CleaverBrooks 4WI, Руководство по эксплуатации, обслуживанию и запасным частям

Страница: 109 / 216

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual 6-23
6.21 — Fuel Oil Combustion Adjustment
6.21 — Fuel Oil Combustion Adjustment
After operating for a sufficient period of time to assure a warm boiler, adjustments should be made to obtain effi-
cient combustion.
Proper setting of the air/fuel ratios at all rates of firing must be established by the use of a combustion gas analyzer.
Efficient combustion cannot be solely judged by flame condition or color, although they may be used in making
approximate settings. Combustion settings should be done so that there is a bright sharp flame with no visible haze.
It is required to set the burner to operate with a reasonable amount of excess air to compensate for minor varia-
tions in the pressure, temperature, or burning properties of oil. 15% to 20% excess air is considered reasonable.
This would result in an O
2
reading of 3% to 4% at high-fire.
Final adjustment to fuel input must be made to produce a minimum of smoke. A maximum smoke spot density of
a No. 2 for light oil, or a No. 4 for heavy oil is acceptable, as measured in conformance to ASTMD 2156-63T.
Through the use of the manual flame control, slowly bring the unit to high-fire by stages while monitoring combus-
tion for overly rich or lean conditions. At the high-fire position, the air damper should be fully opened and the air
and oil pressure readings should be on the order of the readings given in Chapter 5.
Take a flue gas analysis reading. If necessary, adjust the fuel oil controller to increase or decrease oil pressure.
Adjustments to the pressure should be done before attempting to adjust the screws in the metering cam. Ideally, the
cam profile spring should be as close to the cam casting as practical. It is more desirable to lower the oil pressure to
reduce flow, if necessary, than to extend the adjusting screws to an extreme position in an effort to cut back flow.
After being certain that the air control damper and its linkage are operating properly, final adjustment can be made,
if necessary, to the oil modulating cam to obtain constant fuel/air ratios through the entire firing range.
Since the input of combustion air is ordinarily fixed at any given point in the modulating cycle, the flue gas reading
is determined by varying the input of fuel at that setting. The adjustment is made to the metering cam by means of
adjusting screws, which are turned out (counterclockwise from hex-socket end) to increase the flow of fuel and in
(clockwise from hex-socket end) to decrease. Flow rate is highest when the cam follower assembly is closest to the
jackshaft.
If oil pressure, primary air pressure, and linkages are properly adjusted, the metering cam should require minimal
adjustment.
Using the manual control switch, position the cam so that the adjusting screw adjacent to the end, high-fire screw,
contacts the cam follower. Make a combustion analysis at this point.
If an adjustment is necessary, turn the cam adjustment screw accordingly to increase or decrease fuel flow. Take a
combustion reading to verify input. Repeat as necessary until the desired flow is obtained. Continue this process,
stopping at each adjusting screw, until the low-fire position is reached.