This document contains the complete technical description of Keiths standard FastHeat front-loading, high temperature, fiber-lined furnace intended for operation to 1700C / 3100F in an air atmosphere.  These furnaces are shipped ready for installation, complete with a high alumina hearth and ready for connection to the buyers utilities.

CONSTRUCTION

HEATING SYSTEM


Heating Elements
Molybdenum-disilicide heating elements are suspended from the sidewalls along three sides of the heating chamber for maximum temperature uniformity.  Outside panels of the furnace are easily removed for installing the elements.  Our elements have a 6/12-mm diameter, which is twice the diameter used in some competitive furnaces.  Larger diameter elements last longer and are easier to install.

TEMPERATURE CONTROL SYSTEM

Control Panel
All control equipment is installed in a ventilated space beneath the furnace chamber. Instrumentation and all control switches are placed for convenient viewing and are well labeled for ease of operation.  Solid-state digital indicating PID temperature controllers are used for precise temperature control to within 1C.  All furnaces include overtemperature protection, and the controllers are equipped with broken thermocouple protection. Installation of the furnace involves little more than connecting the main electrical service to the furnace power leads since all other internal wiring is provided fully connected.

Temperature Control
A West model 4400 Programmable Controller is supplied as the standard programmer for these furnaces.  The 4400 features 8 totally independent programs each with 16 segments.  Programs can be joined to create longer programs with more segments.

High-Limit Protection
Furnace over-temperature protection is provided by a West model 6700 controller in order to prevent possible damage to the furnace or your process caused by exceeding a user definable maximum temperature rating.

Thermocouple
One (1) type B duplex thermocouple is provided. One leg of the thermocouple is for main temperature control, and the other is for over-temperature protection.

POWER CONTROL SYSTEM

Power Controls
Power to the heating elements is controlled through a phase-angle fired SCR with current limiting.  Total connected power and voltages are listed in the chart near the top of this page.   Only one electrical connection is necessary for all power and temperature controls.  Furnaces may be designed and quoted for other voltages upon request.

OPTIONS AND MODIFICATIONS

Chart Recorder
A chart recorder will allow you to graph your firing cycles.  This option includes chart recorder mounted in the control panel of the furnace, a monitoring thermocouple, and all wiring.  We can quote, supply and install the recorder of your choice.

Atmosphere Port
A threaded 1/4 NPT fitting will allow you to introduce an inert gas, such as nitrogen or argon, into the heating chamber.  Though the refractory lining is not gas-tight, some applications may be enhanced by the addition of such a protective atmosphere.

Exhaust Port
This will allow you to vent any harmful or corrosive gasses from the heating chamber.  It works best when used in conjunction with air or inert gas introduced through the atmosphere port.  The exhaust port measures 2 inches in diameter, and has a plug that can be inserted into the hole when venting is not necessary.  As an additional option this port can be automated and connected as an event on the temperature controller.

Automated 2-position Damper
The exhaust port can be automated and adapted to operate as an event on the temperature controller allowing the damper to open partially or completely to aid in exhausting binders and accelerating cooling times.

Sight Port
A half-inch diameter optical viewing port can be mounted through the center of the door.

TESTING AND DOCUMENTATION

Testing
The furnace undergoes comprehensive functional testing prior to shipment.  No heat is applied to the furnace during these tests to prevent embrittlement of the insulation.  A simulated electrical load is used to setup and test the power control system.

Documentation
One complete Operating and Service Manual including installation instructions, drawings of the electrical system, a troubleshooting guide, and a detailed list of replacement parts is provided.

INSTALLATION AND MAINTENANCE

Installation
Simply position the furnace where desired on a good level surface and ensure that the circuit breaker is suitable for the electrical load.  Install the heating elements and thermocouple, which are packaged separately to avoid shipping damage.  A single electrical connection is made from your circuit breaker to the furnace.

Maintenance
The only maintenance your furnace should require for many years is occasional replacement of heating elements, thermocouples and perhaps some small electrical parts.  The FastHeat has been designed to make all maintenance simple and quick.  Repair parts for your furnace are always available even a complete refractory lining kit should you need one after many years of satisfactory operation.  A complete list of spare parts is included in the Operating Manual for future use.   We suggest you include spare heating elements and thermocouples with your furnace order.

For more information about solutions Keith FastHeat furnaces can provide, click here.

For more details or to discuss your specific requirements, contact a Keith specialist today!