Anytime you build a new kiln or change burners in an existing kiln you create new kiln dynamics. Sometimes this can lead to firing problems. Below are some common problems with their possible causes and solutions. Remember: many perceived burner problems are really kiln problems that show up at the burner.
Problem: Kiln takes a very long time to reach temperature or stalls.
This classic problem is almost always due to insufficient BTU's per cubic foot. This can be because the orifice size/pressure is off or the burners are too small or the gas supply is inadequate. There is a certain range of orifice size for a burner. This needs to be correct. Generally though, people get some free or cheap burners with no idea how many BTU's they produce and stick'em on the kiln. You need to know the size of the kiln and how many BTU's you need. (see Btu Data Guide) If you’re using natural gas, you have to be aware of piping size. Natural gas supply pipe that is too small will not provide the volume needed and reduces the BTU rating on the burners. Propane tank freeze-up can also cause these problems. (see below)
Problem: Pilot won't light or stay lit.
Pilots can be pesky. If you have just built your kiln and are lighting it for the first time it may not light. What gives? All the piping you have put in is full of air not gas. Open up the pipe near the burner and bleed off the air. If the pilot ignites but goes out as soon as you release the reset button, you have a bad thermocouple. The reset button may need to be held down for 30 - 60 seconds. If the pilot blows out easily, you may have the burner positioned incorrectly. You may have back pressure because your exit flue is improperly sized or you may just be in a windy locale.
Problem: Burner shuts down suddenly
This happens when the safety valve loses it's signal from the thermocouple. This is almost always due to improper burner positioning. The pilot is being blown out or is "dancing" on the thermocouple. This dancing is caused by back pressure or wind. It causes signal loss and shutdown. The cold junction of the thermocouple is too hot. (see below)
Problem: Thermocouples fail on a regular basis.
The thermocouples we sell should last for many years. Thermocouples fail if the cold junction end gets too hot on a repeated basis. This is the end where the wire comes out of the sensing bulb. Also, if this end is too hot during the firing, the signal will be lost to the BASO™ or other sensor.
Problem: Uneven temperature
Temperature problems are caused by poor kiln design or improper bag wall positioning. Play around with the bag wall and note what happens after each firing.
Problem: Uneven reduction
This problem is similar to the one above. Adjust bag walls. Also be sure you're introducing a reduction flame by adjusting the burner, not just pushing in the damper to cause back pressure. The damper should be used to reduce, but don't forget the burners.
Problem: Propane tank freeze-up
You are taking too much vapor out in relation to the size of the tank. As the tank starts getting colder, the propane's ability to turn to gas decreases. Turn up the burners, you take out more gas, the tank gets colder. At this point the situation starts cascading towards total freeze-up. You need a larger tank, or better, hook several tanks together. The key is to increase the surface area of the liquid. WARNING: Do not turn vertical tanks on their side!