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The bell prover apparatus showing the collection volume (V c ), the approach volume (V a ), the location of temperature (T) and pressure sensors (P), and the sensors used to measure the collection time (∆t).
Source publication
This document provides a description of the small and medium range gas flow calibration facilities at the National Institute of Standards and Technology (NIST) Fluid Flow Group, as reported in NIST Special Publication 250 (1) for Test Nos. 18010C-18040C and 18050S, Flow Rate Measurements. The Fluid Flow Group can perform gas meter calibrations and...
Contexts in source publication
Context 1
... bell prover system is based on the same principles described above. The bell prover ( fig. 2) consists of a cylindrical tank open at the top and a central "dry well", which together form an annulus that is nearly filled with sealing oil. Into this annulus is placed an inverted cylindrical tank, i.e., the bell, open at the bottom and having a dome-shaped top. Its weight is nearly balanced by counterweights so that it can be ...
Context 2
... make a calibration measurement using the bell prover, the meter and its instrumentation are installed and the piping system is tested for leaks. Flow is established through the flowmeter and the bypass valve ( fig. 2) is adjusted so that the bell is "floated" off its bottom support. Then the valve is closed so that all the flow is diverted into the bell. Like the piston prover, the bell prover is exercised in this manner in order to attain a steady temperature condition prior to the commencement of the calibration process. The bypass valve is then ...
Context 3
... is because at the highest flows, the temperature variations in the course of a collection are as large as 0.15 K (0.05 %). The collected gas temperature is measured with a sensor inserted into the upper part of the bell, the gas pressure under the bell is measured with an absolute pressure transducer connected to a tap in the inflow pipe (see fig. 2), and the collection is timed with an electronic timer. Details of these measurements and their contribution to the total uncertainty of the system are described in a later ...
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... 0.602 cm (0.237 in) change in oil level due to bell displacement over the collection distance is obtained from direct measurement. This oil level change results in a correction to the bell collection volume of 0.320 % (see fig. 2). The uncertainty in the measurement of the drop in oil level stems primarily from the 0.025 cm (0.010 in) standard uncertainty in setting the bell positions at the ends of the measurement stroke of 47.018 cm (18.511 in). This amounts to a 0.076 % relative standard uncertainty in a quantity that is 0.320 % of the collection volume, and ...
Citations
... The volumetric method uses the definition of gas mass as a product of the gas density and a known volume that the gas occupies. The latter methods are further divided into methods with changing volume [5][6][7][8][9][10][11][12][13][14][15] and methods with constant volume (changed density), usually also labelled with the acronym pVTt (pressure, volume, temperature, time) [16][17][18][19][20][21][22][23][24] with uncertainties going down to 0.013% [6] and 0.015% [22] of measured flow rate respectively. In the former the volume can be changed with the translation of a sealed piston inside a known cylinder or the translation of a liquid-sealed bell with a known diameter. ...
The volumetric primary standard with a constant volume (pVTt) determines the flow rate from the rate of change of gas density in the defined measuring volume. The key element of the measuring system that uses the flying start–stop method is a diverter. This paper presents a time correction model that adapts the correction according to the diverting speed implemented in our pVTt system developed for flow rates smaller than 12mgmin−1. A detailed study of the diverter’s effects on the effective collection time and two methods for determining the time correction are presented. One is based on the ISO 4185 standard and the other on measurements of the dynamic pressure upstream of the diverter. A set of correction time measurements were made at different diversion speeds to define the correction model at a flow rate of 9mgmin−1. The results show very good agreement between the measurements with both methods and the defined correction model. Additional measurements were made at smaller flow rates and the results indicate the independence of the time correction from the measured flow rate.
... Por otra parte, el procedimiento preferido en el NIST, hasta el año 1998, consistía en ¨encintar¨ la campana gasométrica para obtener el volumen exterior a través del diámetro promedio y obtener el volumen interno sustrayendo el volumen del metal en la pared de la campana. [5] Con el decursar del tiempo han surgido métodos alternativos de calibración de las campanas gasométricas ejemplificados a continuación. ...
