The following equipment is required for installation on a forehearth to convert it to a colorant forehearth.
- Supply System
The supply system transfers color from the production floor to the weigh system feed hopper. Possible methods include bucket elevator, pneumatic tube, skip hoist or manual loading. Automatic system start/stop using a low- and high-level control in the weigh system feed hopper should be considered. Ferro does not design or furnish supply system equipment.
- Weigh System
The weigh system has three main functions:
- Feed System
- Maintains a supply of color, which is held in a feed hopper. This feed hopper can be fed via the supply system.
- Weighs and/or dispenses color on a controlled basis. There are two methods of feeding color - volumetric or gravimetric. Volumetric feeders use a screw-type feeder; this type of system is not recommended due to the difficulties with controlling feed-rate accuracy. Gravimetric feeders use a scale or load cell to weigh and dispense controlled amounts of color. They allow for greater accuracy in color feeding.
- Delivers weighed color to the forehearth in a gravimetric feed system. The weighed color must be transferred to the feed system at the forehearth. This is most often achieved using a vibrating tube conveyor. This tube conveyor also serves to convert the “batch” weighings into a continuous flow of color.
The feed system delivers color from the weigh system to the interior of the forehearth, where it is dropped onto the glass surface. Typically, a metal-feed tube or distributor is inserted through the forehearth crown refractory. This feeder is cooled with air and/or water.
Proper cooling protects the feeder from damage due to exposure to extreme temperatures inside the forehearth and prevents the color from melting prior to reaching the glass surface. In addition, use of controlled cooling air (using an adjustable valve or damper) allows for modification of oxygen content of the forehearth atmosphere under the feed tube. Atmosphere control is critical for achieving some glass colors.
- Stirring System
The stirring system blends the melted color into the molten glass resulting in a homogeneously colored glass. The stirring system consists of:
- Control System
- Refractory stirrers.
- Stirrer bank with stainless steel chucks, air-cooled carbon bearings, drive chain/sprockets and heat shields.
- Stirrer bank lifting mechanism with winch.
- Variable-speed electric motor with stirrer bank drive shaft.
- Stirrer bank support frame and superstructure.
The control system has three main functions:
- Stirrer speed and direction control. This allows the operator to control the speed and direction of the variable speed drive motors that operate the stirrer banks. This panel also controls the operation of the auxiliary cooling fans used on the drive motors (if required due to high-temperature conditions).
- Color feed and delivery control. This allows operator to set the target weight and cycle (dump) time on a gravimetric weigh system. Provides individual control of various parts of the weigh and delivery system, including the vibrating feeders, tube conveyor and weigh pan.
- System fault alarm. Using various monitoring and alarm set-ups (PLC, inverter output alarms, thermocouple readings, etc), this portion of the system initiates various alarms (both visible and audible) to alert operators to system malfunctions.
Knowledge Base Information:
Forehearth Coloration Standard Equipment Package