Hi to everybody!
Am a newbie on this forum and have a problem with my self-built gas kiln. (following "The Kiln book")
Here the specs of the kiln:
48CuF downdraft Gas Kiln (LPG) with 4 L shaped burners.
Sides in lightweight bricks with rock wool lining and roof in full rockwool 6" thick.
Chiminey in high temp bricks.
4 ports 3" dia and a 28Sq.in outlet.
We Heat the cylinders in a barrel with hot water.
We have been firing the kiln successfully and with low gas requirements for bisque at 850-900deg C.
(Before enlarging the burner ports from 2 to 3" dia we had heavy reduction in the kiln at temps above 900C)
For a cone 9 firing we have had problems . We managed to reach 1150C degrees, with a stable climb but at this temperature the kiln gets stuck.
We slowly try to increase gas pressure but the temperature doesn't rise past 1150C and there is a slight reduction in the kiln.
The only problem I can think of at this stage after repeat firings gone wrong and tweaking is that the nipple/pin hole size is too small. (J size) and therefore when the pressure is increased, the velocity of the gas is too great for this size, therfore reducing the air intake (unforced) resulting in reduction.
We have virtually tried everything to solve this problem and wasted quite a number of cylinders ... any help would be greatly appreciated!!!