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The Blob Mocks Me

4/20/2011

2 Comments

 
Picture
Do you see that blob? That's where one of my kiln elements broke and melted during my last firing, which happened only 8 months and 55 firings after the elements were replaced. And although the tech support from L&L Kilns assured me that some people burn out their elements much faster than that, I'm still bummed. The original set of elements that came with the kiln lasted for over 200 firings. But back then I wasn't making pots full-time, and firing much less frequently. The second set lasted for 120, which is about normal for a cone 6 studio. So truthfully, 55 is really bad. I guess the difference is mostly due to the volume of making pots full-time. These days, I sometimes unload a kiln while it's still about 200°F, so I can fire it again asap. I've been meeting all of my wholesale deadlines comfortably. I could probably afford not to be in such a hurry, and give my elements a break. 

I'm not completely satisfied with the volume explanation, because do you see how distorted and crooked the elements look near the break? The rest of the element looks much better than that. So do the other 5 elements. There is another change I made to my kiln recently ... in January I bought new plate setters, which allow me to fire multiple plates in a very compact and dense stack. I always placed the stack right next to where this element broke. Hmmm. I know an uneven load causes your kiln to work unevenly. Maybe this stack of plates has a lot more mass than I realized. I should keep the stack further away from the elements from now on.

The good news is that because the remaining elements are only 55 firings old, it should be ok for me to replace only the broken element and its zone mate, rather than all 6. At $50 each, that's a relief.

2 Comments
Bronwyn link
6/1/2011 12:16:26 pm

I think it's the unloading at 200 that does it. We often do the same, to keep orders moving out the door, but I am becoming convinced it is too much wear and tear on the elements AND the firebrick... maybe not worth it? We also have an L&L (love it), and yes we have been burning out the elements since our production schedule has ramped up too.

Reply
Roger Kirkwood
6/3/2011 12:52:17 am

I'm going to suggest a different approach to your element failure, more technical in a sense. I notice in the photo the successive turns in the element which burned out are crowded, appearing in a word, "crammed" (sorry) into their recess. When you replace the element(s) take time to separate the successive turns ever so slightly so that they are uniform and not touching, rubbing against each other. The premature failure may have been triggered by one of two considerations: the smallest flake of glaze bridging across successive turns, even kiln wash may be a potential offender. Most modern kiln manufacturers recommend vacuuming the recesses periodically (and carefully). Or it could have been triggered by a number of successive loops of the element in close contact and then short-circuiting when the element undergoes the expansion and contraction of repeated heating (think mechanical abrasion) while in close contact at temperature. I favor this latter explanation because of the apparent bulbous melted appearance of the ends of the element in the photo and the burned look. In my experience when an element fails from long use, it typically just breaks cleanly - there is no vestige of arcing and burning... Try to straighten, separate those "touching" turns in existing (used) elements? Probably not a good idea. Most Kanthal-based elements become brittle with use. The time to make sure the element is uniformly laid into the recess is on installation. I use a plastic picnic knife blade and gentle pressure. Appreciated the time analysis article greatly! Best wishes, Roger

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    Mea Rhee (mee-uh ree),
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