Digital flowmeter adds DSP technology

Edited by the Engineeringtalk editorial team Sep 16, 2002

DigitalYewflo is the latest in a successful line of vortex flowmeters that have been pushing back the boundaries of flow measurement since their introduction by Yokogawa back in 1969.

DigitalYewflo is the latest in a successful line of vortex flowmeters that have been pushing back the boundaries of flow measurement since their introduction by Yokogawa back in 1969.

Built around the field-proven sensor technology of the popular Yewflo series of vortex flowmeters, but with the addition of an advanced digital signal processing system known as spectral signal processing (SSP), DigitalYewflo dynamically analyses the incoming signal from the shedder bar and isolates the flow signal from any accompanying noise caused by pipe vibration, pumps, valves or bends.

The SSP system takes advantage of Yokogawa's dual piezoelectric sensor design to analyse the signal from each sensor individually.

In addition, a high signal/noise ratio allows the instrument to deduce which portion of the signal is flow and which is noise.

An added benefit is the way in which the sensors measure the average flow across the whole of the pipe diameter for increased accuracy and repeatability and shorter straight-length piping requirements (typically ten pipe diameters upstream and five pipe diameters downstream).

In extreme cases of plant environmental noise, the SSP dynamically filters the signal while flow is present, removing the need for start-up tuning and avoiding interruptions to the process during operation.

The result is reduced commissioning and maintenance costs and consequently a lower overall cost of ownership.

Another equally important benefit of the enhanced signal-to-noise differentiation is the ability to provide stable and accurate flow measurement at lower flow rates than ever before, thus providing a more useful signal and further reducing operating costs.

SSP technology also affords the user unique diagnostic capabilities by providing alarms for such process anomalies as entrained gases.

These alarms are clearly defined on the DigitalYewlo's three-line display, which also simultaneously indicates flow, totalised flow and communication protocols.

Typical accuracy is +/-0.75% of reading for liquids and +/-1% of reading for gases and steam.

The rugged design enables use up to ANSI class 2500, and high-temperature (up to 450C) and cryogenic (down to -200C) versions are available.

All units are fully compliant with the current Pressure Equipment Directives and comply with the ATEX hazardous area approvals that come into force in mid-2003.

DigitalYewflo can also be supplied with an optional PT1000 temperature sensor installed in the rugged shedder bar.

This gives the unit the capability to measure volumetric flow and/or mass flow and/or temperature.

This is particularly useful in saturated steam applications where the installed steam tables can be used to output compensated mass flow with no need for additional sensors or flow computers, reducing costs and also limiting the number of potential emission points.

The dual analogue and pulse outputs can also be used to output flow and temperature simultaneously.