In today’s aero­dy­nam­i­cally sophis­ti­cated fans, impellers and inlet rings are usually made of plastic. Injec­tion molding allows for precise design, enabling compo­nents to be manu­fac­tured with very small toler­ances. However, the disad­van­tages of plastic in the event of fire include a build-up of gas and lower dimen­sional stability. For this reason, the use of plastic is often very limited in some markets, mainly in the USA, often in Asia, and to some extent in Europe (France).

Modern manu­fac­turing for high-perfo­mance impellers

The fan experts at ebm-papst are there­fore focusing on new and improved options in sheet metal forming and joining processes in order to develop modern, high-perfor­mance impellers that neither melt nor produce smoke in the event of a fire and can be used effi­ciently in any envi­ron­ment (Image 1). The aero­dy­nam­i­cally most favor­able designs for blades, bases and cover plates can be tech­ni­cally imple­mented (Image 2). Manu­fac­turing toler­ances are also very low today, and the air gap between the inlet ring and the impeller is smaller than in the previous metal design. This also results in higher effi­ciency in the new series (Image 3). If required, hybrid versions consisting of a metal impeller and a plastic inlet ring with a smaller air gap can be assem­bled for even greater effi­ciency.

Image 1: New 3rd gener­a­tion RadiPac centrifugal fan in metal design. (Image | ebm-papst)

Figure 2. New forming and welding tech­niques make it tech­ni­cally feasible to produce blades, bases and cover plates with the most aero­dy­nam­i­cally favor­able design. (Image | ebm-papst)

The indi­vidual parts of the impellers are joined together to form a single unit using modern welding processes. The devil is in the detail: even with high produc­tion volumes, the manu­fac­turing process must always deliver repro­ducible results with high dimen­sional accu­racy and a long service life. However, welding as a thermal process is known to alter the metal struc­ture and can lead to locally reduced strength. By opti­mizing the shape of the fan blades at the higher-stress exit edge, the stress can be shifted away from the joint at the blade root and into the unchanged mate­rial struc­ture.

The indi­vidual parts, designed according to mate­rial-specific and aero­dy­namic consid­er­a­tions, allow for almost unre­stricted 3D shaping. As a result, the impellers with five blades and improved geom­etry operate much more quietly and effi­ciently than their metal prede­ces­sors. Thanks to the improved strength of the impellers, even higher speeds can be achieved with almost iden­tical weight. This also ensures increased air delivery with the same dimen­sions. The maximum impeller diam­eter is 800 mm (Image 3).

The RadiPac M sets new stan­dards

Bern­hard Siedler, global product manager for the RadiPac series, explains what’s behind it.

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Sizes and appli­ca­tions of the RadiPac M

To ensure the most universal appli­ca­tion possible, the changes to the third gener­a­tion of RadiPac fans in metal design from ebm-papst were limited to the rele­vant assem­blies. The mounting plate and numerous edge assem­blies are virtu­ally iden­tical or more compact, making it easy to replace old fans (Image 5). Existing guide grilles for several iden­tical fan units and inlet rings for the fans are also compat­ible. The fans in this series are avail­able with impeller diam­e­ters from 280 to 800 mm and offer a motor power of approx. 170 W to 24 kW.

In addi­tion, the larger sizes 710 and 800 can be equipped with more powerful motors, resulting in higher flow volumes with high effi­ciency. The latter corre­sponds to a flow volume of around 50,000 m³/h (free blowing) for the 800 mm fan and still 30,000 m³/h at a pres­sure increase of 2,000 pascals. Depending on the appli­ca­tion require­ments, RadiPac fans are avail­able in a long (stan­dard type) or, option­ally, a compact short version. In the stan­dard version, the impeller is located at the front of the motor, while in the compact version for space-crit­ical appli­ca­tions, the impeller is attached to the rotor flange so that the motor protrudes into the impeller (Image 6).

Image 5: Thanks to the plug & play design of RadiPac fans and their iden­tical dimen­sions, replacing old fans is simple. (Image | ebm-papst)

Image 6: Depending on the appli­ca­tion require­ments, the fans are avail­able in a long (stan­dard version) or short design. In the long version, the impeller is located at the front of the motor (left), while in the short version, the motor protrudes into the impeller (right). (Image | ebm-papst)

Elec­tronics and motors with auto­matic reso­nance detec­tion

Centrifugal fans are used in a wide variety of appli­ca­tions. Depending on the instal­la­tion situ­a­tion, reso­nance can occur in certain speed ranges. If a fan is frequently oper­ated in such a crit­ical range, the bearing system of the drive motor can be damaged, leading to prema­ture failure of the fan. Although these vibra­tions can be measured by plant oper­a­tors, they cannot be easily elim­i­nated. ebm-papst solves this problem in RadiPac centrifugal fans with auto­matic reso­nance detec­tion. During start-up to nominal speed, this system regis­ters possible appli­ca­tion-specific reso­nance speeds, which are then avoided or quickly passed through during subse­quent oper­a­tion.

This protects the bear­ings and increases reli­a­bility. All fans can be controlled via 0-10 VDC or MODBUS RTU, are equipped with inte­grated EMC filters, and comply with the rele­vant EU and/or UL approvals for the US market. In addi­tion, it is possible to monitor the fans remotely, as well as to simply inte­grate sensors into the fan control system. Further­more, the EC motors have been adapted to current require­ments, which do not require expen­sive rare earth magnets. High effi­ciency across the entire speed range, in conjunc­tion with intel­li­gent control, allows for energy-saving oper­a­tion that is precisely tailored to the respec­tive air require­ments.