UFC 3-240-13FN
25 May 2005
3-2.6.1.1
Deaerator Operation. Two key parameters associated with deaerator
operation are controlled to maintain maximum oxygen removal. First, the deaerator vent
is checked to verify that a plume of steam is always flowing out of the vent. Second,
both the pressure within the deaerator and the temperature of the outlet water are
controlled. Deaerators should operate at a pressure of 20.68 kilopascals (3 pounds per
square inch gauge) or more. At any given pressure, the deaerator water outlet
temperature should be within 1 oC (2 oF) of the water temperatures shown in Table 3-2,
adjusted for the altitude of the installation. If the deaerator is operating with low or no
steam flow or at a low water temperature, the deaerator is not being operated efficiently
and is not removing the maximum amount of oxygen. Schematic diagrams of
mechanical deaerators are shown in Figures 3-11 and 3-12.
Table 3-2. Deaerator Water Outlet Temperature for Boiler Systems
at Various Sea Level Pressures
Deaerator
Deaerator Water
Deaerator
Deaerator Water
Pressure
Outlet
Pressure
Outlet
kPa (psig)
Temperature
kPa (psig)
Temperature
o
C (oF)
o
C (oF)
0.00 (0)
100 (212.0)
75.84 (11)
116.4 (241.6)
6.89 (1)
101.8 (215.3)
82.74 (12)
118 (244.4)
13.79 (2)
103.6 (218.5)
89.63 (13)
119.1 (246.4)
20.68 (3)
105.3 (221.5)
96.53 (14)
120.2 (248.4)
27.58 (4)
106.9 (224.4)
103.42 (15)
121.3 (250.3)
34.47 (5)
108.4 (227.1)
110.32 (16)
122.3 (252.2)
41.37 (6)
109.9 (229.8)
117.21 (17)
123.4 (254.1)
48.26 (7)
111.2 (232.2)
124.11 (18)
124.1 (255.3)
55.16 (8)
112.7 (234.8)
131 (19)
125 (257.0)
62.05 (9)
113.9 (237.1)
137.90 (20)
126 (258.8)
68.95 (10)
115.2 (239.4)
--
--
NOTE: For every 152 meters (500 feet) in elevation from sea level, subtract 0.5 oC (1
o
F) from the listed temperature. A mechanical deaerator that is operating efficiently can
reduce the oxygen content of feedwater from the saturation level to a fraction of a ppm.
However, even a trace amount of oxygen can cause corrosion pitting in the boiler. The
complete removal of oxygen requires the addition of a chemical agent called an "oxygen
scavenger."
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