Improve yourplant efficiency
through accurate
and reliable flaremeasurement
Flares in a refinery, liquefaction or chemical process plant
are first and foremost a safety device. In many countries, it
is required that the flare be monitored to assure pollution
regulation standards are not exceeded. However, a flare
metering device can also be used to help plants operatewith greater efficiency, leading to cost savings, even in theabsence of regulation.

An accurate and reliable flare measurement can identify
problems before they become crises. When properly installed
and maintained, an accurate flare measurement can save anoperator thousands of dollars in its first months of operation,and payback any flare flow meter investment in fewer than
6 months. A properly installed flare monitor not only makes
good environmental sense, it makes good business sense.

The importance of accurate flare measurement
Consider a case of a flare that is operating with 80%
methane. At flows of 200 m3/hr or only .2 ft/sec on a 42”
flare, without an accurate flare measurement, the operator
might think that there are no process leaks and everything isoperating correctly. Over the course of a 6-month period, thiswould mean a loss of 692,000 cubic meters of methane, orabout $46,000 at a market price of $1.90/MMBTU. If the flare
flow meter is not installed correctly or inaccurate, unstable orsimply unable to resolve low flow conditions, the plant may
be wasting a considerable amount of money.

Measuring balance of plant
Plant operators can also use the molecular weight output
on a GF flare meter to help assess if a particular process iscontributing excessively to a given set of flow conditions, oras an important tool for measuring plant balance. The use ofmolecular weight as a diagnostic tool can be invaluable forisolating process leaks quickly so that actions can be taken
to correct the problem.

Added value through computational
fluid dynamics
Additionally, many flare installations from five or ten
years ago have undergone changes to piping layout, flow
dynamics or process conditions. These flare meters may not
be accurately reporting the flow conditions due any pipingchanges or added flows that may be contributing to flow
profile degradation. By using Computational Fluid Dynamics(CFD), a model of the fluid flow in the reconfigured piping
can be performed and correction factors can be determined
to produce more accurate measurements. A full service
agreement that includes a flare CFD improves the overall
performance of the flare meter by better understanding
and accounting for the actual flow profile under the current
process conditions.

Panametrics flare measurement experience
In the early 1980s, a flare gas ultrasonic (a high frequency
sound) flow meter was first jointly developed by Panametricsand Exxon (now Exxon Mobil) in Baytown, Texas, USA,demonstrating great success. Since then, ultrasonic flow
meters have been gaining more and more popularity for flare
gas measurement, mainly because of the high turndown
ratio, relatively low installation and maintenance costs, thecapability of handling unsteady flows, and the independence
on gas composition. In addition, ultrasonic flow meters are
not only capable of measuring flow velocities, volumetric flow
and mass flow, they are also capable of producing a list ofvaluable diagnostic parameters, such as sound speed, signal
strength and molecular weight, which are very useful for
prognostics, preventative maintenance and process defectidentification. Today, ultrasonic flow metering is the mostaccepted technology for monitoring flare gas, with morethan 5,000 installations worldwide.

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