Page 21 - Gi February 2019 - flipbook

FIGURE 1 Typical problems that can occur, which cause mismeasurement
(Han van-Dal, 2018)

Ambient temperature influence Leaks

Ice formation Plugged impulse lines
Disturbed flow profile

Transmitter drift and shift Blockage Debris
Wear Corrosion Damage Pulsating flow

Solids Proving problems Out of range
Calibration errors
Two phases (gas in liquid, liquid in gas) TYPOS

Non-compliance with measurement standards

and vendor recommendations (installation,
geometry, fluid properties, calculation boundaries)
Wrong configuration settings

laboratory, while other measurement process conditions, and definitely far
devices are compared with a traceable from laboratory conditions.
reference device or fluid and, if Due to the high performance
necessary, recalibrated. expectations of these critical
The testing frequency depends on a measuring systems, manufacturers
number of factors, including the have developed sophisticated
relationship between the buyer and methods of checking their health
seller, and some operators have been and accuracy, including
known to test liquid flow meters mismeasurement management
FIGURE 4 Cloud and PC verification before each transfer. (MMM) software, utilising virtual
software provides verification flow computing technology and
of flow measurement devices
SO WHY IS THERE A NEED measurement device verification.
TO TEST THE SYSTEM
ACCURACY SO OFTEN? WHAT IS VIRTUAL FLOW
national/international standards to Measurement devices are expected to COMPUTING AND HOW IS IT
ensure measurement traceability. operate at the highest levels of INVOLVED IN CALCULATING
The level of integration of device accuracy. In practice, however, the MISMEASUREMENT?
data into the flow computer and systems can be operating outdoors in Virtual flow computing involves
higher level systems, such as remote harsh environments with non-ideal mathematically modelling the system
terminal units (RTU) and SCADA and using live data to predict and
systems, is primarily focused on match actual measurement data.
process variables and alarm functions. When a fault condition occurs –
However, these devices contain a FIGURE 2 Meter diagnostics display of such as three-hour loss of pressure
rich source of diagnostic information SpiritIT SmartCen measurements the MMM software
which is largely unused by operators uses – the mathematical model, logs,
and maintenance teams. historical data trending, alarms and
Small errors in custody measurement other information sources calculate
data translate into incorrect billing that the mismeasurement and a report is
will negatively impact the revenues of generated incorporating the
the seller or buyer. recalculated figures.
Companies therefore invest The approach described is a highly
significant sums of money testing sophisticated method of dealing with
their measurement devices to everyday occurrences that can
minimise measurement errors. improve a company’s top and bottom
Flow meters are typically proved in line performance.
the field and/or recalibrated in a test An example of an available MMM

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