- Location
- Illinois
- Occupation
- retired electrician
I don't think that either of those devices would meet the OSHA rules for the verification that the power has been de-energized.
Lock out Tag out verification
- Thread starter cornbread
- Start date
- Status
cdevine
Member
- Location
- Brisbane, Australia
OK RightSwitch certainly won't because its aim in life is to match an MCC isolation point with the equipment in the field ie remote indication. It doesn't do the proof of de-energisation part.
Firstly, please excuse my lack of familiarity with OSHA. The impression I get is that OSHA is predominantly concerned with Lockout Tagout and confirming that electrical equipment won't operate unexpectedly while performing non-electrical maintenance. I seem to recall that OSHA is not specific on how you do this but suggests the use of Try Start which of course is not "verifying that the power has been de-energized" only that the equipment won't operate unexpectedly. Knowing the pitfalls of Try Start detailed in the above posts eg jammed equipment and control circuit elements, some companies have reverted to Live-Dead-Live checks even for non-electrical maintenance. These companies, over time, have recognized that they do much more non-electrical maintenance than electrical maintenance and the Live-Dead-Live checks for non-electrical maintenance are costly and inconvenient. So what if a non-electrical person could perform a Live-Dead-Live check? What would the solution look like and how would it operate? I suppose DeadEasy was an attempt at answering those questions.
So the option some companies face eg the thread starter, is to stick with what OSHA suggests that they know could be inconclusive or opt for an alternative solution that maybe technically better and that is not cost prohibitive. After all they need to stay in business!
Apologies for the dissertation above, particularly if my OSHA interpretation is incorrect, but its obvious that people on this forum are quite expert on the subject of Lockout Tagout. Informed views such as yours are very valuable to the community.
- Location
- Illinois
- Occupation
- retired electrician
I think there is a difference between a lock out for mechanical work and one for electrical work. My comment was based on a lockout for electrical work. There is an OSHA letter interpretation that says the pilot light type devices, even the ones with multiple lamps are not suitable to prove de-energization for electrical work.
cdevine
Member
- Location
- Brisbane, Australia
OK I got the impression that the thread was largely about non-electrical work. My apology.
Yes I received the same impression about "pilot light type devices, even the ones with multiple lamps are not suitable to prove de-energization for electrical work" after reading this. By the way, the device described in this directive is different to DeadEasy. Included in this OSHA advice is that:
"The verification provision of paragraph (d)(6) of 29 CFR 1910.147 requires an affirmative step on the part of an authorized employee to determine if the hazardous energy is effectively isolated, and relying solely on the LED device would not satisfy this requirement. One effective method of compliance would be a deliberate attempt by an authorized employee to start up the equipment"
OK so pilot lights and Try Start is OK, but so too is just Try Start. There is also mention in Compliance Directive CPL 02-00-147 that:
"only through the use of a test instrument [by a "qualified employee" under 29 CFR Part 1910, Subpart S] or a deliberate attempt to start-up a machine that the authorized employee will be able to ascertain whether the steps taken to isolate hazardous energy"...."The use of a test instrument is particularly applicable for verifying isolation and deenergization in the case of jammed equipment"
I would have thought that most motors and the loads they drive could possibly jam, not to mention other faults that may yield an incorrect Try Start result.
So it seems that on one hand OSHA says Try Start is OK, but on the other hand OSHA is aware of accuracy issues relating to Try Start and advocate a test instrument approach? Of course if you go down the track of only using the instrument approach, that in the case of MCCs and field equipment, then you might be exposed to isolating equipment at the MCC and working on incorrectly isolated (possibly energised) equipment in the field. Identifying the right field equipment is one area where a Try Start might have helped.
So could it be that OSHA's fall back position in the event of an accident is that they recommended both Live-Dead-Live check and Try Start for each isolation? Perhaps most businesses could not afford to do both and in that way, should there be an accident, OSHA is in the clear and the site owner is to blame?
So the big question is...
Should a site owner follow OSHA's recommendation of Live-Dead-Live check and Try Start[FONT=Tahoma, Verdana, Helvetica, sans-serif] to protect themselves from legal blame in the rare event of an accident [/FONT]or[FONT=Tahoma, Verdana, Helvetica, sans-serif] should the site owner consider less expensive approaches that similarly reduce the risk to near zero levels, such that no accident is likely to occur and therefore legal aspects are irrelevant.[/FONT]
I guess that's a judgement for each site owner to make.
I'd be happy to learn of any errors in the above as I really want to understand the topic.
This is the exact problem I'm trying to solve. All it takes is one mistake. To reiterate one of my concerns is as we automate more and more where we have DCS stops and interlocks, the try to start method falls way short. It may be locked out it may be interlocked with DCS? Agreed the pilot light may not be up to snuff, but I have to think its better than what we are doing today. Just my humble opinion.
- Location
- Illinois
- Occupation
- retired electrician
That is exactly why our HOAs bypass all interlocks except the overload relay in the starter.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If, for a particular machine, you have operator safety interlocks (proximity, etc.) would you still bypass those in H operation, on the assumption that extra caution would be exercised when using the hand operate control?
- Location
- Illinois
- Occupation
- retired electrician
Yes, but we do not have much of that type of equipment at the plant where we installed the HOAs.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
At first, having just come from a Solar PV board, I wondered how a Home Owners Association came into the LOTO picture.
Ah, the perils of TLAs
- Location
- Massachusetts
Man those HOAs really stick there nose into everything. :jawdrop:
cdevine
Member
- Location
- Brisbane, Australia
I guess you could attempt a Try Start prior to locking out, to prove that there is no problem with the manual start circuit. In that way you reduce your exposure to an incorrect Try Start result resulting from control supply, control circuit, HOA switch faults and jammed motors.
