Kiln Elements - PowerPoint PPT Presentation

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Kiln Elements

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Kiln Elements – PowerPoint PPT presentation

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Title: Kiln Elements


1
Kiln Elements Design
  • Phil Hamling
  • 9-23-08

2
Heating element for use in kilns are available in
many types
  • Metallic Wire
  • Iron Chrome Aluminum
  • Nickel Chrome
  • Platinum
  • Silicon Carbide
  • Moly Disilicide

3
Hobby Kilns
  • Most commonly use Iron - Chrome Aluminum
    metallic Wire.
  • In the form of coiled elements
  • There are many, many manufacturers throughout the
    world.
  • Kanthal makes the premium grades.
  • A, AF, A1 APM

4
Guidelines for Industrial Furnace
  • May or may not be applicable to hobby kilns
  • Serve as valuable reference material

5
Major Guidelines
  • Surface Loading (w/in.2 or w/cm2)
  • 14.5 w/in.2 at 1300ºC (2372ºF)
  • Coil Geometry
  • Diameter Ratio
  • Coil / wire 5 to 8 X wire diameter
  • Stretch Ratio
  • Length of stretched coil loop 2 to 3 X wire
    diameter

6
(No Transcript)
7
Element Issues in an LL e23s
  • Original 1.2 mm APM elements failed after only 69
    10 to 11 cycles.
  • Improvement in life was sought.
  • Possible alternate wire sizes were evaluated.
  • Real Estate limitations!!!

8
Element Analysis
  Original         Revised  
Wired Parallel Parallel Series Series Series Series Series
Wire dia. (mm) 1.2 1.5 1.5 1.7 1.8 2 2.2
Total wire mass (lb) 1.30 2.02 0.82 1.35 1.70 2.59 3.74
Power density (w / sq cm) 3.42 1.75 6.76 4.64 3.92 2.86 2.21
Wire surface (in2) 107.3 209.0 54.2 78.9 93.6 128.3 168.7
Power density (w / in2) (14.5 Target) 22.0 11.3 43.6 30.0 25.3 18.4 14.2
Stretch ratio (2 Target) 2.8 1.5 5.6 3.9 3.3 2.1 1.7
9
Element Selection
  • 2 mm wire was chosen.
  • Power density was lowered from 22 to 18.4 w/in.2
    (Still above 14.5 w/in.2 though)
  • Stretch Ratio maintained above 2.
  • What is really needed is more real estate to
    lower the power density effectively.

10
Wiring Change
  • Changing from parallel to series wiring
    configuration was needed.

11
The e23s kiln just completed its 87th Firing
with 18 firings on this Revised set of elements.
12
Element Related Topics
  • Many sizes and types of heating coil are
    manufactured at ZIRCAR Ceramics, Inc.

13
Element Related Topics
  • Many are custom shaped to fit unique heater
    designs

14
Element Related Topics
  • Annealing takes the springiness out and helps
    them hold shape.

15
Element Related Topics
  • Some are hand fitted on specially shaped
    insulation to form complex heaters

16
Element Related Topics
  • Others are set on vacuum forming molds

17
Element Related Topics
  • To make both small and large custom heating
    elements

18
The Grand FinaleHeating Element Coil Winding
Demonstration
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