Non Intrusive Flow Meter

In fact, non-invasive flow measurement with clamp-on ultrasonic transducers is based on the fact that an ultrasonic signal radiated into a medium flowing in a pipe, propagates faster in the direction of flow rather than against it. The difference between the signal transit times both in the direction of flow and against it, can be measured very accurately and is proportional to the flow velocity in the pipe. The measuring transmitter calculates the volume flow rate based on the geometric parameters of the measuring point entered and the physical properties of the medium which are stored in the internal media database.

In order to set up a flow measuring point with clamp-on ultrasonic technology, there is no need for any pipe work which means there is no production downtime. However, the benefits of non-invasive measurement are by no means confined to its speedy installation: clamp-on ultrasonic transducers are not subjected to any wear by the medium flowing in the pipe and they do not cause any pressure loss whatsoever. In addition to that, the inertia-free, acoustic method has high measuring dynamics and works independently of the flow direction of the medium. Thanks to these advantages, non-invasive measurement technology has long been established as a standard method in the processing industry.

Especially in chemical processes the volume flow rate is often less interesting than the temperature and pressure-independent mass flow rate. The stoichiometric formulae of chemistry signify mass ratios. It is also a question of dosing the correct amount of substances in the form of mass proportions during the process on an industrial scale. The fact that the phase displacement recorded on the vibrating tube of the flowmeter is directly proportional to the mass, is quite undeniably a huge advantage of this measuring principle.

Particularly in the chemical industry where aggressive and toxic media are often used, plant operators like to fall back on non-invasive, clamp-on, ultrasonic technology. The fact that the ultrasonic flowmeter measures the volumetric flow rate is usually put into perspective quickly, as the volume and mass of a substance are linked by density. Many processes are generally performed under constant conditions so that engineers can safely enter the density into the measuring transducer as a constant value and calculate the mass flow rate instead of the volume flow. Non-invasive mass flow measurement is hardly more complicated, when only the temperature changes. In this case, just the temperature must be recorded on the measuring point and fed into the temperature input of the ultrasonic system.