petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
A lot depends on the intended purpose. I am not convinced that a typical operator should be using a disconnecting means as part of routine operations of a machine.
PPE throwing a disconnect
- Thread starter S'mise
- Start date
- Status
A lot depends on the intended purpose. I am not convinced that a typical operator should be using a disconnecting means as part of routine operations of a machine.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
What about for LOTO so they change work on the mechanical portions of a machine, such as clearing a jam?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
have they been trained on testing to ensure the disconnect has actually opened the energy source?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Most companies have LOTO training which meets OSHA requirements.
- Location
- Illinois
- Occupation
- retired electrician
Lockout for mechanical purposes does not require that they electrically verify that the disconnect is open. The LOTO procedure often calls for them to atempt to start the equipment with the normal control system after they have locked out the disconnect. If the equipent does not start, it is assumed that locking out the disconnect has infact disconnected the energy source from the equipment.
If you are in Canada, you can look through the veiwing window on the disconnect to verify that the switch is in the open position.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
All of our Pringle switch's for the DC train transfer cars and cranes all have a verification window, anyone who has experience with a Pringle switch knows all to well that pulling the handle can leave one of the knife blades stuck in even though it sounds like it opened, as they are very common in doing this if not properly maintained and adjusted which we do on a regular scheduled bases, years ago at another plant I worked for I used to hate Pringle switches as for the reason above they were so unreliable in shutting off the power, but the reason wasn't the switch's fault it was our maintenance procedures that we used back then as they were never checked for proper blade pressure adjustment or cleaned and lubricated.
Sure you can try the equipment and it might not start but if you have a stuck knife blade there will be energy at the machine, so our rules require us to test for voltage with proper PPE's our safety stickers say LOTOTO to which means tryout but with testing for electrical voltage, and with making sure all pneumatic, hydraulic, and any other forms of stored energy has been removed or pined so it can not move on its own, we even have lockouts for valve handles as well as for other mechanically stored energy supplys, our company is very serious about safety and if your caught not following the rules you can be fired on the spot, one side of our plant we have machines that require over 150 locks to lock out the whole line and lockout box's are used in these cases and the SJP proto calls are followed to the letter, when I came to work for them I was very impressed with the length at which they go to put safety ahead of all else, yes it can make a simple job take many times longer to do, but what is important is we all go home to our familys intact as we came into work.
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
:thumbsup::thumbsup:
weressl
Esteemed Member
That distinction is NOT made by OSHA, nor is it accepted by them. Direct verification of the removal of the energy source is required in all cases, indirect is not acceptable. (In the example you cite above the unpredictable presemce or absece of interlocks can prevent the equipent operation therefore making the lockout effectiveness uncerain with that verification.)
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- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
1910.147 Appendix A does not agree with you.
If you are not performing electrical work a 'volt check' is not required.
The following simple lockout procedure is provided to assist employers in developing their procedures so they meet the requirements of this standard....
(7) 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. "
When the incident energy level is calculated, or derived by the tables, It is based on a distance from exposed (open door on equipment) conductors.
Then why is there not a lesser ppe requirement for just turning on/off a disconnect with the door closed?
Are you saying if I am not interacting (door open exposing live conductors) with the equipment, I don't need ppe?
Then why is there not a lesser ppe requirement for just turning on/off a disconnect with the door closed?
Are you saying if I am not interacting (door open exposing live conductors) with the equipment, I don't need ppe?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Incident energy is calculated, it is not derived from tables.
The tasks in the tables have been associated with a PPE level (cal/cm?), not the other way around. Effectively the task tables were creating by a group that said, 'if someone does this action while they are wearing specific PPE (items and ratings), then we expect to to survive an arc flash incident.
If an arc flash occurs the doors are considered to not offer any protection therefore the PPE requirements do not change based on their presence.
The primary issue is; "interacting in a manner that will cause an arc flash or an electrical shock" as opposed to simply 'interacting with".
You need PPE whenever there is a hazard. Hazard Risk Category 0 does not mean no PPE.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
And that is the million dollar question.
NFPA70E leaves it up to the employer's Electrical Safe Work Practices program.
