Tennessee Tech University Appalachian Center for Craft Clay Studio Vince Pitelka, 2014 Burner Plumbing on the Appalachian Center for Craft Crossdraft Soda Kiln This kiln is 20 cubic feet interior space, all hardbrick interior, and uses three GACO MR-100 venturi burners fired on LPG with an adjustable regulator. There are three burner ports, and across the left side of the kiln from left to right at burner-port-level there is 9 of front wall, a 4.5 burner port, 7 of side wall, a 4.5 burner port, 7 of side wall, a 4.5 of burner port, and 9 of back wall. With this configuration, the burners are on 11.5 centers, and the plumbing system described below is designed to give that spacing. There is always some discrepancy in pipe fittings, especially in the degree to which they are threaded on each end, and thus the there might be a slight discrepancy in lengths when you assemble your manifold. The materials list includes a few extra pipe nipples of several different short lengths in case you have to slightly adjust the burner spacing. All pipe and pipe fittings must be black iron pipe, as required by codes, except for the gas valves, which will be standard bronze ball valves with 90-degree handle movement. Anything similar to Apollo-brand model #77C10301 is appropriate, and you can see one by going to www.grainger.com and entering 5MU14 in the search box. All of the pipe and fittings are ½ except for two 3/8 nipples and two ½ - 3/8 bushing reducers, one of each on either side of the BASO valve, which has 3/8 ports. When purchasing the LPG regulator, try to get one with ½ ports. If you get a different size, you will need to purchase appropriate nipples and bushing reducers for that size, installed in the same fashion as for the Baso valve. When beginning the plumbing on this kiln, start out by assembling the manifold crosspiece at the bottom below the burners, with the elbow for the left burner and the two tees for the other burners, and with the appropriate pipe sections and couplings between them. Attach a close nipple to the top port on the elbow and each of the two tees, and then you can physically check against the spacing on your kiln burner ports and make any necessary adjustments in spacing before assembling the rest of the manifold. This pipe manifold is designed to have the supply line coming in at floor level at the lower right corner when facing the right (burner port) side of the kiln. If you wanted to have the supply line come in at the lower left, you would just reverse the placement of the elbow and tee at either end of the burner manifold, so that the Baso valve and other components extend out the left end of the assembly. Our kiln is built up on a 3 concrete pad that does not extend beyond the cinderblock base, which was necessary to provide a level surface on the sloping concrete slab apron where the kiln is placed. That adds 3 to the length of the vertical pipes to the right of the regulator in order to bring them down to floor level. The pipe lengths and description below assume that your kiln is on a level concrete pad that extends out beyond the cinderblock base, and thus the vertical pipe extending downwards to the right of regulator is shorter than what is pictured in the photograph of our burner system and plumbing. 1
Parts List Pipe and Fittings Black Iron Pipe (available from plumbing supply or home-improvement center) 12 close nipple, ½ pipe 2 2 nipples, ½ pipe 3 2 ½ nipple, ½ pipe 3 3 nipple, ½ pipe 1 4 nipple, ½ pipe 1 6 nipple, ½ pipe 2 8 nipple, ½ pipe 2 close nipple, 3/8 pipe Black Iron Fittings (available from plumbing supply or home-improvement center) 8 elbow, ½ pipe 2 tee, ½ pipe 2 straight coupling, ½ pipe (try to get the heavy cast black iron straight couplings rather than the thin, smooth machined straight couplings) 2 bushing reducer, ½ to 3/8 pipe 5 union, ½ pipe Other Fittings and Parts 3 GACO MR-100 burners with orifices for LPG (available from Ward Burner Systems) 2 Rolls of yellow Teflon tape (for gas connections available from plumbing supply or homeimprovement center) 4 Ball-type gas valves (as described above), ½ pipe (available from plumbing supply, hardware store, or home-improvement center) 1 Adjustable LPG regulator, preferably with ½ NPT ports (available from Mark Ward or from LPG supplier). If it has smaller ports, you will need to get appropriate bushing reducers and nipples, as is done with the Baso valve in this system. 