Vogt P-24AL, Руководство по обслуживанию

Страница: 101 / 149

P24AL & P34AL Service Manual
SERVICING OPERATIONS
12/2016
9-17
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. After the second harvest cycle, stop the machine, throw the electrical disconnect, and lock-out all
power to the machine.
5. Remove wire #17 from the freezer pressure switch (2PS) and insulate the end to prevent a short
circuit.
6. Restore power to the machine and start the water pump only, to 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 desirable pumpdown is obtained, close the thawing gas stop valve (90), and the
compressor discharge line stop valve. Other valves may also be closed to isolate a particular area
which 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.
Removal of Ammonia Refrigerant from the Machine. Liquid ammonia can be removed from the
machine through the receiver drain valve. Refer to Chapters 1, 2, and Appendix A for special
warnings and instructions regarding the handling of ammonia. Make sure you are familiar with and
technically qualified to handle anhydrous-ammonia refrigerant.
! WARNING !
It is not recommended that refrigerant to be transferred from a refrigeration system directly
into a cylinder. If such a transfer is made, the refrigerant cylinder must be an approved,
CLEAN cylinder--free of any contaminants or foreign materials--and must be weighed
continuously to assure contents do not exceed net weight specified by cylinder manufacturer of
any applicable code requirements.
! WARNING !
If ammonia vapor is released from the machine, it may be purged into water which will absorb it.
Follow the purging instructions. See “Purging Non-Condensables”.
Note: Observe all local codes when handling and discharging anhydrous-ammonia refrigerant.
Refrigerant Leaks. Anhydrous ammonia leaks can be detected by odor, sulfur stick, soap solution,
or test paper. The odor is normally noticed first and the location of the leak is found with soap or
sulfur stick. Soap solution can be purchased from your refrigeration supply house or it can be made
by mixing four parts water, one part liquid soap, and a few drops of Glycerin for better capillary
attraction.