19/02/2018
ESSENTIAL READING IF YOU HAVE A STAINLESS STEEL FLEXIBLE LINER WITHIN YOUR CHIMNEY.
Please see the photos attached to this post. Zoom in and look carefully at the remains of what you may recognise as a flexible chimney liner.
The pictures relate to a customer, who approximately 4 years ago had his chimney lined with a flexible liner hooked up to a 7 kw multi fuel stove.
The chimney was last swept 3 years ago, and since then he has been burning a mixture of coal and wood.
In the space of 4 years the liner has rotted through and collapsed.
Why can this happen? I hear you ask.
Solid fuels such as house coal and solid smokeless fuel , when burnt release chemical compounds of sulphur, hydrogen, nitrogen and water vapour passing up the chimney.
With sufficient heat in the fire, the majority of the gasses will successfully travel up the chimney and out into the atmosphere. However, when the fire is initially started the chimney is cold and there is insufficient energy / heat in the gases to propel them successfully out of the chimney liner. The vapour therefore condenses within the chimney in the form of highly acidic water droplets, which often form near to the pot or cowl.
The water droplets are highly acidic due to the sulphur and nitrogen deposits, and this in turn rapidly sets about attacking the stainless steel of the liner.
The liner develops pin holes, and eventually collapses under its own weight.
Coal and anthracite based fuels will burn for longer than other fuels, such as wood, and will remain alight for up to 12 hours, often burning through the night. However a large percentage of this time will be taken up with the fuel burning at a much lower temperature, which you could call a “slumber” mode. This results in cooler gases being produced, which will then condense once again within the chimney liner further adding to this problem.
In this case the liner is so heavily pin holed that the whole structure collapsed. Some of the fragments you can see are now so thin they are no thicker than a sheet of tin foil.
I have come across other instances where a liner has failed due to this type of corrosion, however not to the same extent as this.
Stove fitters will often recommend that coal and smokeless fuels are not burnt in appliances that use a chimney liner, and that wood and coal are not mixed.
This is sound advice that will ultimately save you a great deal of money and lead to your liner lasting much longer.
Have a think about your burning practices, keep your chimney maintained and make sure harmful deposits are removed regularly by a professional chimney sweep.
