Ron Bush : Yes there are several, I will pick on one, and hope that other Fellow Member Rocketeers Will add to this.
After a successful burn do not discount just how hot the Refractory Firebricks are. In a partially darkened room, and looking down into the Burn Tunnel, the Bricks
will be glowing a dull red.
Paul W. reports that his Brother Tim burned his arm the following morning after the previous days burn, I beleave Tim was checking for
wood ash build-up and
remaining Chunks of Charcoal.
Running an
RMH is usually a family co-operative effort, the bigger Pyromanic gets to start the days initial fire. So here is a likely scenario-
Spouse #1 is assigned tending the
Rocket Mass Heater RMH, for that days burn- this is expected to require a few seconds attention about every hour for 3 - 6 hours,
after which the Fire will be allowed to consume the last embers and go out! Spouse #1 Is out of the house, but expected home soon.
Spouse #2 is not as big a Pyromaniac as spouse #1, and generally leaves lighting their Rocket to S#1, even tho S#2 needs to be out of the house, and is running
late. S#2 decides to start the RMHs Burn, and as the RMH is still retaining great heat from last night this is easily accomplished!
Now S#2 is running late and S#! is not home yet! Spouse #2 decides to use a couple of firebrick to make a 'Cap' over top of the
Feed Tube, smothering the fire so
that there is not a open fire burning in the house when S#2 leaves the house, this is quickly done- exit Spouse #2 stage left - - - - - -
While the House is empty, the extreme heat of the Combustion zone continues to pyrolyse The
Wood fuel and with no Draft possible to draw off the hot, highly
Flammable wood gases, they collect within the Burn Tunnel and also in the Feed tube and the Heat Riser. Literally this fuel needs only the introduction of a fresh
supply of Oxygen to explosively combust !
Some 20 minutes later Spouse #! shows up carrying additional wood to add to the wood stacked for the evenings fire.
Spouse #1 notices the Firebricks 'Caping the Feed Tube and even notices their considerable heat, but takes a few minutes to have tinder and fine split, very dry
wood at hand to start the fire ! Spouse #1 Even goes to the kitchen for an
oven mitt to use to move the[color=red " HOT " [/color]Firebrick!
Immediately when the 1st brick is moved the fresh supply of Oxygen combines with the Wood gases that are still way above their ignition point and burst explosively
into flame.
This Action re-action called by trained members of Fire Services as Flashover, Spouse #1 Will be lucky indeed if they only lose all facial hair while receiving 1st, and
2nd degree burns !
Very early models of Ianto Evans RMHs had additional metal surrounds 14 or more inches in diameter, and several additional inches high, this was an early adaptation
to the problem of occasional smoke-back, with the surround in place it was noted that the smoke would often escape to mouth of the Feed Tube, but seemed to be
trapped within the larger surround float gently in air for a few seconds and then get pulled down into the combustion chamber with the rush of air to sustain the fires
burn.
Any attempt to cap this 'surround' off can cause the afore mentioned flashover. In some cases, especially where the diameter of the 'Surround is not large enough,
It can even cause fire to burn up the wood fuel instead of sideways along the Burn Tunnel, and/or be a principle cause of 'Smoke Back'
This surround is not commonly used, but it is sometimes copied by Newbies who have seen pictures of it used in early RMH Builds ! For The Good of the Crafts! Big AL
