Meeting the challenges of flow and level measurement

July 6, 2022 Editor

Chris Callander explores some of the challenges of flow and level measurement applications in the food and beverage sector and looks at some solutions available to help overcome them.

There are many challenges when measuring level and flow in food processing applications. However, ongoing developments in sensing technologies and the way they are applied is making accurate measurement increasingly attainable. This is a fundamental requirement as the sector faces an ever-greater focus on managing hygiene, ensuring product quality and minimising waste.

Flow

Flow measurement is a critical tool for many food and beverage manufacturers as the industry has a diverse range of processes that require the precise control of liquid flow rates. Production processes, including filling vessels or bottles, measuring liquid ingredients, and controlling cleaning processes, require varying degrees of complexity and accuracy to ensure consistent product yield and minimise wastage.

Neil Hannay, Senior R&D Engineer with ultrasonic flowmeter specialist, Titan Enterprises, explained: “Although there are a wide variety of general flowmeters on the market, only a few high-performance measuring devices will ensure that the vital high levels of hygiene and precision are maintained for applications in the food and drinks sector.”

ifm electronic’s LW2720 sensors can produce dependable results where agitators and the like are present.

The physical properties of each liquid can lend additional complexities to the choice of flow measuring equipment. Whether the liquid is viscous, volatile, corrosive, flammable, or containing solids, for example, or needs to be maintained at a high temperature, are key factors for consideration when specifying a suitable flow meter.

“Flow monitoring of high viscosity liquids, such as cooking oils, sauces and syrups (e.g. syrup injections in beverage lines) requires devices which provide highly accurate flow measurement, such as Titan’s oval gear (OG) flowmeters,” added Neil. “Unlike other flowmeters, measurement accuracy of OG flowmeters improves as the liquid viscosity increases, from a nominal 1% to around 0.1% of flow rate at higher viscosities.”

For low viscosity liquids such as water, beer, wine and spirits, Titan has a solution designed to give high performance over six flow ranges from 0.05 to 15 l/min. Neil explained: “Our NSF-approved 800-series of beverage flowmeters can provide a low-cost drink-dispensing solution. These devices have totally non-metallic NSF-approved wetted components making them ideally suited to applications where food hygiene and precision flow measurement are required.”

In processes where ingredients need to be maintained at high temperatures – chocolate, for example – a flowmeter designed for applications requiring precise flow measurement at elevated temperatures would be needed. Again, Titan has a solution, as Neil concluded: “Capable of operating up to 110°C, Titan’s inline non-invasive Atrato ultrasonic flowmeter is largely immune to viscosity and offers excellent turndown and repeatability.”

Level

Sensing the level of liquids in tanks is a common requirement. This may sound very simple, and sometimes it is, but often level measurements are required in tanks where agitators, stirrers and scrapers are being used, where steam and condensates are present or where foam has been created. In these circumstances, traditional level sensors cannot be relied on to give accurate and consistent results.

Andy Walker, Product Sales Manager at ifm electronic, explained how this could be overcome: “A solution that’s been around for a while is the use of radar level sensors which work by sending out a beam of radio waves that is reflected by the surface of the liquid in the tank. The sensor measures the time it takes for the reflected wave to return and uses this to determine the level of the liquid. This is an excellent principle, but radar level sensors are not all created equal. Some versions, for example, emit a wide beam of radio waves which limits both their accuracy and their range.

“These issues have been addressed in ifm electronic’s LW2720 sensors by using radio waves at a frequency of 80 GHz. This allows a very narrow beam angle to be used so that liquid levels can be measured with an accuracy of ± 2 mm at ranges of up to 10 m. The narrow beam angle also ensures that the sensors produce dependable results where agitators and the like are present. In addition, their accuracy is unaffected by changing pressure and temperature, or the presence of vapours. In short, these new sensors are solving many problems for our customers which would be hard to tackle in any other way.”

The difficulties sometimes faced in level measurement are not limited to liquids; the ability to optimise the material flows of powdered ingredients, for example, flour or sugar in silos, has also been limited.

Operators often have no choice but to settle for a switch point level indication. Attempts to use a non-contact measurement using radar or optical devices could be defeated when the signal is disrupted by dust, moisture, build-up of residue, or other obstructions in the vessel.

Darren Pratt, SICK’s UK Product Manager for industrial instrumentation, explained how his company’s radar sensor solutions could handle these applications: “The SICK SicWave is an innovative non-contact radar sensor for high-availability non-contact continuous level measurement. It uses high frequency 80 GHz free-space radar, a thousand times more sensitive than previous-generation 26 GHz radar technologies, to ensure high availability in even the most challenging conditions. The narrow field of view also avoids the potential for false signals caused by deposits on walls or by other obstructions inside the vessel and ensures focused alignment to enable simple and rapid set-up.

“Remote set-up and interrogation of the sensors are straightforward, either using the onboard WPAN interface to a smartphone or tablet via Bluetooth or through standard HART communication, which also enables easy integration with higher-level controls and diagnostic systems.”

An ideal solution for handling bulk solids level measurement, SicWave also offers a fluid-focused solution, as Darren added: “The SICK LBR SicWave is a bulk solids level sensor with a range up to 120m, and the SICK LFR SicWave is a fluid level sensor with a maximum range of 30m.”

As food production processes become more sophisticated and the requirements placed on food manufacturers by legislation and their supply chain intensify, ever-greater demands are placed on the equipment used in process lines. Thankfully, where flow and level measurement are concerned, innovations from those companies supplying the equipment are rising to the challenge.