AR-001175 Emerson
INDEPENDENT INTELLIGENCE FOR THE GLOBAL BUNKER INDUSTRY
www.bunkerspot.com
Volume 6 Number 2 April / May 2009
BUNKERING OPPORTUNITIES:
Technology and teamwork
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I
nterest in Coriolis direct mass
f low measurement is increasing
for marine applications, and fuel
bunkering in particular. Coriolis
technology provides measurement of
mass f low rate, volume f low rate, density,
temperature and batch totals – all from
a single device. Coriolis meters have no
complex moving parts and require no
maintenance, nor do they require f low
conditioning or straight pipe runs. Flow
and density accuracies of +0.1% and
+0.5 kilogrammes per cubic metre (kg/
m 3) result in unmatched performance
and measurement certainty, making
Coriolis technology an attractive
alternative for fuel bunkering.
While Coriolis measurement is well
suited for fuel bunkering, there are other
considerations and challenges that must be
overcome to ensure optimal performance
in marine applications. These include: the
ability to handle entrained gas; performance
in measuring viscous f luids; and the
importance of technical application expertise
to promote proper installation and operation
practices.
On the other hand, the mass of a gas is so
small that it does not contribute significantly
to the total mass of the mixture. Therefore,
even though a Coriolis meter measures
mixture mass f low rate when a liquid and
gas are present, the mixture mass is nearly
identical to the liquid mass, which is the
quantity needed. So while a volumetric
meter over-predicts liquid quantities by
about 5% in the presence of 5% gas, a mass
f low meter only over-predicts by 0.01% at
typical barge pressures. This is because the
mass of a gas is negligible compared to the
liquid mass.
However, the presence of two-phase
f low can cause significant additional noise
in the measurement signal of a Coriolis
meter and tends to reduce measurement
accuracy. Emerson’s Micro Motion Coriolis
meters answer this challenge directly –
improvements to the sensor stability coupled
with state-of-the-art digital signal processing
algorithms to handle the additional noise –
to deliver accurate, reliable measurement that
is f lexible to changing f luid conditions.
-PN\YL
DĂƐƐǀƐ͘sŽůƵŵĞǁŝƚŚŶƚƌĂŝŶĞĚ'ĂƐ
ϰϬ
Joel Weinstein is a research and applications engineer
for Micro Motion, a division of Emerson Process
Management, which developed and manufactures the
Coriolis flow meter.
Dr Weinstein has recently completed a five-year joint
research project with the University of Colorado
focused on improving Coriolis measurement with
entrained gas for difficult industrial applications such
as fuel bunkering.
Contact:
Joel Weinstein
Tel:
+1 303 530 8415
Fax:
+1 303 530 8596
Email: [email protected]
34
Two-phase flow
ϯϴ
Whether due to tank stripping, turbulence
during f illing or when changing
compartments, it is easy to get gas trapped in
heavy fuel oil (HFO). When gas is entrained
in bunker fuel, it can take considerable
time for it to be released, so measurement
equipment must be able to deal with the
presence of two-phase f low. But before
accuracy can be considered, it is necessary to
determine what measurements are the right
ones when multiple phases are present.
Consider three measurement devices – a
mass f low meter, a volumetric f low meter,
and a tank gauge – all measuring bunker
fuel with 5% entrained gas. Even though all
meters are working perfectly, the volumetric
meter and tank gauge both give liquid oil
batch errors of +5%. The reason for this
is that each meter simply measures what
is going through it, which in this case is a
mixture of gas and bunker fuel. The operator,
however, interprets the measurement as a
liquid volume. Because gas has such a low
density, it takes up a lot of space, and is
interpreted by the operator as a large volume
of oil.
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www.bunkerspot.com
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Joel Weinstein considers
the challenges that are
being overcome in order
to introduce Coriolis
technology to the bunker
industry
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The data in Figure 1 illustrates the benefit of
Micro Motion Coriolis mass measurement in
the presence of entrained gas. In the graph,
liquid-only reference meter measurement
is indicated by bold lines, and test meter
measurement by thin lines. The mass f low
rate of the test meter closely tracks with the
reference meter when 5% gas is entrained.
The test meter also correctly indicates the
mixture volume f low rate, although this
value is about 5% greater than the liquid
volume f low rate given by the reference
meter. Both measurements are correct, but
an operator needs liquid-only quantities, not
mixture quantities, and therefore only the
mass f low measurement is acceptable. Only
when measuring in mass is the liquid energy
content – the quantity of bunker fuel oil paid
for – unaffected by entrained gas.
