Model 4
1500 - 6000 MBTU/hr
Rev. 03-08
Section B2-17
Parameter
Boiler Water
Limit
pH
8.3 -
10.5
Iron
0.1
ppm
Ox
ygen
0.1
mg/liter
Specific
Conductivity
2000
µ
mho/cm
Suspended
Solids
300
ppm
Total
Hardness
0 ppm as
CaC
O
3
Table
B2-13.
Feedwater makeup
rates
Table
B2-14.
Water quality
parameters
Boiler
Size
Gallons/Minute
1500
2.5
2000
3.3
2500
4.1
3000
5
3500
5.8
4000
6.6
4500
7.5
5000
8.3
6000
9.9
Blowdown As steam is produced, unwanted solids are left behind in the boiler water and
become concentrated
within the vessel. If
these constituents
are
allowed
to adhere
to the heat transfer
surfaces,
they will impede the flow of
energy
into the water.
Their removal requires proper blowdown that will include bottom and possibly
surface blowoff. For proper
TDS
control, surface blowoff with a TDS monitoring
device is recommended. Local codes will dictate the manner of treating the
blowdown affluent.
Boiler Stacks
General
- The Model 4 boiler
operates
with a
positive
vent
pressure
and a vent gas
temperature that is
non-condensing.
Therefore, the stack must be a positive
pressure
design.
Proper design
and installation of the flue
gas venting
is critical to efficient and safe
operation of the burner. The vent should be
designed
with proper supports and
clearances
from
combustible
materials. Use insulated vent pipe
spacers
where the
vent
passes through
walls and roofs.
The design
of the
stack
and
breeching
must
provide
the
required
draft at
each
boiler
stack connection.
Although constant pressure
at the flue
gas
outlet is not required,
it is
necessary
to
size
the
breeching
and stack to limit flue
gas pressure
variations.
Consideration
of the draft must be given where lengthy runs of breeching or
unusually
high
stacks
are employed.
Please
note: the
allowable pressure range
for
design
of the
stack
and
breeching
is
negative
0.25
"
w.c. (-62
Pa)
to a
positive
0.25"
w.c. (+62
Pa)
for
proper
light
offs
and
combustion.
NOTE:
This pressure range
does
not pertain to the boiler room; that is, the boiler room must be neutral or slightly
positive, never negative
when
using
air from the boiler
room
for combustion.
When two or more Model 4 boilers are
connected
to a common
breeching/stack,
one should
evaluate
the
affects
of
pressure variations
that may occur during boiler
sequencing while boilers are firing. It may be determined that some type of
mechanical draft system be employed to ensure proper draft at each boiler is
maintained.
Combustion Air
-
The burner
for
each boiler
must be
supplied
with
adequate
volume
of
uncontaminated
air to support
proper combustion
and
equipment
ventilation. Air
shall be free of chlorides, halogens, fluorocarbons, construction dust or other
contaminants
that
are detrimental
to the
burner
or boiler
heating
surfaces.
Combustion
air can be supplied by means of
conventional
venting, that is,
with
combustion air drawn from the area immediately
surrounding
the boiler (boiler
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