i work on maintainance for a health authority based at a medium sized hospital in north cheshire.we've been getting a lot of pin holes in our copper pipework,three in the last two weeks alone.theres no similarity in the age of the pipework (late seventies to late nineties)i was just wondering if any one else has come across this or is it just me!
pin holes
- Thread starter jona
- Start date
Sounds like cheap copper bought in bulk for a large project to me..........is the tube noticibly thinner than the stuff your replacing it with?
no,thats the thing the hospital has been constantly added to and extended since the seventies,the pinholes are appearing on pipework in different areas and fitted at different times.the quality of the water is still the same as it has always been we carry out routine sampling for hardness and contamination.its all very puzzling,luckily enough no serious damage has occured as the leaks have been spotted quickly.
N
Newboy
Came across two pipe runs at a customers house recently - 70's pipework. At first I convinced myself it was condensation on the rising main but with the water off and the pipework wiped dry no problem - put the pressure back on and about a dozen tiny pin pricks over a 2 metre run
That sounds like steel pipe that was widely used for heating systems in the 70s when there was a copper shortage. I believe some of it was copper coated, so it might look like copper on the outside.
As for the hospital problem, could there be any connection with the use of cleaning chemicals (like bleach - chlorine) that might possibly give rise to such corrosion?
Has there been ANY change in or work on the water, chemically speaking?
Has there been any work done on the system recently - thinking here of an appy heavy with acidic flux?
Has there been any new electrical equipment installed?
Yes really. This is secondhand advice - use a sensitive clamp meter to check for currents in the pipes. You need one which will read very low, preferably to 1mA resolution. If it's high, you get corrosion. "Scruff" is where I heard this first - anyone seen him posting recently?? Small hospitals is about his size too.
Earth faults in things like pumps can cause rampant electrolytic corrosion in pipes, as for example tiny air bubbles are a different electrode potential to the copper of the pit in which they might be sitting. I'd isolate and test the leakage currents through anything connected.
If you ever isolate the cause, we'd be fascinated to know!
Has there been any work done on the system recently - thinking here of an appy heavy with acidic flux?
Has there been any new electrical equipment installed?
Yes really. This is secondhand advice - use a sensitive clamp meter to check for currents in the pipes. You need one which will read very low, preferably to 1mA resolution. If it's high, you get corrosion. "Scruff" is where I heard this first - anyone seen him posting recently?? Small hospitals is about his size too.Earth faults in things like pumps can cause rampant electrolytic corrosion in pipes, as for example tiny air bubbles are a different electrode potential to the copper of the pit in which they might be sitting. I'd isolate and test the leakage currents through anything connected.
If you ever isolate the cause, we'd be fascinated to know!
thescruff posts regularly on askthequestion and on argi occasionally. He used to be a screwfix regular too (as doitall) but seems to be keeping a lower profile lately. He's certainly a mine of useful information, especially in relation to commercial sized stuff.
T
TTP_Designer
Just saw this thread on Pin Holes in copper pipework, we were asked to investigate the same problem in a large Hotel, our findings were that the pin holes occured due to both of the following:
Turbulent Flow – Flow of a fluid which is not smooth (laminar). Instead of flowing in straight lines or smooth curves around bends the fluid flow tumbles and swirls. Usually caused by excessive velocity across rough pipe surfaces or other obstructions such as pipe fittings.
Corrosion Erosion – A mechanism whereby the pipe wall is eroded away from the inside towards the outside of the pipe. Pipes, especially copper pipes, are normally protected by the formation of a layer of corrosion products. These prevent any further corrosion from occurring. In corrosion erosion this protective layer is stripped away by the turbulent flow of the fluid. The continued process of the production and removal of the protective layer of corrosion products leads to the formation of horse shoe shaped pits in the pipe wall which can eventually lead to penetration of the pipe itself in the form of a pin hole.
hope this sheds a bit of light on pin holing.
I forgot to add that the water in this particular system had been over softened by the use of water softners which also contributed to the pin holing.
Turbulent Flow – Flow of a fluid which is not smooth (laminar). Instead of flowing in straight lines or smooth curves around bends the fluid flow tumbles and swirls. Usually caused by excessive velocity across rough pipe surfaces or other obstructions such as pipe fittings.
Corrosion Erosion – A mechanism whereby the pipe wall is eroded away from the inside towards the outside of the pipe. Pipes, especially copper pipes, are normally protected by the formation of a layer of corrosion products. These prevent any further corrosion from occurring. In corrosion erosion this protective layer is stripped away by the turbulent flow of the fluid. The continued process of the production and removal of the protective layer of corrosion products leads to the formation of horse shoe shaped pits in the pipe wall which can eventually lead to penetration of the pipe itself in the form of a pin hole.
hope this sheds a bit of light on pin holing.
I forgot to add that the water in this particular system had been over softened by the use of water softners which also contributed to the pin holing.
In Scarborough there are pin holes apearing in 100 year old copper and lead. I've not been to anything newer than that with pinholes.
I thought turbulent flow was pretty much the norm in plumbing systems. Laminar flow only occurs at much lower velocities than would occur when say a tap is opened. If turbulent flow is the norm and pinholes are so rare, there must be other factors which are far more significant.TTP-designer said:
8) The overuse of water softeners interests me, would that change the PH of the water to slightly acidic.
K
keego
jona said:
Just out of curiosity is the pipework on the wards or is it in the culverts linking the wards through to the boiler room etc?
& would you say the corrosion is starting from the inside out or the other way round.
Utter drivel. Ignorant tripe.
What compound pray, are you claiming forms a protective surface on copper?
Who are "we" and how are you qualified and equipped to undertake such an investigation?
Turbulent flow doesn't cause pinholing, and there shouldn't be significant particulates in the water to cause physical erosion - that's trivially simple to find out in a standard test. The water softener would do it by itself; it makes the water full of bleedin' chloride ions, highly undesirable in a copper pipe. That is extremely well known.
I hope you were not paid much.
"Erosion corrosion" A rather overused name for erosion which is taking place either faster than the ability of a metals such as stainless steel or aluminium - to form a protective oxides (which doesn't happen with copper) or at an accelerated rate with soft materials (like copper) where excess cavitation or particulate impingement takes place. It's very obvious because it only happens in specific areas, where there are particularly high flow rates, which means around joint and irregularities, and not down the length of a pipe. The surface shows marked, directional, thinning.
Yes Chrishutt is right, most flow in a CH system is turbulent, but the flow rates are pretty low. Pretty unspecial really.
Pinholing as reported in the hospital, is generally ascribed to pitting corrosion - typically occuring as a process of local anodic dissolution where metal loss is exacerbated by the presence of a small anode and a large cathode. Muck stuck to the side of the pipe or embedded in the metal at manufacture - as folk have suggested above. Though the anode can also be an air bubble.
Classic method of reducing pinholing is to either INCREASE the rate of flow - which destabilises the little "batteries" which form, or remove, or chemically passivate, the deposits/inclusions which are present.
None of this is a blind bit of use to jona in his hospital. Something there has apparently changed, and the most profitable angle would be to find out what it is. Certainly, extra corrosion inhibiting chemicals would probably help, but that wouldn't be something he hadn't thought of.
T
TTP_Designer
ChrisR said:
No point in being rude about people who are giving advice is there?, whats the point in people like you on this forum who only thinks their advice is right? you seem to me a very arrogant & rude person, so why bother answering to you? grow up
T
TTP_Designer
ChrisR said:
No point in being rude about people who are giving advice is there?, whats the point in people like you on this forum who only thinks their advice is right? you seem to me a very arrogant & rude person, so why bother answering to you? grow up
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