check that all of the blades are in the open position...or you could use a disconnect built for use in Canada with a viewing window that permits you to view the blade position without opening the cover.
Some places also use a Meltric receptacle and plug for this purpose in place of a the traditional disconnect.

 

[iwire]

.or you could use a disconnect built for use in Canada with a viewing window that permits you to view the blade position without opening the cover.

I think I saw a company offering a field installed window kit for this purpose.

 

[cdevine]

An extract from Western Mining Corporation's notes on visible break isolators:

Sighting all the physical breaks between the fixed and moving contacts of three phase isolating devices is not restricted to small isolator sizes, but the need to clearly sight each of the three contacts limits the locations where the method can be applied.

Practical viewing difficulties can arise due to:

• Limited lighting / shadows at night.
• Loss of window transparency due to window abrasion, chemical attack, etc.
• Inadequate physical access to see into the isolator windows that are, of necessity, immediate to the isolator phase connections.

The method is highly reliant upon correct pre-commissioning checks and correct maintenance.

Only in favourable operating conditions, can the sighting of physical breaks between each of the fixed and moving contacts of an isolator provide a high level of isolation confidence.

Aside from the above technical challenges the method has merits as indicated above but is very expensive. Safety people generally don't accept expense as an excuse but only the naiive would suggest that cost has no bearing on implementation.

 

[WarAxe]

Could it be that "A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted." provides the flexibility to use other (potentially more reliable) methods of verification other than Try Start?

ABSOLUTELY! That's exactly what that's in there for. And this is echoed in NFPA 70E 120.2(F)(2)(e):

"The procedure shall verify that equipment cannot be restarted. The equipment operating controls, such as pushbuttons, selector switches, and electrical interlocks, shall be operated or otherwise it shall be verified that the equipment cannot be restarted."​

But I have some engineers of electrical work who say that meeting that requirement is too onerous, and that simply skipping it and going right to a live-dead-live is fine.

I't a tedious battle.

 

[GoldDigger]

My reply to that would be that depending on the exact details of the LOTO point and the measurement point it would not be hard to mistakenly open the wrong disconnect but read dead because the controls are off.
Having someone try to activate the equipment via the normal controls will catch this even though live-dead-live voltage checking will not.
There are reasons the procedure is laid out in the exact order it is.
A little demo of that situation might be persuasive.

Tapatalk!

 

[WarAxe]

My reply to that would be that depending on the exact details of the LOTO point and the measurement point it would not be hard to mistakenly open the wrong disconnect but read dead because the controls are off.
Having someone try to activate the equipment via the normal controls will catch this even though live-dead-live voltage checking will not.
There are reasons the procedure is laid out in the exact order it is.
A little demo of that situation might be persuasive.

Tapatalk!

Absolutely!! Quite correct on all counts as I see it. The operational controls check (or equivalent as necessary) ensures you did indeed get the CORRECT isolation. The live-dead-live ensures that if you're going into the box that you didn't MISS anything in there... either another power source or control power or whatever, and that there's no INDUCED voltage.

Thank you for making me feel sane again.

 

[cdevine]

I'm curious. What is being used other than Try Start and Visible Break Isolators for the purpose of verifying isolations for mechanical maintenance?

 

[don_resqcapt19]

The "operational controls" check needs to by pass interlocks that could be preventing the equipment from starting. At a plant I often work at, they had us install HOA switches at all of the motors. The hand position is spring return to off, but when you activate it, you bypass all of the control interlocks except the starter overload relay. Of course "operational control" check only works if the equipment is functional. Often there may be a mechanical reason why the equipment cannot be started, and in that case other types of verification must be used.

 

[WarAxe]

I believe that's exactly right, don_resqcapt19. Attempting to operate the controls is fine as long as you KNOW that the controls would otherwise be operating the equipment had you not just LOTOed the supply. But I'm frequently asked questions about equipment that is a) broken, or b) interlocked. In principle, trying to operate controls that wouldn't have actually operated the equipment anyone is a poor verification that you've isolated power to the equipment.

 

[GoldDigger]

So, in summary what is needed is a process that works all the time for an individual who does not really understand what he is doing, yet can be modified by someone who does know what he is doing whenever the standard procedure does not actually work. :angel:

 

[don_resqcapt19]

So, in summary what is needed is a process that works all the time for an individual who does not really understand what he is doing, yet can be modified by someone who does know what he is doing whenever the standard procedure does not actually work. :angel:

Yes, and that is exactly what many of the changes in the NEC are striving for

 

[WarAxe]

So, in summary what is needed is a process that works all the time for an individual who does not really understand what he is doing, yet can be modified by someone who does know what he is doing whenever the standard procedure does not actually work. :angel:

Wut duh hale iz dat supposta mean?


Yes, you hit the nail on the head exactly. And if I had a dollar for every time I've heard that we're the ONLY facility in the universe who doesn't let the workers skip right to the live-dead-live. :slaphead:

 

[pfalcon]

Could it be that "... or otherwise verify that the equipment cannot be restarted." provides the flexibility ...?

Yes, the "Otherwise Verify" is the OSHA escape clause to allow energy or other checks to be used when strictly operational checks would fail. Operational checks are not required but are stressed as "the first" of many methods that "might" be used.

... but read dead because the controls are off.
Having someone try to activate the equipment via the normal controls will catch this ...

The normal controls would be those that are off. Therefore trying to activate the equipment would catch nothing. Hence Don's HOA being wired to bypass those controls in hand mode. See following.

I believe that's exactly right, don_resqcapt19. Attempting to operate the controls is fine as long as you KNOW that the controls would otherwise be operating the equipment had you not just LOTOed the supply. But I'm frequently asked questions about equipment that is a) broken, or b) interlocked. In principle, trying to operate controls that wouldn't have actually operated the equipment anyone (sic anyway?) is a poor verification that you've isolated power to the equipment.

In your own words - ABSOLUTELY!

 

[cdevine]

So, in summary what is needed is a process that works all the time for an individual who does not really understand what he is doing, yet can be modified by someone who does know what he is doing whenever the standard procedure does not actually work. :angel:

Yes GoldDigger I think that probably is what the legislation is trying to convey. Perhaps because historically, a one size that fits all has been very difficult to achieve and even they know it.

However, engineers I know want "a process that works all the time for an individual who does not really understand what he is doing". In fact some I know think that even people who know what they are doing can be the same people who make simple mistakes at 2am in the morning. Further to that, there are some small businesses who don't have that person "who does know what he is doing" on the payroll and they need to verify at 2am in the morning.

This is a hot topic in the industry that I work and there are some people who have been working on a "one size that fits all" solution for several years who are getting pretty close to pulling it off.

 

[WarAxe]

In your own words - ABSOLUTELY!

Thanks. It's always good to get a sanity check.

 

[WarAxe]

Yes GoldDigger I think that probably is what the legislation is trying to convey. Perhaps because historically, a one size that fits all has been very difficult to achieve and even they know it.

However, engineers I know want "a process that works all the time for an individual who does not really understand what he is doing". In fact some I know think that even people who know what they are doing can be the same people who make simple mistakes at 2am in the morning. Further to that, there are some small businesses who don't have that person "who does know what he is doing" on the payroll and they need to verify at 2am in the morning.

This is a hot topic in the industry that I work and there are some people who have been working on a "one size that fits all" solution for several years who are getting pretty close to pulling it off.

I'd be interested in hearing what the proposed solution is like. There may be elements of it I can take back to my areas.