1 Johnson Controls model H19RA Baso valve (3/8 NPT ports) (available from Ward Burner Systems or from gas company) 1 1/8 NPT x ¼ flare-fitting right-angle shut-off valve for pilot (available from plumbing supply, auto parts store, or home-improvement center) 1 ¼ flare nut for above valve (available from plumbing supply, auto parts store, or homeimprovement center) 1 Honeywell target pilot burner (available from Ward Burner Systems) 36 1/4 copper tubing (hardware store, home-improvement center, or auto-parts store) 4 36 thermocouple for Baso valve (3 extras), such as the White-Rogers/Emerson model #HO6E-36 or the Honeywell model #390A1061 (available from Ward Burner, gas company, or appliance repair business) 1 Small tube or can of anti-seize compound, available from auto parts store. Normally used on bolts and fittings that might seize up over time from heat and/or corrosion. You will use this compound on the pipe unions that allow partial disassembly of the system for maintenance or replacement of components. 2
Required Tools for Assembly of Burner System Two pipe wrenches for assembly of the pipe components. I used a 12 and a 14, and that worked fine. 12 adjustable wrench (Crescent wrench) for the components that have flat facets, like the gas valves, Baso valve, and regulator. Small tubing cutter to cut the ¼ copper tubing for connecting the pilot burner. Tubing flaring tool to do the flared end for the attachment to the pilot valve. Small adjustable wrench to tighten the fittings at either end of the copper tubing to the pilot burner, and to tighten the attachment nut for the thermocouple. Assembly of Burner System This burner system assembles into six component sections separated by five pipe unions three burner sections, the main manifold section including Baso valve, the regulator section, and the master shutoff valve section. A union is a pipe fitting that allows a pipe system to be dismantled in the middle of the system, rather than having to start from one end and remove one fitting after another until you get to the one needing replacement or maintenance. The unions are carefully placed to allow maintenance or replacement of key individual components without having to disassemble the entire system. The three unions below the burners allow removal of individual burners or access to the individual gas valves. The union to the right of the Baso valve allows access to the Baso valve. The union to the right of the LPG regulator allows removal of the entire burner system or access to the regulator or the master shut-off valve. The master shut-off valve is intentionally located beyond this union specifically so that the gas can be shut off when it is necessary to remove the whole burner system at this union. Note below that Teflon tape or pipe-joint compound are never used on the threads that assemble the two halves of a union. 3
Use of Teflon Tape On all tapered pipe connections use the yellow Teflon tape rated for gas plumbing. In this installation, this would include all connections except for the threaded connections that assemble the two halves of a pipe union, as explained below. Wrap the Teflon tape around the male pipe threads on each connection at least four to six wraps, starting barely in from the end of the threads. Never wrap the Teflon tape over the end of the threads, because when you tighten the sections together, thin pieces of Teflon tape may come loose and could be carried with the gas stream and clog burner orifices. In other words, no Teflon tape should be exposed on the inside of the plumbing system once it is assembled. NOTE: Never use Teflon tape or pipe-joint compound on the threads connecting the two halves of a pipe union. Unions feature an internal tapered seat, and are designed to be pressure-tight without any tape or sealant when tightened properly. Putting pipe-joint compound or Teflon tape on the threads that assemble the two parts of the union accomplishes nothing and just creates a mess. Tightening Plumbing Connections There is a certain technique to properly tightening plumbing connections. Aside from the swivel connections that attach the two halves of a union, all plumbing pipe and fitting connections are tapered, and with Teflon tape or pipe-joint compound, become pressure-tight when sufficiently tightened. As they are tightened, it becomes more and more difficult to tighten them further, due to the taper of the threads. When you are tightening pipe connections, you need to be aligning the position of the component parts in the proper directions, and with each connection it is your call when to stop tightening and when to go for one more complete revolution if you think the connection is not tight enough. NOTE: Under no circumstances should you back up the tightness of a tapered pipe connection, because you will destroy the seal you