AZS refractories
Initially used for areas where corrosion resistance was important, but now used in most parts of the furnace. Refractory blocks or tiles in varying proportions of alumina-zirconiasilica.
Burners
Burners mix air (or oxygen) and gas (natural gas or liquid petroleum gases) for efficient combustion and are used to heat glass in furnaces of all sizes.
Bushings
Glass can be fed into the heated bushing either in its molten state from a forehearth (direct melt) or, alternatively, as marbles to be melted (re-melt process) Platinum alloy electrically-heated boxes with numerous nozzles in their bases used as furnaces for the forming of continuous glass fibre.
Dalle glass
Dalle glass (“dalle” is French for “tile”) is used in church and decorative glazing, as well as for furnishings such as door handles. Coloured glass produced in pot furnaces and cast in moulds to form plates in thicknesses of approximately 25 cms.
Day tank
Used for producing larger quantities of glass than is possible with pot furnaces (see “pot”). The type of glass to be melted can be changed at short notice A glass-containing vessel made from refractory blocks mainly used for the melting of batch for coloured glass, crystal glass and soft special glasses. Day tanks are refilled with batch daily, with melting usually done at night and glass production the following day.
Doghouse
The molten glass is covered with the batch material as it flows through the compartment. The doghouse is the name used to describe the batch feeding compartment within the furnace.
Drawn glass
The name of the process for making sheet glass by drawing the molten glass as a sheet directly from the furnace. With this process the thickness of the glass is determined by the drawing rate.
Fibre glass
The principal production process involves blowing jets of steam or air onto molten glass as it emerges from a tank furnace through very small diameter nozzle. Very fine strands of glass (generally with a high boric oxide and content) used in the form of glass wool for insulation, glass fibre for matting, etc., and also for the reinforcement of plastics.
Firing
Firing is the process of bringing a melting glass furnace up to its operational temperature. It also includes maintaining the temperature.
Forehearth
The forehearth usually consists of two sections: a cooling section with burners and cooling ducts which allow the cooling process to be regulated, and a conditioning (equalising) section generally equipped only with burners which ensure uniform temperature distribution through the glass flow as it enters the feeder. A refractory tank whose function is to receive glass from the furnace, reduce its temperature to the desired level and discharge it to the feeder mechanism at a uniform temperature.
Furnace
A furnace is an enclosed structure for the production and application of heat. When glassmaking, high temperature furnaces are used for melting the batch, maintaining pots of glass in a molted state, and reheating partly formed objects at the glory hole.
Furnace, pot
Pot furnaces are used today in the manufacture of mouth-blown glass objects and special glasses.A pot furnace consists of a melting chamber lined with refractory brick, a vaulted roof or “crown” of silica brick, and external walls made of insulating brick. Below the upper chamber in which there may be as many as twelve melting pots, there is a lower section for the pre-heating of the fuel gas.
Fusing
(1) Fusing is the process of founding or melting the batch; (2)Fusing can also be heating pieces of glass in a kiln or furnace until they bond; (3) or heating enameled glasses until the enamel bonds with the surface of the object.
Glory hole
The glory hole is also used to fire-polish cast glass to remove imperfections remaining from the mould. It is a hole in the side of a glass furnace, used to reheat glass that is being fashioned or decorated.
Heating up
Ensuring the homogenous expansion of refractory materials, this term refers to raising the temperature within the furnace to the required operating temperature under strictly controlled conditions.
Hot spot
Also known as the “spring” or “source”.Inside the furnace, the hot spot is that area on the surface of the melt which has reached the maximum temperature (at which batch reactions have been completed and dissolved gases have been reduced to acceptable levels).
Inleakage
Inleakage can result in decreased efficiency and increased fuel costs. The unwanted entry of air into a furnace through expansion-created gaps in the furnace superstructure or through other areas such as burner ports, regenerators and exhaust flues.
Pot
The glass worker gathers directly from the pot. A fire clay container placed in the furnace in which the batch of glass ingredients is fused, and kept molten.
Pyrometer
A tool very important for the use of a furnace or kiln. It is an instrument used to measure the temperature inside the furnace or kiln.
Redox
The term “redox equilibria” is used to refer to the balance between reduction and oxidation in the glass furnace. The abbreviated form of “reduction-oxidation”.
Redox equilibria
Used to refer to the balance between reduction and oxidation in the glass furnace.
Refractories
Used in high temperature furnaces for industries such as glass and steel where raw materials have to be heated to a molten form refractories are Materials capable of withstanding extremely high temperatures.
Regenerative heating
As in recuperative heating , waste heat from the furnace is used to pre-heat combustion air.
Tank
Tanks replaced pots in larger glass factories in the 19th centry. They are a large receptacle constructed in a furnace for melting the batch.
Thermocouple
The wires are encased in a protective sheath that can be introduced as a probe into the float glass furnace or kiln. A pair of different metals in contact at a point, generating a thermo-electric voltage which can serve as a measure of temperature.
Vello process
Glass from the melting furnace forehearth flows down through an orifice (ring) within which is a rotating conical-ended shaft (or mandrel) over and around which the glass flows. The tube-shaped glass is pulled from the end of the shaft by a tractor machine and turned through 90° into a horizontal position ready for cutting. More simply put the vello process is a drawing process used for the production of glass tubing.
Waste gas analysis
Furnace gas testing may be performed with Orsat equipment (gases are absorbed selectively as they pass through a series of specific solvents) or by means of instrumental analysis. Paramagnetic detection may be used for oxygen analysis, and infrared absorption for carbon dioxide analysis. Mass spectrometry or gas chromatography are also used to analyse gas mixtures. Gases emitted by the melt in the furnace can be analysed either in the furnace itself (in order to assess melting efficiency, for example) or as they are discharged from the furnace stack (above all, for pollution control purposes).
