SPX Hankinson HHE Series Instruction Manual page 53

from freezing. If installing heat tracing, observe electrical class code
requirements for type of duty specified. Purge mufflers and their relief
mechanisms must be kept clear from snow and ice buildup that could
prevent proper discharge of compressed air.
9.7 Maximum Inlet Flow Capacity
• Refer to Table 9-1 for maximum inlet flow at rated conditions of
100 psig (6.9 barg) and 100°F (38°C).
• At other conditions, multiply inlet flow from Table 9-1 by the
multipliers from Tables 9-2 and 9-3 that correspond to the pressure
and temperature at the inlet to the dryer.
9.8 Purge and Outlet Flows
9.8.1 Maximum Purge Flow
• Maximum Purge Flow is the amount of purge air flowing through
the off-stream tower when the purge/repressurization valve is
open. After the purge/repressurization valve closes, the purge flow
will gradually decrease as the off-stream tower re-pressurizes to
line pressure.
• For maximum purge flow multiply the Inlet Flow At Rated
Conditions from Table 9-1 by Maximum Purge Flow Factor from
Table 9-6 that corresponds to the dryer MOP, Cycle Time Setting,
and air pressure at inlet to dryer.
NOTE: For Level 2 Controller equipped dryers supplied with the
Automatic Purge Saving System operating in the Demand Cycle
Mode, use ISO Class 2 (10 minutes) as the cycle time.
9.8.2 Average Purge Flow
• For dryers with Level 1 or 2 Controllers operating in the fixed
cycle mode, the Average Purge Flow is the actual amount of flow
used during the entire purge/repressurization cycle. It includes the
maximum purge flow for a portion of the purge/repressurization
time and the volume of air used for repressurization, averaged
over the cycle time.
• For average purge flow multiply the Inlet Flow At Rated Conditions
from Table 9-1 by Average Purge/Repressurization Flow Factor
from Table 9-7 that corresponds to the dryer MOP, Cycle Time
Setting, Energy (purge) Savings % setting, and air pressure at
inlet to dryer.
9.8.3 Minimum Outlet Air Flow
• Determine minimum outlet flow available from dryer by subtracting
Maximum Purge Flow found above from inlet flow to the dryer.
9.8.4 Average Outlet Air Flow
• For dryers with Level 1 or 2 Controllers operating in the fixed
cycle mode, the average outlet flow available from dryer can be
determined by subtracting the Average Maximum Purge Flow
found above from the inlet flow to the dryer.
9.9 EXAMPLE
• Find the maximum inlet flow, maximum purge flow, and minimum
outlet flow for a 60 SCFM unit with a MOP of 150 psig operated
with 120 psig and 100°F inlet conditions on a 10 minute cycle.
Dryer will operate with an inlet airflow of 46 SCFM.
• Step 1: Find Maximum Inlet Flow at 120 psig by multiplying
Maximum Inlet Flow at Rated Conditions from Table 9-1 by Inlet
Pressure Correction Factor for 120 psig from Table 9-2 and Inlet
Temperature from Table 9-3:
60 x 1.08 x 1.00 =64.8 SCFM.
• Step 2: Find Maximum Purge Flow by multiplying Maximum Inlet
Flow at Rated Conditions from Table 9-1 by Maximum Purge Flow
Factor from Table 9-6:
60 x 0.162 =9.7 SCFM.
• Step 3: Find Minimum Outlet Flow available by subtracting
Maximum Purge Flow (Step 2) from actual inlet flow:
46 -9.7 =36.3 SCFM.
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