Cleaver-Brooks CBH 40 - Gas Pressure and Flow

Chapter 5-Adjustment and Maintenance
Then slowly open the regulator until a
flame providing full sight tube coverage is
observed.
This adjustment must be accomplished within the
time limit of the safety switch or approximately 30
seconds after the detector is removed. If the control
shuts down, allow several moments for the thermal
element in the safety switch to cool and then
manually reset it. Replace the detector and repeat
from step 3.
(7)
When a suitable flame is obtained, replace
the detector. Observe the reading on the
micro-ammeter. The reading should be be-
tween two and five micro-amps and the
reading must be steady. If the reading fluc-
tuates, recheck the adjustment. Make sure
that the flame detector is properly seated
and that the lens is clean.
( 8) Reset the timer switch from the TEST
position to the NORM position.
(9) If main flame has not been previously
established, proceed to do so in accordance
with instructions elsewhere in the manual.
(10) The micro-amp reading of the main flame
signal should also be checked. Observe the
flame signal for pilot alone, pilot and main
burner flame together and the main burner
flame at high, low, and intermediate firing
rate positions. Readings should be steady
and in the range indicated in paragraph 7.
If there are any deviations, refer to the
trouble-shooting section in the technical
bulletin.
The gas burner housing surrounding the diffuser
plate should be periodically checked for any signs
of damage that might be caused by an improperly
adjusted burner or by a poor seal to the refractory.
Routine maintenance should include this resealing
which can be done with a mixture of refractory
cement and asbestos pulp. Use care not to clog or
obstruct the holes in the face of the gas housing.
The diffuser should be positioned as shown in
Figure 5-4. Do not attempt to change the gap or
angle of the fins.
GAS PRESSURE AND FlOW
INFORMATION
Because of variables in both the properties of gas
and the supply system, it will be necessary to
regulate the pressure of the gas to a level that
produces a steady, dependable flame that yields
highest combustion efficiency at rated performance
yet prevents overfiring. Once this optimum
pressure has been established, it should be recor-
ded and periodic checks made to veri(y that the
regulator is holding the pressure at this level. Oc-
casional modification in fuel composition or
pressure by the supplier may, at times, require re-
5-12
adjustment to return the burner to peak efficiency.
Since the gas pressure regulator itself is usually
furnished by others, detailed adjustment instruc-
tions and adjusting procedures recommended by
the manufacturer should be followed.
Pressure
The gas supplied must provide not only the quan-
tity of gas demanded by the unit, but must also be
at a pressure high enough to overcome the
pressure-loss due to the frictional resistance im-
posed by the burner system and the control valves.
The pressure required at the entrance to the bur-
ner train for rated boiler output is termed "net
regulated pressure". The gas pressure regulator
must be adjusted to achieve this pressure to assure
full input.
The pressure requirement varies with boiler size,
altitude, and type of gas train. Refer to Table 1 for
pressure requirements.
TABlE 1
Minimum Net Regulated Gas Pressure
For Rated Boiler Output
(Required at Gas Train Entrance)
Boiler
Standard FIA
Size and FM
Approved
(H.P.)
Approved Train
Train
25
4.5
5.0
30
4.5
5.0
40
4.5 5.0
50 A
7.0 7.5
50
4.5
5.0
60
4.5
5.5
70
5.0 6.0
80
5.5
7.5
100 8.5
ll.5
100A 9.5
13.0
100S
9.5 13.0
The pressures listed are based on 1000 BTU/CU.
FT. natural gas and elevations up to 700 feet
above sea level. For installation at higher alti-
tudes, multiply the selected pressure by the proper
factor from Table 2.
TABlE 2
Altitude Correction
Feet
Above Sea Level
Factor
1000
1.04
2000
1.13
2500
1.18
3000
1.22
4000 1.33
5000
1.44
6000
1.57
7000 1.70
8000
1.84
9000
2.01