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Downdraft Reactor

Page history last edited by Daniel Chisholm 11 years, 5 months ago

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Building the Downdraft Reactor for GEK v2.0



Parts needed:    

     - Reactor outside vessel tube

     - Insulation inside vessel tube

     - Bottom end plate

     - Middle flange ring

     - Top flange ring

     - 5/16" x 5/8" bolts (5 count)

     - 5/16" nuts and washers (5 count)

     - 1/2" 90deg plumbing elbows (5 count)

     - 1/2 npt to 15/16 gas flare adapters (5 count)

     - Reduction bell mounting ring

     - Reduction bell

     - 1/2" x 6" pipe nipples (5 count)

     - 1" x 6.125" nozzle tubes (5 count)

     - 3/8" street elbows

     - Clay gasket material

     - 1' of extra 1" pipe for nozzle adjustment spacers


1. Inner Vessel: Weld inner insulation vessel tube onto bottom flange plate.

  • Orientation: Slag side of flange plate is facing down. 
  • Insert (5) 5/16" bolts into small holes, fastening them to the flange plate with nuts on the other side. This will hold them in place as you weld the bolt heads to the plate. Make welds gas tight.
  • Pull the two tabs on the vertical seam of the vessel into the center of the widest slot in the flange plate. One slot in the plate is larger- look closely. The two tabs should slightly overlap, probably not more than 1/4".
  • Fit all tabs on top edge of inner vessel into slots in flange plate.
  • Alignment: The inside edge of vessel tube needs to be EXACTLY aligned with inside of holes for air intakes.  This is what determines plumb for the nozzles.
  • Weld up bottom flange completely
  • Weld up side seam.
  • Finish all welding on this inner insulation tube as you will not be able to get back to it once the outer tube is welded on.




2.  Weld 1/2" 90 deg elbows into bottom flange end plate.

  • You might need to grind off casting debris on the elbows to get them to fit through the holes in the bottom end plate.  If you need to, do NOT grind off the collar as this collar is used for offset spacing during the fabrication below.
  • Align elbows and weld them into bottom flange end plate
    • On Bottom (bottom view): Elbows should radiate outward to the left.  The air lines spiral outwards clockwise, passing as close as possible to the next air inlet tube as they radiate outward.  Thus the elbow should be aligned so that the air line will pass just to the side of the next elbow. See pictures at for clarification.  The collar on the elbow should sit on the bottom end plate.  Do NOT grind off the collar, as this spacing is needed so there is room to screw in the SS tubes.  Do NOT position the elbow further out or it will obstruct the grate when inserted into the gas cowling
    • Inside Reactor.  The elbows need to be aligned so the air inlet nipples rise straight upwards and parallel with the insulation vessel tube wall.  You can use a right angle to draw straight vertical lines up the inside for alignment.  Then use a 12" or so 1/2" pipe nipple with a coupler on the end to sign to this line.  Push the elbow and the coupler up against the wall to ensure parallel orientation to the wall.  A combination square will assist with vertical alignment. The line and the coupler/elbow collars are your jig alignment tools. Use a clamp to hold the jig in place.
    • The elbows need to be welded in gas tight.  It is easy to miss spots around the neck of the elbow. 





3. Outer Vessel: Weld mid flange ring (the one with air holes) onto outer reactor vessel tube

  • Orientation: Use any tab and slot position.  Center your starting tab in the middle of the corresponding hole.  Make sure tabs are pulled all the way into slots with C clamps.  Use C clamps as you weld around circle. We've had the best results with extra deep throat C clamps, see photo.
  • Weld over the tab and slot joint on the INSIDE of the vessel to ensure gas tightness.  You will NOT be able to access this weld point after step 4.
  • Weld in 1/2" NPT to 15/16" gas adapters for air inlet tubes up through the mid flange plate.  The flared end of the adapter should point toward the ground. Make sure the adapters are centered in hole, and aligned accurately with side of vessel tube.  Weld all the way around the top of 1/2" NPT adapters, making sure they are air tight.
  • Clean up flange holes with a 11/32" drill
  • Weld the remaning appropriate flange ring around the top of the vessel. Use the tabs and open slots for fitting, clamping and welding. No special orientation. Tack around first, pulling the ring tight to the edge of the vessel, then stitch weld all the way around to make it gas tight.





4. Outer Vessel: Weld top flange ring onto outer reactor vessel tube.

  • Orientation: Use any tab and slot position, but make sure flange is flush with top of vessel tube
  • Tab and Slot start position: The "center" of the slot at the vessel seam is 3/16" from the material edge.  This results in a 1/4" space between the edge of the tab and slot on the material side of the slot.
  • Pull vessel tube and flange tight together with C clamps as you tack around the circle
  • Weld ONLY on the underside.   No welding on the joint side of the flange
  • Grind top surface flat after welding 
  • Clean up flange holes with a 11/32" drill




5.  Join and weld outer reactor vessel assembly to inner insulation vessel assembly

  • Slip outer reactor vessel assembly inner insulation vessel.
  • A hole is cut in both vessels near the top edge- this will be the ignition access inlet. Align the two holes by eye as closely as possible, while also fitting the tabs and slots together on the bottom.
  •  Pull outer vessel tube and inner vessel end plate with elbows tight together with C clamps as you tack and weld around the circle.  
  • A 1" coupler then needs to be inserted for the ignition access inlet. Fit it in and most of the way through the outer vessel's access hole and aligning with the inner vessel's hole. It should cant upward at about 35 degrees. Weld all the way around it, allowing enough space to insert the 1" plug later.




NOTE: Once you've finished welding the following parts in #6 and #7, further instructions with detailed photos for their installation inside the reactor can be found in Level IV Assembly Instructions )


6.  Reduction Tube

  • Weld reduction tube onto reduction plate
  • Install reduction tube in bottom of reactor. 
    • Put two lines of clay rope on gasketing surface and make sure the seal is good. 
    • Tighten nuts with washers onto bolts in bottom to hold in reduction tube



7. Install Nozzles 

  • Weld 3/8 street elbows onto ends of 1" air nozzle tubes.  Make sure the elbows are angled at 90 degree from the nozzle tubes
  • Screw in 1/2" X 6" pipe nipples into bottom of the reactor.  Tighten modestly with pliers
  • Put clay gasket material around bottom of nipples, and a thin coating around the threads at the top of the nipples
  • Push the nozzles down over the nipples, into the clay.  Take care to not get clay sealant into the nozzle tube passage.
  • Depending on your nozzle preference, and desired final height, you may want to install some spacers on the 1/2" nipple before pushing on nozzle tubes.  In general, you should start with the nozzles at a height above the reduction cone, equal to the diameter of the reduction cone entrance.
  • The nozzles should point inwards towards the center of the reactor, and be firmly positioned in the clay.  They should be difficult to turn.

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