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Lockout-Tagout

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Re: Lockout-Tagout

#81

Post by Nasrudith »

geekamongus wrote: post #7

Side note: The most secure locks that Master makes (in regards to being pick resistant) are their LOTO padlocks, and they are usually about $10. Most of their other consumer locks are pretty easy to bypass with basic picks, but get marketed as being the "best" in security and cost a lot more.

That is ironic since security isn't even the real point of the locks - just providing enough resistance that it can't be done unconsciously and any "accident" is beyond negligence if they were locked out and it was meddled with.

Re: Lockout-Tagout

#82

Post by Cthulhu_ »

JoeAltmaier wrote: post #56
kozak wrote: post #55

Earlier quoted context omitted.

Can someone please point me to details of a biological mechanism that can cause someone to die hours after having seemingly survived an electric zap just fine? I never thought such things are possible.

There's a term ambulance drivers use, "Walk, talk and die". For victims of car crashes that got a hard knock to the head. A brain bleed in the brain stem (if I'm remembering it right) will build up pressure until the stem suddenly disconnects. Not electrical, but such syndromes seem to be real.

Yup, definitely - this is why people will be asked if they blacked out, if only for a little while, after a fall. If they did the impact was severe enough to cause damage. And of course tight monitoring after head trauma.

Re: Lockout-Tagout

#83

Post by amluto »

zaarn wrote: post #63
amluto wrote: post #60

Earlier quoted context omitted.

> Ground and short (put a plug into the socket connecting earth, live and neutral Hmm. Given that breakers in the US don’t disconnect the neutral, grounding the neutral can introduce potentially unpleasant stray currents. On the flip side, as far as I can tell, it’s entirely possible for a code-compliant installation to give you a moderate zap if you touch the neutral with the breaker off: if you have a long feeder t…

Atleast in germany the standard breakers don't either but the GFCI does and 3-phase breakers need to interrupt all phases. The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point. Plus the breakers will trip at 50A inrush anyway. (From experience, 50V AC won't kill you unless you are standing in a bathtub and covered yourself in condu…

> The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point.

Hmm. Are phase-to-neutral loads permitted? If so, does this mean that the building and ground are allowed to carry neutral currents? This seems like a bad idea.

I’m not an electrician, but I’ve seen enough problems caused by “objectionable current” (the US code name for currents through what is supposed to be ground even in the absence of a fault) that I think that neutral should be treated as a hot wire whose voltage to ground just happens to be quite low. This would involve all breakers switching the neutral as well as having a reliable mechanism to detect neutral-to-ground faults.

Newer US GFCI devices are supposed to detect neutral-to-ground faults, so that’s a start, but I don’t think any of them will actually disconnect the neutral if such a fault is detected. They do this by inductively coupling a low voltage 120 Hz common mode waveform on hot + neutral, or maybe just on neutral. It’s a cute trick.

Re: Lockout-Tagout

#84

Post by gtkspert »

symplee wrote: post #45

Any software patterns comparable to this? (Would help to have a use-case example. And how the pattern helped Vs. what was being done before)

Here's one: https://www.reddit.com/r/announcements/comments/4y0m56/why_r...

Failure to isolate (lock-out) puppet from switching things back on during a migration.

Re: Lockout-Tagout

#85

Post by Cthulhu_ »

frankwiles wrote: post #6

When I started at the Lawrence Journal-World (the company who Open Sourced Django) I was forced to watch a really old cheesy video about Lock-Out Tag-Out which at the seemed stupid for a web developer. Then I was walked to the office past some of the biggest machines I’d ever been near to that point in my life. Then I got it. It definitely saved a few peoples limbs at that company alone.

In software development the closest equivalent I can think of would be locking files in older version control systems like SVN.

Re: Lockout-Tagout

#86

Post by Cthulhu_ »

symplee wrote: post #45

Any software patterns comparable to this? (Would help to have a use-case example. And how the pattern helped Vs. what was being done before)

Locking files in SVN so other people can't edit them until you've unlocked it again.

