WO2012152560A1

WO2012152560A1 - A gas meter, particularly for high flow rates

Info

Publication number: WO2012152560A1
Application number: PCT/EP2012/057175
Authority: WO
Inventors: Francesco RAMPAZZO
Original assignee: Metersit S.R.L.
Priority date: 2011-05-12
Filing date: 2012-04-19
Publication date: 2012-11-15
Also published as: ITPD20110148A1

Abstract

What is described is a gas meter apparatus, particularly for high flow rates, comprising a boxlike casing (2) having an inlet section (3) and an outlet section (4) for the flow of gas, and comprising a device (5) for measuring the flow of gas supplied through the meter, wherein the measuring device (5) comprises a mass flow sensor (6) placed inside the casing, through which flows a predetermined part (P) of the total flow (Q) supplied to the outlet section (4) of the meter, the predetermined part of the flow being correlated with the total flow in such a way that the total flow supplied, which is indicative of the consumption of gas, is determined from the measurement made by the mass flow sensor (6), on the basis of the correlation present between the predetermined part (P) of the flow and the total flow (Q).

Description

A gas meter, particularly for high flow rates

Technical field

The present invention relates to a gas meter apparatus having the features described in the preamble to Claim 1, which is the principal claim.

Technological background

The invention relates particularly, but not exclusively, to the field of gas meters designed for remote control of their functionality, which include electronic remote control systems compatible with the regulations of the competent authorities (AEEG Directive 155/08) and in accordance with the current statutes. In this field, there is a need to measure gas flows for metrological purposes, not only for meters for domestic use (such as those identified by the symbols G4/G6 in the Italian regulatory system), but also for high flow rate industrial meters (identified by the symbols G10, G16, G25, G40, and so on, where for example G25 denotes flow rates of up to 48,000 litres per hour).

For these classes of industrial meter, the measurement methods are typically based solely on volumetric principles, and the meters make use of two main technologies, namely the deformable wall and the rotary technology. In both of these volumetric solutions, the measurements are subject to errors of approximation arising from variations of pressure and temperature, making it necessary to use additional volume correctors which for pressure and temperature compensation, and requiring the use of corresponding pressure and temperature sensors.

In the field of meters for domestic use, there are also known technical solutions for meters based on the use of flow meters made in the form of thermal mass sensors. As a general rule, sensors of this type require adaptors in which devices are provided to create a laminar gas flow in order to isolate and protect the sensor from turbulence which might affect the accuracy of measurement. These solutions, which are acceptable for use in domestic gas meters, where the cross sections in use are adequate to provide measurements and pressure drops in accordance with the regulations, must be modified for use in the field of high flow rate industrial meters, because the aforesaid solutions are not sufficiently robust to withstand the stresses and disturbances caused by the flow to be measured. In particular, the known solutions are highly sensitive to disturbances caused by asymmetrical constrictions (typically found in valves) in the gas conduit, especially if they are present in the proximity of the sensor (typically in the vicinity of the outlet neck of the meter), this limitation being mainly due to the high energy of the flow.

Other prior art solutions for high capacity meters propose the use of a multiplicity of mass flow sensors, in which the total flow is substantially divided into a plurality of smaller flows, in each of which a corresponding mass flow sensor of the type specified for smaller capacity meters (G4/G6) is made to operate. However, this solution is subject to the limitations of highly complicated construction and is also costly, owing to the multiplicity of flow sensors required for use in an industrial meter.

The aforesaid known solutions are also subject to the limitation of low "intrinsic scalability" of the sensors, since dedicated flow sensors have to be designed and constructed for each individual class of meter.

Disclosure of the invention

The principal object of the invention is that of providing a gas meter apparatus whose structural and functional design is such that the limitations of the aforementioned prior art can be overcome.

This object is achieved by the invention by means of a meter apparatus made in accordance with the following claims.

Brief description of the drawings

Other features and advantages of the invention will become clear from the following detailed description of a preferred example of embodiment thereof, illustrated purely for guidance and in a non-limiting way in the attached drawings, in which :

Figure 1 is a schematic sectional view of a meter apparatus made according to the invention;

Figure 2 is a cross-sectional view taken along the line II-II of Figure 1; and Figure 3 is a view corresponding to that of Figure 1, in a variant embodiment of the invention.

Preferred embodiments of the invention

With reference to Figure 1 initially, the number 1 indicates the whole of a gas meter apparatus made according to the present invention and illustrated schematically in axial section. It is designed particularly for use as a remote control gas meter suitable for the measurement of high flow rates such as those normally found in an industrial setting.

