Type of Control
Coal (MW)
Oil (MW)
compensation
(Type of Control
Coal (Btuh)
Oil (Btuh)
Positioning
3-50 million
3-40 million
Semimetering
25-72 million
25-66 million
Metering
25 million and above 25 million and above
Metering
68 million and above 68 million and above
with oxygen
compensation)
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Combustion control equipment shall be provided as a system by a single
manufacturer. Automatic combustion control system shall be installed for
each boiler in accordance with the manufacturer's recommendations.
Controllers shall be located on the designated heating plant master control
center panel. The equipment shall operate either pneumatically,
electrically, or electronically. Pneumatic control systems shall conform
to ASME B19.3. Air filter regulator sets shall be installed at each
control valve and transmitter in the system. The master air filter
regulator set on the control panel shall be the dual type where one side
can be cleaned and repaired while the other is operating. Exterior control
air piping and devices shall be protected from freezing by use of
regenerative desiccant dryers. Each system shall be provided with a
selector switch or other means of manual control of the firing rate when
required. Electrical control devices shall be rated at 115 volts and shall
be connected as specified in Section 16402 INTERIOR DISTRIBUTION SYSTEM.
Operating and limit controls shall be wired to interrupt the ungrounded
circuit conductor. Controls and instruments shall conform to the
requirements of ASME CSD-1, NFPA 8501, UL 296, and UL 726, except as
otherwise specified. On multiple boiler installations, a means shall be
provided to base load on individual boilers while on automatic control and
each boiler unit shall be individually controlled.
2.4.1
Combustion Controls
Combustion controls shall be the [positioning] [semimetering] [metering]
[metering with oxygen compensation] type. A plant master controller
sensitive to temperature transmitter in return water header shall be
furnished to provide anticipatory signals to all generator master
controllers. Generator master or submaster controllers shall react to
anticipatory signals from plant master and then adjust firing rate as
necessary in response to generator outlet temperature indication to
maintain preset temperature at each generator outlet. The precision of
pressure or temperature control, expressed in percent, plus or minus, of
the set point of the boiler pressure in kPa psig, or the temperature in
degrees C degrees F during any load swings of up to 10 percent of the
boiler capacity per minute over the entire turndown range, shall not exceed
3 percent.
2.4.2
Stoker Controls
The combustion control system shall be interlocked with the grate drive to
balance the ash discharge with the firing rate. The coal feed flow rate
may be used as the index of fuel feed. Stoker controls shall perform as
outlined for the stoker specified.
SECTION 15555A
Page 35
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