AHT 20-350, User Maintenance Manual

Page: 8 / 44

----EN
EN EN
EN----
2.5 CORRECTION FACTORS
Correction factor for operating pressure changes :
Inlet air pressure psig 60 80 100 120 140 160 180 200
barg 4 5.5 7 8 10 11 12.5 14
Factor (F1) 0.79 0.91 1.00 1.07 1.13 1.18 1.23 1.27
Correction factor for ambient temperature changes:
Ambient temperature ºF
≤
80 90 100 105 110 115 120
ºC
≤
27 32 38 40 43 46 50
Factor (F2) 1.22 1.11 1.00 0.94 0.89 0.83 0.78
Correction factor for inlet air temperature changes:
Air temperature
ºF
≤
140 160 170 180 195 210
ºC
≤
60 70 76 82 90 100
Factor (F3) 1.26 1.13 1.07 1.00 0.90 0.81
Correction factor for DewPoint changes:
DewPoint
ºF 37 41 45 50
ºC 3 5 7 10
Factor (F4) 0.78 0.90 1.00 1.12
How to find the air flow capacity: How to select a suitable dryer for a given duty:
Air flow
capacity
=
X
Factor
(F1)
Factor
(F2)
X
Factor
(F3)
X X
Factor
(F4)
Nominal
duty
= ÷
Factor
(F1)
Factor
(F2)
÷
Factor
(F3)
÷ ÷
Factor
(F4)
Design
air flow
Std. air
flow rate
Minimum
Example: Example:
An AHT 150 has a nominal duty of 150 scfm
(255 m
3
/h)
. What is the maximum allowable flow
through the dryer under the following operating
conditions:
−
Inlet air pressure = 120 psig (8 barg)
−
Ambient temperature = 105°F (40°C)
−
Inlet air temperature = 195°F (90°C)
−
Pressure DewPoint = 45°F (7°C)
Each item of data has a corresponding numerical
factor as follows:
The procedure here is to list the operating
conditions and then to locate the corresponding
numerical factors:
−
Design air flow = 95 scfm (161 m
3
/h)
−
Inlet air pressure = 120 psig (8 barg)
− Ambient temperature = 105°F (40°C)
−
Inlet air temperature = 195°F (90°C)
−
Pressure DewPoint = 45°F (7°C)
In order to select the correct dryer model the
required flow rate is to be divided by the correction
factors relating to above mentioned parameters:
= 137 scfm
→
This is the maximum flow
rate that the dryer can accept under these
operating conditions.
= 104 scfm
→
Therefore the model suitable
for the conditions above is AHT 150 ( 150 scfm
or 255 m
3
/h - nominal duty).
=
x
x x
x
1.07 150 0.94 1.00 0.90
capacity
Air flow
= ÷
÷ ÷
÷
1.07 95 0.94 1.00 0.90
flow rate
Minimum