Then, after locking out, all that it leaves is the risk an incorrect Try Start result resulting from intermittent problems/faults with:
- Overload Relay
- Contactor
- and a fault that occurred in the Try Start Control circuit since locking out
All very unlikely so it sounds like a reasonable plan. So in summary, for each lockout you could:
- Try Start and Confirm Start
- Lockout
- Try Start and Confirm No Start
- The inability/inconvenience to Try Start due to process eg material on belt, dead heading positive displacement pumps
- The inability to repeat the verification to work parties arriving late
- Location
- Illinois
- Occupation
- retired electrician
Yes the policy at the plant where we installed the HOAs is "try-lock-try". Of course if the equipment is not functional that will not work. The "try-lock-try" is used for mechanical lockouts only. If you are going to work on the electrical, you have to use a meter to prove the equipment is de-energized.
cdevine
Member
- Location
- Brisbane, Australia
Thanks Don. So in the event of an isolation for electrical work do you use Try Start to match the field equipment to the MCC equipment? So in summary, for each lockout you could:
- Try Start and Confirm Start
- Lockout
- Live Dead Live Check
- Location
- Illinois
- Occupation
- retired electrician
Actually after the lockout we would try the start again before doing the "live dead live"
cdevine
Member
- Location
- Brisbane, Australia
Yes that mirrors what happens in Australia. Further to that, in order to save costs, many new plants don't incorporate field HOA switches and visible break isolators. Mode selection is performed by SCADA/DCS and all that is available in the field is a start button and emergency stop. I can see how Don's Try-Lock-Try approach makes sense, because to be honest it is the highest integrity method I have seen using existing technologies, but I am not sure that it solves all problems for the following reasons:
- Capital cost of local control stations
- Process safety interlocks preventing Try eg dead headed positive displacement pumps
- Inconvenience of process materials in the system preventing Try eg material on conveyor belts blocking chutes
- The inability to repeat the verification after lockout to work parties arriving late
- The wear and tear caused to large motors by frequent bump starts
- Complexity therefore elevated risk of error eg emergency stop pushed in that went unnoticed on 2nd Try
Even after considering the above issues, The Try-Lock-Try method does not appear Fail Safe / Positive Verification. After all it is still exposed to (unlikely) problems with the 2nd Try eg control circuit power, contactor, HOA switch problems. To put it another way a positive verification system would indicate to the operator on the 2nd Try that the drive contactor had closed and the motor has not rotated. At least that way the operator would get the impression that it is the disconnect that is breaking the power circuit. A positively indicating tool that measures voltage on the load side of the disconnect, that can be self tested, might be an alternative to knowing that it is the disconnect that is breaking the power circuit.
- Location
- Illinois
- Occupation
- retired electrician
I would really like to see some type of "air break" used for lockout, but that is expensive.
The method I would prefer would be a Meltric connection at each motor. It is a plug type of connection and rated for disconnecting under load. You physically remove the power conductors from the motor with this method...absolutely no question that there is no power and that you have the correct motor locked out. However this only really works well for stand alone motors and would be some what difficult for a multi-motor machine.
The method I would prefer would be a Meltric connection at each motor. It is a plug type of connection and rated for disconnecting under load. You physically remove the power conductors from the motor with this method...absolutely no question that there is no power and that you have the correct motor locked out. However this only really works well for stand alone motors and would be some what difficult for a multi-motor machine.
cdevine
Member
- Location
- Brisbane, Australia
Yes Don this method provides a high integrity and simple isolation but it introduces so many more issues eg:
- Regular people contact with cables
- Damage to plugs and sockets when dropped
- Limited current ranges (approx 250A)
- Perhaps not best for hazardous areas
- Introduced foreign bodies into coupling eg water, non conductive dusts
- Removal of earth conductor to equipment on isolation. Can impact on touch voltages in the event of earth fault on other equipment connected by process connections
- Manual handling issues due to weight of plugs and sockets
- Need to use flexible cables yielding low availability and high cost
- Plug/Socket high cost as you have pointed out
I haven't really noticed what's done at McDonalds in the US but in Australia McDonalds use these sockets that dangle from the ceiling to power machinery. It seems like an ideal solution for this type of environment. Anywhere else though I'm not so sure.
- Location
- Illinois
- Occupation
- retired electrician
You don't need to use cables, you can attach LFMC to the Meltric devices.
They are hard to damage...much harder than the traditional die cast pin and sleeve devices.
Yes they do have their limits as far as horsepower and current.
They are available in versions listed for Class I, Division 2.
There are caps available to prevent contamination, but of course some one would actually have to apply the cap to the male end. The receptacle cap is self closing.
I guess that there could be a voltage on the equipment in the event of a fault on other equipment, but I don't see that as very likely when we are talking about systems operating at 600 volts or less.
They are not really that heavy.
No need to use cables.
Yes, they are expensive.
cdevine
Member
- Location
- Brisbane, Australia
Ok I have reached the limit of my expertise on North American installation practices on this one. It didn't take much. My apologies I was referring to constraints relating to Australian (European) requirements. In some cases we may have to beg to differ eg 200A DS plug (largest D Contactor) with connecting cable being lifted and plugged in against the ejecting spring particularly by less muscular humans of both sexes.
On a side note your responses raise a couple of interesting questions:
- Touch voltages on 230VAC systems are a big deal in Australian systems requiring every circuit to have its earth fault loop situation considered. Is that different to NFPA requirements?
- Installing plug/sockets on cables in Australia requires the use of flexible cables rather than building wiring cables. Specifically, greater strand count and more flexible insulation and sheathing. Is that different to NFPA requirements?
- Status