Electricity and Control August 2020

SENSORS + SWITCHES

Radio frequency sensors in pump control

Factory automation continues to develop year on year and pumps are increasingly required to supply real-time operating data to control networks so their performance can be monitored and adjusted to meet constantly changing production requirements. Hard wiring a sensor into a pump’s rotating drive shaft usually requires the use of a delicate slip ring, but an alternative solution is to use a non-contact radio frequency detector. Mark Ingham of SensorTechnology Ltd in the UK explains.

A s industry strives to become more and more pro- ductive, technologies that support smart factories, Industry 4.0 and the Industrial Internet of Things, are being used increasingly on the shop floor. The potential of these and other developments to improve manufacturing quality and efficiency over time is almost limitless. However, such advances are not without their difficulties; one such being the need to connect machines and equipment such as pumps, mixers and conveyors to the control computers. Wiring up one machine is not a major task, but a highly automated factory may have literally hundreds or even thousands of them, so the task becomes considerable. Consequently, even a moderately sized factory has to employ a number of electricians and engineers who work

daily on wiring and rewiring equipment. If the amount of time spent on wiring and installation could be reduced, the factory could reduce its operating costs significantly. One of the most time-consuming tasks is fitting torque sensors to rotating equipment, as this requires the use of fiddly and fragile slip rings. However, torque is a key per- formance indicator. For instance, a gradual increase in a pump’s torque may suggest increasing flow to compensate for growing leakage; a sudden increase may indicate a blockage downstream of the pump, and a sudden reduc- tion may be due to an upstream blockage. So in automated plant it is well worth measuring torque, but can fitting a suitable sensor be made quicker, easier and therefore more cost-efficient? The answer is ‘Yes’. TorqSense is a wireless sensor that

replaces the need for physical wiring and slip rings with radio wave commu- nications. Fitting a TorqSense typically takes about one-fifth of the time required for fitting a conventional hard-wired transducer. How it works A shaft under rotary load will twist very slightly along its length, in proportion to the magnitude of the load. TorqSense measures this twist in real time and its electronics convert the reading into a torque value. TorqSense transducers use two sur- face acoustic wave (SAW) devices, which are attached to the surface of the shaft. When torque is applied to the shaft the SAWs react to the applied strain and change their output. The SAW devices

The use of radio frequency sensors to monitor torque on rotating equipment finds multiple applications in industrial pump-based systems.

22 Electricity + Control AUGUST 2020