The article, aims to show the importance of the use of bell provers, their traditional and more recent calibration methods, as well as the function they have in Cuba and in the world. For this, original publications of scientific studies and international standards were consulted. Besides, visits were made to the Verification Laboratory of Gas Meters (Cuba-Petroleum Union) where several bells provers are used. This topic is interesting mainly because of the emergence of new bell prover calibration techniques in the last twenty years and their use as a reference standard since the beginning of the last century to nowadays.
... Bell prover merupakan salah satu alat yang dapat digunakan sebagai standar dalam pengujian meter gas [1,2,3]. Kebocoran pada saat pengujian harus lebih kecil dari 0,1% debit minimumnya pada rentang tekanan kerja instalasi uji [4]. ...
... ) yang memiliki frekuensi > 20 kHz. Cepat rambat gelombang ultrasonik di udara dapat dihitung dengan persamaan di bawah ini (1) Dengan mengukur lamanya waktu tempuh gelombang ketika dipantulkan sampai diterima kembali, maka jarak antara sumber gelombang dengan obyek pantul dapat ditentukan. Pada Gambar 4 di [8]. ...
AbstrakFasilitas laboratorium pengujian meter gas di Direktorat Metrologi Kementerian Perdagangan menggunakan bell prover sebagai standar. Bell prover yang tersedia masih menggunakan skala jenis mekanis dengan rentang 100 "“ 600 liter dan 1 liter per skala. Ketidaktepatan membaca skala mekanis dapat mempengaruhi hasil pengujian meter gas. Untuk itu dibuat alat bantu pembacaan volume bell prover dengan sensor ultrasonik tipe HC-SR04 yang dipasang pada arduino. Alat bantu ini memanfaatkan jarak bobot pengatur kecepatan pada bell proverterhadap lantai. Perubahan ketinggian bobot pengatur kecepatan sebanding dengan perubahan ketinggian skala volume. Alat bantu ini memiliki akurasi terkecil sebesar 83,17% dan kesalahan sebesar 16,83% pada volume 100 liter, sedangkan akurasi tertinggi sebesar 99,76% dan kesalahan terkecil sebesar 0,02% pada volume 600 liter.
... The volume calibrator applications such as density on measuring tube, flow rate on piston and bell prover, and pressure on manometer, which is shown in Fig. 1 , need the excellent measurement accuracy of fluid displacement [1][2][3][4][5]. The manual collecting data tend to produce error due to human factor. ...
... The excellent limit shield by high reflective characteristic must be applied to achieve the best measurement accuracy. The volume calibrators, particularly piston prover and U-tube manometer [4,5] in Fig. 1, which used mercury fluid, should concern about this refractive problem. To summarize, the time-of-flight laser method has successfully achieved accuracy around 0.5% to measure the distance as a simple automatic solution. ...
The measurement of fluid displacement automatically is an urgent part to build an accurate calibrator of volume. The laser interferometer is the best accurate method, but it is not easy to be implemented. The primary standard of length quantity still refers to the speed of light in vacuum. Therefore, the application of laser to measure the fluid displacement length by time-of-flight technique is the simple best effort to achieve the sufficient accurate results and minimize human error. The emitter and receiver of laser with 940 nm wavelength are implemented to solve this task. The purpose of this research is to measure automatically a small fluid displacement by time-of-flight laser method to fulfill simply the accuracy need on volume calibrator. The measurement results indicated that this simple automatic method successfully achieved the accuracy of distance and displacement below 0.5% and 2%, respectively. However, the light refraction behavior on fluid must be taken into account which can affect 0.6% of accuracy. In addition, limit shield can be applied to improve the measurement accuracy.
... Bell prover merupakan salah satu alat yang dapat digunakan sebagai standar dalam pengujian meter gas [1,2,3]. Kebocoran pada saat pengujian harus lebih kecil dari 0,1% debit minimumnya pada rentang tekanan kerja instalasi uji [4]. ...
