Card 3. Purging the system with air

When a system has been opened for repairs, air may have entered it. If the evaporation pressure is lower than the atmospheric pressure, and there is a leak in the low-pressure section, e.g. at the compressor shaft seal, air may be drawn into the system.

If for any reason, the refrigerant machinery is exposed to internal corrosion, gases are generated which are difficult to condense and which behave in the same way as air.

While the machinery is operating, air gradually collects in the condenser and receiver and the condensing pressure thus becomes abnormally high. It is possible by stopping the machine, closing the out from condenser to receiver and allowing cooling water to flow through the condenser until a state of equilibrium is attained, to determine with a pressure gauge whether there is air in the condenser. If the gauge shows a pressure higher than that which corresponds to the temperature of the cooling water, air is present - assuming, of course, that the pressure gauge is reading correctly.

To remove the air, carefully loosen one of the unions on the top of the condenser (and possibly of the receiver) then air and some refrigerant will escape.

Expel the air by degrees until it is all removed, as indicated by the above-mentioned pressure difference becoming zero or negligibly small. To reduce loss of refrigerant, purg­ing should be done at as low a temperature as possible (cold cooling water).

purging - чистка

leak - течь, утечка

compressor shaft seal - уплотнение вала компрессора

if for any reason - если по какой-либо причине

is exposed to corrosion - подвергается коррозии

which behave in the same way - которые ведут себя также

gradually - постепенно

a state of equilibrium is attained - состояние равновесия достигнуто

to determine - определять

assuming that - допуская, что

gauge is reading correctly - прибор показывает правильно

to loosen - ослаблять

union - муфта, штуцер

expel the air by degrees - стравливайте воздух постепенно

Card 4. Precautions when starting machinery

1. Turn on the cooling water circulation through the conden­ser.

2. Open the compressor stop valves on discharge and suction sides. There must be free passage between compressor, condenser and receiver.

3. At the valve station open the correct gas and liquid valves for the evaporators that are to be in service. Check that the other valves at the valve station are closed.

4. Before starting, the compressor should be turned over a few times by hand so that oil reaches the bearings and shaft seal, particularly if the machinery has been idle for a long time. If the compressor is fitted with capacity re­duction, this should be employed to simplify starting.

5. Start the fans for air-coolers (and brine pumps where applicable).

6. Start the compressor or compressors.

7. If knocking is heard in the compressor stops immediately and restarts after a minute or two. Repeat if necessary.

8. Check the evaporation and condensation pressures, oil level and oil pressure. If the oil pressure fails to rise within a couple of minutes, restart with intervals to get possible dissolved refrigerant in oil evaporated.

9. Regulate the crankcase temperature to between +25°C and +40°C by adjusting the flow of cooling water to the compressor oil cooler.

on discharge side - на выходе

valve station - щит клапанов

that are to be in service - которые должны быть в работе

oil reaches the bearing - масло доходит до подшипников

the machinery has been idle - установка не работала

capacity reduction - клапан разгрузки

should be employed to simplify starting - должны использоваться, чтобы упростить пуск

brine pump - рассольный насос

where applicable - где необходимо

if knocking is heard - если слышится стук

dissolved refrigerant in oil evaporated - растворенный хладагент в испа­ряющемся масле

by adjusting the flow - путем регулирования потока

if the oil pressure fails to rise - если давление масла не поднимается