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FLOW & LEVEL CONTROL MEASUREMENTS IN PARALLEL
Coriolis instruments enable flow and concentration measurements in parallel. In an interview, Dr Jana Knall, product manager for Coriolis flow instruments, Endress+Hauser, explains how this benefits the process control industry
instrumentation specialists to work together hand in hand. Technologies that measure new parameters or provide previously unattainable levels of accuracy play a decisive role here. One example is measuring flow and density in demanding applications with the “multi-frequency technology” at the core of the Proline Promass Q from Endress+Hauser. Q: Dr Knall, Coriolis instruments are first and
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foremost mass flowmeters, but now you’re putting the spotlight on concentration
uccessfully controlling complex processes requires operators, equipment manufacturers and
Concentration measurements play a major role, especially in the food industry
measurements with these devices. Isn’t that merely a niche application? A: On the contrary! It’s precisely the
combination of flow and concentration measurements that is attractive for many users. At the end of the day, for many operators, measuring concentration is not the only task. What really interests most of them is being able to control their process. For instance, they want to know the dosage of a material or substance at the beginning in order to achieve the desired output at the end. In other words, they want a reproducible end product. Or take an application that requires dosages of costly solvents or additives. In this
NON-INVASIVE AND NO DOWNTIME TECHNOLOGY
chloride. A vortex meter was used for quantity measurement and downstream valve control, however valve vibrations were interfering with the measurement, resulting in errors. Receiving plants plan their operation based on exact amounts of hydrochloric gas, and the
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inaccurate vortex measurements made this impossible. Site operators urgently needed a reliable replacement with no downtime for removal of the defective measuring device. Following a convincing demonstration, a permanent FLUXUS G721 flowmeter was installed
for non-invasive flow measurement of the hydrochloric gas. This meter has since been reliably recording the hydrogen chloride levels generated in the MDI plant and delivered to the site, ensuring the operation of the downstream production plant, and avoiding a plant shutdown. Another major chemical company also benefits from FLEXIM’s clamp-on ultrasonic
system’s accurate measurement of hydrochloric gas at the inflow to an absorption column. Historically, a venturi flowmeter installed in the gas supply line ensured the hydrochloric acid
accurate readings.
concentration was regulated to guarantee efficient operation. The added quantity of demineralised water must be metered in accordance with the measured amount of HCI gas. However, the low pressure of the HCI gas and the tallying low differential pressure to be tapped became a problem with this measurement. The moist HCI gas is highly corrosive, so the pipelines are made of plastic. The plastic venturi pipe needed two shut-off valves for installation and maintenance. Maintenance work also required breathing apparatus. FLEXIM’s non-invasive flow measurement was the answer to this challenge, proving reliably
www.flexim.co.uk
28 MAY 2022 | PROCESS & CONTROL
roducing methylene diphenyl-diisocyanate (MDI) as part of the polyurethane production chain, the plant of a major German chemical manufacturer is not only important in terms of the final product, but also supplies the site with pure gaseous hydrogen
case it’s about conserving valuable raw materials as well as achieving a particular mixing ratio. Q: Aren’t there more suitable methods for
defining the material quantities? A: Which methods are suitable for
measuring concentrations depends heavily on the measurement task. Sum parameters such as density are sufficient for many applications. It comes down to what the user already knows and how easy it is to use a method in the real world. The transfer mindset of “lab to field” is especially important here. For a lot of users, being able to use known lab measurement parameters in the process is extremely helpful. Density as a measure of concentration for known mixtures of substances is a very common sum parameter. We are noticing more and more that a lot of users have extensive experience with measurement parameters, have become accustomed to using them in lab environments and like to control their processes with them. While this is a good fit for us, it also creates difficulty in managing certain expectations. Q: What expectations are we talking about
here? Where exactly is the issue? A: Well, one frequent source of errors is
performing a like-for-like comparison of the values measured in the lab and in the field. The lab is typically a highly regulated environment, while in the field the opposite is usually the case. Q: Can you give an example? A: Take brix, for instance, a unit of
measurement traditionally used to monitor concentrations in liquids. Brix is the sucrose, or sugar content, of an aqueous solution and as a result is used to determine the sugar content of fruit juices or syrups. The spindles that have long been used are based on this scale and,
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