Formulas  Calculating Condensate Loads
Warm Up Load ( Heating Loss ) This is the amount of condensate which forms
at starting up a power plant to raise the temperature of the metal of pipes,
fittings, etc. to the operating temperature without including the normal radiation
loss. As far as calculating the condensation load during the warming up period
the required time is extremely important for sizing steam traps. Less warm
up time increases the necessary capacity per trap. Allowing more time for warm
up permits the use of smaller traps in smaller quantity.
W
x (Tt) x Sp. Heat x 60
Q = —————————————
L
x m
Where Q = Quantity of Condensate ( Lbs/hr )
W = Total weight of pipes in
LBS
T = Saturation Steam Temp ( °F ) t = initial temp of pipe ( °F
) usually surrounding air temp
m = minutes to heat up system
L = Latent
heat of steam ( BTU’s/Hr )
Normal Condensate Load ( Radiation Loss )
Once the system is heated up steam
condenses due to normal radiation losses to the surrounding air. These
losses depend of course on the size and length of the pipe, on the pressure
of steam and its latent heat and mainly on the type and thickness of
insulation. The equation from which a normal regulation load can be calculated
is:
F x HL ( T  t )
Q = ——————————
L
Where F = Length of Pipe (ft)
HL ( T – t ) = Heat loss/foot of pipe
at the temperature differential between steam and air
L = Latent heat of steam ( BTU’s/Hr. )
Condensation Load for Sizing Steam Traps
The condensation load builds up
from 0 to maximum at the point where the warming up load drops to 0.
It is assumed, therefore, that the peak is achieved halfway through the warming
up period. Therefore, for sizing of steam traps, we take the maximum amount
of condensate during the warming up period plus half of the radiation load.
Qt= QW + .5QR
Where Qt = Total condensation load at peak (LBS/Hr)
QW = Condensation
load during warm up (LBS/Hr)
QR = Condensation load due to normal radiation
loss (LBS/Hr)
Condensate in LBS/Hr created in steam mains 1” to 24” and pressure
of 600 to 2500 PSI based on the warm up period of 1 hour and 100 feet of pipe,
and based on the above assumption is shown in tables.
For shorter or longer
heating up time, multiply by 60/m where m is the warm up time in minutes.
Properties of Saturated Steam
Standard Dimensions for Schedule 40 Pipe
Examples:
Warm up loss
Ambient Temp = 70°F
Working Temp = 366°F (150psig)
Warm up time = 720 minutes
1000 feet of 10 inch Schedule 40 pipe weighs = 40483
Latent heat = 857
40483 x (36670) x .12 x 60
Q = —————————————
857
x 720
Q = 472 lbs/hr
Radiation loss
Ambient Temp = 70°F
Working Temp = 366°F (150psig)
Differential temp = 294°F
Differential multiplier = .98
1000 feet 10 inch
Schedule 40 uninsulated pipe
Latent heat = 857
1000 x 2600 ( .98 [factor for
296° diff] )
Q = ——————————
857
Q = 2973 lbs/hr
Sizing for steam traps
Qt= QW + .5QR
.5QR = 1486.5 + QW = 472
= 1958.5
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