SPX Hankinson HHE Series Instruction Manual page 51

• The purge pressure adjustment valve should never be fully closed.
Proper purge flow is required to regenerate and re-pressurize the
offline tower. Should the tower fail to re-pressurize, a switching
failure alarm will be initiated, and the cycle will be stopped before
tower switch over.
• After the purge pressure has been correctly set, the handle of the
purge pressure adjustment valve may be removed and stored to
prevent tampering with the setting.
Insufficient purge air will eventually result in saturation of the desiccant
beds and wet air downstream. Verify that maximum operating pressure
mode, cycle time, energy (purge) savings percent selection, and purge
pressure are correctly set.
9.1.5 Bringing the Dryer Online
Establish a normal flow through the dryer. Slowly open the outlet
isolation valve if present. Close any dryer by-pass valves.
NOTE: When dew points below -40°F (-40°C) are required, the dryer
must be run with an inlet flow rate of less than 50% of maximum until
the desired dew point is attained. Depending on the initial dryness of
the desiccant, this can take as long as 2 to 3 days. This stabilization
period is required on initial startup, after the dryer has been shutdown
for extended periods of time, or after dryer maintenance (desiccant
change, etc.) has been performed.
9.1.6 Readjusting the Purge Rate
With the inlet pressure to the dryer at its minimum level, readjust the
purge pressure per the instructions in Section 9.1.4.
NOTE: Adjustment must be made while the appropriate tower is
purging (air exhausting from muffler).
9.2 Operational Check Points
9.2.1 Power to unit
Check periodically that there is power to the unit (indicating lights
illuminated).
9.2.2 Moisture Indicator
Every four hours check moisture indicator. Indicator should be green.
The color change moisture indicator indicates the outlet relative
humidity of the desiccant dryer.
Green indicates a R.H. below 3% and yellow indicates a R.H.
above 3%. Table 9-5 cross references outlet pressure dew points
to moisture indicator changes from green to yellow at various inlet
temperatures.
NOTE: During start-up the indicator may be yellow, however, it should
begin to change to green within four hours.
9.2.3 Purge Pressure Setting
Every four hours check the purge pressure gauge for the proper setting
and adjust as required. Adjustment should be made when the inlet
pressure to the dryer is at its minimum level.
NOTE: Adjustment must be made while the appropriate tower is
purging (air exhausting from muffler).
9.2.4 Alarms
Periodically check for flashing red alarm LED.
9.2.4.1 Alarms –Level 1 Controller
Alarm light will flash if either tower fails to pressurize or de-pressurize
to the required levels at the proper time. Refer to Section 7.4.3 and
Table 7.4.
NOTE: Alarm will activate if dryer is energized without being
pressurized. If this occurs, allow dryer to cycle to next step and press
reset button. Alarm light will continue to illuminate even if fault clears.
To clear alarm, press reset button.
If the tower being regenerated fails to re-pressurize, the dryer will not
switch towers. The switching failure alarm will be activated and the
dryer will remain in this mode until the tower re-pressurizes.
9.2.5 Tower Status LEDs
Illuminated LEDs indicate which tower is on-line drying or off-line
regenerating.
9.2.6 Tower Pressure Gauges
Periodically check tower pressure gauges to verify that the pressure
gauge of the online tower reads line pressure and the pressure gauge
of the offline tower reads below 2 psig (0.14 barg).
NOTE: Read the offline tower pressure gauge when the tower is
purging (air exhausting from muffler).
9.2.7 Check Mufflers For Back Pressure
Excessive back pressure may result due to the accumulation of
desiccant fines (dust) in the muffler cartridges. This sometimes
occurs after start-up due to dusting of the desiccant during tower filling
and dryer transport. If the tower pressure gauge of the off-stream
tower rises above 5 psig (3.5 barg), the muffler elements should be
replaced.
IMPORTANT: Replace muffler cores provided with unit after
5 complete cycles following the completion of the Start-Up
Procedures.
9.2.8 Process Valves
Determine if air control valves are operating and sequencing correctly.
Refer to Section 3.3 for a general description of operating sequence.
Refer to Tables 7-3 and 7-4 for time sequences for Level 1 Controllers.
Refer to Tables 8-3 and 8-4 for time sequences for Level 2 Controllers.
9.2.8.1 Valves – Models 40 through 3000
• Inlet/Outlet switching valves are non-lubricated shuttle valves.
Pressure differences between the online and offline desiccant
towers cause the shuttle valve to shift.
• High Pressure Models 40 through 450 ONLY. Inlet switching
valves are normally open, pneumatically piston-actuated, Y-angle
poppet valves. A yellow indicator can be seen through a clear
window at the top of the actuator when the valve is in the open
position.
• Purge/repressurization valves are normally closed, pneumatically
piston-actuated, Y-angle poppet valves. A yellow indicator can be
seen through a clear window at the top of the actuator housing
when the valve is in the open position.
• 12 volt DC, normally-closed, 3-way pilot solenoid valves are wired
to the controller and are used to direct pilot air to the actuators of
the purge/repressurization valves.
• Purge pressure and subsequent flow is adjusted by means of
a quarter-turn ball valve located in the bypass line of the upper
piping.
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