New Sensonics vibration sensor combats common causes of failure

Condition monitoring specialist Sensonics has developed the new VEL/GLF low frequency velocity vibration sensor for slow-speed rotating machinery.

Slow-speed rotating machinery – typically below 300 rpm – is commonplace in many industrial applications, such as cooling towers and hydro-electric turbines.

To ensure the machinery and the plant are functioning at optimal levels it is essential to measure vibration, as much as it is a critical requirement for standard speed machinery applications.

In all cases the focus should be on understanding the dynamic behaviour, establishing a baseline vibration performance, and detecting the early onset of failure in rotating parts, which can result in more serious damage affecting overall performance.

The use of accelerometers is commonplace on standard speed machinery (i.e. 1,500 rpm), but they are not suitable for lower speeds as the absolute accelerations measured are much smaller in value for similar vibration displacements. 

The Sensonics VEL/GLF is an electro-dynamic sensor offering higher performance compared to piezoelectric devices by combining high measurement sensitivity with a frequency response down to 0.5Hz.

The device is well-suited for measuring velocity vibration on equipment with speeds below 300 rpm.

The sensor offers a standard IEPE type interface to enable easy integration with existing plant protection and monitoring equipment.

The VEL/GLF provides advantages over traditional piezoelectricity-based velocity vibration sensors, which are susceptible to many forms of interference in low frequency applications that can result in spurious readings and alarms.

Typical causes of failure with piezoelectric sensors include base strain effects due to temperature changes amplified through the internal signal processing, high frequency and high G vibration events caused by auxiliary machine items resulting in transducer saturation, and mains voltage interference due to a combination or poor local plant earth and insufficient transducer internal isolation.

The VEL/GLF is designed to combat these effects, offering high noise immunity due to the low impedance electro-dynamic nature of the sensor assembly.

In addition to the filtering of high frequency events and since no electronic integration is required, the design is immune to the saturation problems that impair the reliability of piezoelectric devices.

Typical applications for the VEL/GLF will be found in cooling towers, hydroelectric generation, slow-speed pumps, and structural monitoring.