Isolation and permit to work: the padlock is the easy bit

Everybody’s changed a light fitting at home. You flick the switch off at the wall, get the steps out and crack on. Nothing happens, and that’s exactly the problem. Nothing happening teaches you the switch was enough.

What you should have done is walk to the consumer unit, drop the breaker and put something on it so nobody helpfully flicks it back on while your fingers are in the ceiling rose. That’s the whole of isolation, and it scales all the way up to a 400 volt panel on a production line.

Off isn’t the same as isolated

A stop button stops the machine. It doesn’t isolate it. The control circuit’s still live, the drive’s still holding, and anything capable of telling that machine to run is still capable of telling it to run. I’ve walked onto sites where the lads knew that perfectly well and still worked off the stop button, because it’s quicker and because it’s never bitten them.

Isolation means the energy can’t get to the thing you’ve got your hands inside. Breaker off, locked, and proved dead at the point you’re working. Proving it is the bit that gets skipped. Turning the isolator and assuming isn’t the same as putting a tester on it and knowing.

The padlock isn’t for you

This is where people have it backwards. The lock isn’t there to remind you the machine’s off. You know it’s off. You turned it off. It’s there to stop somebody who has no idea you’re inside it.

That’s why one lock on a hasp with three sets of hands on the job is no good. Everyone working on it puts their own lock on, and it doesn’t come back on until the last one comes off. The tag matters as much as the lock. A padlock with no name on it just tells the next bloke that somebody, somewhere, might be working on something. A tag with a name, a date and the job on it tells him who to go and find.

The energy that’s already in there

Electricity’s the one everybody thinks of, and it’s rarely the one that catches people out. There’s air still sat in the lines, springs under tension, a ram that’ll drop the second you break the seal, product in a hopper over your head, and surfaces still hot enough to take skin off. In most of the factories I walk into the electrical isolation is decent and the stored energy hasn’t been thought about at all.

So the question isn’t only what feeds this. It’s what’s still in it, and where does that go when I open it up. Bleed it, chock it, let it cool. Then prove it.

A permit is a conversation somebody wrote down

Permit to work gets treated as another form, and treated as a form it dies as one. What it actually is: somebody who understands the risk and somebody who’s about to take it, agreeing out loud what’s been done, what’s still live, where the limits are and when it comes back. The paper is the record of that conversation. If the conversation never happened, the paper’s worth nothing.

Here’s the test I’d run. Pick a job that’s under a permit right now and ask the bloke doing it what the permit says. If he can tell you without going to look, it worked. If he has to go and find it, you’ve got paperwork.

None of this costs much. A handful of locks, a set of tags and a habit. The habit is the expensive bit, because it has to hold on a wet Friday afternoon when the line’s down and everybody wants it running. If you’re not sure yours would hold, that’s worth finding out before something makes the decision for you.