The following extract has been reproduced from 'The official guide to approved solid fuel products and services' ~ List no.8 Millenium edition ~ the official list of all products and services approved by HETAS LTD
Section E -- DOUBLE SKIN FLEXIBLE CHIMNEY RELINING SYSTEMS
Types Made from stainless steel these liners have a spirally wound double skin construction that has a smooth inner flueway. These flexible liners are specifically designed for use with solid fuel. Double skin liners are not to be confused with single flexible skin liners which are designed solely for use with gas fires which must not be used with solid fuel appliances under any circumstances.
Approvals At present there are no British standards or British Board of Agrement approvals for this type of product. Proof of suitability has therefore to be made by a recognised test authority. Currently the CSTB, Paris have a recognised testing approval scheme and are members of the European Union of Agrement. These certificates can be used as evidence to satisfy Building Regulations approval. The current validity of their CSTB Certificate should be checked prior to purchase.
Special Notes These liners should give a normal life of 10 years or more when correctly installed, used and maintained. However, these flexible liners whilst being easier to install and replace are not permanent and prolonged periods of slow burning particularly using solid fuels, combined with inadequate cleaning of the flueways can cause corrosion damage which reduces the expected life of the liner to less than 5 years.
If there is a risk that these conditions can occur the non-metallic liner systems are recommended and under normal use should give a life equal to that of the dwelling.
Section G -- NON METALLIC CHIMNEY LINING SYSTEMS
Types There is a variety of different systems where a non-metallic lining is applied to the flue within an existing domestic chimney. In most cases these systems use a special formulation of ceramic or concrete based materials that are installed by specialist contractors that are approved or registered by the lining manufacturer.
Approvals At present there is no British or European Standard that specifically covers these types of chimney lining systems. It is therefore necessary that the suitability of the material and its application as a flue lining is proven by having a recognised independent product approval certification that is accepted as demonstrating compliance with Building Regulations.
Special Notes The Eldfast system listed below is a special formulation of ceramic binders and fine aggregates that are designed to provide a durable flue lining in a sound masonry chimney. The system must be applied in accordance with the manufacturers instructions by an installer who is Registered by the manufacturer.
When installed, used and maintained correctly an extended life can be expected. However, it is essential that the installation is carried out correctly ensuring that the minimum thickness of lining is applied and that the subsequent flue area is suitable for use with the fuel-burning appliance. This form of lining must not be relied upon to provide support to a structurally unstable chimney. The thermal insulation of a chimney lined in this way is greater than an unlined or conventional masonry chimney. It is the responsibility of the customer, installer and specifier to ensure that the lining and installation as a whole complies with current Regulations and is covered by the appropriate approval at the time of installation.
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