TM 5-810-15
impingement of fly ash on the sensing element. The
have positioners with characterizable cams. Open/
analyzer should be equipped to allow daily
shut control drives should have internally mounted
automatic calibration checks without removing the
four-way solenoid valves. Control drives will be
analyzer from the process. The cell temperature in
designed to provide the rated torque with a
the analyzer will be maintained at the proper
maximum 50 psig air supply. The control drive will
temperature by a temperature controller. The
be sized to provide 150 percent of the torque
analyzer will be certified for "in stack" analysis
required to drive controlled device.
(2) Electric control drives. Electric control
technique in accordance with the Factory Mutual
(FM) approval guide. The analyzer will be
drives will consist of an electric motor, gear box,
furnished with all accessories necessary for a
rigid support stand, and wiring termination enclo-
complete installation.
sure. Electric control drives will be weatherproof.
(8) Opacity monitors. Opacity monitors use
The gear box will be dust tight, weather tight, and
the principal of transmissometry to indicate level of
totally enclosed. Electric control drives will be self-
particulate emissions. A beam of light is projected
locking on loss of control or drive power. Drives
across the flue gas stream and a detector registers
for outdoor installation will be designed to operate
variations in the light transmittance caused by the
with ambient conditions of -20 degrees F and a 40
particulate in the flue gas.
miles per hour wind. Drives will have adjustable
(9) Flue gas monitors. Flue gas monitors will
torque limit switches and position limit switches.
be provided for all items required for EPA reports.
Electric drives will be supplied with motor starters,
Flue gas monitors are either in situ or extractive. In
position
controllers,
speed
controllers,
situ monitors are attached directly to the stack or
characterizable positioners, transformers, and other
breeching and access for maintenance should be
accessories as required. The control drive will be
provided. Extractive systems are wet, dry or di-
sized to provide 150 percent of the torque required
luted. Wet extractive system sample line should be
to drive the controlled device.
d. Control valves.
heated to avoid corrosion. Dry systems utilize a
(1) Valve bodies. Control valve bodies will be
cooler to remove water. Dilution systems utilize
clean dry air to dilute the sample eliminating the
constructed in accordance with the applicable
need to heat the sample lines or dry the sample.
ANSI codes. Control valves will be globe type
Either in situ or extractive flue gas monitors should
unless otherwise required for the particular process.
be used and not a mixture of the two for the
Butterfly valves may be used in low pressure water
various gases to be analyzed. All analyzers should
systems. Globe valves will have a single port
be provided with self calibration features and have
designed to meet the design conditions. Restricted
contact outputs for control room annunciation.
ports should be used when necessary for stable
c. Control drives. Control drives will be used for
regulation at all loads. Special consideration will be
positioning of control dampers, isolating dampers,
given to valves which pass flashing condensate to
and other devices requiring mechanical linkages.
assure adequate port and body flow area. The valve
Control drives may be pneumatic or electric and are
body size may be smaller than the line size if the
either open-shut type or modulating type depending
plug guide is sufficiently rugged to withstand the
on the application. Modulating drives may include
increased inlet velocity, but valve body size will not
position transmitters. Control drives will have
be smaller than one half the line size. End
adjustable position limit switches wired to terminal
preparations will be suitable for the applicable
blocks, handwheels or levers for manual operation,
piping system. Valves will have teflon packing for
hand locks or be self locking, position indicators,
temperatures not exceeding 450 degrees F. Bonnet
and adjustable limit stops at maximum and
joints will be flanged and bolted type and designed
minimum positions. Drive arms and connecting
for easy disassembly and assurance of correct valve
linkages will be supplied with the damper drives.
stem alignment. Valve trim will be cage guided and
Control drives will have stroking times as required
removable through the top after bonnet removal.
by the service and by NFPA recommendations.
Seat rings will be easily replaceable. Flow direction
(1) Pneumatic control drives. Pneumatic con-
should be flow opening unless otherwise required.
(2) Valve operators. Control valve operators
trol drives should consist of a double acting air
cylinder with rigid support stand and weatherproof
will be pneumatic diaphragm actuated type except
enclosure. Pneumatic control drives for outdoor
where piston actuators are required. Valve opera-
service will have thermostat controlled space heat-
tors will be adequate to handle unbalanced forces
ers installed and wired to terminal blocks. Pneu-
that occur from flow conditions or maximum differ-
matic control drives for modulating service will
ential. Allowances for stem force based on seating
9-23
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