Torquing about advanced pump controller

October 4, 2021  292  292   

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, as Mark Ingham of Sensor Technology Ltd in the UK explains. As the industry strives to become more and more productive, technologies that support smart factories, Industry 4.0 and the Industrial Internet of Things, are being used with increasing frequency 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 great task, but a highly automated factory will have literally hundreds or even thousands of them, so the task becomes very considerable. Thus, even a moderately sized factory has to employ a significant number of electricians and engineers who spend their days wiring and rewiring equipment. It follows that, 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 performance 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, while a sudden reduction may be due to an upstream blockage. So, in an automated plant, it is well worth measuring torque, but can fitting a suitable sensor be made quicker, easier and therefore more cost-effective?

The answer to this question is ‘yes’. TorqSense is a wireless sensor that replaces the need for physical wiring and slip rings with radio wave communications. Fitting a TorqSense typically takes about one-fifth the time required for a conventional hard-wired transducer, but how do they work? 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 converts the reading into a torque value. 

TorqSense transducers use two Surface 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 are interrogated wirelessly using an RF (radio frequency) couple, which passes the SAW data to and from the electronics inside the body of the transducer.

Sensor Technology’s Mark Ingham explains: “All you have to do is set up a TorqSense is glue the SAWs to the shaft, fire radio waves at them and monitor the waves that are reflected back.  The SAWs are distorted in proportion to the twist in the shaft, which in turn is proportional to the level of torque. The frequency of the reflected waves is changed in proportion to the amount of distortion and electronics within the TorqSense analyses the returning wave and feed out torque values to a computer screen.

As the TorqSense method does not require contact with the rotating shaft it offers complete freedom from the slip rings, brushes or other solutions found in traditional torque measurement systems. TorqSense devices also have high immunity to magnetic forces, allowing their use in, for example, motors where other technologies are very susceptible to electronic interference.”

Bluetooth

Conceptually Bluetooth is very similar to TorqSense. It is a wireless technology that enables data exchange over short distances and, like TorqSense, it transmits using radio waves. It is commonly found in hands-free phones and other mobile devices, so is used by many people daily. In the engineering and industrial worlds, it is often favoured as a wireless alternative to RS232 data cables and can connect several devices simultaneously.

Sensor Technology’s new Bluetooth module creates wireless solutions for torque measurement. In use, the module simply plugs into the TorqSense's existing 15 way ‘D’ digital lead connector. As well as collecting torque signals, the modules can provide power to the TorqSense transmitter/receiver and provides a USB output for connection to a PC.

Bluetooth/TorqSense will be welcome in cable-dense environments such as automated factories and will enable torque monitoring via any Bluetooth enabled device. Sensor Technology has also launched an Android app that allows torque parameters to be monitored via a standard mobile phone or tablet, without the need for a PC.

Applications

SAW-based torque sensors have been used around the world and in many fields, from test rigs to wind turbines and generators based on tidal or river flows. They are used extensively in the high-tech world of the development of engines and gearboxes for Formula 1 and other hyper-performance cars. Torque feedback systems have also been used by security firms to determine the direction their movable CCTV cameras are facing so that they can efficiently watch premises under their protection, in industrial mixing, long-duration scientific experiments, to model aircraft thrust lift and control systems, etc. 

They can be used with virtually all pump-based systems, from microdosing of active ingredients in pharmaceutical production, to cake filling injection in high volume bakeries, to lubricant and coolant circulation in manufacturing machinery, to flow control in industrial washing machines and paint spray robots; they can prove invaluable when coupled with the giant pumps used for freshwater distribution, foul water handling and flood management systems. In fact, it is fair to say that their potential uses with pumps are almost endless.