Cupola Redesign 3D, 18" Bore (Team Review)

Concept model, 2027 cupola redesign, 18" bore variant (22" shell). Same heights, burners and hardware as the 14" rig. A 200 lb bull ladle on a gantry takes a full tap. Not final dimensions.

Tapped-out metal potential: about 180 lb of iron per tap (well floor up to the bottom of the slag hole, 18" bore, molten iron at about 6.7 g/cm³)

Grate cartridge (Rev C, 18" bore, 4 bars per grate) 2" refractory lining Sand bed + fiber board, 7° taper Cold plenum + blower riser Hot plenum, 3" blast duct, downlegs Burners (detail below) 1/2" braided oil trunk 3/8" SS oil branches Atomizing air Flame path Gantry crane, tracks, bull ladle Drag to rotate, scroll or pinch to zoom.

One of two identical burners. 2.0 mm siphon nozzle in a 3" burner tube with a front washer that tri-clamps to the 5" port, and a crimped back end the 3" blast duct elbow slips over. The port tube runs through the 22" shell tangentially, 7.5" off the well center so the 3" bore just grazes the 18" well wall, pitched 7° down, with a 1" refractory liner. The burner itself is the same unit as on the 14" rig; only the port tube is about 1/4" longer, to reach the 18" bore face. Oil and air enter through a side boss. The heater is two black iron tees and a nipple running parallel to the burner tube, with the 300 W element threaded into the front tee. The 3/8" cold feed and the air line both come in level from the back. Hot oil leaves the front tee through a 1/2" close nipple into a 1/2" tee standing on end. A 3" stainless bimetal thermometer (0–250°F, 1/2" NPT back mount, 1-3/4" stem) threads into the top, dial facing up, stem pointing down into the oil stream. The oil leaves the bottom through a 1/2" × 1/4" bushing and elbow, then the needle valve and a second elbow into the boss; air runs through a ball valve. To remove: slide the duct off, open the tri-clamp, lift the burner out with everything attached.

Shell, 5" port, tri-clamp Refractory 3" burner tube, washer, boss 3" duct elbow Nozzle + adapter Black iron tee heater Element head Outlet thermometer Needle valve Ball valve Oil Air

Schematic of a typical internal-mix siphon air nozzle on its brass adapter. It shows the layout most of these nozzles share, not measured geometry: proportions are approximate and makers differ in how the inner parts are split up or pressed together. Compressed air comes in the back of the adapter on a 1/4" line and runs down the center tube, jetting out its tip into the mixing chamber. Oil comes in the top on a 1/8" line and fills the passage around the tube, where a distributor ring spreads it evenly. The air jet leaving the tube drops the pressure around its tip, and that draw pulls the oil down from the line into the mixing chamber with no pump (the siphon), where the air shears it into fine droplets before the mix leaves the exit orifice. Air pressure sets both how much oil gets drawn and how fine it breaks up.

Brass adapter Nozzle body and exit orifice Distributor ring Air tube Seal Air Oil Spray Drag to rotate, scroll or pinch to zoom.

Two 3" grates, each cast in its own 3" steel shell, then tack-welded together into a 6" cartridge with the plenum clamshells tacked on. Each grate has four 1" OD 304 tubes inside 3" octagon EZ Cubed 80-15 sleeves (1" × 1" chamfers), on 4.2" centers with five equal 1.2" slots across the 18" bore, and the grates cross at 85°. The steel shell is 22" ID. Tube ends are cut flush with the shell OD, and the sleeves run full length into the side refractory. Each tube gets a light countersink at its cold (inlet) end to ease the air in, and a wrap of thin ceramic fiber paper before casting so the stainless can grow without cracking the sleeve. Two 3/8" plate lift lugs are welded vertically to the band in the gaps between the plenum clamshells, with the eye outboard of the plenums for a gantry hook or straps. All castable faces get three coats of Asbury BoroKote Max. The plenum clamshells are 5" tall, centered on the 6" shell, leaving ½" of bare shell at top and bottom for the locating collars and joints.

EZ Cubed 80-15 sleeves and ring 1" OD 304 tube 11 ga cartridge shell, 22" ID Cold plenum Hot plenum Drag to rotate, scroll or pinch to zoom.

One 3" grate before casting, shown in its 22" steel shell with the four 1" tubes in place. The green foam pieces fill everything that should stay open. The three inner slots (one on center, one each side) each take a 1.2" × 3" strip with a 1" × 1" 45° chamfer strip on each side, top and bottom, so they cut the corners off the bars on both sides. The two outer slots take a fill piece bounded by the flat bar wall and the curved 18" bore wall of the 2" refractory ring, with chamfer strips only on the bar side. The EZ Cubed is cast around the foam, and what's left is the octagon bars and slots. Strip lengths are trimmed to the bore curve; 18" stock covers the longest piece.

Casting fixture. Glue the straight pieces onto an 18" disc, then spin the disc through a bandsaw circle jig pinned at its center so every piece is cut flush to the disc edge in one pass. The disc drops into an 18" hole in a board of the same thickness, so the top is one flat casting floor. Pins in the board locate the 22" steel shell, and an index mark and key between the disc and board line the bars up with the shell's tube holes. Tape the disc seam and seal the shell's bottom edge before pouring. The foam stays in the casting, so the disc is re-skinned with new pieces for each grate. Disc thickness, board size and pin positions in the model are placeholders.

Slot strips and outer slot fills 45° chamfer strips, 1" × 1" 1" OD 304 tube 11 ga shell Cast refractory (toggle) Disc and fixture board Drag to rotate, scroll or pinch to zoom.