Elecricians' safety slipups

[conny]

The company I work at, (not for), have printing machines which can travel along a track to facilitate maintenance. The manufacturer has installed yellow push buttons on the inner faces of the units. We have to press at least one of these when we are working in between the units. This prevents any of the other units from moving and possibly crashing into the ones we are working between. They are classed as personal protection devices as they cannot be accessed when the print units are locked together.

For emergencies there are red buttons at numerous locations. A red button on one production line will stop all lines running including automatic transfer cars and waste belts. This is because someone can be in danger on another line and anyone distant from him can stop the machine remotely. It does seem like a crazy idea but apparently it was used to good effect a few years ago.

 

[SimonH2]

For emergencies there are red buttons at numerous locations. A red button on one production line will stop all lines running including automatic transfer cars and waste belts. This is because someone can be in danger on another line and anyone distant from him can stop the machine remotely. It does seem like a crazy idea but apparently it was used to good effect a few years ago.

It's always a tradeoff (safety vs scale of disruption) - but as you point out, it avoids having to run across the shop floor to stop a machine causing a danger.

Reminds me of the school workshops where the supplies to everything but the lights went through a contactor with several estop buttons around the room. It do recall casually leaning on one in the woodworkshop one time when the teacher left us unsupervised. Lets just say there were some "non standard" procedures being performed (or attempted) on some of the machines so cutting the supply seemed the logical thing to do.
On another occasion, someone spotted someone about to be strangled by his apron which had become wrapped round the crossfeed drive on a metal lathe. Stopped with the estop button from the other side of the shop.

So it's not such a crazy idea !

 

[DIYTom]

Reminds me of the school workshops where the supplies to everything but the lights went through a contactor with several estop buttons around the room. It do recall casually leaning on one in the woodworkshop one time when the teacher left us unsupervised. Lets just say there were some "non standard" procedures being performed (or attempted) on some of the machines so cutting the supply seemed the logical thing to do.
On another occasion, someone spotted someone about to be strangled by his apron which had become wrapped round the crossfeed drive on a metal lathe. Stopped with the estop button from the other side of the shop.

So it's not such a crazy idea !

At my school there were two of these buttons i each lab or workshop, one on the teachers desk and a locking one on the wall. Isolated the gas and the electric. They were always locked out of use when the teachers left the labs. I remember one being used to good effect once when one of my class mates set a gas tap on fire. Had my chemistry teacher diving across the room and slamming the button.

 

[SimonH2]

... when one of my class mates set a gas tap on fire.

Ah, so I wasn't the only one to do that then - used to be good fun getting a flame 3ft long All it got from our teachers was a stern look and a "stop it" instruction.
The other trick (shown us by a teacher ) was pulling the hose off a bunsen and blowing down the gas tap - puts the other bunsens on the bench out. In hindsight, doing enough to put the whole lab out wasn't a good idea - but luckily it didn't blow up in the pipes

 

[JohnW2]

The other trick (shown us by a teacher ) was pulling the hose off a bunsen and blowing down the gas tap - puts the other bunsens on the bench out. In hindsight, doing enough to put the whole lab out wasn't a good idea - but luckily it didn't blow up in the pipes

A variant of that I saw at school (which resulted in 'serious consequences' for the culprit!) was not to blow down the pipe but, rather, connect it to a water tap and turn the tap on!

Kind Regards, John

 

[diyer56]

We had a similar incident in our chem lab at school whereby one of the gas taps was connected to the vacuum tap via a Bunsen hose!

 

[ban-all-sheds]

Children + gas + means of ignition + chemicals = what could possibly go wrong.

 

[TheKeymeister]

Further if I isolate and earth a section for work, all the keys are given with the Permit to Work to whoever is ding the work, the keys being in a locked box to which only I have the key.

That's interesting to know, round here the east mids SAPs keep the keys in their pocket, west mids will only use key safes (issuer and recipient have individual keys, both required to open safe), and south west/south wales put the keys in a brown envelope that's given to the recipient with the permit

I've heard a tale of someone dropping a jemmy across the busbars in a BT exchange. It glowed dark red, bright red, yellow, and finally dripped off Can't imagine he was very popular.

I used to work at BT on that sort of stuff and have heard a similar tale before, most of the open bars (which still exist as far as I know!) are 27 volt with thousands of amps ready and waiting from the rectifiers and batteries. I've still got a VHS somewhere from BT which was basically "what happens when you short these massive batteries out", when I find it I'll convert it and upload it

 

[SimonH2]

I used to work at BT on that sort of stuff and have heard a similar tale before, most of the open bars (which still exist as far as I know!) are 27 volt with thousands of amps ready and waiting from the rectifiers and batteries.

50(ish)V surely ? Nominally 48V batteries on float.
I've also heard that one gets a large bill for recharging the batteries when that happens.

 

[mikedelta]

Yes, that's correct. Insulated bar 50v DC uninsulated bar is earth.

 

[TheKeymeister]

I used to work at BT on that sort of stuff and have heard a similar tale before, most of the open bars (which still exist as far as I know!) are 27 volt with thousands of amps ready and waiting from the rectifiers and batteries.

50(ish)V surely ? Nominally 48V batteries on float.
I've also heard that one gets a large bill for recharging the batteries when that happens.

Most of the 'Central' 54v power plants were retired before my time, there's a couple still kicking around but mostly replaced with smaller individual units that use cables and distribution boards rather than bus bars back when System X and AXE10 came in. The old transmission stuff, which is amazingly still running, uses 27 volt central power plants still, mostly with open busbars...not sure why they use a lower voltage but they do!

I've had a couple of long nights replacing batteries when we've had prolonged mains failures and the generator didn't start, discharging everything past the point of no return. I suppose the old wet cells would have recovered from that unlike the modern VRLA cells use now.

 

[ban-all-sheds]

The old transmission stuff, which is amazingly still running...

Telcos are even worse than retailers for keeping old stuff running.

"If it ain't broke don't fix it" can be a reasonable philosophy, but when it gets to the point where if it breaks it can't be fixed, and you can't replace one broken thing with a new one because nothing can talk to the old ones still standing....

 

[JohnW2]

The old transmission stuff, which is amazingly still running, uses 27 volt central power plants still, mostly with open busbars...not sure why they use a lower voltage but they do!

What exactly was/is the "27V". Are you perhaps talking about 24V worth of batteries, with about 27V across them when on float?

Kind Regards, John

 

[davelx]

Most of the 'Central' 54v power plants were retired before my time, there's a couple still kicking around but mostly replaced with smaller individual units that use cables and distribution boards rather than bus bars back when System X and AXE10 came in. The old transmission stuff, which is amazingly still running, uses 27 volt central power plants still, mostly with open busbars...not sure why they use a lower voltage but they do!

I've had a couple of long nights replacing batteries when we've had prolonged mains failures and the generator didn't start, discharging everything past the point of no return. I suppose the old wet cells would have recovered from that unlike the modern VRLA cells use now.

Before I retired I was based for a few years at BT's Baynards House exchange, most of which had been converted to office space. There were huge open busbars running along the ceilings in the corridors. I was there when they took all the central batteries out, but the busbars remained. I would think they'd be worth a tidy sum.