Compressor Selection

Chapter from the Pumps & Hydraulics Design Guide.

COMPRESSOR TYPE SELECTION FRAMEWORK

Compressor Type Comparison

Parameter	Centrifugal	Reciprocating	Screw (Rotary)	Axial	Selection Driver
Flow Range	1,000–200,000 ACFM	5–10,000 ACFM	100–20,000 ACFM	50,000–500,000+ ACFM	Flow rate is primary selector
Discharge Pressure	To 5,000 psig (multi)	To 60,000 psig	To 300 psig	To 100 psig	High P → reciprocating
Compression Ratio/Stage	2:1 to 4:1	3:1 to 10:1	3:1 to 5:1	1.2:1 to 1.5:1	High ratio → recip or multi-centrifugal
Molecular Weight	Best >10 MW	Any MW	Any MW	Best <40 MW	Low MW gas → reciprocating
Efficiency	75–85% polytropic	80–95% adiabatic	70–80%	85–90% polytropic	Recip most efficient per stage
Capacity Control	Speed, IGV, suction throttle	Clearance pockets, unloaders	Speed, slide valve	IGV	Recip best for variable load
Maintenance	Low (no contacting parts)	High (valves, rings, rods)	Moderate	Low	Centrifugal lowest O&M
Oil-Free Option	Standard (dry seals)	Available (labyrinth)	Dry screw available	Standard	Process gas quality req't
Pulsation	None (continuous flow)	Significant (requires dampeners)	Slight	None	Recip needs pulsation study
Footprint	Moderate	Large	Small	Large	Screw smallest for given flow
Typical Refinery Use	Recycle gas, wet gas	Makeup H2, instrument air	Flare gas recovery	Air separation, FCC blowers	Application-specific selection

Selection Decision Framework

1. Start with flow rate and discharge pressure → narrows to 1-2 types
2. Check molecular weight → low MW (<10) strongly favors reciprocating
3. Evaluate driver availability → gas turbine favors centrifugal/axial
4. Consider capacity turndown → >50% turndown favors reciprocating or VSD centrifugal
5. Assess gas cleanliness → dirty gas may require screw or special centrifugal
6. Check for pulsation sensitivity → downstream equipment may prohibit reciprocating
7. API standard: centrifugal per API 617, reciprocating per API 618

Source: Pumps_Hydraulics_Design_Guide_v1.xlsx · sheet “Compressor Selection”

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