h. Weigh new bottle, check the content and connect it
to charging line. Open bottle stop valve slowly.
i. Start cooling water pump and open cooling water
stop valve on condenser .
j. Shut liquid stop valve of condenser as well as
compressor suction stop valve.
k. Start compressor.
I. Open refrigerant charging stop valve slowly and
then compressor suction stop valve.
m. Repeat steps 'g', 'h', 'm', and 'n' until required
quantity of refrigerant has been in.
Note : It is recommended to stop the compressor
each time so that bottle is emptied.
n. Shut suction stop valve and refrigerant charging
stop valve, disconnect bottle and remove charging
line.
o. Reset LP pressostat (if fitted) at the correct setting.
Note: When the refrigerant requires topping up,
steps 'b', upto 'e' both inclusive should be carried
out.
3.14 PURGING REFRIGERATING PLANT:
As the presence of air can cause a lot of trouble, the
refrigerant plant should be purged if necessary. Purging
is carried out while the compressor is at standstill and
the cooling water left open to the condenser where air
mainly collects. The air vent valves, which may be fitted
on the gas delivery line and/or on the condenser, as well
as the liquid receiver, should be fitted with a hose,
capable of discharging into water. During purging, the
vent valves should be opened at 1/2 or 1/4 turn only.
On Ammonia Plants, the hose is kept under water
subsequent to opening the air vent valve. Once any
bubbles stop rising, only pure Ammonia gas then
escapes and is immediately dissolved in the water. The
plant is then purged and the air vent valve should be shut
and the hose removed. On Freon plants the air vent
valves should be cracked open and held thus until the
system pressure corresponds to the gas saturation
pressure at the existing cooling water temperature. The
connecting hose must lead to the open air so that the
Freon discharged can escape without dangerous effects.
Normally it will be necessary to repeat the purging
operation. Every time, between each purge, the
compressor should be operated for some time so that any
residual air may be returned to and trapped in the
condenser.
3.15 SETTINGS :
For correct compressor operation the oil pressure must
be adjusted at 1.5 Kg/cm2 above crankcase pressure by
oil pressure regulator.
3.16 PRESSOSTATS :
Pressostats serve as protection against conditions which
may be harmful to plant and/or compressor. The setting
of these devices depends on the plant and the
compressor type. Detailed instructions for this are
contained in the appropriate operation manual for each
installation.
3.17 OPERATING PROCEDURE:
Starting and stopping the compressor should be carried
out to fixed procedure to prevent mistakes and
accidents. Each refrigerant plant has its own sequence of
operations for starting and stopping. As the compressor
only is discussed here, the operating manual for the
plant concerned should be consulted.
3.18 STARTING:
When putting the machine into operation for the very
first time or after complete dismantling, it may happen
that the gears of the oil pump are dry and the pump has
difficulty in picking up the oil. In this case the union nut
on the upper line between the suction oil strainer and the
oil pump should be loosened and the pump casing filled
with oil. The union nut should then be retightened. On
starting the following procedure should be adopted.
a. Make sure that suction stop valve on compressor and
liquid stop valve of liquid receiver are shut. Check
position of manually operated expansion valve. (If
fitted.).
b. Open delivery stop valve on compressor and all other
stop valves in refrigerant circuit, except those
mentioned in step 'a' (see also operating manual of
the refrigerant plant concerned for cooling water
etc.)
c. Start compressor. After about 1 minute it should
become operative.
d. Open compressor suction stop valve slowly.
e. Open liquid stop valve completely.
f. Adjust pressure gauge stop valve in such a way that
the pointers do not vibrate. On compressors fitted
with automatic capacity control nothing further
required to be done. On compressors with manually
operated capacity control, however, the necessary
number of cylinder should be switched in manually.
During the first quarter of an hour after putting the
compressor into operation, its functioning should be
checked carefully and during this time, the attendant
should not leave the compressor room.
g. Refer operating instructions for the refrigerating
plant for further action required.
3.19 SUPERVISION DURING OPERATION:
While the compressor is operating the following should
be checked regularly:
a. Lubrication (oil pressure, oil level and oil return jet
behind oil/evel glass).
b. H.P. safety valve (leakage).
c. Pressure gauges (correct pressure (see also operating
instructions for refrigerating plant) gauge pointers
stationary).
d. Cylinder head cooling, if fitted (adequate cooling
water flow and correct temperature of cooling water
outlet).
3.20 STOPPING:
a. Shut liquid stop valve on condenser and then
compressor suction stop valve.
b. Stop compressor.
c. Refer operating instructions for the refrigerating
plant concerned for further action required.
d. It is mandatory for refrigeration system
provider to make provision for one or more
emergency stop devices at appropriate
locations to avert actual or impending
danger.
CAUTION
12
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