What is the difference between scroll compressor and screw?

Technical analysis of scroll compressor and screw compressor

Scroll compressors and screw compressors are the two mainstream models of positive displacement air compressors and are widely used in the industrial field. There are significant differences between the two in terms of structural principles, performance characteristics, application scenarios, etc. Their technical characteristics and differences are explained as follows:

1. Comparison of structural principles

1. scroll compressor
   • core structure: It consists of a dynamic and static scroll, an anti-rotation mechanism and a drive bearing. The profiles of the movable and stationary scrolls are involute and are installed oppositely with a phase difference of 180°.
   • working principle: The moving scroll wraps around the fixed scroll to make revolution and translation to form a crescent-shaped compression chamber. Gas is sucked in from the outer edge and is gradually compressed to the center as the volume decreases.
   • technical characteristics：
     • The compression process is continuous, with pressure pulsation ≤5%
     • The number of parts is reduced by 40% compared with screw machines
     • Theoretical exhaust process no-clearance volume
2. screw compressor
   • core structure: It consists of male and female rotors, bearings, synchronous gears and shaft seals. The rotor profile is usually asymmetrical.
   • working principle: The male and female rotors mesh and rotate in the casing, and the volume between teeth changes periodically with the rotation of the rotors, realizing the inspiration-compression-exhaust cycle.
   • technical characteristics：
     • Rotor meshing clearance control accuracy reaches 0.01mm
     • Forced gas transmission characteristics, wide pressure ratio range (up to 10:1)
     • Equipped with oil system for cooling and sealing

2. Performance characteristics comparison

1. energy-efficient performance
   • Scroll machine: Significant energy efficiency advantages under part-load conditions (30-70% load), and the comprehensive energy efficiency ratio (IER) is 8-12% higher than screw machines.
   • Screw machine: It has better efficiency under full-load conditions, especially at large displacement (≥20m³/min), and unit energy consumption is reduced by 5-7%
2. noise vibration
   • Scroll machine: Operating noise ≤62dB(A), vibration speed ≤ 2.5 mm/s, suitable for places requiring silence
   • Screw machine: Noise level is about 68-75dB(A), and sound insulation covers are required to meet high standards of noise control
3. reliability index
   • Scroll machine: No wearing parts, the average time between failures (MTBF) can reach 80,000 hours
   • Screw machine: Lubricating oil and oil filter elements need to be replaced regularly, and the maintenance cycle is 2,000 – 4,000 hours

3. Differences in application scenarios

1. Application fields of scroll compressors
   • Medical equipment: ventilators, anesthesia machines and other scenarios with high requirements for air source cleanliness
   • Laboratory instruments: Gas chromatographs, mass spectrometers and other precision analytical equipment
   • New energy field: fuel cell air supply system
   • Special working conditions: Plateau low-pressure environment (power attenuation ≤15% at 5000 meters altitude)
2. Application field of screw compressor
   • Industrial manufacturing: machining, spraying, assembly lines and other large-flow gas scenarios
   • Engineering construction: Mobile gas supply needs such as pile foundation construction and tunnel excavation
   • Chemical industry: high-pressure ratio conditions such as gas transportation and supercharging (exhaust pressure can reach 1.6MPa)
   • Low-temperature engineering: Supporting cold drying machine to achieve-70℃ pressure dew point

4. Key points of maintenance and management

1. scroll compressor
   • Daily maintenance: Check the axial clearance of the moving plate (standard value 0.05-0.15mm) and clean the suction filter
   • Regular maintenance: Replace the bearings of the anti-rotation mechanism every 2 years and check the tightness of the casing
   • Fault diagnosis: Focus on abnormal noise (>65dB requires maintenance), exhaust temperature (>95℃ requires shutdown)
2. screw compressor
   • Daily maintenance: Monitor oil level (observation window 1/2-2/3), oil temperature (≤65℃)
   • Regular maintenance: Replace lubricating oil and oil separation filter elements every 2000 hours, overhaul rotor every 8000 hours
   • Fault diagnosis: Focus on checking oil path blockage (pressure difference>0.15MPa) and rotor wear (gap>0.2mm)

V. Technological development trends

1. scroll compressor
   • Expand applications: Develop dual-stage compression technology to increase exhaust pressure to 1.2MPa
   • Material innovation: Use carbon fiber reinforced composite materials to achieve 30% weight reduction
   • Intelligent: Integrate IoT modules to achieve remote parameter monitoring and predictive maintenance
2. screw compressor
   • Energy efficiency improvement: Using permanent magnet frequency conversion technology, energy efficiency for some loads is increased by 15%
   • Structural optimization: Develop oil-free screw models to meet the needs of the food and pharmaceutical industry
   • System integration: It forms an intelligent gas supply station with cold dryers and air storage tanks to achieve unattended operation

When selecting models, enterprises should conduct technical and economic analysis based on the needs of specific working conditions: for places with large fluctuations in gas consumption and sensitive noise, scroll compressors have advantages; while under continuous heavy load and high-pressure ratio conditions, screw compressors are better choice. With the advancement of technology, the gap between the two models in terms of energy efficiency, reliability, and intelligence is gradually narrowing, and users can make comprehensive decisions based on the equipment’s full life cycle cost (TCO).