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

Section 4.1.5
. 
Trains I and II are supplied by three centrifugal air compressors: 
• two of them are four-stage compressors each with a single, vertically-split 
barrel casing,: one steam-turbine driven and the other electric-motor driven 
• one is a three-stage compressor driven by an electric-motor
Figure 5.22 shows examples of these compressors. 
(a) Electric-Motor Driven Four-stage Compressor (B) 
(b) Electric-Motor Driven Three-stage Compressor (C) 
Figure 5.22: Train I and II Air Compressors (Tag#s 35-K-1 B and C) 

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Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
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Train III is supplied by three, three-stage centrifugal compressors. Each of these has 
two horizontally-split casings: one houses the first two (single impeller) stages on a 
single shaft (or pinion) and the other houses stage three (also single impeller) on a 
separate shaft. 
A gear train connects the two shafts to increase the speed of the third-stage rotor.
This arrangement is shown in Figure 5.23. 
Two of these compressors run all the time. They are driven by steam-turbines. 
One compressor only cuts in when air pressure drops below the normal supply value 
of 8barg. This compressor is electric-motor driven. 
Electric motors can start and stop quickly and are suitable for stand-by operation.
Steam turbines take a long time to warm up before starting and to cool down again 
afterwards, before they can be re-started. They should not be used for stand-by 
operation. 
Figure 5.23: Train III Air Compressor 
Air intake from 
atmosphere 
Air to Train III 
Casing for 
stages 1 and 2 
Casing for 
stage 3 
Gearbox 
Now try 
Exercise 5

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Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
Page 65 of 90