Vogt P18AL TUBE-ICE, Service Manual

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P18AL Service Manual
SERVICE OPERATIONS
3/6/07
9-4
housing to prevent cavitation or loss of prime. The pump is equipped with a mechanical seal which
is self-adjusting and requires no lubrication. However, the pump should not be operated unless
circulating water. The pump manufacturer recommends that a mechanical seal be kept as a spare.
When ordering a seal, specify pump size, type, serial number, and manufacturer’s name as indicated
on the nameplate.
Pumpdown. The function of the pumpdown is to transfer all the liquid refrigerant from the freezer
(evaporator) into the receiver. Pump-down should only be performed when the freezer is clear of
ice. Its main purposes are:
1. To check the total refrigerant charge.
2. To perform service or repair work on the machine.
3. To winterize the machine.
4. To prepare the machine for disconnecting and moving.
5. Before cleaning
Pumpdown Procedure To perform a pumpdown, follow this procedure:
1.
With the machine running, close the liquid feed stop valve nearest the receiver.
2. Open the water tank drain valve partially to allow a continuous flow of warm make-up water into
the water tank and still maintain a good level in the tank. An auxiliary supply of warm water (not
to exceed 100°F) may be used if available. Warmer water affords a more complete pumpdown.
3. Allow the machine to operate and complete two freeze and harvest cycles.
4. Stop the machine, throw the electrical disconnect, and lockout all power to the machine.
5. Remove wire from freezer pressure switch (if installed) and insulate the end to prevent a short
circuit.
6. Restore power to machine and start the water pump (circulate warm water through the freezer).
7. When the suction pressure increases to 70 psig or higher, start the compressor and allow the
machine to stop automatically by the low pressure switch at approximately 15 psig. (Lower
pressure can be obtained by jumping out the pressure switch.) Remove all power from the
machine before opening the control panel cover. With the pressure switch jumped out, the
machine can be manually started and stopped. Do not operate the machine below 2 psig.
8. When the desired pumpdown is obtained, close the thawing gas stop valve, and the compressor
discharge line stop valve. Other valves may also be closed to isolate a particular area that may
require attention.
9.
To perform a total pumpdown, it may be necessary to apply heat directly to the oil trap in order to
boil off the liquid ammonia and oil mixture.