SAW flowmeter in use in a dairy
Hygienic, compact and suitable for a variety of media – Collaboration with the dairy company Molkerei Hainichen-Freiberg
The FLOWave flowmeters meet the most stringent hygiene standards. Since they work without the need for electrical conductivity, Molkerei Hainichen-Freiberg uses them to measure the flow of ultrapure water in the production of baby food.
Ultrapure water in the drying production lines
In 2018, after the commissioning of a new reverse osmosis system, the production lines in the drying area were completely converted to ultrapure water while they were in standby mode. Danilo Beer, Team leader and Deputy Production Manager (Drying) at Hainichen-Freiberg says: “The demineralised water has a very low conductivity of less than 5 µs/cm. The magnetic-inductive flowmeters that we were previously using in the production line were no longer suitable for this purpose. That is why we started looking for a hygienic flow sensor that also measures without conductivity.” The Freiberg company found what it was looking for at Bürkert. They opted for the FLOWave flowmeter, which operates by the patented SAW (Surface Acoustic Waves) process and is suitable for different media, regardless of electrical conductivity, i.e. for ultrapure water as well as for whey or milk.
A measurement method with many advantages
This measurement method has additional advantages: there are no built-in parts or constrictions in the measurement tube and therefore no dead spaces. The measurement tube behaves just like a straight pipeline, which means that nothing can get trapped. In addition, measurements are taken without any contact between the sensor elements and the medium. This means that the fluid has no impact on the sensor elements, nor is there any risk of contamination of the medium. This is hygienic and makes cleaning easier (hygienic design). Since the flow in the measurement tube is no different from that of any other straight tube section in the system, there is no pressure drop. The measurement functions with non-flowing liquids as well as with fast flows or when the medium changes. In addition, the SAW flowmeters are lightweight. The FLOWaves used in drying have a nominal diameter of 50 mm and weigh only around 3.5 kg, so can be easily installed or replaced by one person. The installation position is flexible, ensuring that the display can be easily adjusted for readability and that the flowmeter is easily accessible for configuration during commissioning. During operation, the flowmeter consumes significantly less energy than, for example, Coriolis flowmeters, which are also usually larger and heavier. In addition, no maintenance is required, which further reduces operating costs.
There are no fittings or constrictions inside the measurement tube, so nothing can get trapped or stuck. “This is very apt for us, given our high hygiene requirements in milk powder production.”
A variety of media
A total of eight of these SAW flowmeters are currently in use in the drying process. They measure ultrapure water during standby mode when production is running, but also other media. Three flowmeters are installed before the so-called evaporators. “The flow rates here are considerable,” adds Danilo Beer. “We are getting 20,000 litres per hour.” Two flowmeters are also used in the subsequent heating process, as well as on the feed systems for the spray tower. With the help of the fluidics experts, we were even able to overcome some particularly complex challenges. Danilo Beer recalls: “At a certain point in the production process we need to measure the flow at a dry content of 60%. This is inherently not possible with the SAW process. Nevertheless, a suitable solution was found that was easy to implement.” The FLOWave measures the ultrapure water flow in standby mode. If this is then switched over to the medium during the production phase, the unit detects this and sends a signal to the magnetic-inductive flowmeter which is also deployed at this location, which then takes over the measurement.
Flowmeter before the evaporator
“The fluidics experts also quickly implemented software adjustments that proved necessary during commissioning.”
Accurate and future-proof
Over the period since they were installed, the SAW flowmeters have proven themselves in practice and have impressed with their reliability. They measure the volume flow with an accuracy of ±0.4% of the measured value. At the same time, the temperature measurements are accurate to within <1 °C. The temperature range of -20 to 140 °C is designed to accommodate both CIP and SIP cleaning processes. There are therefore many different settings in which this technology is typically deployed, and not only in the food industry. The devices offer either digital interfaces (via a M12 connector) or are alternatively available with an analogue 4–20 mA interface. Variants with digital data display on site are available, as well as a FLOWave L version with ATEX approval for use in potentially explosive areas, e.g. when measuring alcohol or volatile oils. FLOWave is available for large nominal diameters up to DN 80 and weighs only 6 kg compared to comparable sensors that can weigh up to 240 kg. Even small nominal diameters up to DN 8 are available as standard variants, e.g. for pharmaceutical and cosmetic applications. The installation and removal of FLOWave, as well as recalibration, if required, can be easily carried out by one person.
Flow measurement on the feed system for the spray tower
“At a certain point in the production process we need to measure the flow at a dry content of 60%. This is inherently not possible with the SAW process. Nevertheless, a suitable solution was found that was easy to implement.”