TM 5-810-15
disturbing the main piping. These applications will
maximum rated speed. The pump construction will
also include shafts constructed of stainless steel,
include antifriction bearings that operate in an oil
containing not less than 11 percent chrome. The
bath. Pump and bearing frame and housing will be
impellers will be of the closed type, cast in one
constructed of cast iron. Casing will be constructed
piece. All internal parts of the pumps including
of ductile iron. Minimum casing thickness will be
impellers, sleeves and wearing rings, will be
inch with an additional 1/8 inch corrosion
constructed of stainless steel containing not less
allowance. The shaft, shaft sleeves and wearing
than 11 percent chrome.
rings will be 316 stainless steel.
e. Turbine drives. The turbine drives will be
sized to match the runout hp of the pump. Turbine
7-5. Condensate pumps.
drives will be horizontal split case construction.
a. General. The condensate pumps convey con-
The steam chest will be case iron or cast steel. The
densate from condensate return storage tank to the
rotor shaft will be annealed carbon steel and the
DA.
rotor disc a high strength alloy steel.
b. Design requirements. A minimum of two con-
densate pumps will be used, each sized for at least
7-6. Air compressors.
two thirds of the maximum steam plant demand.
a. Applications. Two compressor applications
This configuration will provide backup capacity for
individual pump failures or scheduled maintenance
are used in a steam plant: plant air and instrument
and will increase pump operation efficiency at
air. Plant air is the dry air used to atomize fuel oil,
reduced loads. Steam turbine driven pumps may be
blow soot deposits from the boiler furnace and heat
more economical than electric motor driven pumps.
recovery equipment, run plant pneumatic tools, and
However, one electric motor driven pump
perform other general plant functions. Instrument
facilitates cold start-up of the boiler plant. A LCCA
air is oil free, dry air supplied to instruments and
will be made to determine the most practical
pneumatic controls control valves and control
combination of condensate pumps.
drives. Instrument air is also used to clean fly ash
c. Condensate pump sizing. The condensate
baghouse filter bags.
b. Compressor types. Compressors are available
pump discharge head needs to be designed to
overcome the water static head to the DA, the
in two types. The first type is positive displace-
piping losses and the DA operating pressure. A 10
ment, such as the reciprocating piston compressor.
percent flow margin for wear allowance will be
The second type is dynamic, such as the centrifugal
included when sizing the pump. The condensate
compressor. Each type can be furnished with single
pump discharge head and suction head available
stage or multiple stage design. Reciprocal and
will be determined when the operating conditions
centrifugal compressors are the industry standard
are defined, an arrangement of the equipment has
for compressors used in boiler plants. Centrifugal
been made, and a pipe size and routing has been
compressors are usually considered for selection
made.
when the compressed air demand is uniform and is
d. Pump construction. Pumps will be constructed
equal to or above 400 standard cubic feet per
so they will provide continuous operation for the
minute (scfm). Otherwise reciprocating com-
expected plant life. Pump manufacturers should be
pressors are usually used.
c. Instrument air compressor sizing criteria.
consulted regarding specific features of
(1) Required volume of air. The required
construction for a particular application. The pump
impellers will be split ring key type. Bearings will
volume of air needed is found by adding all simulta-
be of the water lubricated sleeve type. The
neous air usages together. With instrument air, the
baseplate, outer barrel, inner column and discharge
highest usages generally occur during boiler start
head will be carbon steel. The impeller will be
up when lighters are inserted or when fly ash
bronze and the pump bearings graphalloy. The
baghouse filter bags are being cleaned.
(2) Outlet pressure. The compressor outlet
stage bowl will be cast iron. The shaft, shaft sleeves
and wearing rings will be 11 to 13 percent chrome
pressure will be sufficient to supply air at the
stainless steel. When the pump design conditions
required pressure, after line losses, to the device
do not require a vertical can type pump as
requiring the highest pressure in the instrument air
described above, the pump may be centrifugal,
system. Pressure regulators will limit the pressure
horizontal end suction, top discharge type as de-
to devices operating at lower pressures.
d. Plant air compressor sizing criteria.
scribed below. The pump impellers will be totally
(1) Required volume of air. The required
open type, screw mounted directly to the shaft with
0-ring seal and constructed of ductile iron.
volume of air needed is found by adding all simulta-
Impellers will be dynamically balanced to the
neous air usages together. One of the highest
7-4
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