Chemical Engineering November 2014 - 43

Cover Story
FIGURE 5. A typical flare burner tip
helps to dissipate hydrocarbon gases
via combustion, and can be located at
ground level or on an elevated structure
carbon fluids before they are discharged
to the atmosphere. The
burner fires horizontally into a pit
at ground level.
Flare pilots and ignition. In a
flare system, the flare burner is
equipped with pilot burners, which
are used to ignite the flared gases
when needed. The number of pilot
burners is dependent on the size
of the flare. The pilot burners are
installed at the flare tip. The pilot
burners have their own ignition
system. Two main types of ignition
systems are used to ignite the
flare pilots: flame-front generators
(FFG), and high-energy ignition
systems. Some flares use both
systems as primary and backup
ignition sources. If desired, flame
monitoring can be installed in
the flare pilot.
Burner inspection
Burners are expected to be continuously
reliable and efficient enough
to meet the rigorous requirements
of the CPI. Periodic inspection and
maintenance should be conducted
according to the burner manufacturer's
guidelines. Malfunctioning
burners can result in inefficient
combustion or poor flame patterns.
This can lead to localized overheating
and damage to furnaces or
equipment components, resulting
in increased maintenance costs.
This damage can also cause premature
shutdowns due to failure
of critical equipment components,
such as tubes or refractory lining.
The following is a checklist of the
main burner components that operations
and maintenance personnel
should inspect when developing an
inspection worksheet:
* The atomizer of an oil burner
should be inspected for any defects
or misalignment
* The gas nozzles of a gas burner
should be inspected for any defect
or deterioration
* The nozzle diameter of an atomizer
or gas nozzle should
be inspected to ensure that it
is within the burner vendor's
specification datasheet
* The movement of the mechanical
air registers should be inspected
to ensure proper free movement
* The gasket at the atomizer of an
oil burner must be inspected
* The burner throat should be inspected
by measuring its dimension
and ensuring it matches the
vendor's drawings
* The burner throat must be inspected
to detect any damage
In addition to inspecting the various
burner components, there are
several physical dimensions that
must be confirmed in order to ensure
correct operations. The main
components and allowable deviations
from vendors' datasheets that
must be measured and verified in
the burners are as follows:
* The burner tile diameter must be
within ±1/8 in.
* The burner tile concentricity
(roundness) must be within
±1/8 in.
* The tip port angles must be
±4 deg
* The bolting dimensions must be
±1/8 in.
* The gas tip locations should be
no more than ±1/8 in. deviation
in the horizontal direction, and
no more than ±1/4 in. deviation
in the vertical direction
Piping and auxiliaries
The integrity of the piping and auxiliaries
of the burners also requires
attention, and there are certain
tasks that must be performed to
maintain normal operations. Some
best practices for maintaining
burner piping are as follows:
* Perform leakage tests on the
burners' associated piping and
valves by conducting a soap
test or three-in-one gas tester
procedure
* Check the pilot pressure regulator
setting to ensure that it is within
the recommended setpoint
* Verify the tightness of scanners
and conduit connections to prevent
water intrusion
* Inspect electrical components
to ensure that they are
working properly, including
switches, lights, relays and other
related parts
* Check that the pilot gas jet is
clear and that the pilot flame
is strong
Most burners are fitted with optical
main flame-detection systems,
which also require maintenance.
The following must be checked to
ensure best performance of flamedetection
systems:
* The sight path from the viewing
head to the flame is aligned
correctly to provide visibility of
the flame
* The head mount and sighting
tube are clear from any fouling
* The wiring is installed as specified
by the original operation
and maintenance manual
Burner maintenance
A burner's performance deteriorates
with operating time due to fouling,
plugging and wear on burner
components. Fouling, plugging and
wear reduce the effectiveness of
fuel-air mixing and can affect the
flame and heat flux patterns, resulting
in lower heater efficiency and
heating capability. Burner parts
requiring frequent maintenance
to avoid serious performance loss
or safety issues include the orifice,
tip, atomizer, tile, flame stabilizer,
register, damper, pilot burner and
detection systems.
Gas tip and orifice. In a burner,
the fuel-gas tips and fuel-gas orifice
have drilled ports that direct the
stream of fuel into the airstream
and combustion zone. These ports
must be kept free of foreign mateChemiCal
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Chemical Engineering November 2014

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