International Appliance Manufacturing 2008 - (Page 18) quickly and work closely with these agencies to ensure that their products comply and are properly labeled to demonstrate compliance with the appropriate standards. For custom-designed products, make sure that the compressor supplier is aware of all the agency requirements for your application so that regulatory issues can be addressed in parallel with the development of the product. 9. Altitude Altitude above sea level, barometric pressure and temperature all affect air density – which is a major variable in sizing vacuum and pressure pumps to meet flow requirements. Temperature will have been defined in Point 5. Day-to-day changes in barometric pressure can affect pump performance, but generally these are within tolerance ranges. Altitude, or more specifically its constant effect on diminishing the atmospheric pressure, is therefore the most critical factor. Flow (cfm) PRESSURE Flow vs. Altitude 4.0 3.5 3.0 Flow (cfm) 5 psi 10 psi 20 psi 2.5 2.0 1.5 1.0 0.5 0 10,000 7,500 5,000 Altitude (ft) 50 psi 100 psi 2,500 Sea Level Figure 5 VACUUM Flow vs. Altitude 3.0 2.5 10” Hg 2.0 1.5 1.0 0.5 0 10,000 7,500 5,000 Altitude (ft) 5” Hg As Figures 5 and 6, at right, indicate the effect of altitude on pump flow is magnified at higher pressures or vacuums. A compressor at free flow (high cfm) isn’t affected much at all, while a compressor operating closer to its full, deadhead pressure can lose virtually all of its flow at a very high altitude. Altitude affects vacuum applications even more than it does pressure applications. As the pump gets closer to maximum vacuum, the flow drops off steeply. In 15” Hg 20” Hg 2,500 Sea Level Figure 6 18 International Appliance Manufacturing 2008
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.