Only applicable where no risk of gases cooling to dewpoint. All welded, or in flanged and bolted sections
Choice of Materials and Form of ConstructionĪpplications or operating condition limits The overall design of a chimney, therefore, involves all branches of engineering science and the most satisfactory solution for a particular set of conditions, with the materials at present available, is generally a compromise between pollution control, flow and pressure conditions, effective life, and economics. The most common chimney application is to serve a combustion appliance such as a boiler or furnace, where in addition to normal structural loads such as wind loading and weathering, the flue or chimney liner is also subjected to chemical attack, abrasion, temperature, thermal expansion and possibly thermal shock. Again any of these chimneys can take various forms as previously mentioned.
Where several appliances have to be served there are the choices of an individual chimney for each appliance two or more appliances served by each chimney, or a multi-flue chimney with one or more appliances discharging into each flue. Where only one item of plant has to be served a simple single-bore chimney is the only type to be considered, but this can take various forms: freestanding, self-supporting free-standing guyed supported partly or completely by a building or some other structure or in-built as a composite part of a building structure, as are most domestic chimneys. Each must be used within its limitations, e.g. The flue or liner can also use these materials or refractory brick, acid-resisting brick, insulating brick, Corten steel, stainless steel, glass-lined mild steel, refractory concrete, etc. Typical materials of construction of the structural shell are brickwork, concrete, mild steel or GRP (Glass Reinforced Plastic). In many cases the structural member is considered separately from the gas flue, each using the materials of construction best suited to the function served. Most chimneys are also building structures in their own right. The design must also ensure acceptable pressure conditions on the plant served to permit its effective operation over the entire range of requirements. Chimney DesignĪ chimney is essentially a flue designed to exhaust waste gases and any entrained solid matter at sufficient height to allow acceptable dilution and dispersal before they return to earth.
In The Efficient Use of Energy (Second Edition), 1982 19.4 Chimney and flue designĪdditional notes for small flues are given in App.C7.
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