have created and the connection will leak. If you have accidentally tightened a connection beyond the ideal angle of alignment, your only choices are to continue to tighten further until you come around to the ideal angle again, or to disassemble the connection, clean off the threads, re-apply Teflon tape or pipe-joint compound and reassemble the connection. When tightening pipe connections adjacent to the Baso valve or the LPG regulator, be aware that those two components aluminum, and the black iron pipe will tighten into them more readily. It is a good idea to assemble and tighten the adjacent black iron components first, and then thread them into the aluminum component last to avoid over-tightening those connections. When assembling a series of component parts (aside from the Baso valve or regulator) in a straight line, it is not necessary to tighten each connection individually. You can apply Teflon tape to all the male pipe ends, start all the connections together, and then place one end of the sequence in a pipe wrench or vise, and a pipe wrench on the other end of the sequence, and tighten them all at the same time, going back and tightening certain ones further in order to get the correct alignment of angles. Assembling the Basic Manifold and Verifying Burner Spacing As mentioned earlier, start off by assembling the basic manifold from the elbow below the left burner to the tee below the right burner. The sequence starting from the left is: elbow, close nipple, straight 4
coupling, 8 nipple, tee, close nipple, straight coupling, 8 nipple, tee. Attach the close nipples to the top ports on the elbow and the two tees, and then hold this assembly up in front of the burner ports to assure that each nipple is centered in the burner port. If it is not, you will need to make adjustments by using different nipples. ½ black iron close nipples are usually about 1 ½ long, and nipples are available in 2 and 2 ½ as well. I have included several extra 2 and 2 ½ nipples in the materials list in case you need to adjust lengths to adapt to your kiln. The spacing will not be narrower than what this design accommodates, and if it is slightly wider you can substitute a 2 or 2 ½ nipple. Once you have verified that the spacing is correct you can finish assembling the main part of the manifold. On each vertical leg leading to a burner (where there is already a close nipple installed in the elbow or tee), attach a gas valve with the handle facing towards you as indicated in the photo. The gas valves do not have a particular direction of flow, and can be installed either way. It is your choice whether you want the handle pointing upwards or downwards when it is turned on. Above the gas valve, attach a 3 nipple, and then the male part of a pipe union. Assembling the Burner Sections To each of the burner orifice spuds (the brass part extending out from the back of the burner), attach an elbow, a close nipple, and then the female part of a pipe union. MAKE SURE that you use an adjustable wrench (like a Crescent wrench) on the facets of the brass orifice spud when attaching the elbow to the burner. These spuds are threaded into the cast iron burner housing with a very small-diameter brass thread, and if you attempt to attach the burner to the elbow by rotating the cast iron burner housing, you will strip this thread or break it off. When attaching the unions in this location, it is important that the female part (with the rotating collar) be the upper part of the union. If it is installed as the lower part, water and debris can get into the union threads, making it more difficult to undo the unions when it is necessary to maintain or replace a burner. Please note that I did not do this on the installation in the picture. I didn t notice it until the system was assembled, so I just painted that area fairly heavily in the hopes of minimizing contamination. Once you have finished assembling each of the three burner sections, set them aside. Completing Assembly on the Main Manifold Section On the right-hand end of the manifold you have already assembled, attach one of the bushing reducers into the right port of the tee, and then a 3/8 close nipple. Before installing the Baso valve, be sure to examine it and find the small arrow indicating direction of gas flow, and install it accordingly. The valve will not work if improperly installed. Attach the Baso valve (assuring positioning as indicated in the photo) another 3/8 close nipple, a bushing reducer, and one part of a union (in this case it doesn t matter which way the union is installed). Set this portion of the manifold aside. Assembling the Regulator Section To the other half of the union, attach a close nipple, an elbow, a 6 nipple, an elbow, a close nipple, and the LPG regulator. To the right side of the LPG regulator attach a close nipple and half of a union (in this case it does not matter which way the union is installed). Set this portion of the manifold aside. 5
