Van Air Systems HL-200 - HL2000 - Manual (Page 22)

PAGE 22
11.5-5 CHECKING THE INLET TRANSFER VALVE
The inlet transfer valve will not switch positions unless the pressure
in both desiccant towers is nearly equal. At tower changeover, the
regenerating tower should approach full line pressure before the
inlet valve will switch. Make sure that there are no leaks in the
piping or fittings. Make sure that the purge exhaust valves are
closing and that the purge metering valve is properly set.
The exhaust ports on top of the pilot valves (SV1 & SV2) should not
have air exhausting through them continuously. If air is exhausting
continuously through either of the exhaust ports, the inlet transfer
valve is faulty and should be rebuilt or replaced.
To test the inlet transfer valve for proper operation, turn off the
power, isolate and depressurize the dryer.
Remove the two pilot lines to the inlet valve. The pilot lines are
connected to the outside flanges of the valve. Using an air nozzle
and clean air, pressurize one of the ports. Observe the position
indicator. It should move in the direction of the port that is being
pressurized. No air should be exhausting from the other port.
Pressurize the other port. The valve should move to the other side.
If the valve does not move or air is being exhausted out of the port
that is not pressurized, the inlet transfer valve must be rebuilt or
replaced. Reference Section 12.9 & 12.10 for valve breakdown and
parts listing.
11.5-6 CHECKING THE PNEUMATIC LIMIT SWITCHES
Mounted on the inlet transfer valve is a set of 3-way pneumatic limit
switches. These switches control the pilot air to open and close the
purge exhaust valves.
When a pneumatic limit switch is activated by the inlet transfer valve
position indicator, pilot air is supplied to the purge exhaust valve on
that side of the dryer.
To check the pneumatic limit switches, allow the dryer to cycle.
Check the pilot line to the purge exhaust valve on the side of the
activated limit switch. If no air is present, the limit switch must be
replaced. The limit switches are sold in sets only.
FIGURE 13C INLET TRANSFER VALVE DETAIL
MAINTENANCE & TROUBLESHOOTING SECTION 11
11.5-3 CHECKIING THE 3-WAY PILOT VALVES
(SV1 & SV2) TOWER CHANGEOVER
All 3-way pilot valves have manual override buttons on the top of
the valve. To test SV1 and SV2 do the following:
For dryers with the Standard Control Box make sure the Stop button
is pressed and the dryer is pressurized. For dryers with Cycle Saver
or Emcon II Control Boxes make sure the Power switch is in the
OFF position and the dryer is pressurized. Both towers should be
at full line pressure Pushing the manual override of SV1 should
cause the left tower to depressurize. Allow the left tower to come
back up to full line pressure. Pushing the manual override of SV2
should cause the right tower to depressurize. If this does not
happen, replace that solenoid valve.
EMCON II MODELS ONLY:
With the Power push-button (PB1) in the ON position, the fixed/
auto selector switch in the fixed mode, and the dryer pressurized,
monitor the outputs on the microprocessor. If output 0 is lighted,
SV1 should be activated, the left tower should be depressurized
and the right tower should be pressurized and drying the com-
pressed air. If output 1 is lighted, SV2 should be activated, the
right tower should be depressurized and the left tower should be
pressurized and drying your compressed air. These two operations
can be monitored in one 10 minute fixed cycle.
If the above responses are not observed, first check to see if power
is being supplied to each solenoid valve when the corresponding
output LED on the PLC is lighted. Check the wiring between the
PLC and solenoid valves. If the PLC is not supplying power to the
valve when the LED is illuminated, replace the PLC. If the valve
has power but does not operate, it must be replaced.
11.5-4 CHECKING THE SOLENOID VALVE
(SV3) TOWER SAMPLE SELECT
With the dryer pressurized, the Power push-button in the ON
position, and the dryer in the fixed mode, remove the bleed orifice
from the tower dew point humistat’s sample cell. Monitor the air
flow from the sample cell for one complete 10 minute cycle. There
should be full line pressure coming from that sample cell for the
whole cycle. If air pressure to the sample cell is lost at any part of
the cycle, check the sample line filters and the solenoid valve
(SV3). Repair or replace as necessary.
CYCLE SAVER AND EMCON II MODELS ONLY:
Solenoid valve (SV3) is used to switch the sample line to the tower
that is on line drying your compressed air. It then feeds a sample of
air to the tower dew point humistat's sample cell.
There is no easy way to check outputs 3 through 5. Output 3 can
be checked by causing a switching failure. Output 4 can be
checked by creating a false outlet dew point by setting the outlet
dew point humistat lower than the factory setting and allowing the
dryer to go into HIGH HUMIDITY ALARM. Output 5 can be
checked when either output 3 or 4 are checked. Before attempt-
ing this procedure, consult the factory.