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

6.3 Compressor 
Lubrication 
Most large compressors have an external lubricating-oil (lube-oil) system to supply 
lubricant under pressure to bearings etc. The main parts of an external lube-oil system 
are: 
• oil reservoir—a tank to hold oil not being circulated 
• strainers and filters—to remove solid particles from the oil 
• pumps—to pressurise and circulate the oil 
• coolers—to reduce the oil temperature and increase its viscosity 
A strainer in the pump suction line removes larger solid particles before the oil enters 
the pump. Oil is pumped from the reservoir, through the strainer to coolers and filters 
before reaching the bearings. It then flows back to the reservoir by gravity. 
Because lubrication is so important, there is usually a second, back-up pump in case 
the main pump fails. Two filters are fitted so that lubrication can continue while one 
filter is being replaced. There are controls to monitor pressures, temperatures and 
levels of lubricant in the system. Figure 6.6 shows a P&ID for a typical centrifugal 
compressor lubrication-oil system. 

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Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
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Some systems include a dump tank that feeds oil to the bearings by gravity from a 
small reservoir. The dump tank valve opens automatically if the main system fails. 
Figure 6.7 shows the lube-oil systems for two of the reciprocating compressors on the 
ADGAS plant. 
Figure 6.6: Compressor Lube-oil P&ID

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Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
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Figure 6.7: External Lube-oil Supply Systems 
(a) Lube-oil Supply for VRU Compressor
(b) Lube-oil Supply for New BOG Compressor
Now try 
Exercise 7

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Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
Page 85 of 90