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B.
Burner problems
1.
LIFTING FLAMES:
How to recognize:
When lifting flames occur, part of the flame lifts from the burner port. Lifting flames rise from
the ports to burn some distance above the port. In some cases, these flames will drop back to
the port and lift again intermittently. Lifting flames may occur on a few or all of the burner port
holes. If flames lift from a number of ports, they may create a distinct flame noise. Lifting
burner flames result when the velocity of the air-gas mixture from a port exceeds the flame
velocity.
How to correct:
The simplest way to stop burner flames from lifting is to reduce primary air. However, before
doing this, check the appliance input rate and reduce if necessary. Lifting may be observed with
only one of several burners in an appliance. Check the orifice size of that burner against the
others to make sure the burner is not operating over rated input. When reducing primary air to
prevent lifting flames, make sure yellow tipping does not occur.
2.
FLASHBACK:
How to recognize:
When flashback occurs in a burner, the air-gas mixture ignites inside the burner to burn near
the orifice. This burning in the mixer tube usually creates a roaring noise like a blowtorch.
How to correct:
Flashback on ignition or during burner operation usually can be eliminated by reducing primary
air to the burner. Make sure that the air adjustment does not produce yellow tipping of flames.
The burner may be under rated, so check input rate and adjust it to its correct value if necessary.
The orifice size may be enlarged, or gas pressure increased if rate or supply pressure is found
to be too low. Sometimes only one burner of several in an appliance flashes back. Check the
orifice size of that burner against those of the other burners. If flashback occurs with the burner's
gas valve in off position, the gas valve is probably leaking. Repair the valve or replace it. Replace
the burner, or burners, if the above correction fails to eliminate the flashback.
3.
EXTINCTION POP:
How to recognize:
Sometimes a small explosion of gas in the burner head occurs when the burner is shut-off. Under
these conditions flashback or extinction has taken place.
"extinction pop".
Extinction pop creates a noise or a loud "bang". Ordinarily, it is not followed by burning in the
burner head or mixer tube, since the gas supply is turned-off. The pop occurs at the time the
gas supply to the burner is shut-off. Sometimes it may be delayed for a few seconds.
How to correct:
It may be possible to eliminate extinction pop by reducing primary air supplied to the burner.
Make sure that this iar adjustment does not cause yellow tipping during normal burner operation.
It also may help to increase gas pressure and decrease gas orifice size. These changes provide
a faster flow of the final air-gas mixture, and allow the air shutter to be closed more that with a
larger gas orifice and lower gas pressure. If these actions fail to correct the problem, replace
the burner.
4.
YELLOW TIPPING OF FLAMES:
How to recognize:
Bunsen-type flames should be completely blue. If not enough primary air is supplied, yellow tips
appear in the flames. Do not confuse yellow tips with red or orange streaks which sometimes
appear in flames. These color streaks usually are due to dust in the air supply and should create
no problems. There also have been some reports of humidifiers, operating with softened water,
causing orange flames on burners. The use of some tinted glasses, such as brazing goggles, will
eliminate those discolorations from view, leaving true yellow tips still visible. Yellow tip flames
indicate incomplete combustion in appliances designed for blue flame operation. This condition
is aggravated if the flames impinge on cool surfaces. Yellow flames which produce soot (carbon)
can be a nuisance. Sooting presents a serious problem if it collects to block flue-ways. Plugged
flue-ways impede venting of combustion products and reduce the amount of air drawn into the
combustion chamber. Incomplete combustion can then take place.
This problem is commonly called
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