Sensing change in food & bev needs
11 May 2015
Ever-changing and more exacting operating conditions in the food and beverage processing sector are placing greater demands on the sensors that take the measurements that are vital to safe and effective operation, as Charles Dowling of Morgan Advanced Materials explains
In applications such as milk metering and beverage dispensing, accurate sensing is key to ensure the correct filling of containers. Systems can operate at pressures of up to 50 bar due to the high-specification pumps used to maximise fluid throughput, but with sensors only able to be around 10mm in diameter due to the space constraints within most processing systems, materials which are thin yet physically robust have to be selected – meaning highly sensitive ceramic transducers are sometimes the only option.
Positive displacement meters which consist of two cogs, are used in many applications but cannot distinguish between fluids and gases, causing severe measurement error if any air is trapped in the system. Furthermore, the frictional method of operation of these systems can potentially result in smaller particles breaking off from the sensor body and entering the fluid being processed, with potentially serious ramifications for the end consumer – and therefore for the processor. Not only can ultrasonic sensors distinguish between fluids and gases – ensuring accurate dosing – but the sensing option is solid state technology, eliminating all moving parts and preventing any sort of wear. They are also chemically inert, meaning they will not be adversely affected by the presence of alcohol or solvents.
A meter able to operate in high temperature applications up to 150ºC has traditionally been accompanied by a premium price, with the most common choice being a coriolis flow meter. These products are without doubt highly accurate but, in tandem with their cost, their footprint is significantly larger than that of alternative technologies such as ultrasonic sensors, creating major headaches for system designers.
Other technologies commonly used in food and beverage applications include electromagnetic flow meters. However, due to their mode of operation, these systems are only suitable for use with conductive fluids, limiting their effectiveness and meaning the only option for use with fluids such as sterilised water is an ultrasonic sensor.
Ultrasonic sensors are not just used to control the flow of materials within the process itself. Just as important is ensuring processing equipment can operate safely, effectively and without interruption. As in any production process, an appropriate lubrication regime is key, with insufficient lubricant likely to lead to overheating, physical damage to equipment, and unscheduled downtime. Many applications also require the use of coolants. Once again, the small footprint of ultrasonic sensors allows them to be located, for example, within gearbox housings where they can provide real time information on coolant or lubricant levels, feeding this data back to the control room and informing decisions on when a top-up or replacement will be needed.
With high sensitivity, wide bandwidth, and stable electrical properties demonstrated even at very high temperatures and pressures, ultrasonic sensing represents an efficient option for specifiers requiring optimum accuracy and physical performance in these highly demanding applications.
Also available from Morgan Advanced Materials is a range of high quality mechanical face seals, bearing, bushings, vanes, and rotors, ideal for use in fluid processing applications, manufactured from a variety of carbon/graphite grades, and silicon carbide which have received a favourable letter of opinion from the US Food and Drug Administration (FDA) for use as repeated-use, wear components in food applications.