Thursday, March 24, 2011

Overworked Elements

Today I replaced the elements on an L&L Jupiter kiln. The old elements were well beyond their usable lifespan; they should have been replaced months or years ago. A good rule of thumb is to have a kiln checkup every 1-2 years if you're glaze firing to cone 6 or hotter, or every 2-3 years if you're glaze firing to cone 04. The most important part of the checkup is to check for element wear. If you can't do the checkup yourself, then call your local kiln tech. It will cost about $50- $75 for a checkup.

The simplest, although least accurate, method of testing your elements for wear is simply to take a good look at them. If the coils are starting to bunch up or lay flat, then there's a good chance that they are worn out. The most accurate method is to check them with an Ohm meter, which measures the resistance of the elements. Once the resistance is 10% off from the original, your elements are no longer firing efficiently and should be replaced.

Whatever you do, don't fire your kiln until the elements burn out. It will cost you more in the long run, for two reasons. First, you'll be spending more on electricity due to the inefficiency of worn elements. Second, replacing really old elements is more difficult and damages the kiln. Why? Because as elements wear, they expand. In an older L&L kiln, like the one I worked on this morning, they expand and become wedged into the hard ceramic element holders. To get them out, you have to use a pair of needle nose pliers to pull them out in little pieces. So instead of taking 5 minutes to remove all the elements this morning, it took about 80 minutes. That's an extra $100 at my normal hourly repair rate. In addition to the wedged elements, a couple of the element holders also cracked and had to be replaced, which took another 10 minutes. Add in the wasted electricity from the worn elements, and you've got a couple hundred dollars or more.

In non-L&L kilns, the expanded elements cause major damage to the bricks when you take them out. Because the grooves in the brick are so fragile, they easily break when trying to wedge a now-too-large element out of their grooves. At $10- $12 per brick, plus labor, the extra charges can add up fast. Replacing a brick involves unstacking the rings of the kiln, removing all the hardware from the case, loosening the body bands and sliding out the old brick. Once the new brick is slid into place, it usually needs to be filed down to sit flush with the old bricks, and then the kiln can be put back together. It's not a fast process!

So keep up on your kiln maintenance, just like you do with your car. Your kiln will last longer and save you hundreds or thousands of dollars over its lifespan.

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