Suction scrubbers

As pointed out in Volume 1, Chapter 3, a compressor may have any number of stages. Each stage normally contains a suction scrubber to separate any liquids that carry over or condense in the gas line prior to the compressor cylinder (or case for centrifugal compressors). When gas... 

Suction scrubbers are required on the unit suction to catch any liquid carry-overs from the upstream equipment and any condensation caused by cooling in the lines leading to the compressor. They are also required on all the other stages to remove any condensation after cooling. On each suction scrubber a high level shut-down is required so that if any liquids do accumulate in the suction scrubber, the compressor will automatically shut down before liquids carry-over to the compressor cylinders. 

Pipe length from suction pipeline to suction scrubber... 

Regarding the need for absolute removal of all free liquid mist, such as with a gas turbine compressor suction scrubber, I find a 100-pm particle size selection to be good design practice. This particle size fallout before reaching a demister pad will indeed ensure that most any demister pad will remove all remaining free liquid mist. 

On-off two-position with differential gap Slow Any Any Large-capacity temperature and level installations. Storage tanks, hot-water supply tanks, room heating, compressor suction scrubber... 

At high boiling rates, liquid carryover may result. A flow indicator in the vapor line will display the cerry-over and provide a warning before damage to the compressor can occur if compressor suction scrubbers are not provided. 

In this example, a LOPA is conducted using SIL Comp software, for a gas suction scrubber designed to remove contaminants from gas prior to downstream separation processes (Figure 13.5). 

Low low level in gas suction scrubber resulted in gas blow-by into equipment in excess of design pressure leading to potential rupture and loss of containment with subsequent fire/ explosion and single employee fatality. 

The LOPA analysis is to determine the functional safety requirements for a gas suction scrubber. 

For compressor suction scrubbers and expander-inlet separators, multiply K by 0.7 to 0.8. 

Kp = 0.055 m/sec Scrubbers for design conditions with substantial additional capacity generally used for suction scrubbers. 

HLLSD is normally used for system shutdown and is most commonly used in the compressor suction scrubber. It is required to avoid liquid droplets entering the compressor. A gap of 150 mm is normally kept between HLL and HLLSD. 

The suction scrubber of a gas compressor operates at 4000 kPaG. The liquid collected in the scrubber is discharged to a separator tank, which is open to the atmosphere, through a level-control valve installed on the liquid outlet line. In a particular situation of control valve failure (control valve goes fully... 

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