Gas Pipe spark

[Bernie2]

This is more for the learner than the old hand.

Did you know static charge can build up in a plastic gas pipe?

It releases its charge when you cut into it, possibly earthing out down the saw or cutter your using. In the States people have been killed.

Just what you wanted to know isn't it?

Apparently the build up is caused by the impurities in the gas rubbing on the side of the pipe as the gas flows past.

So if you turn the gas off and cut into the pipe you can get a spark, which you may not expect to get off plastic pipe.

Its best to make sure you purge the pipe and surrounding area, to well below the Lower Explosive Level of about 4%.

I've been in a small gas explosion, a leaking LPG bottle, and I can tell you its blown up, damage done, before you can blink. Its a big tearing fireball all you see is a quick bright flash and then you smell burnt hair.

Anyway saves going the barbers.

So its best to do the health and safety first not afterwards. like some old donkey did, unless of course you do want a short back and singe. 🙂 🙂🙂🙂🙂🙂

 

[Plouasne]

Thanks for the info Bernie, just done a bit of googleing, this link might help to explain

http://www.oildompublishing.com/PGJ/pgjarchive/Dec01/StaticElec.pdf

EDIT:: Just how many plumbers or fitters, "bridge" (with a jump lead) a copper tube before they cut into it ??, in my time I have had a couple of "tingles" caused by stray electric currents, and faulty earth's, one I remember was when I cut into the cylinder hot flow close to the cylinder to fit another service, when measured it was just over 100 volts
I also remember reading some thing from Australia, about plumbers getting killed when working on water service's to properties, because of faulty earth's and the metal service pipe was the only alternative earth return

 

[Plumbstar Tom]

You should never expect the property to be correctly earthed and take precautions

I have heard of people been shocked but not killed, thats is scary

 

[Bernie2]

I must admit you do have to be wary. I once went to a job which had had earthing problems but I was told they where all sorted out.

Anyway I went to cut in a new stop tap in the rising main. I did not have a bridge with me at the time, but thinking "Well its just been sorted it should be okay!" No it wasn't, I got a bang that threw me across the bathroom floor.

I came around, to find the apprentice laughing hysterically and pointing at my head.

I had long hair at the time and it was all standing straight up like one of those cartoon characters. But it took me a while to see the funny side, I can tell you.

Now I won't cut a pipe without a bridge in place. As they say experience is a good teacher.
But then, like many other Plumbers I suppose, in the heat of the moment your prone to forget if your rushing.

Incidentally, I think, its against the gas regs not to have a bridge in place if your cutting into gas lines.

 

[Plumbstar Tom]

It is so easy to think it will be okay and its alot quicker than going back to the van to get a bridge but if you didn't do the work then you cant trust it

Would love to see a photo of the long hair standing on its end

I must admit i have cut many a time with out a bridge and been fine but fear its a ticking time bomb!

 

[Plouasne]

The other "nasty" I have come across (and who ever does this wants castrating in my opinion), and that is to run an electric cable in (both blue and black I have scene) poly water pipe, this is tantamount to a man trap, for the unsuspecting

I have also come across running side by side in a vertical duct, both black poly water main and black SWA 3 phase electric cable, both just about the same size, and when all you can do is just get your arms in to work and its dark, this can be a trap as well, check and check again, work safe

 

[david williams]

you should always carry out you own risk assesment on any job

 

[Plouasne]

A note to the moderators,

Could these postings form another section as a safety section to remind the youngsters and the not so young as to what could happen, and also could other posters post their experiences of dangerous practises they have come across in the past and present, so that others can be aware of what could lie in wait for them

 

[Plumbstar Tom]

Yep

Health and safety is very important, whilst it is time consuming I know there will be a point where I will say to my self.. 'I'm glad I checked that' As I said you cant trust anybodies work accept your own

 

[Bernie2]

Hmm!

Yes a new section may be good.

There is simply so much to Health and Safety as well as general Plumbing Knowledge to cover, while trying to write simple answers to questions or in posing questions.

I also feel it would be good for other reasons. One reason being, is that we could also learn from the experiences and knowledge of others, rather than keeping knowledge confined to just that taught on the perhaps limited knowledge of a Plumbing course.

It may help the new people to the trade.

For instance pure water does not conduct electricity, but nearly everybody tells you it does. Its the impurities in the water that conduct not the water. That may be handy to know for mixed metal systems.

 

[Plumbstar Tom]

Yes, water compound is H2O which is 2 Hydrogen to 1 Oxygen, Neither are metals and the laws of electric conduction require metal to conduct

Impurties such as calcium are metals

 

[flat pack]

around 25 years ago i was installing temp water supply's on sites , black poly.
at the same time on other sites the ground worker digging up black armer cables and guess yes lots of bangs, now days we have blue red and grey,yellow..
thank god/ manufacturers
knowledge is a wonderful thing

 

[Plouasne]

Where I am living, all services, have to be in a protective corrugated outer sleeve, red = electric, yellow = gas, blue = water, green = telephone, these to be laid in sand and no less than 150mm above the sleeve a same colour as the service, plastic grillage is to be laid , stop a lot but not all "accidents", these are mostly down to an over enthusiastic "banks man" or the lack of one

 

[secret squirrel]

Although I don't touch gas, Am I correct in thinking that if the build up electricity is on the gas pipe as I cut into the water the electricity can "jump" over to the copper water pipe and earth through me...

 

[Plouasne]

SS,

The way I understand it, is that the friction of the gas passing down the pipe, on the pipe wall can build up a static charge, on the inner face of the pipe, and the pipe material being an insulant to most normal electric charges, that is where it stays, until the pipe is cut, then the electric charge can leak out via the metal cutting tool to earth sometimes passing through the person holding the tool, and if it arc's this can ignite the gas

At one time the incoming service pipe was used as an earth return, independently of the neutral, this can cause problems like the brass/bronze tapping ferule getting corroded away, it can also be a danger to a person cutting the pipe, also now with that poxy PME system with the earth being bonded to the neutral at the cut out, if further down the street the neutral breaks down the only return path for the electric is via the earth return, the cross bonding of the pipe work in the house, and then via the incoming water, and or gas service, now if this is happening unbeknown to you and you go to cut into the pipe, you have your hand on one side of the pipe, and then you go to hold the other side of the pipe, the only way for the electricity to go to earth is through your body, that's why the gas says that there should be a jump lead fitted either side of the cut, before the pipe is cut, and only removed after the work is finished

I have seen what a dodgy electric supply can do

This was the coaxial cable, copper conductor poly insulation, braided aluminium neutral then poly outer cover, the surmise is that when it was unrolled the cable picked up a nail or a sharp stone which pierced the cable to the conducting core, this was fine and dandy when the soil was dry, but when the soil was wet the water seeped into the pieced insulation the electricity arced across to the surrounding ground, the arcing dried out the ground around the cable, for a time, before the arcing re-commenced, by the time the SWEB arrived a good half a metre of cable had been burnt away, it was like watching a very mini earthquake to see the place where the cable was arcing, has it arced