18
FILL
PLUG
DRAIN
PLUGS
FIGURE 4A
TABLE 4A Amount of desiccant required for complete change (lb)
MODEL
25
40
60
80
115
165
260
370
450
590
ACTIVATED ALUMINA
48
48
72
106
182
182
316
452
528
710
MODEL
750
930
1130
1350
1550
2100
3000
4100
5400
ACTIVATED ALUMINA
926
1172
1468
1766
2064
2592
3930
4920
7750
4.0 MAINTENANCE
WARNING
The heatless desiccant dryer is a pressure containing device.
Depressurize before servicing. (See Section 3.3)
4.1 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.
4.1.1 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 5.0 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.
4.1.2 Procedure for Desiccant Charge Replacement
4.1.2.1 Depressurize and de-energize the dryer. (See section
3.3)
4.1.2.2 Remove the fill and drain
plugs from desiccant tower and drain
the spent desiccant. Place a con-
tainer 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.
4.1.2.3 Replace the drain plug
using teflon tape sealant or equiva-
lent.
4.1.2.4 Fill the desiccant drying
tower as full as possible with dry
desiccant. Do not tamp desiccant.
4.1.2.5 Replace the fill plug us-
ing teflon tape sealant or equivalent.
4.1.2.6 Repeat this procedure
for the other drying tower.
4.1.3 Insuring desiccant dryness
4.1.3.1 Replacement desiccant is shipped in air tight contain-
ers. 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, or the
procedure in 4.1.3.2 can be used.
4.1.3.2 If the dryer is not refilled with dry desiccant, it will be
necessary to operate the dryer with an inlet flow rate of less than 50%
of maximum to dry the desiccant. To do this, set the Economizer
Switch for 100%, and the purge pressure for 45 psig. (3.2 kgf/cm
2
)
NOTE
4.2.2.1 Remove the filter bowl.
4.2.2.2 Clean the filter bowl.
4.2.2.3 Remove the old filter element and discard. Also discard
the small O-ring that seals the filter to the filter assembly head.
4.2.2.4 Insert small replacement O-ring on top of replacement
filter element and replace filter element.
4.2.2.5 After making sure large O-ring in filter head is in place,
reassemble filter bowl to filter head.
4.3 Fuse Replacement
4.3.1 Standard Units Only:
4.3.1.1 Fuses are located on board in electrical enclosure. See
Figure 3A or 3B.
FIGURE 4B
HEAD
HEAD "O" RING
CARTRIDGE "O" RING
CARTRIDGE
BOWL
4.2 Pilot Air Filter - Element Replacement -
Models 370 scfm and larger
4.2.1 Frequency of replacement - Pilot air filter contains a filter
element which should be changed yearly or sooner if pressure drop
across cartridge prevents valves from actuating. Pilot air pressure
must not drop below 60 psig (4.2 kgf/cm
2
).
4.2.2 Procedure for cartridge replacement.
WARNING
THE FILTER IS A PRESSURE CONTAINING DEVICE. DE-
PRESSURIZE DRYER BEFORE SERVICING. (SEE SECTION
3.3)