NFPA70E and PLCs

[mordred]

http://www.avotraining.com/common/documents/avotraining/Electrical%20Hazards%20Analysis.pdf

useful article covering this topic

 

[cornbread]

Don't need a arc flash study for 120 vac circuits unless they are fed by a 125 KVA or larger transformer. The only real hazard is the shock potential. Most of my outputs are fused at 2.5 to 5 amps. Again I contend that using rubber gloves while using insulated, slip proof leads adds very little to my protection.

From the replies I'm reading it looks like most of you do indeed wear rubber gloves / PPE to test an output on a PLC.

Granted its hard to argue aginst additional safety measures but in today competative world it seem that follwoing 70E adds additional cost of doing business. Gloves have to be purchased and tested every 6 months to be compliant, seems to me we are putting US companies at a disadvantage. Looks like our safety department is in sync with the majority of the poster and gloves will be the order of the day.

 

[mordred]

http://www.lanl.gov/safety/electrical/docs/elec_hazard_awareness_study_guide.pdf

another good article including current ratings of how much current does what

 

[kamenges]

Originally posted by MikeW[/b}

The law was created because too many people were having accidents. It has reduced electrical accidents significantly since it was enacted.

Ah, statistics. It is easy to determine the number of injuries from a certain cause. It is harder to determine the reason for a reduction in injuries. At the same time the standard was released most companies (including mine) increased the amount of electrical safety training "at-risk" individuals received. In addition they started providing at least minimal training for people that you wouldn't expect need training.

So, was the reduction in injuries a result of mandated appropriate PPE or was it a result of fewer incidents as a result of better training? What we are really talking about here is better determined by looking at the number of injuries relative to the number of incidents. If the incident rate held constant and the injury rate went down then PPE is the likely reason for it. If both went down it is more likely training. The hard part is getting a solid handle on the number of incidents.

Having said all that we do not use rubber gloves here when testing 120 VAC circuits. As mentioned we use properly insulated slip-proof leads.

Keith

 

[OZEE]

Most of my outputs are fused at 2.5 to 5 amps.

2.5 A will kill you dead -- right now! Don't let that fuse give you a false sense of personal safety!!

And the extra cost of 70E is not even close to the cost of an electrical injury.

We wear gloves for anything >50VAC.

 

[Bobbias]

2.5 A will kill you dead

Actually, 2.5A will kill you dead 50 times over, or more.

 

[Paul T]

Actually, 2.5A will kill you dead 50 times over, or more.

Yeah, but you won't really care about the last 49 times...

 

[Bobbias]

Yeah, but you won't really care about the last 49 times...

Agreed there, but I wanted to point out the scale. It's like the difference between shooting someone in the head with a gun, and shooting them in the head with a tank canon. Same end result, but one is a lot messier than the other.

 

[TurpoUrpo]

Don't need a arc flash study for 120 vac circuits unless they are fed by a 125 KVA or larger transformer. The only real hazard is the shock potential. Most of my outputs are fused at 2.5 to 5 amps. Again I contend that using rubber gloves while using insulated, slip proof leads adds very little to my protection.

Fuse IS NOT PERSONEL SAFETY DEVICE!! Fuse is meant to protect wires from current that would heat them up and thus be fire risk.

 

[cornbread]

Arc flash is a function of fault current and with a 2 amp fuse fed from a control xfmer, there is no arc flash hazard. The only hazard in the case I describe is shock. Shock hazard per NFPA requires insulated tools and rubber gloves. If I have insulated tools / leads I'm protected from the shock hazard... rubber gloves seem redundant. Could I touch a live with my hands..of course, could I touch a live with my elbow..probably..so why not wear rubber sleeves....heck I might bend my knee wrong and hit a termial strip...rubber pants? I'm ranting and I know I'm loosing the fight..so I'll purchase my gloves...set up a PM schedule to have them tested every 6 months and go about my business as safetly as possible.

 

[TurpoUrpo]

Ah, ok i mis understood what your point was, now its clear, agree with you.

 

[mordred]

along this subject anyone know the equivilent regulation for Canada? I've looked under OSHA and must be missing it somewhere

 

[milldrone]

The only hazard in the case I describe is shock. Shock hazard per NFPA requires insulated tools and rubber gloves.

brucechase has the right idea and or concept. See if there is any "safety" money for 24V I/O.

The thing you should be working towards is what I've spent years doing, converting all your field I/O to 24 VDC. There is no problem with working on 24 VDC with your bare hands.

 

[controlled]

Arc flash is a function of fault current and with a 2 amp fuse fed from a control xfmer, there is no arc flash hazard. The only hazard in the case I describe is shock. Shock hazard per NFPA requires insulated tools and rubber gloves. If I have insulated tools / leads I'm protected from the shock hazard... rubber gloves seem redundant. Could I touch a live with my hands..of course, could I touch a live with my elbow..probably..so why not wear rubber sleeves....heck I might bend my knee wrong and hit a termial strip...rubber pants? I'm ranting and I know I'm loosing the fight..so I'll purchase my gloves...set up a PM schedule to have them tested every 6 months and go about my business as safetly as possible.

What would happen if there was an arc caused on the line side of the fuse.

 

[OZEE]

Arc flash is not calculated for <240VAC 3phase. Though there may be an arc less than 240, there simply isn't enough energy to sustain an arc. All the "rules" say that for <240VAC, it's PPE level 0. When we're talking about arc flash, we're typically dealing in the kA range, not A... a 2A fuse is going to provide ZERO protection against an arc FLASH. What you're concerned with in arc FLASH is the AIC rating, not the overcurrent protection. They're two entirely different things...

The discussion here seems to be on two entirely different faults. The worst of these is arc flash. That's why we do studies -- to know how much energy might be available to the system in the event of some catastrophic fault. Then, based on what the study indicates, we either try to eliminate the problem (reduce the available energy) or we wear the proper FR PPE.

The second hazard that's being discussed is shock. That is absolutely unrelated to arc flash. As has already been pointed out, only a few milliamps can be fatal -- doesn't matter whether it's 120 or 480V, single phase or three phase.

Cornbread's company policy is dealing with SHOCK HAZARD. We wear rubber gloves (with proper leather liners!) to reduce the possibilities of contact. I believe that if you look at the OSHA regs, it'll indicate anything >50V requires proper PPE against contact.