Abstrak Fasilitas laboratorium pengujian meter gas di Direktorat Metrologi Kementerian Perdagangan menggunakan bell prover sebagai standar. Bell prover yang tersedia masih menggunakan skala jenis mekanis dengan rentang 100-600 liter dan 1 liter per skala. Ketidaktepatan membaca skala mekanis dapat mempengaruhi hasil pengujian meter gas. Untuk itu dibuat alat bantu pembacaan volume bell prover dengan sensor ultrasonik tipe HC-SR04 yang dipasang pada arduino. Alat bantu ini memanfaatkan jarak bobot pengatur kecepatan pada bell prover terhadap lantai. Perubahan ketinggian bobot pengatur kecepatan sebanding dengan perubahan ketinggian skala volume. Alat bantu ini memiliki akurasi terkecil sebesar 83,17% dan kesalahan sebesar 16,83% pada volume 100 liter, sedangkan akurasi tertinggi sebesar 99,76% dan kesalahan terkecil sebesar 0,02% pada volume 600 liter. 1 Pendahuluan Bell prover merupakan salah satu alat yang dapat digunakan sebagai standar dalam pengujian meter gas [1, 2, 3]. Kebocoran pada saat pengujian harus lebih kecil dari 0,1% debit minimumnya pada rentang tekanan kerja instalasi uji [4]. Adapun pengujian tera dan tera ulang dilakukan pada 3 (tiga) debit yaitu : debit minimum (Qmin), 0,2 debit maksimum (Qmaks) dan debit maksimum dari meter gas yang akan diuji [4]. Bell prover yang digunakan pada instalasi uji meter gas diafragma di Direktorat Metrologi Kementerian Perdagangan menggunakan skala jenis mekanik pada penunjukkan volume gas yang dialirkan. Akurasi pembacaan volume gas yang dialirkan oleh bell prover ke meter uji bergantung pada ketepatan dalam melihat skala. Skala volume bell prover dari 100 liter sampai 600 liter. Jarak antar skala penunjukkan volume yaitu 2 mm. Bell prover yang digunakan memiliki ketidakpastian pada nilai skala terkecil yaitu 0,58 liter [5]. Untuk meningkatkan akurasi dalam melihat skala, dirancang sebuah alat bantu penunjukkan volume gas yang dialirkan dengan bantuan sensor ultrasonik tipe HC-04 yang terhubung dengan pada arduino. Alat bantu ini memanfaatkan jarak antara pemberat dengan lantai yang posisinya diarahkan vertikal. Perubahan jarak ini sebanding dengan perubahan jarak pada skala penunjukkan volume gas yang dialirkan. Sehingga, perubahan penunjukkan jarak pada skala memperlihatkan jumlah volume gas yang dialirkan dari bell prover. Alat bantu ini dapat dikembangkan menjadi alat yang dapat mengatur valve sebelum dialirkan ke meter gas yang diuji [6]. Selain itu, bisa diatur jumlah volume gas yang dialirkan sesuai dengan kondisi pengujian. Untuk meningkatkan akurasi pengukuran jarak dengan sensor ultrasonik, bisa ditingkatkan menggunakan laser-rangefinder atau laser-interferometer [7]. 2 Prinsip Kerja Bell Prover Pada Gambar 1.a adalah penampakkan bell prover di Direktorat Metrologi yang akan dipasang alat bantu penunjukkan skala. Gambar 1.b adalah komponen dari bell prover. Sedangkan pada Gambar 1.c adalah penunjukkan skala volume bell prover.
... The bell prover is one of the primary standard calibration system for the gas flow rate quantity. In a survey stated that the primary standard which the most widely used is the bell prover which found in 23 of 27 NMI laboratories worldwide [6]. The bell prover is included to the positive displacement calibration system because the volume of gas transferred into the bell to move it. ...
... The piston-prover concept is commonly used for primary standards in the field of gas flow measurements12345678910. Its principle of operation is based on determining the time interval that a piston needs to pass a known volume of gas at a defined pressure and temperature. ...
