D6.3.4/0715-0716/E 7
2.6 Design features
2.6.1 Construction
Standard
Figure 1
All K-, L- and S-Series compressors are fitted with “Reed” valve plates.
Depending on the number of cylinders, the motor cooling and the kind of application, there are
three different compressor families:
Air- or water-cooled single-stage compressors, models K, L with 2 cylinders and a
displacement between 3.97 m³/hr and 22.5 m³/hr; model LH is air-cooled with a
displacement of 26.6 m³/hr.
Refrigerant-cooled single-stage compressors, models D2S, D3S, D4S, D6S and D8S with 2,
3, 4, 6 and 8 cylinders and a displacement between 22.4 m³/hr and 210 m³/hr.
Refrigerant-cooled two-stage compressors, model 6T with 6 cylinders and a displacement of
84.7 m³/hr.
NOTE: D2SA-450, D2SA-45X, D2SC-550 & D2SC-55X can be suction gas-cooled or air-
cooled compressors depending on the position of the suction service valve.
In addition, air- or water-cooled compressors have two different kinds of lubrication:
K & L compressors using mineral oil or semi-synthetic oil and R22 (HCFC) are equipped
with a centrifuge lubrication system.
K & L compressors using ester oil for chlorine-free HFC refrigerants like R404A are
equipped with an internal oil pump. The LHA compressor has an external oil pump.
Refrigerant-cooled compressors from D4S upwards are also available as TWIN (Tandem), ie,
two compressors of the same type coupled together via a common suction chamber.
Two-stage compressors are used when high pressure ratios are required with acceptable
discharge temperatures. On the low-pressure stage (LP, 4 cylinders on 6T) the suction gas is
compressed to the inter-stage pressure. The gas enters the motor housing and crankcase via
the intermediate pressure mixing line. On the high-pressure stage (HP, 2 cylinders on 6T), the
gas is compressed to the condensing pressure.
IMPORTANT
Pressures in two-stage compressors are different from those in single-stage
compressors, eg, motor compartment and crankcase are under inter-stage
pressure.
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