— 50 —
•
Models 40 through 3000 are equipped with a single safety relief
valve that has been sized at a minimum to provide overpressure
protection due to a fire for both desiccant towers.
9.2.8.2 Valves – Models 4100 through 5400
•
Inlet switching valves are resilient seated butterfly valves with
double acting pneumatic rack and pinion actuators. A yellow arrow
indicator located on the top of the actuator output shaft points
to valve position indicator icons. Pilot air is directed to actuator
ports to open both inlet valves upon loss of power.
•
Purge/repressurization valves are resilient seated butterfly valves
with spring return, fail closed, pneumatic rack and pinion actuators.
A yellow arrow indicator located on the top of the actuator output
shaft points to valve position indicator icons. Pilot air is directed to
actuator ports to close both purge/repressurization valves upon
loss of power.
•
12 volt DC, single solenoid, 4-way pilot valves are wired to the
controller and are used to direct pilot air to the actuators of the
inlet switching and purge/repressurization valves.
•
Two mainline outlet and two smaller purge line check valves are
installed in the upper piping to control the flow of outlet and purge
air. Check valve sticking will result in excessive air discharge
through a muffler. Excessive air discharge through the muffler
can be associated with a leaking outlet check valve on the same
side or a purge check valve of the opposite side tower.
•
Purge pressure and subsequent flow is adjusted by means of
a throttling globe valve located in the bypass line of the upper
piping
•
Models 4100 through 5400 are equipped with multiple safety relief
valves that have been sized to provide overpressure protection
for capacities equal to or greater than the adjusted capacity of
the dryer at its maximum operating pressure.
•
The tower pressure gauge of the online tower should read line
pressure. Air should not be leaking from the purge-repressurization
valve of the on-line tower.
•
The tower pressure gauge of the offline tower should read below
2 psig (0.14 barg) while that tower is purging. If excessive air is
exhausting during the purge cycle, the inlet-switching valve on
the same side may have failed to close or a check valve may be
sticking.
9.3 Operating Sequence
9.3.1 Operating sequence – Timer Based Controllers
The operating sequence for dryers equipped with Timer Based
Controllers appears in Tables 6.1 and 6.2.
9.3.2 Operating sequence – Level 1 Controllers
The operating sequence for dryers equipped with Level 1 Controllers
appears in Tables 7.3 and 7.4.
9.3.3 Operating sequence – Level 2 Controllers
The operating sequence for dryers equipped with Level 2 Controllers
appears in Tables 8-2, 8-3, and 8-4.
9.4 Dryer Shut Down
•
If the dryer installation is equipped with dryer bypass and inlet
and outlet isolation valves, the bypass valve should be opened
and the inlet and outlet isolation valves closed.
•
De-pressurize the dryer by allowing the controller to run through
tower change cycles until pressure gauges on both towers read
zero. Manual test mode may be used to speed up this process.
NOTE: Below 60 psig (4.1 barg) purge/repressurization valves
may not open. Opening the manual drain on the pilot air filter
or any mounted pre or afterfilters may bleed off remaining
pressure.
•
Turn dryer off using on-off switch (indicating LEDs
extinguished).
9.5 Loss of Power
Control valves are designed so that upon loss of power the air dryer
is capable of drying air until the desiccant exposed to the airflow is
saturated.
9.6 Operating Parameters
Verify that dryer is operating within the following design parameters:
9.6.1 Maximum Operating Pressure (MOP):
•
150 psig (10.3 barg) is standard.
•
250 psig (17.2 barg) is optional.
Refer to Dryer Serial Number Tag.
WARNING - Do not operate the dryer at pressures above the
maximum operating pressure shown on the serial number tag.
NOTE: Consult factory for applications requiring higher maximum
operating pressures.
9.6.2 Minimum Operating Pressures:
9.6.2.1 For 150 psig (10.3 barg) MOP models -
•
60 psig (4.1 barg) is the minimum operating pressure for dryers
operated on a 4,10,16, or 24-minute cycle.
9.6.2.2 For 250 psig (17.2 barg) MOP models -
•
120 psig (8.3 barg) is the minimum operating 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.
9.6.3 Maximum Compressed Air Temperature at Dryer Inlet:
•
140°F (60°C) for all models.
9.6.4 Ambient Temperatures:
9.6.4.1 Minimum Ambient Temperature:
•
Standard units: 35°F (2°C)
•
Units with optional low ambient package: -20°F ( -29°C)
9.6.4.2 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
