The wireless online CMS VIBCONNECT RF from PRUFTECHNIK Condition Monitoring is transmitting the data also in the WIFI range but is also coming along in versions that broadcast the data via radio frequency (RF) at 868 MHz or 916 MHz. The radio frequency offers a long range in a less crowded frequency band. Additional equipment to extend the range is not required under normal conditions. Apart from the battery powered versions, VIBCONNECT RF is also available in a 24 Volt powered version via cables
(if available at the machine) in order to guarantee a maximum flexibility and to adapt the monitoring system to existing resources. With the power supply permanently available through wires,
this architecture is suitable for more critical machines
that require more frequent measurements.
Wireless systems and sensor position
Choosing the best measurement location for a vibration transducer is most essential. Several guidelines [1,2] exist, which recommend for the positioning of transducers. One critical factor to obtain meaningful data with high amplitudes is the positioning of the sensor within the load zone of a machine. In many cases, this zone is directed to the bottom and no direct line of sight is available for transmitting the data wirelessly. Neighboring machines, pipes, conduits or parts of the machine foundation typically are present and attenuate or even block the wireless signal transmission. Because of this, compact wireless online CMS (magnet, transducer and battery in the same housing) cannot always be placed at the optimal measurement position of the machine. Apart from compact systems other wireless online CMS in the market separate their sensors and the transmitting unit with short wires that are already part of the system. The RF Sensor Unit of PRUFTECHNIK’s monitoring system VIBCONNECT RF offers such an architecture. It consists of a robust, compact case that contains the exchangeable batteries and connects the output of the signal electronics to the transmission antenna. The case can be placed on top of the machine in order to ensure the best signal quality. On the other side, two 2,9 meter wires connect to one sensor each. The PRUFTECHNIK-made sensor consumes very little power in order to ensure a long battery life. A combined vibration and temperature sensor also delivers bearing information (envelope analysis) in addition to machinery vibration monitoring.
Case study 1: Monitoring of cooling tower drives
Cooling towers exist in various architectures. Medium size units for heat rejection are typically driven by a constantly running motor that connects via a long shaft to a gearbox. Since the gearbox is located within the tower, it cannot be accessed during a route-based data acquisition with a portable system. However, the criticality of a cooling tower drive demands periodical monitoring. Online wireless CMS help significantly reduce the data collection effort on such a remote location. The Gendorf Industrial Park, Bavaria’s
largest chemical park required monitoring of cooling tower drives and cooling water pumps. The objective was to check the condition of shaft and motor bearings and fan imbalance at regular intervals.