Third Rail - Safety on Track?

[43066]

Breakdown voltage in dry air at sea level is around 30,000 volts per centimetre, which means for 750 volts, the distance would be around a quarter of a millimetre if my sums are right. I have read about London Underground staff wearing 'shunter's shoes' with thick insulating soles and also Tyvek trousers (Tyvek is a non-conducting plastic material that is very difficult to tear or cut). Of course even if you don't touch the rail you could make a short by dropping something metal and the flash would be dangerous. There is a well known fatal case of a staff member in shorts and tee shirt going between wagons and touching the juice rail momentarily with a leg and a wagon buffer with a bare arm. There was, sadly, a probable reason for lack of caution.

Is there any publicly available accident report for this? Curious as to the “reason for lack of caution”.

 

[contrex]

Another third rail hazard that I hadn't realised was mentioned by Richard Catlow on the uk.railway Usenet group. A short-circuiting device had been put down bridging a juice rail and running rail, and forgotten. The attending staff stepped back when power was to be restored. At the moment this happened, the magnetic effect of the huge and fast rise in current through the not-insubstantial metal bar caused it to fly violently some feet in the air.

== Doublepost prevention - post automatically merged: 12 Dec 2022 ==

Is there any publicly available accident report for this? Curious as to the “reason for lack of caution”.

I said a 'probable' reason for lack of caution; I think on balance that 'possible' would be fairer. Page 37, 'Medical Evidence'.

https://assets.digital.cabinet-office.gov.uk/media/547c9048e5274a42900001bf/R142007_070529_Deal.pdf

 

[43066]

Another third rail hazard that I hadn't realised was mentioned by Richard Catlow on the uk.railway Usenet group. A short-circuiting device had been put down bridging a juice rail and running rail, and forgotten. The attending staff stepped back when power was to be restored. At the moment this happened, the huge rise in current through the not-insubstantial metal bar, combined with the Earth's magnetic field, caused it to fly violently some feet in the air.

== Doublepost prevention - post automatically merged: 12 Dec 2022 ==



I said a 'probable' reason for lack of caution; I think on balance that 'possible' would be fairer. Page 37, 'Medical Evidence'.

https://assets.digital.cabinet-office.gov.uk/media/547c9048e5274a42900001bf/R142007_070529_Deal.pdf

Thanks - makes complete sense now. What a sad business.

 

[E27007]

On AC lines the running rails are the earth return but unless there is a total fairly pure of multiple bonding points they will always be effectively at a safe voltage to Mother Earth.

om DC Lines they are the Hegative return conductors but again unless the return bonds at the substations are missing they will also always be at a safe voltage.

For AC line. Do not forget the famous "Red Bonds" the bonding cable usually found at ballast level , the red bond connects running rails for the AC Traction Return, usually the metalwork of the Portal or Post
As per the Rulebook AC Instructions, do not touch or approach a broken Red Bond, phone and report to the ECO, one end of the bond will be at earth, but the other end could be live at 25kV

 

[jamiearmley]

Do not forget the famous "Red Bonds" the bonding cable usually found at ballast level , the red bond connects running rails for the AC Traction Return.
As per the Rulebook AC Instructions, do not touch or approach a broken Red Bond, phone and report to the ECO, one end of the bond will be at earth, but the other end could be live at 25kV

It's my understanding that a recent rule book update declared that all bonding cables should now be treated as 'red' : i.e. not all "red bonds" are actually coloured red anymore...

 

[E27007]

It's my understanding that a recent rule book update declared that all bonding cables should now be treated as 'red' : i.e. not all "red bonds" are actually coloured red anymore...

I have just checked the AC Instructions Rulebook for December 2022.
You are correct in your information, and it is a new instruction

 

[contrex]

For AC line. Do not forget the famous "Red Bonds" the bonding cable usually found at ballast level , the red bond connects running rails for the AC Traction Return, usually the metalwork of the Portal or Post
As per the Rulebook AC Instructions, do not touch or approach a broken Red Bond, phone and report to the ECO, one end of the bond will be at earth, but the other end could be live at 25kV

I once saw a gruesome photograph of some incinerated would-be cable thieves in South Africa who, I think, had used a hacksaw to sever the hefty earthing conductor at a substation.

 

[Aviator88]

Voltage is rather irrelevant imo. Current ( amperes ) kills not voltage.

You need voltage to create a current - they're directly proportional. Due to the resistance of dry skin, you generally need at least 250-500 volts to enter the body. Once you have current flowing through your bloodstream, if your heart lies along the easiest route to earth, that's when you're in trouble.

Incidentally, this is why you'll generally only tend to see voltage warning signs above ~ 100 volts and why you can grab hold of both terminals of a 24V battery without consequence!

 

[Seejwalker]

As we sometimes say in the army " fear keeps you sharp" don't let the fear control you.

What army is that in? I’ve never come across this ‘saying’ before.

 

[Newboysouth]

You need voltage to create a current - they're directly proportional. Due to the resistance of dry skin, you generally need at least 250-500 volts to enter the body. Once you have current flowing through your bloodstream, if your heart lies along the easiest route to earth, that's when you're in trouble.

Incidentally, this is why you'll generally only tend to see voltage warning signs above ~ 100 volts and why you can grab hold of both terminals of a 24V battery without consequence!

