2202MYJE-MY-C8-N_2018.02.
Chapter 2 Compressor Specifications and Structure
Compound 2-stage Screw Compressor 3225**C 2.1 Overview of MYCOM 3225**C
2-1
Chapter 2 Compressor Specifications and Structure
2.1 Overview of the 3225**C
The 2-stage compression system, which has hitherto required two units of standard-type screw
compressor for its embodiment, can now be realized by a single unit of compound 2-stage screw
compressor.
Generally, screw compressors use oil injection to keep discharge temperature at a low level during
operation without loss of volumetric efficiency even at high compression ratios. It can, therefore, be
operated with a single-stage compression system even at evaporative temperatures near -40°C.
However, for normal use at low temperatures, a 2-stage compression system is applied in order to
improve kW/RT (ratio of power consumption versus cooling ability). If the 2-stage compression system
is configured with standard-type screw compressors, at least two screw compressor units need to be
installed, one on the high-stage and the other on the low-stage, which inevitably requires double
installation of the entire system including machinery, motors, utilities, etc.
This 2-stage screw compressor is produced to solve this problem. It is a single unit that has two
single-stage compressor units combined into one.
The 3225**C model has a capacity control mechanism for startup load reduction on the high-stage, and
a capacity control mechanism for coping with load change on the low-stage.
In addition, there are four rotor lengths for the low-stage and three rotor lengths for the high-stage.
Moreover, customer is able to select each low-stage and high-stage volume ratio from two
specifications. Employing these combinations of each specification, 3225**C is providing a high
versatility that can satisfy a wide range of operation conditions required by different applications at the
load side. Therefore, the 3225**C models are the long-selling products which last to
more than 30 years since the developed in 1982 as the large sized compound 2-stage screw
compressor.
2.2 Model Designation of the Compressor
This manual describes 3225**C-*B*-51 and 3225**C-*B*-61 models.
The meaning of the type designation, which is engraved on the MODEL column of the compressor
nameplate, is as follows.
*3225**C-*B*-51/61
5: Power frequency (6: 60Hz)
1: Indicates that it is a motor directly connected type.
* Unless specifically specified, machines manufactured in
September, 2010 or after do not have this indication engraved
on their nameplate.
Vi (volume ratio) specified for the high-stage discharge port,
standard value of which is L or M
Means a booster (low-stage machine)
Vi (volume ratio) specified for the low-stage discharge port, standard
value of which is L or M
Stands for Compound (compound 2-stage machine)
Specifications of high-stage rotor length, which is L, M or S
Specifications of low-stage rotor length, which is LL, L, M or S
High-stage rotor diameter of 250
Low-stage rotor diameter of 320
Indicates working fluid
(Example: N = Ammonia, F= Fluorocarbon, P = Propane, HE = Helium)
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