PUMPS, VALVES & ACTUATORS THE PARAMETERS OF VACUUM PUMP SELECTION


Busch Vacuum Solutions outlines the different types of mechanical vacuum pumps available, and shows how to select the right pump for the parameters of different conveying systems


systems to the various process steps. In food processing, the pharmaceutical and chemical industry and for material feed in plastics processing, suction conveying is indispensable when powder or granular materials have to be transported. The proper choice of the vacuum generator determines the operating costs of a pneumatic conveying system. Modern vacuum technology today enables the economical and environmentally friendly operation of vacuum conveying systems. In order to be able to select the most


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effective method of vacuum generation, it is vital to be familiar with the operating conditions of the vacuum conveying system and to apply this knowledge when selecting the vacuum pump. These parameters are important in order to select the most suitable one from various principles for vacuum generation. On the one hand, the conveyed material and its properties must be known. Additional influential parameters are pipe routing, length and diameter as well as the type of conveying (fig. 1). These parameters can be used to determine the required differential pressure (∆p). The differential pressure and the volume flow are the main influential parameters for the technical selection of the vacuum pump or vacuum system. For the economic efficiency calculation, operating costs must be considered in addition to acquisition costs. This includes the energy consumption, possibly further acquisition costs for throttle regulation, valves or control depending on the vacuum generation, the operating time (e.g. continuous operation, batch operation) as well as the maintenance effort and costs. The following mechanical vacuum pumps,


which achieve different differential pressures or vacuum levels, are mainly used for suction conveying (fig. 2): • Side channel blowers • Rotary lobe blowers


owadays, pneumatic suction conveying is an important technology for feeding bulk goods gently through piping


• Rotary vane vacuum pumps • MINK claw vacuum pumps Side channel blowers – Small side channel


blowers achieve high volume flows, making them suitable for use in short conveyor tracks and in flight conveying when low differential pressures and high volume flows are required. Side channel blowers compress oil-free and are relatively inexpensive to acquire. However, side channel blowers do not have a stable characteristic curve and are therefore not stable in volume. If they are operated at their performance limits, they have an above- average energy requirement. Rotary lobe blowers – Rotary lobe blowers


operate contact-free and thus without oil in the compression chamber. They can be used for differential pressures up to 500 hPa (mbar). Due to these relatively low differential pressures, the use of rotary lobe blowers in suction conveying is limited to applications requiring high volume flows at low differential pressures. In this area of application, rotary lobe blowers are characterised by their low power requirement. Rotary vane vacuum pumps – Rotary vane vacuum pumps are the ideal vacuum


Fig 3: MINK claw vacuum pumps are energy efficient and nearly maintenance free


All images supplied by Busch Vacuum Solutions


generators for suction conveying when high differential pressures are required and long conveyor tracks must be overcome. In addition, rotary vane vacuum pumps are always suitable when products must be conveyed slowly (plug conveying, fig. 1). Ultimate pressures of up to 0.1 hPa (mbar)


can be achieved with rotary vane vacuum pumps, which corresponds to a vacuum of 99.99 percent. No other vacuum generator in suction conveying achieves such a high vacuum (fig. 2) and can also operate at lower differential pressures. This guarantees a stable characteristic curve over the entire pressure range from atmospheric pressure to operating pressure. Rotary vane vacuum pumps are lubricated with circulating oil. This means that they have an internal oil circuit, which requires regular maintenance. MINK claw vacuum pumps –MINK claw


vacuum pumps (fig. 3) from Busch Vacuum Solutions have been the standard vacuum generators in pneumatic suction conveying for several years. This is a development that has been justified by their energy efficiency, the fact that they are nearly maintenance- free and can be controlled on a demand-driven basis. MINK claw vacuum pumps are available in various versions and sizes from 60 to 1200m3


/h each with standard


motors or with variable speed drives. Busch also offers individual central vacuum supply systems for several conveying systems or entire plants. Which vacuum pump is the right choice for


Fig.1 Fig. 2


pneumatic suction conveying depends on the technical parameters of the conveying system, so it’s important to be familiar with all these parameters. In the economic efficiency calculation, the acquisition costs, the operating time and the maintenance effort and costs must be considered. Busch Vacuum Solutions has all the vacuum pumps and blowers presented here in its product portfolio.


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MARCH 2021 | PROCESS & CONTROL 9


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