TM 5-810-15
construction of the coolers will allow the
mendations of the boiler manufacturer. Depending
circulating water or dirtier water to pass through
on the boiler and down period, such steam parts
the tubes allowing more practical cleaning. The
filled with treated water or a nitrogen purge are the
cooler tubing and tube sheet material selection will
economizer, water walls, superheater, reheater,
be based on water quality. Materials can be
feedwater heater (tube side-water; shell side-
admiralty, copper nickel, or for corrosive
nitrogen) and drum. In some cases freezing may be
applications stainless steel. The coolers will be the
a problem and treated water can be replaced with
straight tube type with fixed tubesheet, removable
nitrogen. The amount of nitrogen required, for
channel construction. The shell will be carbon steel
boiler purging will be given by the boiler
and the channel heads will be fabricated steel. The
manufacturer or can be calculated from the volume
shell will have 150 pound raised face flanged or
of the steam parts. The nitrogen system is a low
3000 pound screwed connections. The channel will
pressure system. However, the nitrogen is stored in
have 150 pound flat faced flanged or 3000 pound
high pressure cylinder bottles and the piping will be
screwed connections. The coolers will be
connected to a high pressure boiler. A pressure
manufactured with shell, channel vent and drain
regulator and high pressure valving will be
connection.
required.
7-16.
Ignitor fuel oil pumps.
7-18.
Carbon dioxide (CO2) system.
a. Design. Ignitor fuel oil pumps will be rotary
a. Application. A carbon dioxide system in a
screw type pumps. Two pumps will be provided,
boiler plant is most commonly used to extinguish
each rated at 100 percent capacity, with one pump
fires in coal bunkers. A CO2 system can also be
used for backup service. A fuel oil unloading pump
used to extinguish electrical hazards, such as
will be applied if required and will have the same
transformers, oil switches and circuit breakers, and
characteristics as the ignitor fuel oil pumps. No. 2
rotating equipment. CO2 extinguishes fire by
fuel oil is more commonly used for ignitor systems
reducing the concentration of oxygen and the
and will be assumed herein. The pumps will be able
gaseous phase of the fuel in the air to the point
to pump oil with a viscosity of 200 Saybolt
where combustion stops.
b. Design. The CO2 systems are classified as
Seconds Universal (SSU) against the design dis-
charge pressure at the design capacity. Fuel oil
automatic, manual or automatic-manual. Fires or
viscosity will be expected to vary between 33 and
conditions likely to produce fires may be detected
200 SSU. Pump motors will be totally enclosed and
by visual (human senses) or by automatic means. In
explosionproof.
the case of coal bunkers, methane detectors can be
b. Types. Unlike a centrifugal pump, a rotary
used to alarm a fire or actuate the CO2 system and
screw pump is a positive displacement pump, that
an alarm. CO2 can be stored in cylinder bottles and
will displace its capacity to the point of failure
pipes through a pressure regulated system to
regardless of the resisting pressure. A fuel oil
discharge nozzles at the area of combustion. The
recirculation system will be designed to allow the
amount of CO2 in the system will be at least
pump to recirculate the fuel oil as the ignitor fuel
sufficient for the largest single hazard protected or
oil is modulated according to demand. In a fuel oil
group of hazards to be protected simultaneously.
loading system the fuel oil is not modulated and a
The CO2 system will be designed and erected in
recirculation system is not necessary. In sizing the
accordance with NFPA 12 of the National Fire
fuel oil pump, the pressure to overcome will be
Codes.
calculated from piping losses and elevation change
to get the required pump discharge pressure. The
7-19.
Chemical feed pumps.
ignitor fuel oil pump capacity is determined from
a. Application. Chemical feed pumps are small
maximum fuel oil demand plus 20 percent for pump
capacity pumps used to inject chemicals into the
wear and safety factor.
condensate, feedwater and steam system at a
controlled rate. Most chemical feed pumps are
7-17.
Nitrogen system.
specified and purchased as a chemical feed unit that
a. Application. The nitrogen system is used to
includes a pump, tank, mixer and piping. Typical
purge the boiler for protection from corrosion
chemical systems used in a boiler plant are
between hydrostatic test and initial operation and
hydrazine, morpholine, phosphate and a metal
after chemical cleaning periods and outages.
surface passivating agent.
b. Design. The boiler steam parts are filled with
b. Design. The pump selection will have the
treated water until overflowing and then capped off
capacity and discharge head to inject the chemical
with 5 psig of nitrogen according to the recom-
into the system. Pumps are rated by capacity in
7-15
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