Adjustments - CleaverBrooks FLX Operation, Service And Parts Manual

Chapter 2
D. Adjustments
While each burner is tested at the factory for correct operation
before shipment, variable conditions such as burning
characteristics of the fuel used and operating load conditions
may require further adjustment after installation to assure
maximum operating efficiency.
Prior to placing the boiler into initial service, a complete
inspection should be made of all controls, connecting piping,
wiring, and all fastenings such as nuts, bolts, and setscrews to
be sure that no damage or misadjustments occurred during
shipment and installation.
A combustion efficiency analysis made during the initial
startup will help to determine what additional adjustments are
required in a particular installation.
COMBUSTION ADJUSTMENT ON OIL AND
GAS
Efficient combustion cannot be properly judged by flame
appearance, although it may help in making preliminary
settings.
The proper settings of air-fuel ratios must be determined by
flue gas analysis. Combustion gas analysis indicates the air to
fuel ratio and the degree of complete combustion.
Instruments are available to measure carbon dioxide (CO
oxygen (O ), and carbon monoxide (CO). At no time should
2
CO measurements alone be used to indicate proper excess
2
air levels. Only O measurement can definitively show
2
whether sufficient air has been provided for combustion.
STACK TEMPERATURE
Net stack temperature is obtained by subtracting the ambient
temperature from the flue gas temperature. A high net stack
temperature indicates wasted heat. Decreasing either the
temperature or the volume of the flue gas, or both can reduce
stack heat loss. Flue gas temperature is reduced by improving
heat transfer or by reducing excess combustion air. A certain
amount of excess air is necessary to complete combustion.
More efficient burners require minimum excess air.
SMOKE MEASUREMENT
Smoke measurements can be made using a variety of
different methods. The standards will vary somewhat
according to the equipment used, and instructions
accompanying the instrument should be followed.
Smoky combustion can result from:
• improper air delivery
• insufficient draft
• improper fuel viscosity
• improper fuel-air ratio
• excessive air leaks in the combustion chamber
2-22
• improper fuel oil temperature
TEST EQUIPMENT
The following test equipment should be used to set up and
adjust the burner correctly:
1. Combustion analyzer with O
2. U-Tube manometer, or pressure gauge, to measure gas
pressures (Main and Pilot), vacuum and pressure gauges
for oil.
3. Inclined manometer to measure draft pressures.
4. Smoke spot tester for oil burners and CO analyzer for
gas fired units.
5. Voltmeter/Ammeter.
6. Stack Thermometer and Thermocouples.
AIR FLOW ADJUSTMENTS
The V/Series burners have a two-blade air shutter design.
Both blades are coupled together, and attached to the
modulation motor. Changing the positions of the linkage rods
on the linkage control arms will change the way the damper
blades open and close.
),
2
COMBUSTION SETTINGS
Fuel and air flow rates are individually adjusted at low-fire
and at high-fire to achieve rated input, firing rate turndown,
optimum efficiency, safe operation, and the ability to cope
with environmental changes (including air temperature,
humidity, barometric pressure), and fuel property changes.
Turndown capability for oil is less than that for gas due to the
excess air requirement of oil for clean combustion. Therefore,
on combination fueled burners, gas turndown performance
may be restricted (or determined) by the excess air levels set
initially for oil combustion. For burners equipped with the
optional Siemens modulating motor, gas turndown will not be
limited to the oil setting. Each fuel will have a separate
modulation range, independent of each other.
Two key components residing in flue gas are used to optimize
combustion efficiency are excess air and unburned fuel. The
system should be adjusted to the minimum excess air quantity
that provides low levels of unburned fuel with sufficient
remaining oxygen to cope with normal atmospheric and fuel
related changes. Unburned fuel is measured as carbon
monoxide (CO) when burning natural gas, and smoke spots
when burning oil.
GAS ADJUSTMENTS
Low-fire combustion analysis typically is 6% to 9% O
less than .04% CO (400 ppm). High-fire reading typically is
3% to 5% O and less than .04% CO. The V/Series burners
2
Profire V Burner
indication.
2
and
2
750-177