Glossary

A

A-weighted decibel

To reflect the sensitivity of the human ear to different frequencies, a weighting is applied to sound levels measured in decibels by sound level meters. For environmental noise, only A-weighting is used today, and results are expressed in dB(A).

Absorptive treatment

Acoustic treatment based on a material's ability to absorb incident acoustic energy.

Acoustic spectrum

Graphical representation of the sound levels of a noise broken down by frequency.

Ambient noise

Total noise existing in a given situation over a given period of time. It is made up of all the noise emitted by all nearby and distant sources.

Anchor template

Welded steel element embedded in a concrete base, designed to receive the base of a chimney and withstand the loads caused by its weight and by the wind.

B

Balanced flue boiler

A low-output gas boiler used in housing. It is fitted with a flue made of two concentric pipes that lead directly outside, horizontally through a wall or through the roof. The first pipe brings in combustion air, the second evacuates the flue gases. This type of boiler does not require an air inlet in the room, since combustion air is supplied through the concentric pipe.

Biogas

Gas resulting from the biological breakdown of organic matter in the absence of oxygen. It contains a high proportion of methane (50%) and therefore has a high calorific and energy potential. In our field, it is produced in landfill sites, anaerobic digesters and sewage sludge digesters. It must be captured to avoid odour nuisance and its contribution to the greenhouse effect. Once captured, it can be recovered as an energy source that replaces fossil fuels.

Bracket

Wall or ceiling fixing used to hold the flue in place. The term can also refer to the safety clamp that holds two flue sections together.

C

ChemInnov®

Free-standing or self-supported steel industrial chimney suited to all conditions (sites and operating modes), whose main advantage is its speed of assembly: just one hour.

Chimney flue

“A chimney flue is a vertical duct designed to evacuate the combustion products of common fuels [coal, fuel oil (domestic, light, heavy no. 1 and no. 2), liquefied hydrocarbons, gas and wood]. It begins in a room on the same level as the appliance, at foundation level or at an intermediate level between the two, and ends at its upper outlet into the atmosphere (excluding soot collectors, cones and other accessories).” [Extract from DTU no. 24.1]

Clearance to combustibles

Minimum distance to be kept between the inner walls of a flue and any part made of flammable material.

Cogeneration (CHP)

Technique for producing heat (steam, superheated water or a mixture of air and combustion products) and electricity simultaneously from a single fuel (fuel oil, natural gas, etc.). The overall efficiency is much higher than with separate production. Cogeneration is currently growing strongly worldwide. The term “cogeneration module” is reserved for machines with an output below 1 MWe. [Source: Gaz de France]

Compressed wood logs

Compressed wood logs are made by recycling by-products from sawmills and the wood industry, which avoids cutting down trees to produce firewood. They can be used in all types of wood-burning appliances (closed and open fireplaces, stoves, boilers, cookers and wood ovens).

Condensate

Distilled water in liquid form obtained by condensation of vapour.

Condensation

The change of a vapour into a liquid. It can be caused by a large temperature difference or by flue gas falling below its dew point.

Connecting flue

System carrying combustion products from the appliance outlet to the chimney flue. It must:

• be correctly sized for the appliance;
• offer a level of performance suited to the appliance (tightness, fuel type and mechanical strength);
• be installed in accordance with good practice.

Customer

Natural or legal person who buys products or services in return for fair payment.

D

Dew point

Temperature at which condensation begins. It depends on the gas temperature, the outdoor temperature and the relative humidity of the air.

Double-wall insulated flue

Flue consisting of two concentric cylindrical walls separated by a layer of insulating material.

DTU (Documents Techniques Unifiés)

French unified technical documents published by the CSTB (Centre Scientifique et Technique du Bâtiment), specific to each type of building work, setting out the codes of practice whose validity has been confirmed by experience. In France, DTUs are often the technical reference in disputes over design or installation. They are not regulations as such, which consist of laws, decrees and orders.

Dynamic vibration damper

In collaboration with CETIM, BEIRENS has developed this technique, which eliminates vibration problems and reduces loads on the structure. It offers economic benefits for construction and civil engineering, and is very well suited to stacks located in seismic zones.

E

Elbow

Flue component used to change direction. There are several types, for example segmented (angled) elbows and pleated elbows (made by successive folds).

Energy efficiency

Improving energy efficiency reduces energy consumption for the same level of service, and therefore the environmental, economic and social costs of producing and consuming energy.

Expansion bellows

Flexible elements that compensate for dimensional changes in a flue caused by thermal expansion.

Explosion relief valve

Valve that can instantly relieve overpressure caused by explosions in flues.

F

Fire-rated

In fire safety, fire-rated components meet the following criteria: mechanical strength, flame-tightness, no emission of flammable gases, and thermal insulation such that the temperature rise of the unexposed face does not exceed 140 °C on average and 180 °C locally.

Flue duct (carneau)

Term used by heating professionals for the roughly horizontal duct connecting one or more appliances to a chimney flue.

Flue gas evacuation system

Equipment used to discharge combustion products.

Flue gas extractor

Fixed device that improves the draught of a flue. It can be electric (motorised and controlled by a variable speed drive), mechanical (with moving mechanical parts) or static (with no mechanical or electrical action).

Flue lining

Process of inserting a metal flue into an existing chimney. Lining is essential whenever existing flues are too large, not gas-tight, cracked, or present risks of fire, condensation or poor draught (oversizing, for example).

Free-standing chimney

Chimney whose base, by means of anchors embedded in concrete, keeps the structure perfectly stable. Installed inside or outside a building.

