Abu Dhabi Gas Liquefaction Company Ltd Job Training Mechanical Technician Course Module 9 Compressors

Figure 4.11 shows a section through a two-cylinder, two-stage, in-line reciprocating 
compressor. 
In Figure 4.12 you can see a two-stage angle, or L-type compressor. Notice the 
connection from the first-stage cylinder to the second and the sizes of the two 
cylinders. 
Figure 4.11: Two-stage In-line Compressor 
Stage-1 cylinder 
Larger diameter 
Stage-2 cylinder 
Smaller diameter 

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Some multi-cylinder compressors have some cylinders connected in parallel and some 
in series. In Figure 4.13 you can see a large two-stage balanced-opposed compressor.
The two cylinders on one side of the crankshaft are connected in parallel by a snubber 
to form the first stage. The gas then passes to the two cylinders on the opposite side 
of the crankshaft—a series connection. These two cylinders, also connected together 
in parallel by a discharge snubber, are the second stage.
The cylinders of large, multi-cylinder compressors are often separate units attached to 
a common crank case. You can see the four separate cylinder casings in Figure 4.13.
This compressor may be described as having four casings instead of four cylinders.
The balanced-opposed compressor shown has two first-stage casings and two second-
stage casings. 
The compressor shown in Figure 4.12 has two casings: one low-pressure first stage 
and one high pressure second stage. 
Figure 4.13: Balanced-opposed, Two-stage, Four-cylinder Compressor 
Suction snubber 
Discharge snubber 
Electric motor driver shed
First stage—2 cylinders 
Second stage—2 cylinders 
Crank case 

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Crank 
Case 
LP Stage-1 cylinder
HP discharge air to 
sulphur STOREX 
instruments, etc.
Intake air from 
atmosphere