Product category:
Oil & Gas Fiscal Flowmetering systems
News Release from: Siemens Automation and Drives | Subject: US flow in fiscal duties
Edited by the Processingtalk Editorial
Team on 14 May 2007
Ultrasonic flow measurement for custody
transfer
Ultrasonic flow meters are a versatile and competitive technology for hydrocarbon custody transfer applications, but have always been regarded as high capital cost: until now
Matt Bird, of Siemens Automation and Drives, outlines the benefits of ultrasonic flow metering and puts to rest the cost issue for once and for all If your flowmetering system were a bank would you make money or lose money? At every stage of the oil and gas sector there is the potential to lose money and impact the bottom line
This article was originally published on Processingtalk on 10 Apr 2006 at 8.00am (UK)
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This is the primary reason that ultrasonic flow metering has gained many supporters in the oil and gas industry with the equipment enjoying rapid growth in recent years, in comparison to more traditional forms of measurement technology, such as turbine meters, Coriolis meters and positive displacement.
Ultrasonic meters can be used in a wide variety of environments, from offshore platforms through to tankers, oil terminals, refineries and pipeline systems.
In operation, the meters can take measurements over a large viscosity range from crude oil, liquid petroleum gases (such as butane and propane), refined oil products and petrochemicals.
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The equipment is now used in hydrocarbon flow metering to ensure the highest standards in inventory control, allocation measurements and custody transfer loading and offloading operations, pipeline leak detection along with liquid identification and interface detection in multi-product pipelines.
The key benefit of ultrasonic flow meters is that, unlike more traditional meters, ultrasonic flow meters have no moving parts and therefore do not require frequent recalibration and maintenance.
More traditional custody transfer equipment requires frequent and expensive proving recalibration to ensure that the required levels of accuracy are maintained when a change of product or fluid occurs.
This recalibration can be extremely time consuming and can often mean that pumping operations have to be suspended while the recalibration takes place.
In contrast ultrasonic flowmeters do not require reproving when the fluid properties change, saving valuable time and money.
The absence of moving parts also benefits ultrasonic flow meter reliability.
Extreme reliability is a crucial requirement in custody transfer applications which depend on high availability without any breakdown, particularly when used in rugged applications common to hydrocarbon applications.
A further benefit is the measurement accuracy available with ultrasonic systems which ensures this type of equipment reaches OIML R117 custody transfer standards.
The oil and gas industry is heavily regulated by the DTI and must meet the OIML standards.
To meet these standards, the accuracy of the meter needs to be +/-0.15% and repeatability needs to be within a 0.04% Band.
The Siemens F US range, for example, achieves accuracy rates of +/-0.15% of actual flow.
The accuracy and reliability of ultrasonic measurement is attributable to the fundamental technology in the equipment, consisting of wall to wall transit time signal transmission.
The flowmeter does not physically enter the medium flow and is therefore not exposed to wear.
Being non-invasive, the flowmeter does not alter the flow properties during measurement and causes little or no pressure drop.
The ultrasonic measurement principle is independent of measurement conductivity and the technology is therefore ideal for either water or non-conductive media.
A further benefit is that ultrasonic flow meters have no filtration requirements are much simpler to clean than, for example, turbine alternatives.
All in all, ultrasonic flowmeters are simply less complicated to run.
Detection capabilities are a key issue in hydrocarbon measurement, particularly in regard to pipeline leak detection, which is an area of growing international concern.
An ultrasonic flow meter, equipped with a transmitter, such as the Siemens FUS060, outperforms the traditional alternatives with superior communications and diagnostic facilities which co-ordinate flow data to pinpoint unexpected losses, allowing for early identification and repair of leaks.
A further major benefit is the small size and weight of ultrasonic systems when compared to PD (positive displacement) or turbine systems.
Traditionally skids installed on offshore platforms or FPSOs (Floating Production, Storage and Offshore loading) are based on PD or turbine technology.
However, ultrasonic technology enables an innovative alternative skid design which is considerably smaller than either a PD or turbine system both in volume and wetted mass.
If you consider a typical 4000 m3/h (600,000 BPD) skid a positive displacement system would include 3 x 16in PD meters in parallel streams and a 30inch NB bi-directional ball prover.
In total this would measure 930m3 in size and weigh 112 tonnes wet.
A turbine skid would typically include 3 x 12inch turbine meters in parallel streams and a 30inch NB bi-directional ball prover.
In total this would measure 950m3 in size and weigh 101 tonnes wet.
In contrast a skid equipped with ultrasonic flow meters, such as the Siemens Sitrans FUS060 Ultrasonic flow meter, would typically be equipped with 2 x 20 inch Ultrasonic meters in series with no requirement for provers, valves or filters would be 60m3 in size and 11 tonnes (wet).
The total skid price for this equipment is equally as impressive.
A PD skid as outlined above would typically cost in the region of USD1.1 million.
The turbine skid would typically cost in the region of USD900,000.
The ultrasonic flow meter outlined above would typically cost approximately USD880,000, in this case showing a saving of nearly USD20,000.
It is clear that the ultrasonic skid saves on both capital and operating fronts, initially in meters of piping, pipe diameter and quantity of instrumentation.
Most significantly traditional meters require considerably more maintenance labour and expense compared to ultrasonic flow meters.
Over a lifetime, increased throughput for reduced capital outlay, as maintenance and recalibration delays are considerably reduced, adding considerably to the bottom line.
Furthermore, reductions in volume and mass naturally also result in significant capital and operational savings when designing offshore platforms and tankers.
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