Step 2: Control Methodology - Eclipse TFB030 Manual

Tube Design
1. Elbows
a.We recommend the use of standard and sweep
elbows only.
b.The first elbow should be at least eight tube
diameters from the face of the burner.
2. Stack
a.Make sure that the stack is large enough to handle
the exhaust flow plus the dilution air.
b.The stack must be at least one pipe size larger than
the tube exhaust.
NOTE: Detailed guidelines for flue sizing calculations are
in the Eclipse Combustion Engineering Guide (EFE 825).
3. Draft breaking hood
Figure 3.8.
A draft breaking hood is an open connection between the
heater tube exhaust and the exhaust stack. It allows fresh
dilution air to pass into the exhaust and mix with the
exhaust gases.
The advantages of a draft hood are:
• the burner operation is less sensitive to atmospheric
conditions
• the temperature of the exhaust gases is lower when
they pass through the roof.
NOTE: Make sure that it is possible to get access
between the draft hood and the tube exhaust. Then you
can install a damper plate if acoustic feedback occurs in
the tube.

Step 2: Control Methodology

The control methodology is the basis for the rest of the
design process. Once you know what your system will
look like, you can select the individual components. Which
control methodology you choose depends on the type of
process that you want to control.
10
Stack
Draft breaking
hood
Dilution air
Tube exhaust
Control Methods
There are two main methods to control the input of a TFB
system:
1. Modulating control
A burner system with modulating control gives an
input that is in proportion with the demands of the
process. Any input between high and low fire is
possible. The burner operates at 15% excess air at
high fire, and 100% excess air (min.) at low fire.
2. High/low control
A system with high/low control gives a high or low fire
input to the process. No input between high and low
fire is possible. The burner operates at 15% excess
air at high fire, and 100% excess air (min.) at low fire.
The only difference in the components is the type of
actuator on the automatic butterfly valve (control
valve , page 11).
On the next page you will find schematics of these
control methods. The symbols in the schematics are
explained in the Appendix on page ii.
Automatic gas shut-off by burner (optional)
As an option, an automatic gas shut-off valve can be
installed. If the flame monitoring system detects a failure,
the gas shutoff valve closes, interrupting the gas supply to
the burner that caused the failure.
System schematics
1. Air
The control valve  is in the air line. It sets the air flow
to the required value.
2. Gas
The ratio regulator  allows the required amount of
gas to go to the burner. Low fire gas is limited by ratio
regulator . High fire gas is limited by the manual
butterfly valve .
Eclipse TFB, V2, Design Guide 310, 11/14/2014