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Envelope kilns and furnaces

Envelope Kilns provide large volume batch processing for heavy or fragile loads while minimizing required floor space,  allowing rapid turn-around times from the end of cycle to the start of the next cycle through the use of 2 fixed firing bases and a kiln “envelope” that is moved from one firing base to the other. This allows almost continuous use of the firing capacity while providing unloading and loading time for the second fixed base.


  • Ceramic Membranes – Solid Oxide Fuel Cells (SOFC) , Gas Separation, Filtration
  • Multiple Processes in a Single Kiln – Debinding, Sintering, Conditioning, Annealing
  • Metals Heat Treating – Stress Relieving, Annealing, Billet Reheat, Forging Preheat
  • Enameling – Cast Iron, Stampings, Tubs, Sinks, Pump Housings, Pipes
  • Consumer Ceramics –  Dinnerware, Giftware, Home fixtures
  • Structural Ceramics – Ceramic Matrix Composites (CMC), Tile, Brick, Refractories, Metrology Standards
  • Electronic Components – Hard Ferrites, Insulators, Power Resistors
  • Porcelain, Stoneware, Terra-Cotta, Architectural Ceramics
  • Decorating, Glazing, Bisque Firing, Calcining, Sintering

General Capabilities:

  • Temperatures to 2450°F (1340°C)
  • Designs from 36 to 1000 ft3 of working volume
  • Setting lengths to 30 feet (9.14 meters)
  • Electric heating for kilns / furnaces with settings to 5 ft. (1.52 meters) wide
  • Gas heating for kilns / furnaces with settings to 6 ft. ( 1.83 meters) wide
  • Single or multiple zones of control
  • Manual or Fully Automatic Firing Control
  • UL approved control panels
  • FM, IRI and NFPA 86 compliant heating and combustion safety equipment
  • Available with integral Thermal Oxidation (Tox) of organic effluent

Why use an Envelope Kiln?
The key design feature of an envelope kiln is that it rolls on track and wheels over one of several supplied stationary ware platforms. This one feature provides the advantage of rolling over and firing one ware setting while another is being unloaded and reloaded, without ever having to move the stationary ware setting. This makes the envelope kiln especially well-suited for firing tall products like insulators and pipe or fragile products like ceramic wafers, and is very useful for product that takes time and care to properly set.
An envelope kiln can be programmed to provide multiple different process cycles. You can hard fire a load one day and glaze fire or decorate a load the next by simply changing the chosen recipe.
Programmable multi-segment ramp-soak controls with Touch-Screen Interfaces automatically fire the kiln through the complete firing cycle.  Automatic damper control. Pre-heated or cooling air injection and Thermal Oxidation can all be integrated to allow a “one button” start of the process cycle that runs to completion.
Whatever your process, Keith’s user-friendly control system can be depended upon to fire the kiln with ease and repeatability cycle after cycle.
With an integral Thermal Oxidizer option the envelope kiln can perform debinding followed by sintering for fragile products like green ceramic membranes such as ceramic oxide fuel cells (SOFC) and ceramic matrix composites (CMC) in one system.
The envelope kiln uses a 1/3 less floor space than a comparably-sized shuttle kiln.
A ceramic fiber lined envelope kiln is energy efficient due to low thermal mass.
An important  advantage of this furnace design is the temperature uniformity which can be achieved by having heated surfaces on five or even 6 sides.
When parts that will not tolerate movement are being processed an envelope kiln may be the only large capacity choice.  For this reason alone, this construction is favored for many ceramic applications.
For more robust parts that permit movement on a shuttle or bogie, a Keith Shuttle Kiln design may have an economic advantage due to reduced duct work, fixed utility connections, and more options with floor 

Contact Keith Company to order an envelope or shuttle kiln for your application, or to learn more about any of our products.