Free-standing chimney (base plate)

Chimney whose base, by means of its base plate, keeps the structure perfectly stable.

Frequencies

Frequencies characterise the pitch of a sound and classify it into three main groups: low (bass), medium and high (treble). They are expressed in hertz (Hz). A “young and healthy” human ear can hear frequencies between 20 and 20,000 Hz.

G

Galvanised steel

Steel coated with a layer of zinc (by hot-dip or electroplating) to make it more resistant to corrosion. Galvanised steel is used in particular in the automotive industry and in the construction of buildings and structures such as pylons.

Generator

Device that converts any form of energy into electrical energy.

Guyed chimney

Chimney fitted with guy wires that keep it perfectly stable.

I

Industrial chimney

Structure used to discharge combustion gases (gas, heating oil, heavy fuel oil, wood, coal, biogas or biomass) from district heating, industrial processes or thermal power generation.

Inspection hatch

Door fitted in the side of a flue for inspections, sampling, etc. A well-made inspection hatch must not alter the physical characteristics of the flue and must be airtight.

L

Low frequencies

Frequencies between 0 and 300 Hz.

M

Medium frequencies

Frequencies between 300 and 2,000 Hz.

Multi-flue chimney

Chimney comprising several flue liners grouped together inside a structural shell.

Multigigogne chimney

Multi-flue chimney made of flues of decreasing size (up to 5) nested inside one another, giving significant space, cost and energy savings and reducing heat and noise reverberation, in compliance with legislation.

N

Noise

Unwanted sound signal perceived when equipment is started up. The basic unit for a noise level is the decibel.

Noise emergence

Difference between the ambient noise level (installation running) and the residual noise level (installation stopped).

Nomograph (abacus)

A nomograph is a direct-reading chart that makes numerical calculations easier.

R

Reactive treatment

Acoustic treatment based on the dissipation of acoustic energy as it passes through a specific medium (volume, temperature, pressure, etc.). The dissipative resistance of that medium is called “acoustic impedance”.

Renewable energies

Renewable energies are a diverse set of sources whose use in no way depletes the initial resource, which is renewable on a human timescale:

• Wind: wind turbines, wave power.
• Sun: solar thermal, photovoltaic, thermodynamic.
• Earth's heat: geothermal energy.
• Water: hydroelectric, tidal power.
• Biodegradation: biomass.
• Biofuels.

Renewable energies are therefore many and fundamentally diverse in their physical, chemical or biological mechanisms.

Residual noise

Ambient noise level minus the specific noise generated by the installation identified as the source of the nuisance.

Rock wool

Insulating material obtained by melting and spinning volcanic rock. BEIRENS uses rock wool in its insulated flues. Classified as non-carcinogenic, it is non-combustible and releases no smoke or toxic gas. It does not absorb water and keeps all its properties over time.

Roof outlet

External part of a chimney flue, visible on the roof. Very important for draught efficiency, it is protected from the weather by a cap or cowl that helps evacuate flue gases. Its shape varies with the architectural style of the region.

Room-sealed boiler

Another name for a balanced flue boiler (see definition). The term “room-sealed” comes from the flue made of two concentric pipes, one supplying air and the other evacuating flue gases.

S

Self-supported / tied chimney

Chimney on which wind loads can be absorbed by a connection to a support that allows the flue to expand freely. Installed inside or outside a building.

Silencer

Equipment that reduces intake and exhaust noise from industrial fans, turbines, engines and boilers.

Single-wall flue

Flue consisting of a single cylindrical wall.

Storm collar

Ring-shaped circular part that sheds rainwater running down the flue in order to keep it watertight.

Structural shell

Casing that groups together and supports one or more flues.

T

Technical assessment (Avis Technique)

An Avis Technique is the opinion expressed, after a neutral and impartial expert review by a group of specialists, on the fitness for use of a construction product, component or system. It takes into account both French regulatory requirements and the performance and durability objectives resulting from good practice in the corresponding traditional techniques, where these exist. [Definition: CSTB]

Tee

Flue component used to connect the flue to the heating appliance.

Thermal bridge

A thermal bridge encourages heat (or cold) transfer between two points. The lower the thermal resistance, the greater the transfer. Thermal regulations require thermal bridges to be minimised in order to improve the energy efficiency of buildings.

Thermal insulation

Calculated using three coefficients. The K coefficient measures the insulating power of a wall: the lower it is, the better the insulation. The G coefficient gives the amount of energy needed to offset heat losses when the difference between outdoor and indoor temperature varies by 1 °C. The R coefficient measures a wall's ability to lose or gain heat: the higher it is, the better the performance.

Thermal lagging

Insulating covering that reduces heat transfer between the inside of a flue and the outside.

Thermal resistance

A material's ability to slow down heat transfer (whether the flow is hot or cold). It increases as thermal conductivity decreases and as density and thickness increase.

W

Wall guide bracket

Bracket used to fix the chimney flue along a wall and guide it. It complements the ground anchor, which bears the load and supports the flue.

Wall-supported chimney

Chimney on which wind loads can be offset by a connection to a support that allows the flue to expand freely (DTU 24.1).

Waterproofing

Function of making a structure impermeable to water coming from outside or inside and remaining in contact with it. By extension, the processes and coverings that provide this function.

Welded fabrication

Technique used to manufacture large rigid parts by welding together various elements (especially thick plate) before machining them on machine tools.

Wood pellets

Small cylinders made by compressing sawdust at high pressure, 6 mm in diameter and around 20 mm long for heating purposes. Pellets are light in colour, which may vary slightly as wood is a natural product. They are used in all types of pellet appliances: boilers, stoves and inserts.