Title: Kiln Elements
1Kiln Elements Design
2Heating element for use in kilns are available in
many types
- Metallic Wire
- Iron Chrome Aluminum
- Nickel Chrome
- Platinum
- Silicon Carbide
- Moly Disilicide
3Hobby 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
4Guidelines for Industrial Furnace
- May or may not be applicable to hobby kilns
- Serve as valuable reference material
5Major 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)
7Element 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!!!
8Element 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
9Element 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.
10Wiring Change
- Changing from parallel to series wiring
configuration was needed.
11The e23s kiln just completed its 87th Firing
with 18 firings on this Revised set of elements.
12Element Related Topics
- Many sizes and types of heating coil are
manufactured at ZIRCAR Ceramics, Inc.
13Element Related Topics
- Many are custom shaped to fit unique heater
designs
14Element Related Topics
- Annealing takes the springiness out and helps
them hold shape.
15Element Related Topics
- Some are hand fitted on specially shaped
insulation to form complex heaters
16Element Related Topics
- Others are set on vacuum forming molds
17Element Related Topics
- To make both small and large custom heating
elements
18The Grand FinaleHeating Element Coil Winding
Demonstration