8
2. Average Purge Flow
The Average Purge Flow (APF) is the actual amount of
flow averaged over the entire purge/repressurization
cycle. It includes the maximum purge flow (MFP) for
a set amount of the purge/repressurization time and
the volume of air used for repressurization. Refer to
Table 1 for Average Purge Flows at 100 psig.
3. Purge flows at pressures other than 100 psig
To determine Maximum or Average Purge Flow at inlet
pressures other than 100 psig, multiply purge flow at
100 psig from Table 1 by the multiplier from Table 4
that corresponds to system pressure at inlet to dryer.
C. Outlet Air Flow
1. Minimum Outlet Flow
Determine minimum outlet flow available from dryer
by subtracting Maximum Purge Flow from inlet flow
to dryer.
NOTE:
Air compressor should be adequately sized to
handle air system demands as well as purge loss. Fail-
ure to do so could result in overloading air compres-
sors and/or insufficient air supply downstream.
2. Average Outlet Flow
Determine average outlet flow available by subtracting
Average Purge Flow from inlet flow to dryer.
NOTE:
Average outlet flow may be used to determine
available downstream air supply if a storage vessel (re-
ceiver tank) of sufficient volume is available between
dryer and point of air usage. Otherwise use 3.2.3.1 To
compute downstream air available.
EXAMPLE:
Find maximum inlet flow, maximum and average purge
flows, and minimum and average outlet flows for a 13 scfm
unit operated at 120 psig. Dryer will operate with an inlet air
flow of 14 scfm.
Step 1: Find Maximum Inlet Flow by multiplying
Maximum Inlet Flow at Rated Conditions from
Table 1 by Inlet Pressure Correction Factor from
Table 2 and Inlet Temperature Correction Factor
from Table 3: 13 x 1.17 x 1.00 = 15.2 scfm.
Step 2: Find Maximum Purge Flow by multiplying
Maximum Purge Flow at 100 psig from Table 1 by
Purge Flow Correction Factor from Table 4:
3.7 x 1.17 = 4.3 scfm, the maximum purge flow.
Step 3: Find Average Purge Flow by multiplying Average
Purge Flow at 100 psig from Table 1 by Purge Flow
Correction Factor from Table 4: 2.7 x 1.17= 3.2 scfm,
the average purge flow.
Step 4: Find Minimum Outlet Flow available by subtracting
Maximum Purge Flow (Step 2) from inlet flow of
14 scfm: 14 - 4.3 = 9.7 scfm.
Step 5: Find Average Outlet Flow available by subtracting
Average Purge Flow (Step 3) from inlet flow of
14 scfm: 14 - 3.2 = 10.8 scfm.
4.3 Operating Conditions
A. Maximum Working Pressure: 150 psig (10.5 kgf/cm
2
)
B. Minimum Working Pressure: 50 psig (3.5 kgf/cm
2
)
It is recommended that the air dryer be operated at the
highest available pressure not exceeding the maximum
working pressure since the dryer capacity increases and %
of purge air decreases at higher pressures.
C. Maximum Operating Temperature: 120°F (49°C)
4.4 Operational Check Points
A. Check periodically that there is power to the unit - Power
on light is on.
B. If unit is equipped with optional moisture indicator, check
at least once a day. Outlet relative humidity of the desic-
cant dryer is indicated by the color change humidity indi-
cator. Green indicates R.H. below 3% and yellow indicates
R.H. above 3%. Table 5 indicates outlet dew point when
moisture indicator changes from green to yellow at vari-
ous inlet temperatures. During startup the indicator may
be yellow, however, it should begin to change to green
within 4 hours.
C. If supplied with optional prefilter/afterfilter. Check that
indicators are in green area. If indicator is in red area ele-
ment replacement is necessary.
4.5 Dryer Shutdown
To shut down the dryer, de-energize using the on-off switch
(Power-on light extinguished). Unit will remain pressurized.
4.6 Depressurization
To depressurize unit
A. Open by-pass valve (if one is installed) and close inlet and
outlet valves.
B. Run timer through a complete tower change cycle or
until all air has been exhausted from the dryer.
4 MINUTE CYCLE TIMING CHART
Cycle Time (min:sec)
0:00 - 0:30
0:30 - 2.00
2:00 - 2:30
2:30 - 4:00
All
Models
SOL1
Left Purge Valve
Closed
Closed
Closed
Open
SOL2
Right Purge Valve
Closed
Open
Closed
Closed
All
Models
LED
Left Tower
Flashing
On
Flashing
Off
LED
Right Tower
Flashing
Off
Flashing
On
