1. A “standard system” is defined as a rotary screw compressor installed with 1 gallon per cfm storage receiver capacity, standard filters sized to the capacity of the compressor with 3 psid total pressure differential, and non-cycling refrigerated dryer sized to the same capacity as the compressor with 4 psid differential
2. A Canadian Electricity Association Technology Profile Report, “Air Compressors–Rotary Screw, Reciprocating, Centrifugal and Axial,” December 1995, found that, out of 52,000 compressors of both reciprocating and screw, 48% were under 25 hp and 75% were under 100 hp, and of these 78% were reciprocating style
3. The Compressed Air and Gas Institute (www.cago.org) has adopted recognized performance standards and a “Compressed Air Data Sheet for Rotary Screw Compressors.” Manufacturers that are members of CAGI are required to publish their specifications on their websites. Note that CAGI data sheets for small reciprocating compressors are rarely published
4. The data compare a 25 hp Ingersoll Rand Model UP25, 125 psi-rated screw compressor with an Ingersoll Rand 2000, two-stage 125 psi reciprocating unit. Data supplied by Ingersoll Rand
5. A 2008 internal Manitoba Hydro Survey (of customers applying for the Performance Optimization Incentive Program) regarding 71 rotary screw compressor systems 50 hp and below showed average system loading of 24% of the full-load capacity of the main compressor. Peak loading is normally much higher, hence the reason for a larger compressor