April / May 2009
bunkerspot
Online Metering
THECHALLENGES
An added benefit of Micro Motion
Coriolis measurement is shown by the Drive
Gain data represented in Figure 1. The
Drive Gain output is a powerful diagnostic
tool to check for gas or other impurities
during bunkering operations. When gas,
liquid, or solid particles of differing density
than the bulk f luid are entrained, vibration
of the f low tube requires more energy and
the Drive Gain output immediately rises.
Drive Gain is more reliable than density as a
diagnostic for entrained gas because density
is also affected by changing f luid conditions
such as composition and temperature.
Measurement of viscous fluids
Heavy fuel oil or bunker fuel is thick, viscous,
and in many cases must be heated to f low.
With no moving internal parts to clog or
wear down, Coriolis meters offer advantages
over other mechanical f low measurement
devices. Even more importantly, Coriolis
meters are calibrated on water, which directly
transfers to measurement of any f luid – from
gases to viscous oils. Also, mass of oil is
conserved regardless of changing temperature
and pressure, making f luid look-up tables
unnecessary. The result is an easy-to-use,
robust device that is capable of both accurate
measurement and lasting performance in the
most challenging of conditions.
Emerson regularly pursues independent
third party testing of its Micro Motion
Coriolis meters to ensure performance on
difficult f luids. The data from the Société
du Pipeline Sud-Européen (SPSE)
laboratory in France (represented in Figure
2) shows excellent performance from the
Micro Motion CMFHC3 Coriolis meter on
widely varying f luid types, including fuel
oil, all from a single water calibration. MID
and OIML certificates have been awarded for
+0.2% mass accuracy on liquids.
-PN\YL
NMi certification testing at SPSE in France, May 2008, CMFHC3 .
Widely varying viscosities and densities. Meter passes all tests and is
certified for +/- 0.2% mass measurement on products other than water
1.0%
0.8%
0.6%
Mass Flow Error
0.4%
0.2%
0.0%
-0.2%
>ĂďhŶĐĞƌƚĂŝŶƚLJ>ŝŵŝƚƐ
-0.4%
-0.6%
-0.8%
-1.0%
0
500
1000
1500
Volume Flow Rate (m^3/hr)
Fuel oil
bunkerspot
ARH
Oural
April / May 2009
Naptha
2000
Technical expertise
Even with a Coriolis meter that can
handle two-phase f low and offers proven
performance measuring highly viscous
f luids, the importance of technical
application expertise cannot be overstated.
In order to maximise the performance
of Coriolis measurement in bunkering
applications, it is critical to consider
installation best practices and be able to
rely upon actual, real-world experience.
Of the measurement challenges that exist
in marine applications, and bunkering in
particular, ensuring proper installation to
minimise – and in some cases completely
eliminate – entrained gas, is critical. In
order to further understand the specific
operational trade-offs, but installations B
and C have proven to be the most effective
for applications involving batching from
empty pipes. The reason is that when the
batch begins, the long empty pipeline
completely packs before f luid enters the
meter. Even a slight elevation increase,
such as in schematic B, can dramatically
reduce gas entrainment during a batch.
Other issues such as drainability, product
hold-up, and available deck space are
important and should be considered
carefully for each application. Many simple
and effective measures can be taken to
allow for the best possible performance
and ease of use in difficult metering
applications.
-PN\YL
measurement challenges, Emerson has
visited numerous global customers who
experience multiphase f low. It is clear that
application requirements are extremely
diverse, and that specific guidance on
installation and operation best practices
for bunkering is imperative to ensure
operational performance. For example, the
meter must be sized so that velocity in
the f low tube is relatively high during
bunkering, which ensures a homogeneous
mixture if gas is present. Careful placement
of the meter on board can reduce or
eliminate entrained gas, while intelligent
valve sequencing allows barge pipelines to
properly pack before f luid enters the meter.
Consider the schematics A, B, and C for
meter placement in a bunkering application,
represented in Figure 3. Which is the
most effective installation? The answer, of
course, involves a set of performance and
www.bunkerspot.com
Summary
There are many benef its to using
Coriolis direct mass f low measurement
in bunkering. Inherent advantages, such
as multi-variable measurement and no
moving parts are shared among all Coriolis
meters. However, the challenges for fuel
bunker measurement are clear. The
ability to maintain ongoing measurement
performance and reliability in the presence
of entrained gas or two-phase f low is not
characteristic of all Coriolis meters. Nor is
the ability to deliver accurate measurement
in the presence of highly variable process
conditions. It is important, therefore, that
measurement devices installed can deliver
needed technical performance in harsh
conditions, and that device installation and
operations are backed with proven Coriolis
application expertise in fuel bunkering
applications.
35
BUNKERING ♦ SHIPPING ♦ TERMINALLING ♦ POR T SECURIT Y ♦ CREDIT AND FINANCE
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6-8 JULY 2009, THE LABADI BEACH HOTEL, ACCRA, GHANA
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