Rank: Forum user 
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Does anyone know of any issues/hazards of using wet cutting techniques of concrete/stone with a stihl saw or such near to overhead lines?
In particular I'm being told that due to the spray off the blade its been 'banned' near railway overheads and third rail because the spray would put the operator in danger of electrocution.
We use the hand pump water cans, so surely the risk of the spray from a burst pipe hitting overheads would be minimal?
Has anyone come across this before?
Thanks.
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Rank: Super forum user 
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Are the "Railway" overheads & 3rd rail d.c.?
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Rank: Forum user
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Rank: Super forum user 
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Brown900431 wrote:Yes, they would be.
3rd rail is 650V to 750V DC Overheads are 25kV AC.
I'm not aware of a general prohibition, but you'd need to justify teh method by which teh water doesnj't get near the electrics.
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Rank: Forum user
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My mistake. Thanks.
I would imagine its the same as a 'normal' overhead, go through the risk assessment process. I've never read anything in HSE guidance but the guy said it was a HSE 'ban;.
I'd be more concerned if we were using a water supply from a higher pressure source, not a hand pump. Obviously the need to be in a place of safety for the trains makes a reasonable distances from the overheads and 3rd rail.
I've figured out now whether to laugh or cry!
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Rank: Super forum user
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Brown900431 wrote:My mistake. Thanks.
I would imagine its the same as a 'normal' overhead, go through the risk assessment process. I've never read anything in HSE guidance but the guy said it was a HSE 'ban;.
Well, straight away you know he doesn't know what he's talking about, because HSE is not the enforcing authority on the railways - responsibility for health and safety policy and enforcement on railways (including including heritage, metros and light rail systems) transferred from HSC/E to the Office of Rail Regulation (ORR) years ago.
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Rank: Super forum user
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Not sure I understand this question. If a bit of spray was a real safety issue what would happen when it rained?
Have I missed something?
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Rank: Super forum user
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Ok, one issue you have is that whilst water is an insulator "tap" water is not, neither would the slurry from the cutting operation.
d.c. never passes through 0V so if conduction and current flow is initiated, then if will sustain.
25kV overheads can "jump" a serious gap.
I had not even got as far as HV stuff.
Brian, the issue with the slurry from the operation is the conductivity and the potential for contamination, I suspect.
Rain water, whilst not pure, is clean in comparison.
As far as DNO overheads go, ask your DNO, they are legally bound to tell you safe working distances IIRC, due to the requirements of ESQCR, though, that is from memory & I would have to check that that piece of info is correct.
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Rank: Forum user
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Thanks for the comments.
Network Rail has very clear rules about safe distances from overheads and 3rd rails, but they talk about metal objects, tools and water JETS not sprays.
The persons point was to do with the spray from the blade and what would happen if the water hose burst.
Brian that was my point exactly, what do we do when it rains? But I do take your point as well Paul that consideration to the slurry is important (from an environmental point as well).
He was absolutely adamant that this was only a construction site issue and water suppression was banned on the railway.
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Rank: Super forum user 
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Brown900431 wrote:............The persons point was to do with the spray from the blade and what would happen if the water hose burst. ..........................He was absolutely adamant that this was only a construction site issue and water suppression was banned on the railway.
Firstly, I am assuming the work is to be carried out on NR controlled infrastructure, and not in an area outside of NR's boundary. NR can't control works outside of their boundary [in most cases], even when they say they can.
What role does the 'person' fill - does he work for Network Rail, or is he someone in your organisation?
If in doubt about spray issues - speak to your Network Rail 'interface person', asking for details of where any restrictions are set out, in Standards etc.
If this is a proper restriction, ask how NR solves the problem. [hand sprays and a tent spring to mind. But it does seem to be 'overkill']
Good Luck
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Rank: Forum user
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Thanks for the help, sorry its taken a while to reply.
It was one of our senior managers, not network rail.
I think I'll need the offer of luck!
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Rank: Super forum user
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I can’t see how a “spray” will conduct a current. A continuous flow yes but spray no. As mentioned when it rains, this does not affect the power lines. You hear the electrical discharges as the charged raindrops come off the lines (sounds like bacon frying) but there is no massive discharge.
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Rank: Super forum user
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A,
You need to remember that pure water is an insulator, so the lower the level of contamination the less an "arc" can "ionise" across a spray, but, a heavily contaminated spray can conduct depending upon what it is contaminated with as the current merely needs to track along a conductive path.
Think hopscotch for electrons. Bionic electrons if it is HV too!
Also, you need to think about the almost anything is flammable if in a small enough powder form, there is a similarity to conductivity, remembering that it is electrical bonds that bind atoms together even in insulators.
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