How can I determine if my flow conditioner is suitable for custody transfer applications
For Orifice Metering your flow conditioner must pass a set of extremely detailed tests outlined in A.G.A.-3 Part 2 “Specification and Installation Requirements” Pages 45 through 47 “Appendix 2-D – Flow Conditioning Performance Test. A.G.A -3, the exactly same data and criteria is required for ISO 5167. The tests must be done in accordance with the requirements outlined in the standards.
These rules must be followed exactly “to the letter”, in order to use a flow conditioner for orifice metering. The flow conditioner tests that are carried out to comply with Appendix 2D, must also be carried out with statistical correctness, i.e. testing a flow conditioner until one data point accidentally falls into the acceptable region while discarding all those other data points accidentally is not going to cut it. Probably having 3rd party testing results rather than having your own testing results should fix this and add credibility to the data. If you are seeing very few data points in each test, be afraid, be very afraid i.e. 2 or 3 data points.
For Ultrasonic Metering. Step 1. Order a copy of A.G.A.- 9, the new version is now available to the public, and order this Paper as well, “Ultrasonic Meter Installation Configuration Testing” Terrence A. Grimley, Principle Engineer, Southwest Research Institute, A.G.A. 2000 Operations Conference, May 7-9th, Denver Colorado from the proceedings archives.
Ultrasonic meters have a characteristic sensitivity to change in flow profile and they are very repeatable on a volumetric basis, so they are becoming as you know very popular. Flow Conditioner performance confirmation has to be conducted in the following manner:
Basically what A.G.A. – 9 calls for is a limited measurement accuracy shift of the metering assembly from good baseline or calibrated flow conditions to actual in-situ conditions, i.e. from long straights at the test lab to downstream of elbows, tees, headers etc. A popular tool being used to infer that a shift in accuracy may have occurred is an ultrasonic meter “path to path” ratio comparison.
Calibration occurs at a test facility. The ratio of path to path comparisons is recorded as calibrated condition. One then ships the assembly to the meter station and continues to monitor the path to path ratio comparisons. Measurement accuracy shift in a qualitative fashion is inferred from the change in the ratio comparison, and this tool is successfully used to problem solve installation problems; blocked flow conditioners, liquids etc.
What the ultrasonic meter can not do is measure the velocity flow profile. In order to measure the velocity flow profile downstream of a flow conditioner to determine if it is isolating the meter properly, one must use; hot wire anemometer, or micro-pitot tube. Below are sample measurements of a velocity profile for a flow conditioner carried out with a hot wire anemometer device;
Figure 2 – Hot Wire Anemometer measurements of a flow conditioner downstream of a single elbow and two elbows out of plane.
For example; Figure 2 shows that the hot wire traverses indicate that the flow conditioner is bringing the velocity profile back to a reference or fully developed flow profile downstream of common installation effects.
Using this type of detailed information is absolutely essential, using this along with orifice meter performance results and accuracy shift data using the ultrasonic meter and flow conditioner downstream of good flow conditions and installation effects can help to determine if the flow conditioner is working or is effective. If you don’t ask for the flow conditioner data in this format you can use any type of flow conditioner for your ultrasonic flow measurement needs and you will never know the difference.
The challenge with a flow conditioner design is to maximize effectiveness while minimizing pressure drop. IF we did not care about pressure drop one could easily build a flow conditioner which isolates the meter perfectly. But compression loses would be insurmountable. Keep this in mind as well.
For Turbine and all other meters. We have never linked the flow conditioners in any way to the meter. What we guarantee is that we provide some level quality of velocity profile and turbulence intensity after pipeline installation effects. You can place what ever meter you wish at that location and can expect baseline or calibration quality measurement from the meter.
How much pressure drop is created by the conditioner
References:
1) Flow of Fluids through Valves, Fittings, and Pipe. Crane. Technical Paper No. 410M, Second printing.
2) A Compact Orifice Meter/Flow Conditioner Package. Dr. U. Karnik Novacor Research & Technology Corporation 2928 – 26th Street N.E. Calgary, AB, Canada, T2E-7K7
Methodology
The methodology employed to determine the pressure losses as a result of fluid movement past the Canada Pipeline Accessories Company Ltd. CPA 50E Flow Conditioner is the following typical Pressure loss approach:
Where: k = head loss coefficient – Experimentally determined by NRTC = 1.5 to 1.7
r = density via AGA-8
v = mean fluid flow velocity
Density
Using Gas Composition provided by reference #2 and carrying out an AGA-8 calculation at 750 psia and 60°F) we have:
Yes. Any time fluids flow past a restriction there is a propensity for noise. Usually this noise occurs a specific harmonic flow conditions or flow rates, it is not broad band. As a result noise at the meter station occurs infrequently, but it can occur.
