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APPLIED TECHNOLOGY SENSORS & SENSING SYSTEMS TESTING TIMES fOR ACTuATOR DESIGNS
Companies around the world rely on Rotork actuators for use in applications ranging from power generation, water and sewage, to industrial processes, subsea, marine, HVAC, incinerators and cement plants. Products used here face challenging environmental conditions, extremes of temperature, and high costs associated with any downtime, so absolute reliability of the valve actuators is vital. TorqSense torque transducers from Sensor Technology are therefore a key element of the company’s test rigs. Rotork Controls designs custom actuator
designs built around motorised gearboxes, using non-standard open frame motors. A variety of motors are used depending on the particular application, including DC motors, single-phase motors and three-phase motors. Rather than relying on off-the-shelf products, the company uses open frame motors that it integrates directly into its own systems. “Performance testing is very important,”
explained Rotork Controls chief development engineer, Geoff Beeho. “The duty cycle is atypical – our motors are not in continuous use, only running intermittently and for a short period. What is important to us is the short term ratings, and this data isn’t always readily available. We have to have performance data that will tell us exactly what we need to know about the motors in these most demanding applications.” Rotork Controls therefore designed its own
rig to test the motors, with Sensor Technology TorqSense transducers at its heart. Beeho commented: “We needed non-contact torque sensors in the rig. The early design used
magnetically coupled torque sensors but we were never completely happy with these. So when we upgraded the rig to be able to perform a wider range of tests, we took the opportunity to look around the market and we found the TorqSense transducers.” He added: “The TorqSense transducers
immediately struck us as being a much more robust solution, better suited to handling the torques we were subjecting them to.” The common practices of over-specifying
a motor to guarantee reliable operation in standard applications simply doesn’t apply in valve actuation. “Motor sizing is critical,” said Beeho. “If we put in a motor that is too big, then we can risk damaging the valve. We can use motors that appear to be under-rated, but because our duty-cycle is so short we can get better performance from the motor. But, the performance data to support this sort of motor use isn’t always available, or isn’t always reliable, so we need to perform our own tests. We also need to know how our motors will handle extremes of temperature in given applications so that reliability is never compromised. The TorqSense transducers allow us to make all the required tests.” The TorqSense transducers used in the test
rig provide both analogue and digital outputs. Beeho commented: “Not only can we use one output to check the calibration of the other, but it also means we have the flexibility to use both outputs performing different tests. For example, we might use the analogue output to feed torque and speed data into the power analyser during a performance test, and then use the digital output for a temperature test. Here, we run the motor for 15 minutes at constant torque and see how hot it gets. The output from the TorqSense transducer allows us to close the loop so that we can keep the torque constant.” So, with its comprehensive testing procedures
built around the TorqSense transducers, Rotork Controls has the confidence that its electrically operated valve actuators will always meet the application requirements.
sensor technology t: 01869 238400
sensor solution for container loading
Combilift’s new CSS (Container Slip-Sheet) loading system enables fast and efficient freight container loading for the transportation of timber, flat-packed furniture, etc. This has a large platform where goods are pre-loaded on a powered steel slip-sheet. With integral laser-assisted container alignment and hydraulic levelling, the slip sheet and its payload are driven directly into the container hold using Combilift’s patented push-pull mechanism. Reducing the loading time of a full load to as
little as six minutes while ensuring safety and simplifying the loading process, the Combi-CSS control system relies on SGJ series cable extension transducers (CETs) from Variohm EuroSensor to monitor the slip-sheet’s position over CAN SAE 1939 for the loading and retracting procedure. The SGJ series CET was chosen for its industrial
grade quality and IP67 environmental protection rating. Its rugged glass-filled polycarbonate housing protects a precision high-cycle plastic hybrid rotary potentiometer in a spring-loaded cable and winding drum arrangement. The stainless-steel measuring cable is attached to the moving element in a ‘free-release’ tolerant design that safeguards against damage if the cable is accidentally released. Combilift chose the SGJ model with an integrated
CAN SAE J1939 output communication profile. The 0-80in measurement version (2032mm) provides an accuracy of 0.5% and a full-scale repeatability to 0.02%. The position data, in 12-bit resolution, and device status information is transmitted as ‘Proprietary B’ messages over the J1939 network. The Node ID, baud rate and date rate options are easily set using dip-switches, and versions are available with or without terminal resistors. The 80in travel version can be mounted in a volume of less than 100 x 67 x 127mm; and a larger 120in travel version is also available. CETs provide a cost-effective technology for long
travel linear displacement measurement. Variohm eurosensor
detecting the presence of cheese
At one producer, cheese portions are cut to size and sent along a conveyor to the packaging station. Prior to packaging, a buffering station regulates the flow of the cheese portions to give a predetermined spacing to suit the machine’s throughput, which depends on the dimension of the cheese portion being produced. To synchronise the packaging operation with the
buffering, a sensor needs to reliably detect each cheese portion, irrespective of its size, colour or texture, while ignoring the conveyor. For this application, the suitable sensor needed to be ‘food- grade’ with the ability to withstand aggressive cleaning agents, and be remotely adjustable. The 20 x 30 x 10mm background-suppression diffuse photoelectric sensors from Contrinex’s
1 design solutions MAY 2022 8
C23PA product family met the requirements. The sensor is mounted high above the product conveyor thanks to its 300mm sensing range. It is placed immediately after the buffering station and triggers the packing operation when it detects the presence of the cheese portion passing underneath. The sensors are rated to IP67 and are approved by ECOLAB for being able to resist cleaning with harsh food-grade cleaning chemicals. In addition to the standard PNP, normally-
open output and M8 connector, the IO-Link communication protocol for sensors is utilised for configuration between production runs. Rather than using IO-Link, the optional second
www.variohm.com
switched output is used for the preventative maintenance ‘stability alarm’. This is switched on if the sensor detects reduced performance.
Plus automation
www.food.Plusax.co.uk
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