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Submitted
Articles: ARTC03112501
Article: Optical Flow Meters
Submitted
by: Photon Controls
Submit date:25/11/03 |
Optical Flow
Meters
Photon Control is currently developing a line of optical
flow meters for use in measurement of the flow rates of
gases and clear liquids in process control and custody
transfer applications. This market worldwide is estimated
at 7 billion dollars per annum and growing. Global construction
of pipelines is expected to place extraordinary demand
for meter manufacturing capacity worldwide as China begins
a rapid program of gas pipeline infrastructure construction
in the upcoming decades
One thing which sets Photon Control apart from its competitors
in the sensor and flow meter markets is the fact that
no wires or electricity are involved in the areas where
measurement is conducted or where the signals are transmitted
to a data collection system. In both of these areas, only
light and optical components are present. Not only does
this protect against accidental ignition of combustible
vapors, it also makes these devices immune to electromagnetic
interference. We think both these traits make our units
attractive today, and will do even more so in the future
There are other important advantages of the future Photon
Control optical flow meter products which are:
Size and Form Factor. Because the measurement is made
in a direction orthogonal to the axis of the pipe, it
requires very little length. This means that it may be
possible to place an optical flow meter in an existing
flow system with virtually no cost of installation, or
for very low cost in new piping.
Large flow range measurement. Early estimates are that
velocities ranging from 0.3 to 100 meters per second should
present few problems making the optical flow meter range
the largest of the available technologies.
High Accuracy. The optical flow meter is capable of measuring
flow with an accuracy better than 0.5% which makes it
suitable for fiscal gas metering.
Immunity to Swirls or Other Non-Axial Flows. A very significant
advantage of our technology is that the meter measurement
is not adversely affected by the swirl of gas in the pipeline
and which requires significant remediation and expense
for other meters.
No Obstruction in Pipes. Because there are no elements
protruding into the pipe, there is no pressure drop or
other effect on the flowing gas as a result of the measurement.
This can save the costs and infrastructure related to
repressurizing the pipeline and will also prevent damage
from flow anomalies. In steam measurement for example,
a very significant amount of damage is caused by the “hammer”
of high pressure condensate which routinely builds up
in the flow.
Price-Manufacturing Costs. We believe the small, non-fiscal
versions of the meter can be sold at a price of less than
USD 3000 which should allow us to displace inferior devices,
such as variable-area meters in many process control applications,
and to provide affordable measurement in other places
where today no measurement is the norm.
Ability to Operate at Any Pressure. There is no reason
why this device won't work at pressures ranging from atmospheric
up to 1000 bar which makes it suitable for a number of
applications for which there is not a good metering solution.
Integral Optical Sensors. The fact that pressure and temperature
sensors could be bundled together in a compact, all-optics
package is a strength.
Bi-Directional Flow Measurement. The optical flow meter
can measure flow in either direction for applications
where flows must be reversed. Another feature shared with
few other meters.
Multi-phase Flows. Optical methods can distinguish gas
and liquid fractions in the flow due to their distinct
optical properties.
Beyond flow, there are other elements in the flowing gas
which can be measured optically for further diagnostic
or process purposes. For example, it should be straightforward
to determine the distribution of particle sizes in the
gas. A later project will incorporate infrared (IR) absorption
technology to determine constituents of the gas. Also,
it should be possible to use the technology to measure
the flow rate of clear liquids as well as gas
Given all these perceived advantages and the many markets
that look particularly attractive for the optical flow
meter, Photon Control has chosen to concentrate on developing
the highest priority meters by engaging with major customers
The first priority meter opportunities that have emerged
are:
Low-Pressure Natural Gas. In many parts of the World,
flow measurement is not practical because there is no
reliable and economical means of metering gas flow at
atmospheric pressure. One prime example of this is coal
bed methane, which in 2000 accounted for approximately
7% of US annual natural gas consumption, about 1.4 TCF.
Another is the measurement of gas vented from oil wells
during production, sometimes called casing head gas. In
light of the greater emphasis on controlling the emission
of methane and other greenhouse gases, as well as the
possibility of trading credits internationally, we think
measurement of these is likely to become increasingly
important with time. There is currently no good method
for measuring gas flow in either of these cases. The Photon
Control optical flow meter should be a clear winner in
both.
Saturated Steam. Measuring of saturated steam is a challenging
task because of high operating temperature (200C and higher)
and a risk of the “hammer” effect. This latter
problem represents a major challenge for any intrusive
mechanical flow meters used for steam metering. A market
exists which includes high power industrial boilers for
steam generating plants used in heavy oil production and
low power boilers for the food processing industry. Automation
in the latter industry is inhibited for want of appropriate
steam flow meters. Photon Control has completed initial
testing on saturated steam using the steam generation
facility at the University of British Columbia to establish
the feasibility of optical flow measurement for steam.
Photon Control's optical steam flow meter is being designed
in such a way that it will be capable of measuring the
steam quality (percentage of water in steam) as well.
Flare Gas. Environmental, political and economic factors
are pushing the oil and gas industry away from flaring
vent gas. In addition to the safety concerns, national
legislation in many countries requires controlling emissions.
The market for flare gas metering is estimated to be tens
of thousands of units worldwide. From a technical prospective,
the optical flare gas flow meter will be very similar
to that Photon Control is developing for low-pressure
vent gas metering with the difference being larger pipe
sizes (16” or even 72” for flare gas versus
1” or 2” for vent gas). In addition to flow
measurement, the optical flow meter will have the potential
to provide data on gas composition of value in managing
processes for industry.
Hydrogen Flow Measurement. At the other end of the pressure
spectrum is measurement of hydrogen and other gases that
have been hyper-compressed. Although one other type of
meter has been used with compressed natural gas at pressures
up to 350 bar, the makers of hydrogen delivery systems
say that they need as much as 800 bar operation, perhaps
more.
With the evidence of need and the suitability of our technology
to provide economical measurement under conditions that
have been very difficult for existing metering technology
to operate satisfactorily, Photon Control has started
working on the steam meter and the low-pressure gas meter.
Field-testing is expected in the fall of 2003, with first
commercial product expected to be available in 2004 |
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