Midco Unipower G-Series - Manual (Page 5)

III Combustion Chamber
Continued
■ ■ When raising the floor,
maintain sufficient firebox
volume to limit the heat release
to 50,000 BTU per hour per
cubic foot or less. Use the entire
floor as a combustion chamber
and cover the water leg base to
6" from the bottom. Floor
construction should conform to
Figures 1, 2 or 3.
■ ■ Firing door installations will
usually entail removal of the
grates. Figure 8 shows a typical
installation. A steel plate floor
can be supported from the
grate lugs, if suitable. In any
case, the floor must be rigid
enough to prevent sagging,
being supported by brick piers
as necessary.
■ ■ If firing over the grate, level it
off with rubble of common
brick or firebrick if necessary;
then cover over with insulating
block before laying the
refractory floor.
■ ■ The hearth of worm feed
stokers can be used as a floor
base. Level off the hearth to a
suitable height, remove worm
feed mechanism and fill the
tuyere with rubble. Cover at
least the tuyere area with block
insulation; if using castable
refractory, pour a new floor over
a leveling surface of sand. The external stoker parts should be removed to eliminate clutter under the
b u r n e r .
■
■ The burner mounting in the door must be rigid and refractory lined as shown in Figure 8. The burner
nozzle must not protrude directly into the combustion chamber. The refractory liner must be flush with
or extend beyond the burner face as shown in Figure 4. A sheet metal rim should encase the refractory
up to the inside of the boiler wall. It should be intermittently bent inward to retain the refractory or
other means of anchoring should be provided.
■ ■ As an alternate, the burner mounting plate can be extended externally to locate the nozzle face and
refractoy wholly within the door opening. Seal carefully to prevent flue products from entering the boiler
r o o m .
■ ■ In double door boilers it is recommended that the openings be enlarged to a single opening by
removing the center post so that the burner can fire in the center. If a pressure part of the boiler must
be cut away, be sure to make modifications in accordance with your local code covering boiler repairs.
■ ■ Since firing door installations will generally leave no openings for flame observation, a peep sight
must be installed in the burner mounting plate.
Figure 5: Conventional Boiler-Small Firebox
Figure 7: Tubular Combustion Chambers
Figure 6: Conventional Boiler-Large Firebox
5