Application note

Operators’ flare operations remain compliant
and down-time avoided thanks to Panametrics’
Computational Fluid Dynamics
Benefits:• Easy upgradation process• No process interruption• Proven experience in CFD• Put the flare measurement in ETS
regulatory compliance• Strong local support

Summary
A downstream operator installed a Panametrics GF868 ultrasonic flare gas metersome 25 years ago in a line where the pipework does not provide the 20D upstream
and 10D downstream of straight pipe after a single disturbance.
The flare and flare meter were no longer in use, so it did not cause a complianceproblem regarding the Environmental Trading Scheme (ETS) mandated for emissions
monitoring and reporting.

Challenge
However, the flare in use required maintenance. To avoid down-time, the operator
wanted to use the old flare. To do so and remain compliant, one of two solutions wereconsidered:Fig 1. A 30” horizontal pipe 12 meters (39’+) above ground level1. Relocate the old meter to a new position in the flare linethat complied with the requirements.

The flow profile is represented in several ways as
shown below:2. Carry out Computational Fluid Dynamics modeling of theexisting installation and create corrections for the flow
profile as measured by the meter.
The first option would be costly and would haveconsequences for the company in the form of a shutdown torelocate the meter. The second option, although technicallychallenging, was thought viable and worth exploring further.
Panametrics’ technical experts were invited to discuss
potential solutions. The customer supplied isometricdrawings of the pipework and all the process cases thatthe meter would be required to measure. A variety of fluid
compositions and flow calculations were carried out toascertain flow velocities and Reynolds numbers for eachcase.

Fig 3. It appears that we are looking at tendons in the figure above butwhat is shown is the individual paths for small groups of gas molecules.
Note the orientation of the lines change with velocity. The color indicates
their velocity.

Fig 2. Layout of customer pipework

The solution
Panametrics’ CFD team then used this information to model
the flow in the above pipe to work out the velocity profile atthe point where the meter is installed.

Fig 4 and 5. Axial velocity contours and secondary flow vectors

Although every CFD is unique, Panametrics applies the same
approach for each of them. The team uses flow, temperature,pressure, gas composition, and pipe isometric dimensional
data to generate the flow profile at various positions down
the line. In this specific case, only the performance at
8.85D where the meter is located was required. Generally,
distortions fade out traveling further downstream.
The CFD helped understand the flow behavior at different
velocities and provided the recommended correction
factors for the non-fully developed flow profile under several
flowing conditions. In addition, it confirmed the total meter
uncertainty stayed within 3% of the measured value underthese non-ideal conditions which was perfectly acceptable
to the customer.

The outcome
The customer was pleased that Panametrics technology
enabled the upgrade of its existing flare meter to the latest
regulatory requirements, keeping the company compliant
with the ETS for monitoring and reporting emissions. This
saved significant cost and resource avoiding, for example,
the interruption of operations, erecting scaffolding,contracting welders and the burden of complex and lengthy
change management processes that would have beenrequired otherwise.

This 3% uncertainty may seem high in comparison to
the typical value to that for a standard 2 path solution.
Panametrics would normally claim an accuracy in the rangeof 1.5% for a non-calibrated application. One of the outcomesof the CFD is the calculation of the additional uncertainty
coming from a disturbed flow profile which is both velocity
and molar weight dependent. The second outcome is toprovide a set of k-factors to be entered into the meter tooffset the additional measurement bias from the specificnon-ideal flowing conditions.
A Panametrics service engineer implemented these
correction factors in the GF868 electronics.

Panametrics, a Baker Hughes business, provides solutions in the
toughest applications and environments for moisture, oxygen, liquidand gas flow measurement.
Experts in flare management, Panametrics technology also reduces flareemissions and optimizes performance.
With a reach that extends across the globe, Panametrics’ criticalmeasurement solutions and flare emissions management are enablingcustomers to drive efficiency and achieve carbon reduction targets acrosscritical industries including: Oil & Gas; Energy; Healthcare; Water andWastewater; Chemical Processing; Food & Beverage and many others.
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BHCS39318		

(04/2023)

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