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

 
Figure 5.35: Anti-surge Control 
Downstream flow 
Upstream supply 
Ant-surge 
control valve 
Side-stream 
supply 
Now try 
Exercise 6

---

Personnel & Training Division
Job Training—Mechanical Technician 
Compressors/Rev. 0.0 
Page 76 of 90
6 Compressor 
Auxiliaries 
Compressors usually have additional equipment to help them to work efficiently and 
to reduce the chance of damage. Snubbers have already been described for 
reciprocating compressors. They are pulsation dampeners that smooth the flow of gas 
entering and leaving the compressor cylinder on each discharge stroke of the piston.
Snubbers are items of 
auxiliary
equipment for reciprocating 
compressors. 
Other auxiliary
 
equipment: 
• helps to cool the gas during and after compression 
• removes liquid droplets and solid particles from the gas stream 
• supplies lubricating oil to the compressor 
• supplies sealing liquid to shaft seals 
6.1 Gas 
Cooling 
Increasing the pressure of a gas reduces its volume, but it also raises its temperature.
When gas gets hotter it tries to expand, increasing its volume again. This reduces the 
capacity of the compressor as the gas becomes less dense
Remember what was said about compressor capacity in 
Section 2.4
of this module.
The capacity, or volume flow rate, is measured as if the gas was at atmospheric 
pressure (1.1013bara) and at a temperature of 15
o
C. A compressor may be 
discharging a vary large volume of gas every hour but if its temperature is high, that 
volume would be a lot less at 15
o
C and the capacity may be quite low. Gas at high 
temperature reduces the efficiency of a compressor. 
Gas must be compressed and cooled to change it to liquid. If the compression is part 
of a gas liquefaction process, cooling during compression increases the efficiency of 
the process. 
The gas is cooled between compressor process stages and after final discharge. 
Something that is