bonding a short section of water supply pipe

So the post Second World War policy of combining the functions of neutral and earth in just one conductor, as opposed to TN-S to save materials and labour, has resulted in us now having to main bond conductive pipes and other extraneous conductive parts with millions of metres of heavy copper cable. Were the original designers of P.M.E. short sighted?


Z.

PME was never a good idea, it is a bodge. But we are stuck with it now it seems, more patches on patches.


This thread seems to have got to a ridiculous point, whilst there MAY BE a theoretical risk of a bond carrying hundreds of Amps for an extended period, I have never seen one in any way melted or fused, and I expect this is the same for everyone here. The risk imagined by Zoomup is not reasonable, this simply does not happen, and with plastic service pipes and mains never will in the future.


If you want something to worry about, consider the MAD idea to distribute Hydrogen in the Gas system. First Hydrogen causes embrittlement to steel pipes and leaks through the smallest space in fittings, valves, etc. When it leaks it is very dangerous due to lack of any smell (the Hydrogen will leak out but not the smell gas), and it forms a fairly wide range of explosive mixtures with Air. It is also debatable whether it will leak through plastic pipes even with fusion joins, which is most of the Gas distribution system. The metal plumbing in most houses with compression joints will probably leak to some extent, and most appliances with valves almost certainly will, because the Hydrogen will react with the grease which is used for the moving part seals. Again we see that those in positions of power as so bereft of knowledge that they make suggestions that are impractical on simple Engineering grounds. They then say that Engineers should invent something to make them actually work! Electric everything is unworkable unless we have many years and "a magic money tree". Hydrogen is dangerously unworkable and very energy inefficient. Batteries are a serious problem in the supply of materials, the danger of fire, and the inability to recycle them economically. Heat pumps are too complex, very expensive, not very efficient at winter temperatures, and air source ones noisy. If you want an instant problem ask a GREEN politician, so green they know nothing!


Now all that is really something to worry about because they are hell-bent on wrecking our entire infrastructure and lifestyle!

Thread drift further..

Yes PME is a hack, but of the options for a street distribution system without a CPC Is it worse than TT ? Sometimes. But it is still acceptably safe - actually in much of the world there is neither, and there are not many accidents  you may recall that post  about the building in Azerbaijan   - such a construction would be seen as perfectly normal in parts of South America or Africa, and even so electrocution is not a significant cause of death compared to traffic accidents or diseases - so quite correctly it is not a govt. priority there. In the same way, there are a few tens of folk electrocuted  by the  wiring in their homes every year in the UK, compared to a few thousand being killed by being run over, or the 3/4 million or so that must die from natural causes to match the birth rate to keep  check an uncontrolled  population expansion.


We cannot eliminate all risk from one small area of life without neglecting others, that may become more significant.

Now Gas in steel pipes.

Dave I'm sure that both you and I are both old enough to recall the cloying taste of the old town gas, long since replaced by methane courtesy of the north sea. I'm hoping that you like me played with treacle tins and  the gas wand on the cooker, and realised that the stuff was pretty fun and quite explosive, and sadly the north sea stuff was not half as frisky. This is due to the large hydrogen fraction - about 50%, , while the lethality required for all the Agatha Christie style murders, and quite a few tragic suicides, came from the fact that a significant part of the remainder was carbon monoxide, and then methane ethane, benzene and all sorts of ripped up hydrocarbon junk made up the rest. Lovely stuff.  But the street mains were cast iron, and the house piping a mix of black iron and thin walled lead pipes, and the problem of embrittlement was not really seen.

It certainly is a big issue at high pressures and temperatures used in some industrial processes, especially over a period of many years, but do not imagine like some scare mongers have suggested that a half inch black iron gas pipe will turn to powder after a decade or two with a pressure comparable to blowing bubbles into a milk shake. Actually, quite a bit of work has been done on this, and it is really not a big issue, except for high pressure storage , and in a way the experiment with the public gas mains has already been done in the past successfully. The pipes fail first from rusting through.

A  low pressure pure hydrogen leak will burn with a pale blue flame and is  visible in low light - and we could always add some sparkles in the form of any other hydrocarbon, though perhaps not carbon monoxide, much as we would add a gas leak smell


Adding hydrogen to dilute the mains gas may or may not be a good idea, depending how we make it, but embrittlement of metal fittings is not a serious downside.


(Hydeploy trials at Keele university have gone well with 20% H2 blending.)  ( Nearly ready to do the same for a larger area with a  village near Gateshead.)

Mike.

Have you ever noticed the large nuts on the gas pipes at the gas meter Andy?

Yes many times - they're unions usually between brass and brass or brass and steel - rather a different beast to compression joints for pipes that have an olive to make the seal - and aren't used to join copper pipes together. Normally even the joint between the brass union itself and the copper pipe is soldered.

The pipes fail first from rusting through.

Steel gas pipes certanily don't last indefinitely. Some years ago I had a problem with low gas pressure, which turned out to be caused by "rust" inside the steel gas supply pipe under the garden. Gas engineer explained that it was a common problem and why they'd had to keep replacing the gas distribution system every couple of generations. He said it was caused by "moisture" in the gas causing the inside of the pipes to rust (but I suspect a slightly more interesting chemical reaction).


Certainly I've noticed a few times now that older houses seem to have at least three generations of gas supplies - the original I guess Victorian Iron ones, later galvanised steel ones (I'd guess 1970s - so probably only had North Sea gas in them) and finally yellow MDPE.


   - Andy.

I think this thread is now considerably longer than the length of water supply pipe to which the title refers.......