Bs En 13384-1 Calculation
Sandra Grady
The methods in this part of this European Standard are applicable to negative or positive pressure chimneys with wet or dry operating conditions. It is valid for chimneys with combustion appliances for fuels subject to the knowledge of the flue gas characteristics which are needed for the calculation.
The methods in this part of this European Standard are applicable to chimneys with one inlet connected with one appliance. The methods in Part 2 of this European Standard are applicable to chimneys with multiple inlets and one inlet with multiple appliances. Part 3 describes methods for the development of diagrams and tables for chimneys serving one combustion appliance.
The information of the generator is used to define the material and the section of the flue and check its height with the environmental limits imposed by local regulations.
The technical data required for the execution of the study will be used in accordance with the EN 1991-1-4: 2007 and EN 13384-1 STANDARDS
Definition of the diameter
The calculation of the diameter of the freestanding chimneys is done following the specifications of the EN 13084-1 standard. This standard establishes that for heights of less than 20 m the calculation method envisaged by the EN 13384-1 standard can be used. For heights equal to or greater than 20 m, the calculation of the diameter must be performed according to the terms established in annex A of the EN 13084-1 standard.
FIXING WITH AN ANCHOR CAGE
This fixing system consists of an anchor cage template supplied by the manufacturer, sized and consisting of two flanges spaced by screws, which also allow the correct leveling of the assembly. The anchor cage template is embedded in the concrete during the execution of the foundation following the procedures communicated by the manufacturer.
FIXING ON EXISTING FOUNDATION
The freestanding chimney will be fixed on the base by means of specific screws depending on the base foundation and the resulting forces, tightened directly on the base flange of the chimney. It is important to proceed as follows:
INTERMEDIATE SUPPORTS AND FIXING ELEMENTS
The use of intermediate supports in the systems allows to optimize the resistant sections of the chimney or structure and allows the simplification of civil works. Therefore, they should always be used whenever possible. The different types of supports are classified as follows and furthermore the supports can be used individually or in combination:
PLATFORMS
The platforms are used to facilitate access to the measuring and sampling points of the chimney or structure and to facilitate the maintenance of elements such as lightning rods or signal lights. The materials that are normally used for the construction of our platforms are:
STAIRS
The stairs allow easy access to the platforms and normally start at the reference level of the installation. The maximum distance between the starting level and the upper finishing level must not exceed 9 m, as per current legislation. For distances greater than 9 m it is necessary to use an intermediate rest and can be obtained through two different configurations:
LIGHTNING CONDUCTORS
According to the terms established by the European standard UNE-EN 13084-1, freestanding chimney can be considered metal structures with continuous electrical conductivity. For this reason do not need specific protection against lightning or electric shocks. However, the chimney may include a lightning rod in order to protect nearby buildings or equipment from receiving electric shocks. The system normally used consists of a Franklin point installed on a stainless steel pole.
VISIBILITY
The characteristics of the report must be defined in the project report, and based on the geographical coordinates of the plant, generally the configuration used for the report is composed of the following elements:
It is an Excel-based program oriented to customers with the aim of allowing to make lists of parts of multiple product ranges and diameters, generate budgets or place orders for our product ranges, in a simple, agile and versatile way.
The program is based on the European calculation standards for Modular Metal Chimneys EN 13384-1 and EN 13384-2. Calculations can be made for individual equipment such as boilers, stoves and generators; as well as calculations with multiple equipment in multi-inlet or cascade systems.
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Every building must be designed and constructed in such a way that any component part of each fixed combustion appliance installation used for the removal of combustion gases will withstand heat generated as a result of its operation without any structural change that would impair the stability or performance of the installation.
The fire service attends many calls to chimney fires and other fires where a chimney defect has allowed fire spread into a building. Whilst the guidance in this standard cannot prevent fires, the structural precautions recommended help to limit the damage to flues and thus prevent fire from spreading into the building.
It is essential that flues continue to function effectively when in use without allowing the products of combustion to enter the building. Chimneys and flue-pipes are now tested to harmonised European standards to establish their characteristics relative to safe operation.
Very low flue-gas temperatures are achieved by modern, high efficiency appliances, particularly during night conditions, thus causing condensation. Materials need to withstand these aggressive situations.
Combustion appliances are very often changed after the original installation. Unless an appliance is supplied to be used with a specified system chimney or with an integral duct assembly, e.g. balanced flue, it is desirable, and sometimes more economical, to cater initially for the most severe conditions as regards the danger of fire, generally a traditional open fire, and to ensure that all components are compatible.
Combustion appliances, other than flueless appliances such as gas cookers, should incorporate, or be connected to, a flue-pipe and/or a chimney that will withstand the heat generated by the normal operation of the appliance. A chimney of a higher specification than the designation strings given (see clause 3.18.2) may be used if required, such as a chimney generally suitable for use with an open-flued solid fuel appliance may be used with an open flued gas-fired appliance.
Sweeping chimneys - the process of burning will naturally cause deposits of soot in the flue. Chimneys and flue-pipes therefore should be swept at least annually if smokeless solid fuel is burnt and more often if wood, peat and/or other high volatile solid fuel such as bituminous coal is burnt. Mechanical sweeping with a brush is the recommended method of cleaning.
A flue should be free from obstructions. The surface of the flue should be essentially uniform, gas-tight and resistant to corrosion from combustion products. Chimneys should be constructed in accordance with:
Designations for chimneys, according to BS EN 1443: 2003, are dependant on the fuel to be used, the type of appliance and the operating conditions. The designation string prescribes limiting values or categories for temperature, pressure, condensate resistance, corrosion resistance, soot fire resistance and distance to combustibles. Values for which the chimney is suitable are specified by the system chimney manufacturer or the designer of a custom built or re-lined chimney. For a new chimney installation the chimney designation should be chosen to suit the intended appliance installation. For an existing chimney the appliance performance should be chosen to match the designation of the chimney. Advice on the appropriate chimney specification should be sought from the appliance manufacturer.
The pressure designation P2 is regarded as the default specification. However the chimney can often generate an adequate natural draught, so that the appliance can be safely used with chimneys and flue-pipes with the negative pressure designation even if the appliance is fanned. The draught generated in a chimney may be calculated according to BS EN 13384-1: 2002. If there is any doubt, and/or unless the appliance manufacturer specifies N2, the designation P2 should apply.
The pressure designation P2 is regarded as the default specification. However the chimney can often generate an adequate natural draught, so that the appliance can be safely used with chimneys and flue-pipes with the negative pressure designation even for many fanned draught gas appliances, including condensing boilers that may otherwise have positive pressure at the outlet to the flue. The draught generated in a chimney may be calculated according to BS EN 13384-1: 2002. If there is any doubt, and/or unless the appliance manufacturer specifies N2, the designation P2 should apply.
A new masonry chimney, usually custom-built on site, and normally with an outer wall of brick, block or stone, should be well constructed and incorporate a flue liner, or flue-blocks, of either clay material or precast concrete. A masonry chimney should be constructed in accordance with the recommendations in BS 6461: Part 1: 1984. If an outer wall is constructed of concrete it should be constructed in accordance with BS EN 12446: 2003.
It is a complex operation to upgrade the chimney at a later date to serve a new appliance that needs a higher classification of chimney to operate safely, thus a chimney designed for solid fuel will also serve for oil or gas. See clause 3.18.6 for guidance on flue liners.
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