Step 6: Main Gas Shut-Off Valve Train; Step 7: Process Temperature Control System - Eclipse TFB030 Manual

Table 3.5 Fuel Gas Heating Values
Stoichiometric*
Fuel Gas
Natural Gas
(Birmingham, AL)
Propane
Butane
*Stoichiometric: No excess air. The precise amount of air and
gas are present for complete combustion.
Example Blower Calculation
"A batch furnace has been designed and requires a heat
input of 2,900,000 Btu/h. It has been decided to provide
the required heat input with four burners operating on
natural gas using 15% excess air."
Calculation example:
a.Decide which TFB burner model is appropriate:
Q (total heat input) of
2,900,000 BTU/hr
4 burners
- Select 4 Model TFB075 TFB burners based on the
required heat input of 725,000 Btu/hr for each
burner.
b.Calculate required gas flow:
Q
V = =
gas
q
- Gas flow of 2,894 ft
c.Calculate required stoichometric air flow:
= air/gas ratio x V
V
air-Stoichiometric
= 27,235 ft
- Stoichiometric air flow of 27,235 scfh required
d.Calculate final blower air flow requirement based
on the desired amount of excess air:
V
air
= (1 + 0.15) x 27,235 ft
- For this example, final blower air flow requirement
is 31,320 scfh at 15% excess air.
NOTE: It is common practice to add an additional
10% to the final blower air flow requirement as a
safety margin.
3. Find the blower model number and motor horsepower
(hp). With the output pressure and the specific flow,
you can find the blower catalog number and the motor
hp in Bulletin / Info Guide 610.
Eclipse TFB, V2, Design Guide 310, 11/14/2014
Air/Gas Ratio Gross Heating
 (ft
/ ft ) Value q (BTU/ft
3 3
air gas
9.41 1,002
23.82 2,572
30.47 3,225
= 725,000 BTU/hr/burner
2,900,000 BTU/hr
= 2,894 ft
1,002 BTU/ft
3
3 /hr is required
= 9.41 x 2,894 ft
gas
3 /hr
(1 + excess air
x V
=
air-Stoichiometric
%)
/hr = 31,320 ft
3
4. Eclipse Combustion recommends that you select a
Totally Enclosed Fan Cooled (TEFC) motor.
5. Select the other parameters:
)
3
• inlet filter or inlet grille
• inlet size (frame size)
• voltage, number of phases, frequency
• blower outlet location, and rotation direction
Clockwise (CW) or Counter Clockwise (CCW)
NOTE: The use of an inlet air filter is strongly
recommended. The system will perform longer and the
settings will be more stable.
NOTE: When selecting a 60 Hz Blower for use on 50 Hz,
a pressure and capacity calculation is required. See
Eclipse Combustion Engineering Guide (EFE 825)
The total selection information you should now have:
• blower model number
• motor hp
• motor enclosure (TEFC)
• voltage, number of phases, frequency
• rotation direction (CW or CCW)
Air Pressure Switch
The air pressure switch gives a signal to the monitoring
system when there is not enough air pressure from the
blower. You can find more information on pressure
switches in:
3 /hr
• Blower Bulletin 610
■ Eclipse Combustion supports NFPA regulations,
/hr
3
which require the use of an air pressure switch in
conjunction with other safety components, as a
minimum standard for main gas safety shut-off
systems.

Step 6: Main Gas Shut-Off Valve Train

Eclipse can help you design and obtain a main gas shut-
off valve train that complies with the current safety
standards. The shut-off valve train must comply with all
the local safety standards set by the authorities that have
/hr jurisdiction. For details, please contact Eclipse.
3
NOTE: Eclipse supports NFPA regulations (two shut-off
valves) as a minimum standard for main gas safety shut-
off systems.
Step 7: Process Temperature Control
System
The process temperature control system is used to control
and monitor the temperature of the system. There is a
wide variety of control and measuring equipment
available. For details, please contact Eclipse.
WARNING
13