But, as I have mentioned before, in today's society what ever policy is written the employer needs to be prepared to defend it. This sound ominous, but companies make safety decisions (trade-offs?) all of the time, like hazardous material handling and confined space entry, electrical is just the latest topic.
zog
Senior Member
- Location
- Charlotte, NC
The note in the definition refers you to the task table as examples of interactions that may cause an arc flash hazard. Operating a disconnect is one of those tasks.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Informational note #1 says under normal conditions enclosed equipment may not be a hazard.
Informational note #2 says operating equipment could be a hazard.
One definition, two conflicting opinions.
When a hazard has been identified, PPE must be worn.
Hazard Risk Category 0 does not mean no PPE.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Not necessarily conflicting. I do not need to wear PPE to walk past the disconnect, regardless of what else is going on around me.
But if I am going to operate it (not just let it continue to "operate" on its own), then the hazard may change and I need to put the PPE on.
(Difference between "operating equipment" = "equipment that is currently operating" and "operating equipment" being the action of operating (interacting with) it.)
Ain't English a fun language!
zog
Senior Member
- Location
- Charlotte, NC
I read it the same way as digger, as do the vast majority of people on the IEEE 1584 and 70E working groups.
"Normal" is static, not being operated or interacted with in any way. The purpose of the 1st note is to state the risk of an arc flash occuring when the equipment is just energized but not being interacted with has a very low risk factor. Just so people don't get all crazy and require PPE to just walk past energized equipment. (However I do know a guy that was burned from an arc flash last year doing exactly that, so risk is not zero, just very low)
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
And I know of multi-national companies, some with members on IEE1584 and 70E, that interpret the informational notes in the way that I describe.
If NFPA70E had meant 'static' there would not have been the necessity to use the specific clarifying language of "provided a person is interacting with the equipment in such a manner that could cause an electric arc"
Then there is the exception to NFPA70E 130.2, that discusses the operation of disconnects, for connected equipment, and a risk assessment has been performed.
And of course there is the informational note #2, to 130.7(A) that says normal operation of equipment does not pose a hazard. If they had really meant 'static' they should have used a different phrase. I am sure most people consider the automatic opening and closing of a motor starter or motor operated disconnecting device as being 'normal operation'.
As written, 130.7(C)15 says that the task tables (130.7(C)a and b) are to be used if a study has not been performed per 130.5(B)(1). So, if a study has been done these tables can be ignored, yet these tables are the only place that actually mentions causing equipment to change state.
The point is:
PPE is required when hazards exist.
Risk assessments must be performed, per 110.3(F).
Opening a 2000A bolted pressure service entrance switch that has not been maintained, poses a different risk than a 60A non-fused switch used to LOTO a machine to clear a mechanical jam.
zog
Senior Member
- Location
- Charlotte, NC
That still leaves it open to interpretation, which is why I said "as I read it", they really should clarify, but I know they won't take a hard stance either way.
Neither would I, but again, not black and white, what is "normal"? Reclosing a breaker after a fault? Some may consider that normal.
The 70E also discusses equipment that has been properly maintained. What determines that? 70B? NETA? Neither one if you ask me. Even if you test your breakers on a regular basis that does not tell the true story. To test a breaker per ANSI/NETA specs you have to open the breaker, remove it, then test it via primary injection. Most breakers just sit there closed for years, lubricants dry out, mechanisms get sticky, trip springs are fatuiged from being loaded for years. When you open a breaker, then test it you are not getting an accurate trip time because everything has been exercised. Really the only accurate way to know your actual fault clearing time, which your entire arc flash analysis and PPE requirements are based on, is to perform "first trip" testing. We often see 30 cycle clearing times on breakers that have an assumed 5 cycle clearing time per the TCC's.
Yet another issue with the 70E, to use the tables you have to know the fault current and clearing times and verify they are within the limits of the notes in the tables. So to use the tables you have to do a study, but if you do a study you ignore the tables.
I agree with that, really it comes down to the owner of the equipments risk evaluation process, but in my experience the people making those decisions are don't know enough to do so, and peoples lives are on the line.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Normal and routine are also different items. Just because an action is routinely done, does not mean that it was intended to be performed. Have you seen manufactuerer instructions for installing bus-plugs onto live busway?
There is an established OSHA rule for dealing with reclosing breakers - basically don't do it.
However that same rule says you can close the breaker if you absolutely know why it opened, like due to a manual LOTO operation.
The issue is the risk assessment.
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