is 240v really that dangerous

[Dave54]

Where I worked, there was often more than one thing fed from an isolator or a fuse. Nothing labelled up of course. Had that thing of some idiot putting the power back on happen several times. Including removal of signs. "You'd stopped the whatever so we put the fuse back in" Fair enough, something shouldn't be switched off, but what about finding whoever has pulled it first and telling them?
Lighting boards fed all sorts because there was a neutral in there. Instruments were a favourite. The feed for the coolant temperature recorder for the mill was on the same fuse as the lighting over one of the control desks on a completely different strip processing line. You can guess how I know, and why I remember!

 

[SimonH2]

The feed for the coolant temperature recorder for the mill was on the same fuse as the lighting over one of the control desks on a completely different strip processing line.

But that would have been obvious from the records ... err ... oh yes, I see the problem

At my last place I tried to get to a state where we had a plan of the building with layers for the various services - my specific interest was the IT cabling, plus the HVAC (that's heating and ventilation, not high voltage). It never happened.
Part of the problem was that stuff got labelled (either on the equipment for distribution boards, or in the database for the IT stuff) with things like "Sue's Office" or "FD office" which was fine until people did the periodic musical offices.
I couldn't even get people to agree on giving offices/locations a code or number that could persist across changes in use or occupant.

 

[JohnD]

in the old days you could take the fuse out and put it in your pocket.

 

[JohnW2]

in the old days you could take the fuse out and put it in your pocket.

I've heard stories of that approach being thwarted by someone who had a supply of spare fuses!

Kind Regards, John

 

[Dave54]

The feed for the coolant temperature recorder for the mill was on the same fuse as the lighting over one of the control desks on a completely different strip processing line.

But that would have been obvious from the records ... err ... oh yes, I see the problem

At my last place I tried to get to a state where we had a plan of the building with layers for the various services - my specific interest was the IT cabling, plus the HVAC (that's heating and ventilation, not high voltage). It never happened.
Part of the problem was that stuff got labelled (either on the equipment for distribution boards, or in the database for the IT stuff) with things like "Sue's Office" or "FD office" which was fine until people did the periodic musical offices.
I couldn't even get people to agree on giving offices/locations a code or number that could persist across changes in use or occupant.

A you say, "the records " The problem was of course that there had been numerous modifications, additions, and repairs over the years. All carried out by numerous people on different shifts, many of whom had left or retired. Although there were fairly comprehensive drawings, and I suppose cable schedules and so on (although I never saw those), most of the records hadn't been modified or updated. Distribution boards had often not been properly marked in the first place, or the paper had been eaten by the wonderful steel dust and hydrofluoric acid atmosphere in places there!

As JohnD says you could and did put the fuse in your pocket. Unfortunately that didn't stop someone removing a fuse from another circuit to replace it with! That's what happened with the job I mentioned above.
ETA Missed the later post about spare fuses.

 

[Adam_151]

As JohnD says you could and did put the fuse in your pocket. Unfortunately that didn't stop someone removing a fuse from another circuit to replace it with!

I think I would be tempted to add a link from the outgoing way of the fusecarrier to earth and leave the fuse in the bottom of the board... one who puts a 3036 fuse in against a short isn't normally in a hurry to repeat the experience!

 

[PBC_1966]

I think I would be tempted to add a link from the outgoing way of the fusecarrier to earth and leave the fuse in the bottom of the board... one who puts a 3036 fuse in against a short isn't normally in a hurry to repeat the experience!

One way of doing it! But certainly if there's no way of guaranteeing that some idiot won't ignore your notice and just shove a fuse back in anyway (borrowed from another position if necessary), disconnecting the live from the terminal and leaving isolated (or earthed) in the board sounds like a good idea.

 

[Adam_151]

That doesn't teach them not to do it again though!

 

[Jackrae]

As an observer, with no knowledge of their particular working practices, I admire the linesmens' technique of strapping all phase lines together and then down to earth. Covers for both unauthorised errors and lighting strikes.

My offshore sparkies all had serial numbered padlocks for personal application to lock-off claws. Every isolation had to be logged and everyone working on the circuit was required to fit their personal padlock to the claw and log it in the book. That way no-one could re-energise the circuit until all locks were removed and all personnel clear of the hazard. Woe betide the individual who went off on leave without removing his personal lock beforehand. Of course such systems are only 100% effective if circuits are constructed as intended and everyone plays by the rule.

 

[ban-all-sheds]

I couldn't even get people to agree on giving offices/locations a code or number that could persist across changes in use or occupant.

Did you document a risk assessment and send it to the chief exec and the HSE?

 

[SimonH2]

I think I would be tempted to add a link from the outgoing way of the fusecarrier to earth and leave the fuse in the bottom of the board... one who puts a 3036 fuse in against a short isn't normally in a hurry to repeat the experience!

A friend from long ago used to work in the broadcast industry. One of his tales was when sent to work on a faulty transmitter - where the fault made one of the big valves glow "quite hot". Suddenly there was a bang and all the breakers tripped. He looked round the end of the rack to see the apprentice, "frozen in time", with a can of spray freezer aimed at what was left of the valve - once the cold spray hit the hot glass, the glass just disintegrated into a ring of dust round the base of the valve.
I bet he never did that again

Oh yes, that same "friend" also had this trick of getting someone to do something - in my case we were playing with signal generators and oscilloscopes. He suggested that while the signal genny was connected to the x input, I touched the signal output and y input with my fingers. I hesitated, and then did it - and I bet most of you have already guessed that as I "made the circuit" he shouted BANG from right behind me B'stard
Then we went on to see what lissajous figures we could make like that - basically only ovals of various shapes when both signals are the same frequency.

Did you document a risk assessment and send it to the chief exec and the HSE?

No, because for the areas I was involved in it wasn't a safety issue, and those responsible for/involved in the electrical side were happy enough with the situation. We're I to find myself back there (not very likely) then I'd probably push it a bit harder - back then the people maintaining stuff were the same ones that put it in - now none of them are still there the "local knowledge" is gone.
It's still not "bad" though - the electrical work was fairly well done, circuits were fairly logical, there are loads of tallies for which circuit sockets are on. AFAIK none of this borrowed neutral stuff going on - the guys that used to do the electrics wouldn't have allowed that.

 

[jackthom]

One of my favourite old BBC2 Trade Test Films, "On the Safe SIDE"
A little more than 240V here....

 

[SimonH2]

Ah, nostalgia. I remember watching a film that was very similar to that when I was a bit too young to understand what they were on about. But I recall I knew just about enough to know that high voltages give big flashes, so I enjoyed the "punchline"

 

[mattice]

Never store PVA glue with your multi-meter...... my wife found me....

 

[PBC_1966]

One of my favourite old BBC2 Trade Test Films, "On the Safe SIDE"
A little more than 240V here....

Then there were the short TV public information films - "Only" 240 volts or thereabouts here, but another demonstration of how it can be more than "just a tingle."