I've never seen it used, and the only references I can think of was where it was just annoying, if not a risk (someone locking a file then leaving over the weekend or the company entirely).

Re: Lockout-Tagout

#87

Post by kom0 »

ajhurliman wrote: post #35
taneq wrote: post #9

After working in mining for a long while, where this kind of isolation procedure is standard and is taken very seriously (pretty much any breach of procedure is an instantly firable offense) it's terrifying coming back home and seeing people working on house wiring etc. with nothing more than a turned-off circuit breaker protecting them from electrocution or other injury. I've seen some trades start to pick up isolat…

Nuclear also takes this very seriously.

+1 for this one, I work in a nuclear power plant and we use this system even for patch panels.

Re: Lockout-Tagout

#88

Post by zaarn »

amluto wrote: post #83
zaarn wrote: post #63

Earlier quoted context omitted.

Atleast in germany the standard breakers don't either but the GFCI does and 3-phase breakers need to interrupt all phases. The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point. Plus the breakers will trip at 50A inrush anyway. (From experience, 50V AC won't kill you unless you are standing in a bathtub and covered yourself in condu…

> The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point. Hmm. Are phase-to-neutral loads permitted? If so, does this mean that the building and ground are allowed to carry neutral currents? This seems like a bad idea. I’m not an electrician, but I’ve seen enough problems caused by “objectionable current” (the US code name for curren…

Any building since 2007 has a GFCI installed (TAB2007-6.1§10 in Germany). Not as is common in the US in the sockets but in the breaker box itself. GFCI sockets and plugs are very rare and only exists for legacy installation that cannot be upgraded (insurance is expensive without one).

We use the TN-C-S system, wherein before the GFCI you have 3-phase with a PEN that is shorted to ground when it enters the building, then it is split into PE and N wires. The GFCI is 3-phase with only 1 phase being put into the building (usually, though multiple phases aren't uncommon in larger housings). The PE wire is connected to the heating system and various other ground potential points (either to provide ground or obtain ground potential). The N wire is shorted to PE before entering the socket (or the socket itself shorts these two). Once it leaves a socket the entire thing becomes unpolarized, so to speak, so devices after the socket can't short PE and N without polarized plugs.

This avoids problems with the inrush since the inrush voltage against ground will be grounded away shortly after entering the socket (and trip your breakers). It also means that it's less likely that a single broken wire results in the entire GFCI becoming useless, though if neutral is broken it can become somewhat dangerous (but the device stops working).

Re: Lockout-Tagout

#89

Post by Chirael »

n0ric wrote: post #15
black6 wrote: post #10

Earlier quoted context omitted.

In my experience this is not true. Some LO/TO locks even have plastic shackles and bodies (for the obvious electrical work). They’re not supposed to be pick proof and super secure—they’re a visual and physical reminder that the system is secured for worker safety. If a lock needs to be removed by someone other than the lock owner there is an OSHA process to remove out that involves cutting and discarding that particu…

I recommend watching LockPickingLawyer's video on the lock the parent comment is talking about: https://youtu.be/y4XGY0_cwcM . Master used a very pick resistant core for their LOTO locks but skimped out on the higher priced general-use models.

Yes, lock pickers love to work on LOTO locks because of this; you can see a lot of these videos by searching YouTube for #LotoLockTuesday

Re: Lockout-Tagout

#90

Post by PudgePacket »

Cthulhu_ wrote: post #86
symplee wrote: post #45

Any software patterns comparable to this? (Would help to have a use-case example. And how the pattern helped Vs. what was being done before)

Locking files in SVN so other people can't edit them until you've unlocked it again. I've never seen it used, and the only references I can think of was where it was just annoying, if not a risk (someone locking a file then leaving over the weekend or the company entirely).

I've seen it used in games. Often serialised assets won't be text diff friendly. Two people editing the same data will conflict and it won't be possible to merge the result. The solution is only one person checks out the file at a time.
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