Baffled by metal flecks from external gas supply

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ColinEberhardt

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Location
Newcastle upon Tyne
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United Kingdom
Hi,

In the past couple of months we've had to get the boiler engineer out to fix our boiler. Both times the fault has been the same, the gas valve has been blocked up by a small heap of metal flecks / filings. Last time the engineer had to do this he tapped out the valve over a sheet of paper, and quite a big pile of these metal flecks fell out. He said that this was coming from the external gas supply.

I called the gas board and an engineer came out. He thought it could be coming from our internal piping, but this has very recently been replaced all the way between the boiler and the gas consumer unit. He mentioned that no-one else in the street had reported problems and that the supply was from plastic pipes, so didn't seem to convinced that it was their problem! He said he would report the issue and get back to me - this was a month ago!

Just wondering if anyone else has experienced this?

I've also had a few people mention magnetic filters as a potential solution - but from searching the internet it looks like these are applied to central heating loops, not the in-bound gas supply.

I'm baffled as to where this stuff is coming from! Perhaps it is the pipe that connects our house to the main gas supply in the street? I presume the gas board are responsible for this, even though it is on our land?

Thanks in advance!
 
Black Dust
Although it might sound quite harmless, Black Dust is causing big problems for gas consumers throughout the UK and Ireland. Black Dust is caused when hydrogen sulphide attacks metal. Hydrogen sulphide is present in natural gas, which is commonly used in the home in central heating systems. Hydrogen sulphide has a distinctive smell – that of rotten eggs – and is a toxic gas. It is highly corrosive and reacts with metals by creating a layer of metal sulphide, which covers the surface of the metal. In boilers this metal sulphide occurs as copper sulphide - a black film present on copper piping.

Natural gas used by consumers in their homes normally contains very low levels of hydrogen sulphide (commonly less than 1 part per million). At this level a film develops inside of copper pipes but it is relatively harmless as it remains intact. If the amount of hydrogen sulphide rises the copper sulphide layer can fracture and break off into metallic-like pieces. These pieces break down further to form Black Dust which can block valves and injectors in appliances. The blockage normally causes a reduction in heat output from the boiler. In rare cases Black Dust can block gas pipes.

Unfortunately there seems to be no way to eradicate Black Dust other than reducing hydrogen sulphide levels in natural gas. There are methods that can be used to help control it which include:

  • cleaning affected appliances (however, copper sulphide and Black Dust will remain in the pipework);
  • fitting filters (however, filters need fairly regular removal and cleaning);
  • sealing internal pipe surfaces to help stabilise film and prevent Black Dust (however, the long term efficiency of this method has not yet been proved).
Care of http://www.ciphe.org.uk/professional-members/public-health/black-dust/
 
From
https://www.bes.co.uk/products/027.asp :
Sulphidation Filters

6143.gif
The reaction of gas on the bore of tubes can create particles which obstruct the burners on gas fires (and other equipment).
These brass-bodied filters have been designed as a compact means of addressing the problem. The filter element is a 50 micron stainless steel mesh; it may be cleaned after removing the filter from the pipework. Taper threads both ends. Pressure rating: 25 bar.
Used by British Gas plc.

For Natural Gas and LPG.
Part No. Description Unit Price Qty
6143 1/4" BSP TF x TM £33.60
6144 1/2" BSP TF x TM £46.40
6145 3/4" BSP TF x TM £46.40
 
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