Flexible Liner
Corrosion
The majority of linermanufacturers state their316L and 904L grade stainlesssteel products are suitable formulti-fuel appliances.
Thismeans they are designedto be used with appliancesburning solid smokeless fuels,
bituminous coal, peat andlignite briquettes as well aslogs and wood briquettes.
However, there are instances where flue linershave failed as a consequenceof corrosion within only afew years of installation.
Why is this?
Solid mineral fuels containmany chemical elementswhich, when burned,discharge a cocktail ofsubstances up the chimney.
Burning any hydro-carbonwill always create water vapour as part of the process.
Typically, you would expectflue gasses to contain various compounds of sulphur,hydrogen, nitrogen andwater vapour passing up thechimney to atmosphere.
Withsufficient heat in the flue toprovide buoyancy the gasses will successfully dissipate toatmosphere from the terminalwithout any risk.
However,with a cold chimney and cool flue gasses a nightmarescenario presents itself.
The water vapour entrainedin the flue gasses are likelyto condense back into waterdroplets wherever the innerflue surface is cold enoughthe create dew-point.
Unfortunately, the condensateis acidic due to contact withthe other chemical elementspresent, as a consequence thesurface of the stainless steelsuffers acid attack, usuallynear the top.
In time, thestainless steel develops pinholes and eventually collapsesunder the weight of the liner.
Anthracite based fuels, suchas manufactured ovoids, willremain alight for many hoursin slumber mode withoutattention.
At least 8 hoursburn is the norm, whilst 12-14hours is not uncommon for asingle filling of fuel.
Alas, the downside isthat slow burning of thismagnitude results in very lowflue gas temperatures whichexacerbates the problemdescribed above.
Wood burninghas its own set of problems.
It is essentialthat logs have a moisturecontent of no more than20 per cent, and preferablylower if possible.
Burninghigh moisture content woodleads to serious condensationproblems within the fluewhich forms a substanceresembling creosote.
This material is almost impossibleto sweep, runs down the innersurface of the flue and leaksout of any fissure by capillaryaction.
It is also volatile,hence the increase in numbersof chimney fires.
The solution?
Periodically burn the fire brightly in order to raise theflue gas temperatures andwarm the flue surface whichwill help dry out the moisturepresent.