Linda Arbuckle on mon 24 may 99
Sorry. Saw my post on ClayArt, and sooo much was lost in the ether.
Here's a second try at Tom Buck's post.
___________________________
> Date: Wed, 19 Feb 1997 10:04:06 EST
> From: Tom Buck
> Subject: Re: firing schedules to enhance element life
>
> ----------------------------Original
message----------------------------
> Since there have been several questions relating to element life,
perhaps
> this quote from the developer of Kanthal alloys is appropriate:
>
> Life of KANTHAL alloys
>
> "The life of a resistance material is directly dependent on service
conditions, i.e. furnace atmosphere, ceramic ,ountings, temperature,
radiation possibilities, surface loading, frequency of switching, and
the construction of the element.
> "For practical reasons the manufacturer of resistance
materials must, during the manufacturing process, use a system of
testing which will give quick results with sufficient accuracy. For this
reason, Kanthal resistance materials are given a life test as specified
by the American Society for Testing Materials. The Kanthal tests wires
are suspended in a U shape between two adjacent contacts, without any
additional weight, and are energized. Most of the tests are performed at
1200 degrees C (2190 F).
> "The test wire has a diameter of 0.0285" (0.72mm). The
necessary current and voltage are controlled by resistors in series
until the desired wire temperature, as tested with an optical pyrometer,
is reached. By intermittent current application, the wire is alternately
cooled and heated so that it expands and contracts. The material is
therefore subjected to more stringent demands than in normal operations,
thus accelerating the test."
>
> The results of this testing are then displayed in a graph. For Kanthal
A1 alloys (the usual element material), the graph shows a lifetime of
almost 800 firings to 1150 C, 2100 F, and 360 firings to 1200 C (2192
F), 200 firings to 1250 C 2280 F, 110 firings when going to 1300 C 2370
F, 80 firings when reaching 1350 C 2460 F, 60 firings at 1375 C 2500 F.
These results are under the best test conditions at Kanthal, and hence
may be looked upon as the top number of firings to be expected when
going to the specified temperature. Lower lifetime will be obtained if
the firing conditions cause damage to the surface of the element wire.
>
> Cheers Tom.Buck@freenet.hamilton.on.ca
> Hamilton, Ontario, Canada
>
I charted Tom's info:
> Temperature Cone (small cones) Element life (# of firings)
> 2100 F 02-01 800
> 2192 F 3-4 360
> 2280 F 6 200
> 2370 F 8 110
> 2460 F 12 80
> 2500 F est. 14-15 60
>
>
Euclids on wed 26 may 99
Hi,
Just a couple of points regarding this post.
>>"The material is therefore subjected to more stringent demands than in
normal operations,
>> thus accelerating the test."
I would disagree with this statement. I think that between a glaze
atmosphere & an electronic controller switching the elements on & off
throughout the firing (normal operation), this would be more stringent
test.
The other point is that for the results of the test to apply to actual
elements in a kiln, the surface loading should be the same. How many people
inquire about the surface loading of the elements before they pruchase a
kiln?
Chris @
Euclids Kilns & Elements
1-800-296-5456
euclids.com
mail@euclids.com
--------------------------------------------------
> > From: Tom Buck
> > Subject: Re: firing schedules to enhance element life
> > Since there have been several questions relating to element life,
> perhaps
> > this quote from the developer of Kanthal alloys is appropriate:
> > Life of KANTHAL alloys
> >
> > "The life of a resistance material is directly dependent on service
> conditions, i.e. furnace atmosphere, ceramic ,ountings, temperature,
> radiation possibilities, surface loading, frequency of switching, and
> the construction of the element.
> > "For practical reasons the manufacturer of resistance
> materials must, during the manufacturing process, use a system of
> testing which will give quick results with sufficient accuracy. For this
> reason, Kanthal resistance materials are given a life test as specified
> by the American Society for Testing Materials. The Kanthal tests wires
> are suspended in a U shape between two adjacent contacts, without any
> additional weight, and are energized. Most of the tests are performed at
> 1200 degrees C (2190 F).
> > "The test wire has a diameter of 0.0285" (0.72mm). The
> necessary current and voltage are controlled by resistors in series
> until the desired wire temperature, as tested with an optical pyrometer,
> is reached. By intermittent current application, the wire is alternately
> cooled and heated so that it expands and contracts. The material is
> therefore subjected to more stringent demands than in normal operations,
> thus accelerating the test."
> >
> > The results of this testing are then displayed in a graph. For Kanthal
> A1 alloys (the usual element material), the graph shows a lifetime of
> almost 800 firings to 1150 C, 2100 F, and 360 firings to 1200 C (2192
> F), 200 firings to 1250 C 2280 F, 110 firings when going to 1300 C 2370
> F, 80 firings when reaching 1350 C 2460 F, 60 firings at 1375 C 2500 F.
> These results are under the best test conditions at Kanthal, and hence
> may be looked upon as the top number of firings to be expected when
> going to the specified temperature. Lower lifetime will be obtained if
> the firing conditions cause damage to the surface of the element wire.
> >
> > Cheers Tom.Buck@freenet.hamilton.on.ca
> > Hamilton, Ontario, Canada
> >
> I charted Tom's info:
>
> > Temperature Cone (small cones) Element life (# of firings)
> > 2100 F 02-01 800
> > 2192 F 3-4 360
> > 2280 F 6 200
> > 2370 F 8 110
> > 2460 F 12 80
> > 2500 F est. 14-15 60
> >
> >
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