Fans for use in ventilation, refrigeration and air conditioning technology and other industrial applications are usually subjected to rigorous testing. They have to prove themselves with the manufacturer in long endurance tests under harsh conditions and are balanced to the latest state of the art. But in practice, failures still occur in some applications after far fewer hours of operation than specified in the catalogs.
A typical example is a damaged bearing system, usually caused by vibrations resulting from the way the fans are installed. If several fans are used in parallel, e.g. in a FanGrid (fan wall), this problem can be exacerbated by interactions between the fan and the design properties of the system. In addition, fan vibration characteristics usually change when the fans are installed in the customer’s device. An additional imbalance caused, for example, by damage during transport or handling can also have a negative impact on the service life and lead to the fan falling short of its usual 40,000 operating hours.
Critical speed ranges “overrun”
If a fan is operated frequently at excessive vibration levels, the bearing system may be damaged and premature failures may occur. Although vibrations can be measured, it is not easy to stop them. Motor and fan specialist ebm-papst now solves this problem with its RadiPac centrifugal fans with automatic resonance detection: in as-delivered condition, each RadiPac centrifugal fan has its own resonance characteristics, induced, for example, by an unavoidable residual imbalance.
If the fan is now installed in a ventilation unit, the resonant frequency range may shift and/or the vibration velocity increases to impermissible values. Integrated vibration sensors detect resonances and the software prevents operation in the detected critical ranges. In addition, a test start-up can be performed during commissioning in which the vibration velocity is analyzed over the entire speed progression from standstill to nominal speed.
If excessive vibration velocity are detected in certain areas, the control software adjusts itself after activation by the customer so that these speed ranges are “passed over” in the future. This means that the ranges are passed through, but continuous operation in them is avoided. Operators can manually edit the software settings at any time, meaning that they always have full control.
Protection during operation
However, the vibration velocity may also increase during operation, for example due to dirt deposits on the impeller, which results in additional imbalance. In this case, the software emits an automatic warning. The operator can now check the system for additional imbalances and can perform troubleshooting measures (e.g. cleaning and/or new start-up). Vibrations that are injected by devices that are installed nearby, e.g. from defective compressors, can be detected but not avoided. In this case, the operator can initiate suitable measures.
This makes automatic resonance detection a useful option for increasing the operational reliability of the centrifugal fans in critical applications. The RadiPac product range also has a lot to offer. Thanks to aerodynamic optimizations, innovative materials, sophisticated design details, and highly efficient EC motors with intelligent control electronics, they not only deliver a lot of air performance, but they are also particularly quiet and efficient. High speeds ensure high air flow and high pressures, meaning that even high-pressure applications can be covered. A static pressure increase of well over 2,000 Pa can be achieved.
Energy-efficient, quiet and adaptable
The driving force behind RadiPac centrifugal fans are high-efficiency GreenTech EC motors in the power range from 500 W to 8 kW with configurable control interface for analog and digital signals, which can be individually adapted, as well as a serial MODBUS RTU interface. This enables operating data such as speed, power consumption or operating time to be read out and processed digitally, for example. The external rotor motors also achieve high efficiency levels in accordance with the requirements for efficiency class IE5 set out in IEC/TS 60034-30-2. They do not require any rare earths and are also very compact thanks to the typical ebm-papst external rotor design.
The impeller plays a significant role in creating high efficiency levels. A glass-fiber reinforced composite material was used, enabling the complex shape of the five spatially twisted and strength-optimized 3D blades. The optimized blade channels achieve high efficiency levels and the fans operate extremely quietly.
Flexible installation options
To meet the requirements of different installation situations, the new centrifugal fans are available in a standard and short version. For the most powerful standard types, the impeller is attached to the motor in such a way that it has no negative influence on aerodynamic efficiency. In the short version, the motor is immersed in the impeller. These fans are more compact and are much more efficient than comparable predecessor models in spite of the slightly shorter axial installation dimensions in comparison to the standard version.
In the standard types, the powerful motor is completely pulled out of the flow area, ...
in the short version, the motor is immersed in the impeller. (Photo | ebm-papst)
Both RadiPac versions are available as a motor-impeller combination or as a ready-to-install plug & play solution in a compact support bracket for easy wall mounting. The support plates have been dimensioned to make the best possible use of space on a Euro pallet, thereby saving transport costs and improving the CO2 footprint.