Ambient Temperatures; Average Purge Flow; Minimum Outlet Air Flow; Average Outlet Air Flow - Gardner Denver DGH Series Instruction Manual

8.6.2 Minimum Operating Pressures:
8.6.2.1 For 150 psig (10.5 kgf/cm
•
60 psig (4.2 kgf/cm
2
for dryers operated on a 4,10,16, or 24-minute cycle.
8.6.2.2 For 250 psig (17.6 kgf/cm
•
120 psig (8.44 kgf/cm
pressure for dryers operated on a 4,10,16, or 24-minute
cycle.
Refer to Dryer Serial Number Tag.
WARNING - Do not operate the dryer at pressures below the
minimum operating pressure shown on the serial number tag.
NOTE: Consult factory for applications requiring lower minimum
operating pressures.
8.6.3 Maximum Compressed Air Temperature at Dryer
Inlet:
•
140°F (60°C) for all models.

8.6.4 Ambient Temperatures:

8.6.4.1 Minimum Ambient Temperature:
•
Standard units: 35°F (2°C)
•
Units with optional low ambient package: -20°F ( -29°C)
8.6.4.2 Maximum Ambient Temperature:
•
120°F (49°C)
NOTE: If dryer is installed in ambients below 35°F (2°C), low
ambient protection requiring heat tracing and insulation of the
prefilter bowls, auto drains and/or sumps, and lower piping with
inlet switching and purge/repressurization valves is necessary
to prevent condensate 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.
8.7 Maximum Inlet Flow Capacity
•
Refer to Table 8-1 for maximum inlet flow at rated
conditions of 100 psig (7.0 kgf/cm 2) and 100°F (38°C).
•
At other conditions, multiply inlet flow from Table 8-1 by the
multipliers from Tables 8-2 and 8-3 that correspond to the
pressure and temperature at the inlet to the dryer.
8.8 Purge and Outlet Flows
8.8.1 Maximum Purge Flow
•
Maximum Purge Flow is the amount of purge air flowing
through the off-stream
purge/repressurization
purge/repressurization valve closes, the purge flow will
gradually decrease as the off-stream tower re-pressurizes
to line pressure.
8. Operation
) MOP models -
2
) is the minimum operating pressure
) MOP models -
2
) is the minimum operating
2
tower when
valve is open. After
•
For maximum purge flow multiply the Inlet Flow At Rated
Conditions from Table 8-1 by Maximum Purge Flow Factor
from Table 8-6 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.

8.8.2 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
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
Purge/Repressurization Flow Factor from Table 8-7 that
corresponds to the dryer MOP, Cycle Time Setting, Energy
(purge) Savings % setting, and air pressure at inlet to
dryer.

8.8.3 Minimum Outlet Air Flow

•
Determine minimum outlet flow available from dryer by
subtracting Maximum Purge Flow found above from inlet
flow to the dryer.

8.8.4 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.
8.9 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 8-1 by Inlet Pressure Correction Factor for 120 psig
from Table 8-2 and Inlet Temperature from Table 8-3:
•
Step 2: Find Maximum Purge Flow by multiplying
Maximum Inlet Flow at Rated Conditions from Table 8-1
by Maximum Purge Flow Factor from Table 8-5:
•
Step 3: Find Minimum Outlet Flow available by
the
subtracting Maximum Purge Flow (Step 2) from actual
the
inlet flow:
.
- 48 –
of flow used during
from Table 8-1
60 x 1.08 x 1.00 =64.8 SCFM.
60 x 0.162 =9.7 SCFM.
46 -9.7 =36.3 SCFM.
the entire
by Average