This volume explains the basic principles underlying the practical and theoretical aspects of installing and servicing gas appliances and associated equipment, from the basics of combustion, to burners, pressure and flow, transfer of heat, controls, as well as materials and processes, electrical aspects, and metering and measuring devices. Covering both Natural Gas and Liquefied Petroleum Gas, the many illustrations and worked examples included throughout the text will help the reader to understand the principles under discussion. Volume 3 of the Gas Service Technology Series will enable the reader to put into practice the safe installation and servicing procedures described in the companion volumes: Basic Science and Practice of Gas Service Volume 1 , and Domestic Gas Installation Practice Volume 2. Combining a comprehensive reference with practical application in real-world engineering contexts, Volume 3 provides an essential handbook for all aspects of fundamental gas servicing technology, ideal for both students new to the field as well as professionals and non-operational professionals e.
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Laying out the tank ends Prepare the tank using the instructions in Chapter 5, Step 1. Use a block of wood to support the ink marker at the right height. Center punch the line to preserve it during the "cooking" and sanding of the paint. This is for the standard lid. Mark the line at about 4-inch up from its curve to get the lowered lid version shown in the opening drawing.
The standard lid is easiest to build, while the lowered lid gives maximum access to small crucibles. Now, follow the instructions in Chapter 5, Steps 2 through 4, in order to lay out an 8-inch circle on the other end.
But, instead of laying out a six-inch long flat line, use the dividers to find and scribe four equidistant places on the circle and punch mark them for later drilling. Then, fill the tank with water up to the beginning of the curved end, and screw in the 1-inch pipe plug. Cutting the exhaust opening Prop up the tank on this end, and stabilize it to keep it from shifting during grind- ing.
Remove the foot ring, and clean the weld scars. Use the dividers to layout a 6-inch circle. Use a thin grinding disk or a metal cutoff disk at an angle to cut just within the circular line. Drain out the water, turn the tank over, remove the plug, and drill the four inch holes on that end.
Foundry Furnaces 3. Drilling out the opening for the burner collar Make a mark directly over one of the four holes on the end of the cylinder and place the tank on the threaded 1-inch opening according to the drilling instructions given in Chapter 5, Step 7. Measure up 4 1M-inches from the supporting surface and ten- ter punch.
Drill the burner opening out 4. Next, sand the hole smooth by using the flap disk turned up at a steep angle or use a half round file if it makes you feel more comfortable. Cutting the tank in two Prop the shell on its side using wood or angle iron to keep it from rolling. Use a metal cutting disk to cut along the punch marked seam. You can first use paper, or a flexi- ble plastic ruler to ink a solid line to follow if desired. Afterward, smooth the cut edges with the flap disc.
There is an alternate cutting method given in Chapter 11, Step 3. Constructing and mounting the burner collar The 1 x 3-inch pipe is now going to be laid out, for use as the burner collar. Unlike the forge in Chapter 5, burners are positioned horizontally in furnaces. This requires better support from the thumbscrews, so there will be six screws used instead of three. The burner sits at an angle to the curve of the forge shell so that the flame can be aimed between the furnace wall and the crucible.
This provides a swirling path for it between the crucible and the furnace wall, without directly impinging on either of them for the first few inches. Allowing the heat of the flame Fig. The center hole left after the plug is removed will become the emergency drain hole. In the left and right hand areas, two of the four inside nuts are vis- ible.
The other two nuts are hidden below the cardboard tube, which is projecting into the shell from the inner face of the burner collar. The space between the edge of the cardboard tube and the curve of the shell should measure 2-inches.
This assures the correct aim for the flame path once a 2-inch refractory lining is poured Gas Burners 9 to spread out before touching does much to preserve both of them. Save the cardboard tube from a roll of paper towels. Remove the six thumb- screws, and file the inside of the pipe smooth. If your thumbscrew holes are placed in a vertical and horizontal pattern, one of the six screws might not clear the shell.
