COMBUSTION AND COOLING UNITS
To control the heating and the cooling BDF provides a unit which is normally supplied preassembled and ready to be installed.
The same ventilators are used for the combustion and for the cooling. The air is fed into a main box to which the heating–cooling section are connected.
The burners are installed on the forehearth sides, and they are fed with an air-gas mix, that is introduced in the room over the glass and that burns thanks to the ambient high temperature.
The air-gas mix ratio must be kept constant, since any change compared to the optimal value could cause defects (most of all seeds and blisters). This can be achieved by regulating the gas flow rate depending on the air flow rate, whose valve is operated by the control system.
Each cooling and equalizing zone is equipped with an independent group feeding the burners. The temperature control system regulates the opening of the air valve depending on the value detected by the temperature sensor (optical pyrometer or thermocouple), independently on each zone.
The air -gas mix to be sent to the burners is generated independently per each section. A linear characteristic regulating valve with electric actuator is driven by the temperature control system to control the air flow which is passing trough a mixer. The air pressure is detected after the air regulating valve and it is used to control the gas flow by a gas regulator. The gas is fed into the mixer to achieve a proper air–gas mix to be sent to the burners.
The system is designed to assure a constant air–gas ratio in a range of 1 to 10 in terms of supplied energy. The cooling air flow is controlled independently per each section by a butterfly valve with electric actuator driven by the temperature control system.
The same actuator drives the air to be sent to the air damper to control the pressure into the forehearth superstructure in order to avoid fresh air infiltration through the chimney when the cooling is working at low capacity.
COMBUSTION ROOF BLOCK COOLING
Over the superstructure is installed a small refractory channel that runs parallel to the foreheart axis. When cooling air is blown along this channel, the upper surface of the roof block is cooled. This reduces the temperature of the lower surface of the tile and energy is removed from the glass bath by radiative heat transfer to the cooled tile.
The cooling air travels in the direction of the glass flow and is exhausted, together with the combustion gases, through the centrally located cooling air exhaust.
The volume of the cooling air blown along the channel is adjusted to vary the cooling effect, that is controlled by the flow regulation of the cooling air stream.
The automatic control system will control heating and cooling functions within each independent zone.
AIR DAMPER SYSTEM
- Air barrier creation
- Parasite air entry prevention
- Pressure stability inside forehearth
- Air flow automatic regulation by cooling and combustion rack via control system
All exhausts are fitted with automatically controlled air dampers. The air damper is made of a series of internal concentric air jets creating an air curtain which is controlled to allow either cooling air enter into the superstructure or products of combustion to exhaust from the forehearth, depending on whether they act as a cooling air inlet or flue.
Air dampers represent an effective means of controlling forehearth pressure without the use on any moving parts, hence minimizing maintenance requirements.
The amount of cooling air entering the cooling channel and the position of the dampers are automatically regulated according to the cooling requirement of the forehearth.
The same actuator, that controls the cooling air flow, drives the air to be sent to the air damper to control the pressure into the forehearth superstructure in order to avoid fresh air infiltration through the chimney when the cooling is working at low capacity.
COMBUSTION & COOLING CONTROL UNIT
The rack is designed to control the gas-air mix, the cooling air and the damper air pressure, for each forehearths zones, by fully automated gas and air regulating valves.
- It is designed to keep the air/gas ratio steady
- Cooling and heating are grouped in one rack only
- Linear regulation valves are used to vary the flow according to valve opening
- Critical components for good forehearth management are pre-assembled and installed in a dedicated unit, usually positioned in an area less exposed to the heat coming from forehearths and w/e.
COMBUSTION AND COOLING AIR
To supply the correct volume of cooling and combustion air to the forehearth, only one blower is used, with significant saving in terms of investment costs and operating costs.
The system is preassembled in one unit, it contains the necessary number of operating fans and fans in stand-by and it is equipped with adeguate absorbent support and filters.