Kiln elements

[ronfire]

I have a Skutt 1027-3   240v single phase.  I purchased this kiln used and don't know how many firings on the elements .  The kiln is still hot so I will not open it yet but I know I have top broken element as I get no resistance on the meter.

The bottom element reads 22.9 Elements 2 @ 5 are 32.9. I have not yet tested the 2 centre elements yet as I do not want to disturb the Sitter until the kiln is empty.

Attached is a screen shot from Skutt. My question is would you change all the elements or just the 1 broken element. Looks like all the other elements are within the range of resistance but I will check again when the kiln is room temperature.

Last inspection of the elements they looked fine with no coils slumping over.

 

 

 

 

[neilestrick]

Since it's a used kiln and you don't how many firings on them, I would go ahead and change them all. They're barely off from new, not really off enough matter, but often they start to change very quickly once they reach a tipping point.

[ronfire]

Thanks Neil, I was thinking the same way . Not sure how many firings I have as I don't keep a log but must be over 100  with 04 and max cone 6.

It is more that I don't want to place the wear and tear on the bricks but it would be good to have a complete new set. I will wait to see the inside before I order $550 worth of elements.

 

[Dick White]

Ron, wait until it is cool and unloaded and then inspect everything carefully. There are several possibilities with those manual Skutts.

There could be a broken element - that will need to be replaced as there are no long-term solutions to broken elements.

There could be crapped out connections where the lead wires are crimped to the element pigtail. Those can be fixed in place.

There could be a failed 3-way switch so that no power is getting to the element. That is harder to detect without removing the switch to inspect it. Note just FYI, the original manufacturer of those switches ceased production of it, so Skutt has a new source. Switch knob on the outside works the same, but the connections on the inside are different; they include an instruction sheet in the bag with it, so not a problem, just be aware it will be different.

[ronfire]

I used an ohm meter at the element connection and found no continuity so I know the element is bad. Just got a full replacement set and plan to install them today.

Was wondering when I do the first break in fire with the kiln empty should I run the kiln vent or don't bother.

  I have a sitter on the kiln so I was going to run on low for 45 min then med for 45 then high until it shuts off on a cone 04 . I think I will also place a set of witness cones in the middle of the kiln on a stilt to see that the sitter is close to being set right. I do fine adjusts on the sitter with a feeler gauge and find that a 004 to 006 clearance works the best with bars.

Any recommendations for changes to this idea is welcome.

 

[Min]

For the first firing to condition new elements I know most people fire the kiln like you have described by going to 04 then shutting the kiln off. I follow the instructions that Euclids gives that they received from Kanthal. From this pdf from Euclids, pages 9-10. (I fire to cone 6-7)

"The durability of resistance alloys in air at high temperatures is greatly increased by an oxide surface layer formed by a reaction with the oxygen of the air. The protective nature of this oxide layer is proportional to its area and depth. Foreign matter usually interferes with the formation of the oxide layer, and this causes a reduced life. ... At high temperatures the protective layer of Kanthal materials consists almost entirely of aluminum oxide. This has a light grey colour and good chemical resistance. At temperatures below 1000oC (1832oF) the oxide layer has a dark colour since the aluminum oxide is impure." 10 In order to protect elements from the effects of harsh environments, it is very desirable to condition the elements, by pre-oxidizing them. This is accomplished by firing them to a temperature of 1050oC/1922oF and soaking for several hours, 7-10 if possible. The process is enhanced by allowing good air flow into the kiln - leave the peepholes open, or the KilnVent on. If you are doing reduction firings in an electric kiln it is desirable to periodically re-oxidize the elements, for best life expectancy. This is not recommended if normal use will not exceed 1050oC (1922oF), or for fibre lined kilns. The results of element conditioning can be quite dramatic. It may not have much affect for normal, low temperature firings, but can be significant for harsh operating conditions."

[ronfire]

I replaced all the elements today and found the top element was broken with a bad burn spot. There must have been something that got onto the element. There was about a 1/2 inch of slag to dig out of the brick. Never had anything explode or shatter on the top so I wonder what caused it. Might have been there before I purchased it 4 years ago.

Ran the kiln on low and could not see much of a glow on the coils, then onto medium. Found only elements where working when there should be 3. Pulled 2 rotary switches and found there was a difference in continuity terminals to the bad section. Those switches are hard to understand the pattern but easy when you just  have to compare 2. Managed to open up the switch and found a bent contact terminal, straiten it up and assemble the switch. Now the elements work as they should.

The switch was probably faulty from the factory as it was bent inside so the 2nd element would not work on medium. I would never find it if I had not done an empty run on the kiln to be able to see all the elements. I never open the Kiln with wares in then  and hard to see across all the peep holes.