It definitely saved a few peoples limbs at that company alone.

EDIT: This is obviously mentioned in the article! Mea culpa ;-)

#edit: Oxford comma ocd

Pretty recent death caused partially by not following this procedure.

SRE's and operations people can pick up good habits from manufacturing gigs. A lot of the same concepts like uptime, good documentation, procedure, discipline are really important to the business at all levels. When lives are at risk good companies put a large sum of time and money in making sure everyone is on the same page.

(Would help to have a use-case example. And how the pattern helped Vs. what was being done before)

There's a concept called the hierarchy of hazard control [2]. At the top is eliminating the hazard - just removing it completely. It goes down through substitution, engineering controls, admin controls and then protective equipment is right at the bottom as the least effective method of protection. I&L aims to address the hazards right at the top by eliminating them, which is by far the most effective means of ensuring safety.

It does this by following a process: First, isolate the energy source. Secondly, lock that isolation out so it cannot be reactivated. Third, test for dead by showing that a) the isolation cannot be removed, and b) that there is no residual energy source remaining.

For example, an electrical isolation point might be a switch, which when thrown firstly breaks the circuit, but then also drains out any capacitors or other residual energy storage. The isolating person throws the switch, locks it out, tries to throw the switch back against the lock to show it's secure, then tests the system for dead by trying to power it up or by testing terminals for a voltage to prove that the energy sources have been drained. Once that's all done, they'll then complete the rest of the process and let others lock on to the system.

When someone locks on to an isolated system, there should be sufficient documentation and indication to show that the system is isolated and safe. It might mean that if a mechanical latch is rotated to the 'safe' position, there's a sign that rotates into view from the isolation point so the protected person who is locking on to the isolation can see it, whereas when it's not locked out they cannot. The protected person can in theory go and test the lockout to ensure it's in place, but usually (where I'm at) it's controlled by a dual sign-off process when the above can't be achieved. Then the protected person throws their lock on the isolation point, and that ensures that none of the isolations can be released until they remove their lock. Critically, those who place the isolation are generally a controlled set of people who are trained more highly than the protected person level who just has to know how to verify isolations are in place and then lock on. In general, the people working on the isolated system don't place their own isolations unless it's a simple system/process.

The whole process essentially provides a method of accounting for every person working on a system, and letting them be confident that it can't be powered up whilst working on it. It's not supposed to be secure locks. Mine, for example, have plastic casings, and ones designed for electrical work have a plastic bolt which I could probably easily remove with a bit of percussive persuasion. However, you also realistically generally can't stop a malicious person bypassing those safety measures, e.g. by wiring around a circuit-breaker or by undoing some bolts to remove a latch. So it's not intended to stop malicious parties, but it prevents the vastly more frequent case of were someone starts a machine when someone else is working in it.

It gets far more complex than all that too, for example covering how you pass secure isolations between shifts, or how you chain together layers of an isolated system to a single isolation point, but the above should hopefully provide some insight into why this stuff exists and why it takes the form it does.

[1]: I would consider the concept of 'safety in design' higher overall because that's about removing the hazard from existing at the design stage, but once it exists then I&L is generally the gold standard for dealing with it.

[2]: https://en.wikipedia.org/wiki/Hierarchy_of_hazard_controls

Specifically, in many rail signalling network systems, a signal will turn red when it detects a short between the two rails in its section (i.e. an axle rolls into it). It will then turn back green when that short disappears. Workers can therefore clip something between both rails, which triggers the signal relay and makes the signal light green.

This is absolutely not isolation & lockout though, because it doesn't actually remove the energy source. That's not to say it's not a valuable process though, but an isolation & lockout for this sort of circumstance either involves locking the track switches to direct traffic away from the worksite, or installing a derailer [1] on the track that phyiscally throws the train off the rail into the dirt so it stops well clear of the work site.

The above obviously doesn't work if you're working on a running system, though (which does happen, occasionally). In that instance, the track clip lets trains stop at the red light, radio to the worksite, have the worksite clear, then remove the clip, let the train through, then resume work. It's different levels of safety for different perceived risks.

[1]: https://en.wikipedia.org/wiki/Derail

My hand was in a shitty position kind of around a table leg, and the shock caused me to clamp down with my hand and kind of "chokehold" the table leg. It took me a lot longer than I thought it would to even register what was happening, and then to kind of throw myself away. I'd been shocked before, but this just kept going after I realized that it was happening and I just didn't know how to process it.

I ended up with some nasty burns on my hand, a really sore whole arm, and a scary realization of how it could have been a lot worse if just one or 2 things were slightly different.

Luckily, human skin is not highly conductive and neither are rubber soled shoes.

So if you are taking proper precautions and not kneeling on a wet floor while using all metal tools on bare wires when someone flips a breaker back on, then your risk is rather minimal.