This paper deals with heat exchange effects in a compact, high-speed, clearance-sealed version of a piston prover for gas flow measurements that has the temperature measurements limited to the time-averaged temperature of the gas flow. A lumped-element mathematical model is used to study the physical background of the heat exchange effects. Experimental testing is performed to validate the theoretical results, estimate the required temperature homogeneity in the piston prover and propose a modified measurement model that considers the heat exchange effects. These effects are almost linearly related to the temperature difference between the gas flow into the piston prover and the cylinder wall, with the sensitivity coefficient being dependent on the measured flow rate. The piston-prover configuration with the gas temperature sensor in the mixed inlet /outlet flow is found to be advantageous in comparison to a measurement of the inlet temperature.
... The piston-prover concept is widely used for primary standards in the field of gas flow measurements1234567. The general principle of operation is based on determining the time interval that a piston needs to pass a known volume of gas at a defined pressure and temperature. ...
This paper deals with the dynamic temperature effects in a high-speed, clearance-sealed realization of a piston prover. A dynamic mathematical model was built to study the temperature variations and to estimate their influence on the flow measurements. The mathematical model is formulated on the basis of lumped-element models of the piston and the gas cavity. The energy balance for the gas cavity includes the convective heat exchange with the surroundings. One of the potential effects results from the temperature differences between the inlet gas flow and the cylinder wall. In addition, the piston prover's operation generates dynamic temperature variations, which are mainly related to the pressure change due to the flow redirection and to the pressure oscillations due to the piston's resonance effects.
... The piston-prover concept is widely used for primary standards in the field of gas flow measurements1234567. The general principle of operation is based on determining the time interval that a piston needs to pass a known volume of gas at a defined pressure and temperature. ...
The dynamic pressure effects and their corrections in a high-speed, clearance-sealed realization of a piston prover for gas flow measurements are discussed. The experimental results show the deterministic, rather than stochastic, nature of the dynamic pressure conditions and, consequently, the repeatable nature of their influence on the flow measurements. The experimental validation proves the advantage of the polytropic/adiabatic pressure correction model, which was proposed by the authors, as compared with the isothermal pressure correction model. The paper ends with an estimation of the measurement uncertainty related to the pressure corrections using either the adiabatic or isothermal model.
... Table 2 shows the bell outside diameter measurements obtained by the water draw method and the π -tape method. As a result of Table 2, the maximum deviation of the outside diameter between the π -tape and water draw methods is 0.27 mm, and the uncertainty due to elliptical bias was 5.1 × 10 −5 % [11]. As the water draw method has many factors contributing to measurement uncertainty, such as the calibration of the length scale, the thermometer, pressure gauge and height measuring instrument which is using an electrode based on the surface tension of water, and the vertical installation of the bell, it is difficult to accurately measure the bell inside diameter in the field according to the water draw method. ...
... The volume of oil adhering to the bell, V oil,ad , is given as Eq. (10) [11]. Table 7 Uncertainty of the collection volume, ...
Many NMIs (national measurement institutes) and calibration laboratories worldwide use a bell prover as a calibration system for gas flow meters. The basic definition and procedure to estimate the bell prover uncertainty have been given in previous studies. After the announcement of a mutual recognition agreement (MRA) in 1998 by the BIPM (Bureau International des Poids at Mesures), many NMIs have needed to have more details of uncertainty evaluation procedure of the bell prover. In this study, more details of the test procedure of bell prover uncertainty are presented with a modification of position of the temperature and the pressure sensor to measure more exact values. The other modification is to use three precise guide rods with bearings to make the pressure in the bell more stable. Furthermore, a laser interferometer is used to enhance the measurement accuracy of the testing time and the traveling length of the bell. The uncertainty of the bells estimated by the procedure given in this study is 0.13% at the confidence level of 95%, rather than 0.17% of the previous one. Recently, the results of CCM.FF-K6, which is an international comparison of NMIs organized by the CIPM (Comité International des Poids et Mesures), show that the uncertainty of the KRISS (Korea Research Institute of Standards and Science) bell prover estimated by this study is reasonable.
