CEMP-E
TI 810-10
1 February 1999
(2) Steel firebox boilers may be of a fire tube or water tube design. A principal
advantage is the capability of interchanging fuels such as coal for oil or gas if necessary.
Capacities up to 6900kW (23,500 MBtuh) gross output are available.
(3) Whenever the fuel choice is either gas or oil and there is no likelihood of converting
to coal, package boilers may be installed. Package boilers are either of a fire tube (including
Scotch marine) or water tube design.
b. Multiple Boiler Installations.
(1) Provide adequate room, connections, piping, etc., in boiler installations where future
expansion is likely. Boilers and related auxiliaries used for future loads can be added as
necessary.
(2) Determine the number and size of boilers to efficiently serve both the maximum winter
design load and the minimum summer load. With the largest boiler off line, the remaining
boiler(s) will be capable of carrying not less than 65 percent of the maximum winter design load.
Where the smallest boiler installed has a capacity of more than twice the minimum summer
load, consider adding an additional boiler or hot water heater sizes for the anticipated summer
load.
c. Steam Boiler Accessories. Provide a chemical feed system in accordance with TM 5-
650 based on an analysis of the makeup water to be used. Depending upon the size of the
installation and the pressure at which steam is generated, use boiler accessories such as
feedwater heaters to increase the steam generation cycle efficiency where applicable.
d. Feedwater Heating Systems.
(1) Install heaters for the de-aeration of feedwater for all installations with steam
capacities in excess of 6,000kW (20,000 MBtuh). This should be considered for installations of
4,500 kW (15,000 MBtuh) to 6,000 kW (20,000 MBtuh) capacity where estimated makeup rates
are 15 percent or more or where the plant serves a number of buildings. Installations operating
with either hot lime-soda or hot lime plus hot sodium zeolite softeners incorporating provisions
for the de-aeration of the treated water and condensate separately require no additional de-
aeration.
(2) Provide steel surge tanks for the storage of condensate. Install the surge tanks
upstream of the feedwater heaters where the space-heating load predominates, where large
quantities of condensate are returned by condensate pumps, and where steam-driven
auxiliaries are used. Size surge tanks to provide 20 minutes of condensate storage based on
boiler steaming capacity.
(3) Feedwater flow rate to the heater should equal the boiler demand. Size feedwater
pumps 10 percent larger than the capacity calculated to allow for pump cooling requirements.
(4) Install feedwater heaters above the boiler feed pump suction at a height sufficient
to prevent flashing at the pump inlet at the design feedwater temperature. With a feedwater
temperature of 100 degrees C (212 degrees F) and a back pressure on the feedwater heater of
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