5. OPERATING INSTRUCTION AND
CAPACITY CONTROL SYSTEM TWO STAGE
COMPRESSOR
5.1 GENERAL
We are manufacturing following 9 types of Two Stage
Compressors in KC versions.
1. KC-21 Ref Fig, No, 15
2. KC-31 Ref Fig, No, 16
3. KC-42 Ref Fig. No, 17
4. KC-51 Ref Fig, No, 18
5. KC-63 Ref Fig, NO,19
6. KC-72 Ref Fig, No. 20
7. KC-84 Ref Fig, No. 21
8. KC-93 Ref Fig, No, 22
9. KC-102 Ref Fig. No. 23
Last single digit of nomenclature indicates no. of HP
cylinders and remaining one or two digit indicate no. of
LP cylinders in the compressor e.g, KC102 2=no. of HP
cylinders and 10=no. of LP Cylinders.
All these compressors are equipped with Electrically
operated Solenoid Valves for capacity control operation
of compressor. The details of no. of Solenoid Valves and
% capacity achieved with these valves is shown in figure
15 to 23. Against each capacity control step, ratio Ø is
indicated, This Ø is defined as ratio.
NO. OF LP CYLINDERS IN OPERATION
TOTAL NO. OF HP CYLINDERS IN OPERATION
This Ø ratio plays an important role in selecting steps to
move for higher capacity control operation.
5.2 INTERCOOLERS:
Two stage Compressors are fitted with an intercooler
between LP delivery and HP Suction of compressor.
While being compressed the gas in LP Cylinders, gas
temperature rises to such a level that, without
intercooler, further compression in second stage would
raise the temperature to dangerous level. The intercooler
reduces the temperature of gas from the LP Cylinder,
thus bringing operating temperature within reasonable
limits.
There are following types of intercooler :
1) Inter cooler system - A, For Ammonia and R-22
2) Inter cooler system - B, For R-22
3) Inter cooler system - C,
4) Inter cooler system - D,
Unless and otherwise specified, We are supplying inter
cooler system A only.
5.3 STARTING OF TWO STAGE COMPRESSOR:
Starting of two stage compressor and loading of
compressor from unloaded start to 100% load, is to be
done very carefully, otherwise discharge temperature
and pressure of compressor will exceed beyond limits of
operation, resulting into failure or breakdown of
compressor.
Following steps are to be followed to start and increase
the capacity of compressor. Note that these operation
steps are applicable only to the compressors fitted with
inter cooler system-A For compressor with other inter
cooler systems refer to KPCL (R & D) only.
5.4 STEPS OF OPERATION:
1. Note down following parameters of your
Refrigeration system.
Ø =
}
For Ammonia
a) Compressor model used
b) Gas used in Refrigeration system
c) Design condensing saturation temp. of system.
d) Design saturation evaporation temp. of system.
2. Go through the capacity control diagram given for
various two stage compressor (figure 15 to 23), Note
down various capacity control steps and Ø values
pertaining to your compressor.
3. Refer "FIELD APPLICATION DIAGRAM" for two
stage compressor pertaining to gas used in
Refrigeration system (Fig. 24) Draw horizontal lines
for designed system condensing temperature for
each value of Ø. These horizontal lines will intersect
to bold lines of field application diagram, select right
side intersecting points and draw vertical lines from
these Intersecting point. These vertical lines will
indicate minimum evaporation temperature required
to shift to this capacity control step.
4. Note down each switch over evaporation temp-
erature for every corresponding capacity step say
For Ø evaporation temp is t - (minimum
1 1
capacity step)
For Ø evaporation temp is t - (second larger
2 2
capacity step)
For Ø evaporation temp is t - (third larger
3 3
capacity step)
and so on.
5. There are two major situations where compressor
need to start
A) Compressor is started at relatively high
evaporation temp. Such situation may occur
after prolonged period of compressor at
standstill, or when compressor operates on
batch type freezing process, just loaded with
warm product.
UNDER SUCH SITUATIONS:
a) Start your condenser water pump, chiller
water/brine pump, cooling tower fans/
pumps etc.
b) Put all capacity control solenoid valve to
OFF position by operating electrical toggle
switch provided on control panel. If such
switch is not provided then, OFF all
solenoids by operating manual over ride.
c) Start the compressor. Only HP Cylinders
will be in operation. Let compressor to
operate on HP Cylinder only. Just similar to
single stage compressor, till evaporation
saturation temperature reaches to t
1
d) Once temperature t is attained, load the
1
compressor to minimum capacity step.
Compressor will now be in two stage
operation. Let compressor run on this
capacity step, till evaporation temperature t
2
is attained.
e) Again, as temperature t is attained, go to
2
larger capacity step of compressor i.e.. step
Ø2.
f) Repeat step d & e sequence wise, till
compressor reaches to 100% load.
Always keep watch that discharge temp-
erature does not exceed 110° to 120°C, &
intermediate pressure does not exceed
2
4kg/cm .
19
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