Blowers for High Pressure Applications
High pressure blowers are used in compression, vacuum and industrial process applications. Compression regenerative blowers can be used or configured as a compressor or air supply unit. Vacuum regenerative blowers can be used or configured as a vacuum pump or exhauster for removal or suction of air, fumes, or gases. Selecting regenerative blowers requires an analysis of compressor or vacuum specifications, power sources, and features.
Compressor specifications to consider when selecting regenerative blowers include: maximum free air delivery, maximum pressure, and motor power. Free air delivery (FAD) is the actual air produced by the compressor pump at the rated pressure. Maximum FAD is usually rated at a pressure somewhat less than the maximum pressure available. Volume per unit time is the unit of measure. Maximum pressure is the maximum level of air pressure generated by the compressor. Typically, these units are referenced to one atmosphere, as in psig or psi gauge. Note that maximum flow may not occur at maximum pressure. Motor power is the rated power of motor or engine driving compressor pump.
Vacuum specifications to consider when selecting regenerative blowers include: operating vacuum and pumping speed. Vacuum is often measured in torr, or mm Hg referenced above absolute zero pressure. Sometimes, the following reference terms are used: 1 torr and above, Rough Vacuum; 0.001 to 1.0 torr, Medium Vacuum; Below 0.001 torr, High Vacuum. There are other terms and standards used, such as medium vacuum and ultra-high vacuum; consult suppliers for application specifications. Pumping speed is the air volume capacity of vacuum pump. Typically, vacuum pumps are flow-rated according to the volume of air exhausted with no pressure differential across the pump.
There are four power source choices for regenerative blowers: DC power, AC single-phase, AC three-phase, and engine. Features for regenerative blowers include: control panels and pressure or vacuum gauges. Most control panels include adjustment controls instead of a simple, regulator knob. Regenerative blowers can also have a pressure or vacuum gauge or sensor with a dial or digital readout that monitors the pressure or vacuum levels in the system.
Chicago Blower Canada Co. has introduced many high pressure blower systems to achieve static pressure, previously unachievable by single stage centrifugal blowers.
Series and parallel connected blower installations are often used to meet performance ranges beyond normal single stage blower capacities. For systems that require high ststic pressure, and especially high pressure TOGETHER with high temperature (where standard multi stage, positive displacement, screw, or regenerative type blowers can not be used) series of single stage centrifugal blowers can be used. Many times additional blower in the system can be advantageous. For instance, where two blowers are operating in series and one breaks down, the other may be able to “limp” the system along while the necessary maintenance is performed. Having on blower continue in operation can often allow limited production while the other is being repaired. Also, there are cases where having one blower continue in operation could prevent or at least minimize system or equipment damage from such things as high temperature ot contaminated airstreams.
Caution is necessary in selecting blowers for series installtion. It is generally accepted that most pre-engineered blowers are capable of withstanding twice their catalog rated static pressure. In other words, where two blowers are installed in series the second blower housing should withstand the higher pressure. There is, however, a need for concern when the combined pressure exceeds twice the rated static pressure for one blower. In series applications involving three or more blowers, or in any system in which positive or negative pressure exists prior to the consideration of the blowers, special housing reinforcement may be necessary.
Oleg Tchetchel
Air Moving Specialist
Chicago Blower Canada
http://chicagoblowercanada.com/centrifugalfan.html
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