Maintenance; Desiccant Replacement; Purge Mufflers; Pilot Air Filter Element Replacement - Gardner Denver DGH Series Instruction Manual

9. Maintenance

WARNING - The heatless desiccant dryer is a pressure-containing
device. De-pressurize before servicing. (See Section 3.3)
Note: Level 1 and 2 Controllers are equipped with Service
Reminder functions for filters, desiccant and valves.

9.1 Desiccant Replacement

NOTE: The use of the correct replacement desiccant is
necessary for proper dryer operation. Never use hygroscopic
salts of the type commonly used in "deliquescent " type dryers.
9.1.1 Frequency Of Desiccant Replacement
Desiccant should be replaced whenever the required dew point
cannot be maintained while the dryer is being operated within
its design conditions and there are no mechanical malfunctions.
Refer to section 10.0 for troubleshooting hints.
NOTE: Desiccant life is determined by the quality of the inlet
air. Proper filtering of the inlet air will extend the life of the
desiccant. Typically desiccant life is 3 to 5 years.
9.1.2 Procedure for Desiccant Charge Replacement
•
De-pressurize and de-energize the dryer.
•
Remove the fill and drain plugs from desiccant tower and
drain the spent desiccant. Place a container at the base of
the vessel to collect the desiccant. If necessary tap the
sides of the vessels with a rubber mallet to loosen
desiccant.
NOTE: Use extreme care when inserting rods or other tools
through the desiccant fill or drain ports to loosen packed
desiccant. Internal flow diffusers at the ends of the desiccant
beds can be damaged or punctured by sharp instruments.
These diffusers are necessary to distribute the airflow and keep
the desiccant beads within the tower. Desiccant beads in
exhaust mufflers, afterfilters, or the piping connected to the
desiccant towers may indicate a perforation of a diffuser.
•
Replace the drain plug using Teflon tape or another pipe
thread sealant suitable for compressed air service.
•
Fill the desiccant tower as full as possible with dry
desiccant. Do not tamp or otherwise pack the desiccant.
•
Replace the fill plug using Teflon tape or another pipe
thread sealant suitable for compressed air service.
•
Repeat this procedure for the other tower.
9.1.3 Insuring Desiccant Dryness
Replacement desiccant is shipped in airtight containers. Keep
the covers on these containers tightly closed until use to avoid
moisture contamination. If desiccant is exposed to air it can be
heated in an oven at 400°F (204°C) for four hours before use.
Alternatively, if the dryer is not refilled with dry desiccant, it may
be necessary to operate the unit with an inlet flow rate of less
than 50% of maximum rated inlet capacity until the desiccant
has regenerated fully.

9.2 Purge Mufflers

•
Purge mufflers should be checked regularly, changed
annually. Muffler disseminator elements become clogged
with desiccant dust over time, creating backpressure and
restricted purge flow.
•
Refer to section 8.2.7.
9.3 Valves
•
Process and pilot valves should be checked frequently for
leaks and proper operation.
•
Purge pressure adjustment valve should be checked
frequently for proper adjustment.
•
Refer to section 8.2.8.

9.4 Pilot Air Filter Element Replacement

9.4.1 Frequency of replacement
The pilot air filter contains a filter element that should be
changed yearly. Replacement may be required sooner if
pressure drop across cartridge prevents valves from actuating
properly. Pilot air pressure should be in the range of 60-120
psig (4.2-8.4 kgf/cm
that has been set and sealed at 120 psig (8.4 kgf/cm
Warning – The pilot air filter housing is a pressure-containing
device, de-pressurize before servicing. Slowly open manual
drain valve on bottom of filter bowl by turning clockwise to verify
that the housing is de-pressurized before removing bowl.
9.4.2 Procedure for element replacement
9.4.2.1 Models 40 through 450
•
Isolate dryer from air supply
•
De-pressurize dryer by running dryer and allowing system
pressure to purge to atmosphere. Loss of pilot pressure
will eventually prevent purge/repressurization valves from
opening. Remaining pressure can be vented to
atmosphere through the manual drain on the pilot air
filter. The system must be fully de-pressurized before
removing the bowl.
•
Remove the filter bowl by pushing up, turning
counterclockwise and then pulling straight down.
•
Clean the filter bowl.
•
Replace the element – Unthread the deflector disc/nut
from the bottom of the element, replace the element
(smaller internal diameter goes at the bottom to mate with
the disc/nut pilot) and reassemble with disc/nut.
Clean and lubricate o-ring at top of bowl and reassemble
•
in reverse order.
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9. Maintenance
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9. Maintenance
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