Of course, it wasn’t a jibe I was just saying that it doesn’t matter whether it is 700 volt or 7000 volt, it’s the amps that will do the damage fwiw.

 

[Ducatist4]

10mA is enough to stop your heart.

 

[AndrewE]

You need voltage to create a current - they're directly proportional. Due to the resistance of dry skin, you generally need at least 250-500 volts to enter the body. Once you have current flowing through your bloodstream, if your heart lies along the easiest route to earth, that's when you're in trouble.

Incidentally, this is why you'll generally only tend to see voltage warning signs above ~ 100 volts and why you can grab hold of both terminals of a 24V battery without consequence!

Not true... I believe that the hundreds of amps available in low-voltage (like 24) DC bus-bars in electro-plating shops (maybe which used to be) are/were quite a serious electrocution risk.

 

[Elecman]

The various standards nominate safe voltages to be 55 volts ac and 60 dc so 24 volts are perfectly safe provided there is no penertration of the skin the points of contact

 

[contrex]

The various standards nominate safe voltages to be 55 volts ac and 60 dc so 24 volts are perfectly safe provided there is no penertration of the skin the points of contact

Years ago the driver of a milk float was found dead under his vehicle, and electrical entry/exit marks were found on his chest. He was wedged under the vehicle (had crawled there to fix something) and was pressed hard against the 48v battery terminals. I believe death during electrocution by a low-voltage current is often secondary to a heart rhythm disorder. It is very rare.

 

[Vespa]

You l

What army is that in? I’ve never come across this ‘saying’ before.

You probably haven't heard it at all, it's still true "fear do keep you sharp"

 

[Seejwalker]

You l

You probably haven't heard it at all, it's still true "fear do keep you sharp"

No it doesn’t. It makes you hesitant, and hesitation is a killer.

 

[Vespa]

No it doesn’t. It makes you hesitant, and hesitation is a killer.

If you allow it control you of course, if you use it to as a motivator to react quicker that's improves your chance of survival and awareness.

We're going off topic now.

 

[Seejwalker]

If you allow it control you of course, if you use it to as a motivator to react quicker that's improves your chance of survival and awareness.

We're going off topic now.

 

[AndrewE]

If you allow it control you of course, if you use it to as a motivator to react quicker that's improves your chance of survival and awareness.

We're going off topic now.

No we're not. The OP said

but I'm paranoid I'm gonna slip one time and be brown bread. Do you think it's a stupid reason not to pursue the opportunity?

and I think that is stupid. You pay attention during your safety training and make sure you keep it in mind and do what you were told. You think carefully about how your workmates behave and make sure you don't copy the casual ones. You look at the way you work, compare it with your training and talk to the supervisor or COSS (if they still exist) or your Safety Rep of you don't think it seems right.

If you are that risk-averse then I don't know how you manage to cross a road, & I guess you would fail a driving test from being unable to judge whether it was safe to pull out into a gap in the traffic on a roundabout...

Just accept that most humans are extremely good at risk assessment, and normal life depends on just that.

 

[E27007]

No we're not. The OP said

and I think that is stupid. You pay attention during your safety training and make sure you keep it in mind and do what you were told. You think carefully about how your workmates behave and make sure you don't copy the casual ones. You look at the way you work, compare it with your training and talk to the supervisor or COSS (if they still exist) or your Safety Rep of you don't think it seems right.

If you are that risk-averse then I don't know how you manage to cross a road, & I guess you would fail a driving test from being unable to judge whether it was safe to pull out into a gap in the traffic on a roundabout...

Just accept that most humans are extremely good at risk assessment, and normal life depends on just that.

I'd take the job and not worry, they teach you how to step over the juice rail in your PTS (Personal Track Safety) course, at first they use a dummy non-live track, then they take you onto a quiet line somewhere to try the "real thing" you cannot go on the track without the course under your belt. Tens of thousands of railway workers have and continue to step over the juice without mishap, it is becomes routine, just like a pedestrian crossing a road. Very few workers ever have a juice incident such as by falling or tripping.

 

[Aviator88]

Not true... I believe that the hundreds of amps available in low-voltage (like 24) DC bus-bars in electro-plating shops (maybe which used to be) are/were quite a serious electrocution risk.

I can absolutely assure you that current cannot exist without a voltage.

24 VDC bus bars in the application you mention are a burning risk, not an electrocution risk - the current is so high because the resistance of the material is so low. It's possible to create a short that will superheat and melt the material that will then cause a nasty burn, but that's it. Unless you have a gnarly wet open wound on your hand, you could hang off a 24V source all day long without consequence!

 

[Trackman]

I always thought you work near third rail during a isolation or they use what I can only describe as kick boards that go over the third rail I’m sure if wrong I will be corrected by more experience track workers

Do you mean 3rd rail shields? Only used in iffy places during live work and very temporary.

If you allow it control you of course ...

True, you control the juice rail not the other way around.

 

[QueensCurve]

I’ve seen people in possessions sitting on the juice rail having a smoke! Admittedly that is a situation where they knew it would (or should!) be isolated, but it wouldn’t be my choice of a place to sit during a break. It presumably only takes one wrong switch in the ECO and they’d suddenly find themselves sitting on old sparky…

I know overhead line sections being worked on are physically isolated and padlocked - not sure if anything similar happens for the third rail.

Are they always physically isolated or are they sometime tagged out?