John Baymore on sun 20 sep 98
Judy, please note that in Marc's reply he is assuming you're firing with
burners. If you're using blowers, and the power shuts down, for a minute
(until the BASO valves shut down) you get a wonderful column of flame
the kiln. Right up somewhere near the rafters. I'm working with our gas
company to put a fusible link failsafe over the burner for just such a
Couple of thoughts here that might be of use.
First of all make sure that the flame safety thermocouples on the
individual burners are located so that they are not being heated greatly by
the radiant heat from the burner port. In most cases it is best to have an
individual pilot for each main burner nozzle, and the thermocouple is used
to =22proof=22 the pilot flame rather than the main flame. The stable =
level) pilot flame is used to maintain positive ignition on the main
burner. (BTW... I am talking about areated bunsen burner / venturi
pilots... not the unstable little gas stove type yellow flames.) That is
the basic industrial approach to the situation. You want that thermocouple
to cool off quickly and drop the BASO out faster than a couple of minutes=21
Also if it is kept cool.... it lasts longer.
There is a simple and relatively inexpensive solution for this =22flame to
the rafters=22 problem you mentioned that is FAR easier and probably more
reliable than the =22fusible link=22 you are thinking of. In fact, in many
areas if you are using forced air burners on a gas kiln it is a typical
requirement of the gas company in the installation's general flame safety
Place a 110-120 V AC solenoid actuated valve in the main gas supply line to
the entire manifolding, that is hardwired in and powered by the curcuit
breaker that powers the blower motors for the burners (should be hardwired
in too). This type of valve is open only when there is 110 VAC present.
Place it downstream of the main shutoff valve and upstream of the
individual burner (or burner bank) flame safety and control valves and
guages. If there is AC to the overall system, then the main line valve is
open and the line is pressurized up to the =22BASO=22 units. If the power =
out for even an instant, the main line closes in less than a second. If
the power then comes back on, the valve will reopen...... but if it has
been down for a significant time, the individual BASO type safety units
will have lost flame proof and shut down individually.
The cost of these valves is related to the pipe diameter and CFH
capacity..... but for most smaller kiln uses they are in the =24150.00 =
Penn/Baso and Johnson Controls make such units. Look them up in your
local Yellow Pages.
Hope this thought is of help. Done it many times on installations.
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA