IMEKO Event Proceedings Search

   

Page 419 of 977 Results 4181 - 4190 of 9762

Henk Jan Panneman, Cornelis W. Koreman, Sjoerd Toonstra, Floris Huijsmans
THE USE OF ULTRASONIC GAS FLOW METERING TECHNOLOGY FOR THE DEVELOPMENT OF ACCURATE ENERGY METERS FOR NATURAL GAS

Gasunie Research gained their years of experience in efficient energy utilization, gas transport and gas measurement as the in-house laboratory for N.V. Nederlandse Gasunie. This company, which was an integrated gas transport and trading company until the beginning of 2002, has been one of the largest gas suppliers in Europe for several decades. As part of this company, Gasunie Research has always striven to guarantee the continuity of the gas supply, to ensure the safety of gas transport and to enhance the added value of natural gas as a fuel. Gasunie Research developed a wealth of new technology for domestic, commercial and industrial end users, and for the energy sector itself. The expertise that Gasunie Research has acquired through these activities and the years of practical experience is now made available to third parties.
Energy measurement is one of the main tasks of gas transport companies. New challenges in the gas world confront gas transport companies with new requirements regarding energy measurement. (e.g. the variation in gas composition will be larger and will occur more frequently). These changes are the driving force for a number of new developments in energy metering. Present energy measurement systems for natural gas comprise of volume metering, volume conversion from field conditions to reference conditions and calorific value determination at reference conditions. The calorific value, HSR , is mostly determined by compositional assay using a process gas chromatograph. The volume is commonly measured by a turbine flow meter, an ultrasonic flow meter or an orifice plate. The volume conversion factor is mostly determined from thermal equations of state, using the gas composition or some gas properties as input. The cost of ownership for accurate energy meters based on process gas chromatographs is high. These high costs were the main reason for Gastransport Services (the transportation company of N.V. Nederlandse Gasunie) and Ruhrgas AG to join forces on the development of new energy flow measurement methods.
These new methods are based on the measurement of three suitable properties (e.g. physical properties or component concentrations) and an accurate correlation between these properties and the gas composition. The inferred gas composition is used to compute a variety of gas properties like the superior calorific value, the density, the compression factor under reference and field conditions and the Wobbe-Index.
Within the joint project Gasunie Research focussed on the development of an energy meter based on velocity of sound measurements. The new meter is based on the measurement of the velocity of sound at high pressure (VOShigh), the velocity of sound at low pressure (VOSlow), and the molar fraction carbon dioxide (XCO2). This combination is particularly suitable for stations with high pressure gas available (P > 40 bar).
In this paper results for the superior calorific value of natural gas obtained with both a dedicated double velocity of sound meter and with velocity of sound measurements obtained by an ultrasonic gas flow meter will be discussed.

Michael Reader-Harris, Bill Brunton, Ian Nicholson, Ronnie Rushworth, David Hodges
THE COMPLIANCE TEST FOR FLOW CONDITIONERS AS APPLIED TO A ZANKER FLOW CONDITIONER PLATE WITH A VENTURI TUBE

This paper describes the test work undertaken to establish that the compliance test in ISO 5167-1:2003 is satisfactory for Venturi tubes and also to determine the required upstream lengths when a Zanker Flow Conditioner Plate is installed upstream of a Venturi tube. In essence the Zanker Flow Conditioner Plate met the compliance test upstream of a Venturi tube provided that there is at least 3 D between the plate and the upstream pressure tapping of the Venturi tube and 7 D between the plate and any upstream fitting. However, if the compliance test were to apply to flow conditioners with Venturi tubes at high Reynolds number, it is worth noting that the shift in discharge coefficient due to a flow conditioner does not have a single value for all ReD > 3 × 106. Moreover, the requirements of the compliance test in terms of range of friction factor may be too restrictive.

Jos G. M. van der Grinten
CONFIDENCE LEVELS OF MEASUREMENT BASED DECISIONS

Metrological decisions are based on measurements that have uncertainties. Examples are car velocity measurements for law enforcement, initial verifications that lead to the decision to approve or reject an instrument, and the significance of differences found during intercomparisons. The paper shows for each of these examples the relationship between acceptance criterion, tolerance, uncertainty and confidence level. From the discussion of these examples it can be concluded that uncertainties must be known in order to evaluate the risk on an erroneous decision. Confidence levels are associated with decisions for which it is impossible to achieve 100% confidence. Conformance and non-conformance are not two complementary notions. If the accepted risk on an erroneous decision is less than 50% there is a range of observations for which the instrument is not conforming and not non-conforming at the same time.
For verifications an increasing number of verification points leads to an increased risk of making an incorrect decision. In order to appreciate the extra information of more observations a curve fit procedure described by Van der Grinten and Peters can be followed. If there are sufficient data, i.e. at least 6 degrees of freedom, it is best to make a curve fit with a 95% confidence envelope.
In all of the above-discussed examples the statistical distribution of the observed results is not known. So the risk analysis is based on the assumption of a Gaussian distribution of the measurement results that is the worst-case representation of our knowledge. If other distributions can be demonstrated to describe the measurement results this will certainly lead to a higher degree of confidence or acceptance criteria that are closer to the tolerances.

G. J. van Essen, S. Bakker, H. J. Dane
TESTING THE PERFORMANCE OF ULTRASONIC SINGLE PATH HOT-TAP FLOW METERS

In its gas transmission system Gasunie Transport Services (in this paper further called “Gasunie”) uses hot-tap single path ultrasonic meters for process control purposes. For these meters, a number of minimal requirements has been established, relating to meter performance (accuracy, response time, reliability, output signals), operating conditions (gas properties, mechanical, environmental and safety requirements) and documentation (manufacturing log, hot-tap procedures).
For many of these requirements it can be determined relatively easy whether or not they are met. However, in most practical situations, the accuracy and response time of a hot-tap meter cannot be determined. Since accuracy and response time are important properties for applications in the systems of Gasunie, it was decided to set up a test program. At the Gasunie Research test and calibration facility in Westerbork (the Bernoullilab), it is possible to carry out a hot-tap installation of an ultrasonic meter under high pressure conditions (up to 65 bar) and to calibrate this meter against the Dutch high pressure flow standards.
Six manufacturers were invited for the testing of a single path 12” hot-tap ultrasonic flow meter. Three of these manufacturers (Instromet, Panametrics, Ultraflux) have offered a single reflection path meter. In the last three years (2000 to 2003) these meters have been tested at the Bernoullilab. The hot-tap activities have resulted in a spool piece with two nozzles and valves on which the insertion mechanisms for the transducers can be mounted. All three manufacturers us ed the same spool piece for the installation of their meter.
The purpose of the test was to answer the following questions:
- What is the quality of the hot-tap and installation procedures of the manufacturer?
- What is the accuracy of single path ultrasonic meters “in practice” ?
- What is the accuracy of the meters when the gas flow is disturbed by swirl?
- What is the effect on the accuracy of a disturbance at 20D and 30D?
- What is the dynamic response of the meter to changes of the flow?
- What is the effect on the accuracy of a single path ultrasonic meter when the transducers are not accurately positioned in the pipe (for example as a consequence of inaccurate procedures)?

Olivier Broca, Joël Escande, Bruno Delenne, Gérard Mouton, Pierre Gajan, Alain Strzelecki
INFLUENCE OF FLOW CONDITIONS ON AN ULTRASONIC FLOW METER

Multipath ultrasonic flow meters have been more and more used in gas industry for the last ten years, this technology represents an interesting alternative to orifice and turbine meters. In fact, ultrasonic meters offer significant advantages such as bi-directionality, low pressure loss, large range and self-checking capabilities. Nevertheless, in some specific configurations, ultrasonic meters are still sensitive to the installation conditions. During the last decade, this topic has been widely investigated on several aspects, however many questions still remain.
In Ultraflow project, Van Bloemendal et al. and Vulovic et al. examined the behaviour of multipath flow meters located downstream of different pipe fittings, single bend, in or out of plan bends. Their study also focused on the influence of steps in the pipe diameter, the influence of the pressure and the flow meter orientation with respect to the upstream pipe configuration. Lunde et al. performed similar measurements and completed their study with numerical simulations. The work performed at the Gas Research Institute by Grimley combined flow metering error observations with velocity distribution measurements in the pipe. Hilgenstock et al. applied CFD techniques in order to simulate installation effects on ultrasonic flow meters.
A detailed analysis of these works has been carried out, and the metering discrepancies obtained for a same pipe fittings have compared. We tried to determine the influence of different parameters such as the distance between the upstream fittings and the flow meter, the orientation of the flow meter or the pressure level. In most cases, the error decreases with the distance. The influence of the orientation is not obvious and depends on the flow characteristics at the flow meter location. Finally, this analysis indicates that the metering error is quasi-independent of the pressure line. Nevertheless, pressure drop had an influence on the signal to noise ratio and thus on metering error. The CFD techniques has given satisfactory results when applied to relative simple geometries like diffusers or contractions. For more complex geometries, the predictions becomes more hazardous.
Recently, ONERA has developed the ultrasonic tomography to correct the installation conditions influence on different kind of flow meters (Escande et al. and Demolis et al.). The new research program presented in this paper is financially supported by Gaz de France and Gaz du Sud Ouest.

Alex S. Kun, Balazs Rekasi
PERIODICAL CONTROL AND DYNAMIC TRACEABILITY TEST OF AN SNPS TO THE NATIONAL STANDARD OF GAS FLOWMETERS CALIBRATION

The tested Sonic Nozzle Prove ring System (SNPS) stepped into service at the Gas Works of Budapest almost five years ago. To keep its parameters in a dedicated and good condition a continuous checking process is carried out. During this checking process those tested were the SNPS main accuracy and repeatability, as well as the individual sonic nozzles (SN).

M. P. van der Beek, R. van den Brink, I. J. Landheer
GAS-OIL PISTON-PROVER, A NEW CONCEPT TO REALIZE REFERENCE VALUES FOR HIGH-PRESSURE GAS-VOLUME IN THE NETHERLANDS

The paper describes the recently developed "GOPP" – Gas Oil Piston-Prover. This primary standard for high-pressure gas-volume is created to realize units of volume at various pressures for the Dutch National traceability-chain of high-pressure gas-flow measurements.
The paper presents the design, working principle, simulation calculations and first results to realize a calibrated rotary-piston gas-meter. Furthermore, the actual physical process is compared to simulation calculations, and temperature characteristics are discussed. With internal harmonization processes at NMi VSL with "input" reference values from the three other primary standards, viz. DDD-conventional, DDD-extended pressure level and NMi TraSys, the aim of 0,1% uncertainty at 4.000 m³ / h and p = 60 bar is within reach. This will improve the uncertainty as well as the stability of the Dutch National reference values considerably.
The developed Gas-Oil Piston-Prover has the potential to become an important primary standard at NMi VSL, generating straight-forward Reference Values for high-pressure gas at a desired pressure. The gas can be of any nature, but the major aim is Natural Gas.
The paper presents describes the design, construction, working principle and features of a hydraulic driven piston-prover system. A 12 meter long, 600 mm bore piston-prover is used for the realization of Reference Values for Gas-Volume at any pressure between 1 and 90 bar and any type of Gas. The paper explains the coherence between the Gas-Oil Piston-Prover system and the other available traceability generators. Following the philosophy of NMi, a "tripartite" traceability-chain for high-pressure gas-flow Reference Values is created. GOPP is one of the current developments at NMi to reduce the uncertainty of its traceability-chain considerably.
The paper shows block diagrams, describing the coherence between physical equilibriums, simulation calculations and graphical simulations, compared to the results of full-scale experiments with a special duo-rotary piston-meter.
A method is described to demonstrate an absolute leak-free piston-seal operation. Also a special measuring method was designed for the determination of the average gas-temperature inside the expanding measuring-chamber during the movement of the piston.
Finally, real-time temperature and pressure readings, as well as the first calibration results of a duo-rotary gas-meter, established values for repeatability of the piston-prover system and first estimates of uncertainty budgets will be presented.

R. van den Brink, M. P. van der Beek, I. J. Landheer
QUADRATIC WEIGHING, APPLIED IN HARMONIZATION, A TOOL TO COMPARE THE PERFORMANCE OF TEST-FACILITIES

Measurement-data of laboratories participating in comparisons are often treated equivalently with respect to operational conditions and statistical impact. When analysing the comparison, this may distort some conclusions because no attention is paid to deviations caused by differences in operational conditions (e.g. pressure). A better way to perform a comparison is to transpose the sets of flow-rate data to Reynolds numbers, to make it easier to see whether or not the points are in the same Reynolds-region and thus allow for a valid comparison.
Next, not all participating laboratories contribute equally to establish a Mean (Average) Value, because the laboratories with a low uncertainty must have a greater impact on the final result than laboratories of a lesser quality. So the data -sets must be weighed and to do so, weighing-factors are needed. Finally, a common way to analyse the comparison-results is by using Youden-plots.
This paper shows the "flow-rate to Reynolds-transformation" to compare test-data, and demonstrates which weighing-factors must be used to get the "Best Known Mean Value" with the smallest uncertainty. In the end, this method is also applied in Youden-plots.

M. P. van der Beek, I. J. Landheer
'NMi TraSys', THE ULTIMATE CARRIER & MULTIPLIER FOR THE UNIT OF VOLUME FOR HIGH-PRESSURE NATURAL GAS

The paper describes the newly developed 'NMi TraSys' - NMi Traceability System. This travelling carrier & multiplier of traceability has been realized to embody a significant part of the Dutch National traceability-chain for high-pressure gas-flow measurements. The number of contributions of uncertainty as well as their values, due to 'copy-losses' and 'installation-effects'during the traditional transfer of traceability from one facility to another, are decreased.
First results are presented about observed repeatability and reproducibility, uncertainties and consistency checks. The device will include in time, reference values of three different independently realized primary standards (viz. DDD - Dynamic Displacement Device, GOPP – Gas-Oil Piston-Prover and NMi TraSys itself). With internal harmonization processes at NMi VSL with "input" reference values from the three other primary standards, viz. DDD-conventional, DDD-extended pressure level and GOPP, the aim of 0,1% uncertainty at 4.000 m³ / h and p = 60 bar is within reach. This will improve the uncertainty as well as the stability of the Dutch National reference values considerably.
NMi TraSys will be used as a set of Travelling Reference Meters, creating an efficient availability of stable and validated Harmonized Reference Values for high-pressure gas-flow.


A. J. M. Herwijn, M. P. van der Beek, I. J. Landheer
Z/Z-METER, ON-LINE MEASUREMENT OF COMPRESSIBILITY-RATIOS FOR REFERENCE VALUES OF VOLUME AT OPERATIONAL CONDITIONS

One of the methods to realize reference values for Volume of e.g. Natural Gas at increased pressures is via a calibration under a pressure difference (i.e. with expansion). In such a process, applied since the sixties in the Netherlands, the "un-known" meter or Meter-under-Test (MuT) is compared through expansion with the "known" meter or Reference Meter (RM) at low-pressure. In a "normal" calibration-process the difference in pressure between the two compared meters is relative small and the resulting difference between the compressibility at the Reference Meter ZRM and the compressibility at the Meter-under-Test ZMuT has hardly any effect on the ratio ZRM / ZMuT and can be neglected (the ratio is thus considered to have a value of 1). However, in a calibration under expansion a comparison is made of a gas-flow under significant differential pressure-conditions and one of the most important contributions of uncertainty stems from the real gas constant Z. So, the ratio ZRM / ZMuT is of importance, rather than the absolute values of the compressibility factor. The Z / Z-meter is one of the current technical developments at NMi VSL-Flow. The uncertainty contribution in the conventional method of calculation, described e.g. in M-GERG of 1991, is rather high (0,1% for the compressibility factor) and the resulting uncertainty of the ZRM / ZMuT ratio is 0,14%.
Therefore, a method leading to a lower contribution to this source of uncertainty offers advantages. In the presented approach is the ratio ZRM / ZMuT is considered to be the measurand. The ratio should then be measured more accurately than the one resulting from calculation of the absolute values of the compressibility factor. As a consequence, the impact of this source of uncertainty is reduced. NMi has developed a device that is able to measure the ratio ZRM / ZMuT directly.
In this paper, the development of a new measuring instrument is described that measures the Z1 / Z2 ratio of gases (at pressures P1 and P2 between 1 and 70 bar) with a maximum uncertainty of 0,03%. The measuring principle of the Z / Z ratio meter is based upon the accurate measurement of a piston-displacement. The piston is displaced by a controlled gas expansion from high-pressure to a low-pressure condition (or for compression, vice versa) in a measurement cell. The measurement cell with an adjustable volume is mounted inside a high-pressure vessel for an adequate control of temperature and pressure. The cell is constructed as a cylinder-piston combination together with small ball-valve actuators that can be opened and closed to connect or disconnect the chamber of the cell to the surrounding vessel and to fill or empty the system.
During its operation, measurements are taken of the piston-displacement, together with measurements of pressures and temperatures. For the calculation of the ratio Z1 / Z 2 basically only the ratio of the cell volumes at pressures P1 and P2 needs to be established.

Page 419 of 977 Results 4181 - 4190 of 9762