All Twinflex MF liners come with a 25 year 316 liner warranty & 35 year warranty for 904 grade liner. Your invoice confirms you purchased the liner from Turner & Wilson.

Please complete the liner registration form on our website to apply and actvate your warranty. click here.

The melting point of Austenitic Stainless Steels is in the region of 1300 to 1400 degrees Centigrade, varying slightly according to the precise grade. However they start to become iincreasingly plastic after the threshold point of 1000 - 1100 degrees is reached. 316 grade being is at the higher end of these spectrums. At higher temperatures surface oxidisation will cause discolouration. This usually takes place above 600 degrees. Although this decreases the life of the steel, it is usually insignificant.

There are two schools of thought on this matter, both with valid merits. Back-filling with vermiculite increases the insulation, keeping the flue warm, reducing condensation with the result of improved drawing powers on the flue and perhaps extending the life of the lining. There are two draw backs to insulating. One is that the insulation must remains dry. Should it become wet then it will be worse than useless. The other is that should the lining have to be removed, then the insulation becomes a considerable problem - particularly vermiculite. Leaving the void un-insulated, however avoids these problems. True the insulation is not as good but when the installation is viewed as whole, then there is the liner, an air gap , then the masonry. Together these form a pretty good level of protection which, except in the most extreme of circumstances, is quite adequate. Removing or changing the liner is a very easy matter. On balance Turner and Wilson prefer not to insulate, but if the installer thinks it is best then that is fine with us.