Hy-Bon Engineering Midland, Tx - Compressor Selection Criteria

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"As president of Hy-Bon Engineering, I pledge the full resources and undivided attention of our employees toward meeting your compression needs, large or small"

– Larry S. Richards, President

Technical Library

COMPRESSOR SELECTION CRITERIA

Typical Compressor Types Used in Vapor Recovery :

	• • • • •	Rotary Vane Compressors Eccentrically mounted rotor Centrifugal force causes vanes to slide in or out Gas is forced into decreasing space thereby causing compression Jacket water cooling system RPM range 400 to 1600

	• • • •	Flooded Screw Compressors Twin helical rotors Oil is both the cooling medium and the compression medium Various configurations of gears, internal porting and loader/unloader valves available Gas mixed with oil. Must be separated after compression

	• • • • •	Reciprocating Compressors Piston/cylinder arrangement May be air, water or oil cooled Ages old technology May be slow speed or high speed Not typically used for Vapor Recovery

	• • • •	Scroll Compressors Two compression elements - one fixed sroll, one orbiting scroll Oil is both the cooling medium and the compression medium All scrolls are paired with a Variable Frequency Drive for capacity control Gas mixed with oil. Must be separated after compression

Typical Operating Parameters :

	• • •	Rotary Vane Compressors Differential pressure equal to or less than 60 psig (for single-stage models). Volume from approximately 15 MSCFD to 2 MMSCFD (for single-compressor units). Relatively low suction temperatures (< 120° F)

	• • •	Flooded Screw Compressors Differential pressure equal to or less than 300 psig (for single-stage models). Volume from approximately 20 MSCFD to 2.5 MMSCFD (for single-compressor units). Virtually any temperature (< 180° F)

	• • •	Reciprocating Compressors Differential pressure in excess of 2000-3000 psig (for multi-stage models). Volumes in excess of 20 MMSCFD (dependent upon suction pressure). Relatively high suction temperatures (< 200° F)

	• • •	Scroll Compressors Differential pressure equal to or less then 275 psig. Volumes from approximately 20 MSCFD to 260 MSCFD (for single-compressor units). Virtually any temperature (<180° F)

Relative Advantages and Disadvantages of Various Compressor Styles in Vapor Recovery Service:

Rotary Vanes :
Advantages:	• • • •	Excellent for relatively high volumes and relatively low differential pressures Efficient at low pressures Can handle wet gas relatively easy Comparatively low initial cost and ongoing maintenance

Disadvantages:	• • •	Limited as to discharge pressure Limited as to suction temperature capabilities Free liquid causes blade breakage problems

Flooded Screws:
Advantages:	• • •	Excellent in a large volume/medium differential pressure range Can handle wet gas better than rotary vanes Excellent temperature control for controlling condensate fallout

Disadvantages:	• •	Higher maintenance Higher operational expense (oil, filters, etc.)

Reciprocating Compressors:
Advantages:	•	High volume/high pressure

Disadvantages:	• • • • •	Low suction pressure results in large first stage cylinder size Inefficient at low pressures Rings and valves fail in wet gas applications Control is difficult at atmospheric pressures Not recommended for Vapor Recovery Service


Scroll Compressors :
Advantages:	• • • •	Excellent in a small to medium volume/medium differential pressure range Can handle wet gas better than rotary vanes Fewer moving parts Extremely low noise level Once per year maintenance

Disadvantages:	• • •	Cannot accept sour gas Somewhat limited as to volumes Compressors cannot be repaired
Applications of Various Compressor Types:

Rotary Vane Compressors	• • • • •	Vapor Recovery Low Pressure Gas Boosting Digester Gas Recovery Landfill Gas Recovery Casinghead Pressure Reduction

Oil Flooded Screw Compressors	• • • • •	Vapor Recovery Wellhead Compression Medium Pressure Gas Boosting Landfill Gas Recovery Casinghead Pressure Reduction


Reciprocating Compressors	• • • •	Wellhead Compression Gas Boosting (medium to high pressures) CNG Casinghead Pressure Reduction

Scroll Compressors	• • • •	Vapor Recovery Wellhead Compression Medium Pressure Gas Boosting Casinghead Pressure Reduction

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