MINIMUM 8 inside pipe diameters in front of the meter, and MINIMUM 5 inside pipe diameters in front of the flow conditioner. Any distance combinations longer are perfectly acceptable.
The only exception is the 2” TBR, it has to be exactly 8 inside pipe diameters from flow conditioner to meter and 5 or more inside pipe diameters to the upstream ends of the meter run from the flow conditioner. This is because the 2” TBR flow conditioner is made wider than the CPA 50 E flow conditioners and had to be recertified. We recertified it for only one installation position.
How does Reynolds number affect the performance of the conditioner.
Our measurement business must be conducted at Reynolds Number (Re) above laminar and transition. Re above the 2000 to 4000 at least. We use Re as the “measuring stick” to determine the “shape” of the fully developed velocity profile.
At Re 100,000 to infinity we use the CPA 50 E flow Conditioner (50% porosity, iteration “E”), the velocity profile generated is 99% to fully developed state in this Re range. The pipe between the meter and the flow conditioner is used to develop the velocity profile completely.
For Re lower than 100,000 we may recommend the CPA 50E, or a CPA 60 depending on pipe lengths available.
Does a flow conditioner work better than a tube bundle.
The tube bundle is an excellent swirl eliminator. It is however detrimental to correcting any type of asymmetric flow profiles due to normal pipe installation effects like two elbows out of plane. In fact it actually freezes the asymmetric flow profile in a 19 little jets that make a distorted flow state.
For example below; a tube bundle and a CPA 50 E downstream of various installation effects upstream of an orifice meter. The tube bundle causes extreme error when strong asymentric flows are impinging upon the tube bundle.
One can gain a relative appreciation from this performance for application to other type of meters as well for the tube bundle. In fact the following paper:
“Ultrasonic Meter Installation Configuration Testing” Terrence A. Grimley, Principle Engineer, Southwest Research Institute, A.G.A. 2000 Operations Conference, May 7-9th, Denver Colorado from the proceedings archives.
Indicates that tube bundles should be avoided for ultrasonic meter applications.
If I am calibrating my meter why should I use a flow conditioner.
The function of the flow conditioner is two fold; one, to provide a reference flow profile that is very similar to the flow profile you are experiencing in a long straight piece of pipe, two, to isolate the meter from upstream pipe installation effects like elbows and tees.
Meters are sensitive to installation effects, and meters should be calibrated in good flow conditions. It therefore is required that the flow conditioner be in front of the meter when calibrating – if calibrating is required.
How does the flow conditioner affect my calibration.
In the case of the Ultrasonic flow meter, the flow conditioner will have a very small “foot print” where each flow meter brand will indicate slightly different sensitivities to the slight nuances of the CPA 50 E flow profile. These small deviations are calibrated out when correction factors are applied at the testing facility.
The main requirement of installing a flow conditioner in the meter tube, is isolating capability. The ability to “HOLD” the calibration state then the flow conditioner is installed in the field, after calibration.
In gas orifice meter applications why is it important to have test data for 0.75beta.
The error sensitivities of the orifice meter to velocity profile, pipe roughness and eccentricity are more pronounced at beta ratios above 0.60. You need to see the testing data at these larger beta ratios to gain an insight into the limitations of the flow conditioner you wish to use. All performance secrets are eliminated then.
Using an orifice meter run at a reduced beta ratio will result is significantly reduced capacities. You will in effect have to purchase additional meter runs to make up for the reduced capacities. i.e. two meter runs and a header at 0.6 beta, or one meter run no header at 0.72 beta – it’s your choice.
Why should the testing for API and AGA compliance be performed on high pressure natural gas
Re number applicability. We feel that there was an oversight when the standards were being developed; that testing would be done in natural gas conditions for natural gas applications by the flow conditioner manufacturers, and the Re sensitivity testing would be done at the “other” Re, not the other way around. i.e. do all the testing in water, and then check ONE point in natural gas – this is a no no.
Because of the higher viscosities at the lower Re, it is in fact easier to pass the compliance testing. You could probably use a 1956 Ford hub cap and pass the API testing in lower Re.
How does an HPFC compare to other types of flow conditioning devices
A high Performance Flow Conditioner (HPFC) is one that produces a fully developed flow profile while isolating the meter from installation effects while minimizing the pressure drop. It is a fine balance of which very few flow conditioners comply with.
