Plant Services - January 2008 - (Page 37) EFFICIENCY Compressors Table 1: Comparison of Compressor Types (100 hp To 500 hp) Category ** Size and weight System completeness Can be located close to points of use Maintenance costs Foundation requirements Reduced capacity efficiency* Lubricant-free air (lube**/lube-free) Lubricant carry-over (lube/lube-free) Lubricant changes or make-up (lube/lube-free) Equipment cost Installation cost Full-load operating kW/100 cfm Two-stage double acting reciprocating 3 3 4 3 4 1-2 4/1 4/1 4/1 4 4 15-16 Lubricant-injected screw (single-stage) 1 1 2-3 1 1 1-4 2 3 3 1 1 18-19 Lubricant-injected screw (two-stage) 2 1 2-3 1 1 1-4 2 3 3 2 1 16-18 Lubricant-free screw 2 1-2 2-3 1 1 1-3 1 1 1 2 1 18-22 Centrifugal 2 1-2 3 1 1-2 1-3 1 1 1 2 2 15-20 Key: 1 = Very good; 2 = Good; 3 = Fair; 4 = Poor. These evaluations are very general and might not cover specific features of a given compressor type or manufacturer. They are intended to provide a general guide in how to compare compressors. It’s important to evaluate each point in any comparison of quoted equipment. Other factors to be considered include warranty and service requirements. * It’s important to compare kW/100 cfm ratios at reduced capacity. Rotary compressors having variable displacement or variable-speed drive capacity controls might provide substantial energy savings when operating at reduced capacities. ** Any compressor requires appropriate downstream air quality treatment. Specific power kW/100 cfm based upon full capacity at a discharge pressure of 100 psig and a full-load motor efficiency of 92%. Higher motor efficiencies are available. Source: “Best Practices for Compressed Air Systems,” a Compressed Air Challenge Publication (McCulloch and Scales 2007) THREE DEFINING STRENGTHS ONE EXCEPTIONAL COMPANY Engineering and ingenuity from around the globe. 150 years of experience. And a new partnership with Fu Sheng, a precision manufacturer of some of the world’s most respected brands. Experience what the power of our new partnership can do for you. VISIT WWW.DISCOVERCURTIS.COM The rotary-scroll compressor is a relatively new design in sizes from fractional to 7.5 hp. Because of its small footprint, multiple compressors and drives can be mounted on a common base to provide higher capacities. One of two identical intermeshing spirals or scrolls is stationary and the other oscillates in relation to the stationary scroll. (Editor’s note: January 2008 www.PLANTSERVICES.com DISCOVER ©2007 Curtis-Toledo, Inc. 17640_2 07 CTGNL GENRL Wrap Up.indd 1 9/19/07 37 8:02:37 http://www.discovercurtis.com http://www.discovercurtis.com http://www.PLANTSERVICES.com
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