Mass flow and concentration meter for sulphuric acid and oleum

Measurements on the safe side

Sulphuric acid is one of the most important raw materials in the chemical industry. Its manufacture and processing calls for the use of highly robust technology. The Piox S721 SA ultrasonic system non-invasively measures the concentration, density and mass flow of the acid flowing inside using clamp-on transducers mounted on the outside of the pipe.

Clamp-on ultrasonic technology has always been preferred where the medium to be measured is reason enough not to open the pipe if at all possible. Other positive arguments in favour of non-invasive measuring technology, such as the unrivalled ease of installation and unimpaired plant availability, mean that today it is no longer just challenging media that are measured non-invasively. The Piox S721 SA clamp-on ultrasonic system from Flexim combines non-invasive flow measurement with simultaneous non-invasive determination of concentration and density, offering users maximum convenience.

At Flexim, Piox stands for the process analytics product line. Like their Fluxus counterparts, Piox S clamp-on measuring systems work with ultrasonic transducers mounted on the outside of the pipe to measure the acoustic velocity in the medium. This depends on the medium density – and therefore also on the temperature – and is specific to each substance. The Flexim Piox S721 SA on show at Achema is the first representative of a new generation of measuring systems for simultaneous, non-invasive measurement of mass and volume flow, density and concentration.

The measuring system is based on the powerful hardware of the Fluxus F721 and was specially developed for use in the sulphuric acid and oleum manufacturing and processing industries. The substance dataset, which maps the relationships between the concentration, density, temperature and acoustic velocity parameters of sulphuric acid and oleum, is therefore preconfigured in the device. The acoustic velocity of aqueous sulphuric acid solutions is dependent on the concentration and changes significantly at high concentrations, which is where the measuring effect is best. The Piox S721 SA is hence the instrument of choice for non-invasive, online concentration monitoring of highly concentrated sulphuric acid (i. e. from about 80 to 100 % by mass). Mass flow measurements are possible at a constant density over the entire concentration range.

Huge scope of applications

The production and industrial use of sulphuric acid and oleum are characterised by challenging operating conditions. Production takes place in exothermic reactions with correspondingly high temperatures; both substances are highly corrosive. As basic chemicals, they are manufactured in large quantities requiring large pipes to match. Safety and the highest possible plant availability are just as crucial for manufacturing as they are for processing. The non-invasive measuring technology provides the perfect solution to all of these challenges: since clamp-on ultrasonic transducers are simply mounted on the outside of the pipe, they are not subjected to any wear and tear by the medium flowing inside, no matter how corrosive or contaminated with abrasive particles – a typical problem in metallurgical processes. In the opposite direction, clamp-on measuring technology poses no risk of contamination, which is particularly important when producing or using high-purity sulphuric acid. Once installed, the measuring system is permanently maintenance-free and works without any drift. The clamp-on ultrasonic transducers can be operated directly on the pipe up to a temperature of 200 °C. Flexim’s Waveinjector was developed for higher temperatures. This patented sensor mounting device extends the range of use for non-invasive measuring technology from cryogenic temperatures to more than 600 °C.

The measuring point is set up during ongoing operation and does not disrupt production in any way. The installation work is minimal and requires no lifting device. To attach the clamp-on transducers, the technician simply needs access to the measuring point. Since there is no need to open and empty the pipe, no welding work is necessary and no flange connections have to be made. The measuring system can always be installed in the main stream without a bypass. All measurements are thus carried out on the safe side. The Piox S721 SA is offered in three design variants covering nominal diameters from DN 25 to DN 2000.

Fit for Industry 4.0

The Piox S721 SA supports all common communication protocols. Hart, Modbus, Foundation Fieldbus, Profibus PA and BACnet allow bidirectional field communication, parameterisation and online diagnostics. User-defined configurations ensure optimum adaptation to the respective application. The Fluxdiag software opens up extensive possibilities for transmitting, visualising and evaluating measured values or diagnostic parameters. The latter, in particular, not only help assess measurement quality but also provide important evidence of changes in the process. Remote, worldwide access to the measuring system is possible as an option.

Online search: cpp0318flexim

Author: Jörg Sacher

Press and Public Relations,


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