So, they are positioned at seven, eleven, and three o-clock. Make a single weld tack on the top of the pipe, check the horizontal position, and make a bottom tack.
Check the aim, and then tack the two sides. Weld the collar on permanently. The burner can be repositioned using the thumbscrews if your work is a little off. Attaching the legs, parts 1 4 Run a nut on each of four allthread legs. With the parts dangling in a vice or a pipe, center punch three or four places between the two parts threads. This "peening" of the thread locks the parts together. Spray paint the bottom shell half before inserting the legs in it.
The locking washers go between the shell and outside nuts, which are now run up the thread. Lock them down tightly. Screw the remaining nuts 1- inch up the allthread. Run the coupling nuts gently up against them. The lower nuts are used as locking devices for the coupling nuts.
Level the furnace base, and lock the nuts. Later, the additional lengths of allthread are used as extensions to raise the height of the furnace for large melts.
The rest of the time, a lower center of gravity is better, even though the outward angle of the legs automatically increases the base size along with the added height. Still, it is best to keep the distance that liquid metal falls to a minimum.
But, the furnace must sit high enough in the sand filled bucket to Fig. In the middle is a cutaway view of the same joint. On the right is a see through illustration show- ing the peened end nut along with a section of furnace shell with the allthread leg and its locking nut on the bottom side. Foundry Furnaces accommodate all the spilled metal from a shattered crucible. So, leg additions for the occasional large melt are prudent.
Mounting the handle and attaching the lid The handle is a "U" shaped x inch flat bar, part Bend the bar up 90" at 6-inches from one end. Make another 90" bend 6-inches further along to form a "U" shape. Even up the two ends. The furnace lid hinge assemblies are made from x 1 inch flat bar. Three of them are cut 2 inches long, part One of them is cut 7-inches long. Lay out the four pieces for inch holes, which are centered and 2-inches from one end.
Cut a x inch setback on the end furthest from the holes. Three of the parts have the other end ground into a matching radius around the outside end of the holes. The fourth part is only ground around one corner of the end. The other cor- ner is left. A hole is drilled for one of the "S" hooks near the corner.
This part becomes the top member of one of the two pairs of parts. Note the exaggerated cut- backs on the ends away fiom the holes. This is done to facili- tate welding. The long tab allows the locking pin to hang awayfiom much of the furnace heat. It is not safe to use this extended hinge tab for a han- dle.
Screw the coupling nut onto the x 4-inch length of allthread, and center these two parts. Place the two pairs of flat bars on the two threaded ends, and screw on the nuts. Make sure their cutbacks are positioned over the furnace section to which they are not welded.
It is best for the hinge assembly to be centered over the two legs on the burner port side of the furnace, so that you end up handling the crucible on the side away from the burner and its fuel hose. The pin will still heat up, but not too much for gloved hands.
Check to make sure the furnace is sitting level. Align the lid with the furnace bot- tom, and place the hinge assembly in position over the burner port. Tack one of the bottom flat bars and then check that the assembly is sitting level. Tack the other bot- tom flat bar. Finish weld the tacks. Then, loosen the two nuts enough to let the lid move freely and cut off the excess allthread. Install the linchpin chain at Gas Burners 9 your convenience.
When the lid is lifted up a linchpin, part 26, is inserted through a hole in the flat bars. Then the lid is allowed to close until the hinge closes against the pin, leaving the lid erect and leaning forward slightly over the exhaust.
This position is a neutral bal- ance point, so there is little tendency for it to overbalance the furnace. The lid is also being continually heated by the exhaust gases, thus increasing efficiency when doing multiple pours, while reducing stress from thermal shock. Yet, the lid sits clear of the crucible, so it creates no interference during removal and placement. Note the cut and peened allthread. Also note the flattened and drilled end of the linchpin.
Once the lid is mounted, open it and then let it close until the bottom of its for- ward edge is even with or just a little way beyond the inner edge of the furnace wall.
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