Assembling the Master Shutoff Valve Section To the other half of the union attach a close nipple, an elbow, a 2 ½ nipple, a gas valve, a 4 nipple, and an elbow. This is the point where you will attach the connection from the LPG main line or tank. Assembling All Portions of the Manifold As you know, soda kilns produce corrosive fumes, and over time the threads on the unions can corrode, making it very difficult to disassemble them when a part of the system needs maintenance or replacement. To eliminate that problem, apply automotive anti-seize compound to the threads that assemble the two parts of the union. It is messy stuff, but you will thank yourself later on. Once you have all of these sections assembled, you can attach them together, tightening the unions securely. As mentioned above, never use Teflon tape or pipe-joint compound on the threads connecting the two parts of a union. Unions feature a tapered brass seat, and are designed to be pressure-tight when assembled and tightened properly. Putting pipe-joint compound or Teflon tape on the threads that assemble the two parts of the union accomplishes nothing and just creates a mess. Mounting Burner Assembly on Kiln If your kiln frame features the same kind of burner cradles we used, as indicated in the photo, once you have assembled all the parts as indicated above, you can mount the system on the kiln. In the photo, our burner manifold is supported by the cradles and by a temporary stack of bricks under the lower part of the manifold. The pile of bricks will be replaced by several steel arms welded to the kiln frame. Installing the Pilot Valve, Pilot Burner, and Thermocouple Using a thin piece of Teflon tape (tear it lengthwise or fold it in half lengthwise) install the pilot valve in the side port of the Baso valve. Measure the approximate distance from the valve to the tip of the middle burner, and cut a piece of ¼ copper tube, allowing extra length for bends and adjustments. Slip the flare nut over one end of the copper tube, and with a flaring tool, flare the end of the tube. The target pilot burner comes with a compression-sleeve nut threaded into the attachment port. Hold the pilot burner assembly with the large adjustable wrench. Slip the unfinished end of the copper tube as far as it will go into the compression nut, and without letting it slip out at all, tighten the compression nut until the copper tube is firmly locked in place. At the other end of the copper tube, attach and tighten the flare nut to the pilot valve. Thread the thermocouple fitting into the bottom of the Baso valve and tighten slightly with a wrench. Stretch the thermocouple lead along the copper tube and insert the thermocouple probe in the provided hole in the target pilot burner assembly so that the tip of the thermocouple probe will be squarely in front of the little deflector that bends the pilot flame. Make a loop in the thermocouple lead somewhere along its length to take up the slack. Wrap some copper or iron wire around the thermocouple lead and copper tube and tighten firmly, binding them together so that the thermocouple probe cannot slip out of the pilot burner assembly. 6
Do not use the provided nut to hold the thermocouple probe in place in the target pilot assembly, because it will very quickly corrode and will be impossible to remove. Bend the tube and lead to place the pilot burner assembly directly against the side of the middle burner tip, just below and off to one side of it, and with the tip of the pilot burner just back from the tip of the GACO burner. Securely wire the copper tube and lead to the burner housing or steel frame, and to the pipe manifold so that it is firmly held in place. Under no circumstances should the tip of the thermocouple extend beyond the tip of the burner (closer to the burner port), because it will overheat and fail very quickly. Testing for Leaks Once you have the burner system mounted on the kiln and connected to the gas line, close the three burner valves, open the tank valve and the master valve, and adjust the regulator to 10 PSI. Brush a water/soap solution over all pipe joints and look for foaming, indicating a leak. If there are any leaks, shut off the master valve, disassemble the offending section and tighten or replace the problem fitting or connection. 7