The meter comprises a boxlike casing 2, preferably made of metallic material, in which are provided an inlet section 3 and an outlet section 4 for the flow of gas. These inlet and outlet sections are conveniently made in the form of cylindrical sleeves or necks with appropriate threaded connectors which can be fixed in a gas-tight way in corresponding through holes formed in a wall 2a of the boxlike casing. Thus the sections 3 and 4 have principal axes (defining the directions of inflow and outflow of gas to and from the meter) indicated by 3' and 4' respectively, these axes being parallel and spaced apart from each other. The meter also comprises a device for measuring the flow of gas supplied, indicated as a whole by 5, which comprises a thermal mass flow sensor 6 in an adaptor casing 7. The sensor, with its casing 7, is located at one end 8a of an auxiliary conduit 8 which extends within the casing 2 and which is connected, at its opposite end 8b, to the outlet section 4 of the meter.

More specifically, the sensor and the conduit 8 are designed to allow the passage through them of a predetermined part, denoted P, of the total flow Q of gas supplied at the outlet section 4 of the meter. Part P of the flow, which represents a calculable and specifiable percentage of the flow Q, is therefore correlated with the total flow, and consequently the supplied flow Q, indicative of the gas consumption, is determined on the basis of the measurement made by the sensor 6 (which measures part P of the flow), in accordance with the correlation between this part P of the flow and the total flow Q.

The conduit 8 also opens at its end 8b into the outlet section 4 of the meter, thus forming part of the section 4. In this way the passage cross section of the end 8b of the conduit forms a part of the width of the whole outlet section 4 of the meter, the correlation between these widths reflecting the correlation ratio between part P of the flow and the total flow Q.

More specifically, the end 8b of the conduit 8 is circular in shape and is coaxial with the outlet section 4 which is also circular. Thus the part of the total flow Q which does not pass through the auxiliary conduit 8 is supplied through an annular passage cross section delimited between the outlet section 4 and the central section of the conduit 8. The number 10 indicates spacer elements, conveniently made in the form of radial appendages, shown purely schematically in Figure 2, for supporting the conduit 8 in a centred and coaxial way in the outlet section 4 of the meter. In the example described, four appendages 10 are provided, spaced at regular angular intervals, but a different number and corresponding arrangement could be provided for the purpose of supporting the conduit 8 in the area of the outlet section 4.

As shown in Figure 1, the sensor 6 housed in its adaptor casing 7 is positioned at the end 8a of the conduit 8 so as to be remote from the area close to the outlet section 4, thus substantially reducing the effects caused by the high energy of the flow present in the section 4 on the measurements made by the sensor 8, and therefore attenuating the disturbing action of the flow on the sensor 8. In the adaptor casing 7 associated with the sensor 8, means can conveniently be provided to create a laminar flow of gas and isolate or in any case protect the sensor 6 from the turbulence of the flow.

Also provided is an electronic circuit board (not shown), suitably connected to the sensor 6 through connections 11, for implementing the metrological application functions (such as acquisition of measurements, their processing according to the corresponding load curves and consolidation into bands, tariff programs, and the like) and for communicating with the remote control acquisition system based on ordinary mobile communications technology (GSM, GPRS, UMTS, and the like).

Figure 3 shows a variant of the invention which differs from the preceding example mainly in that a by-pass conduit 12 is provided on the auxiliary conduit 8, the by-pass conduit being connected in fluid communication with the conduit 8 by means of a section 12a which is upstream and a section 12b which is downstream relative to the direction of the flow through the conduit 8.

The flow sensor 6 is fitted in the by-pass portion 12 between the sections 12a and 12b, and is suitably designed to provide a measurement of the flow passing through the conduit 8 by determining the flow passing through the by-pass 12. In this example also, the conduit 8 can be provided, in the portion between sections 12a and 12b, with flow straightener devices adapted to ensure the accuracy and reliability of the measurements made by the sensor.

In operation, the meter according to the invention is designed to measure flows and consequently high consumption levels on the basis of an accurate and reliable measurement of smaller flows, these smaller flows being obtained from an auxiliary conduit in which the sensor is located, the sensor and the corresponding conduit being selected so as to allow a known and specifiable percentage of the total flow to pass through them. By means of this correlation it is therefore possible to measure high flow rates such as those encountered in meters intended for industrial applications, by using sensors and measurement methods as described previously in relation to smaller meters mainly intended for domestic use.

By simply modifying the auxiliary conduit or the by-pass present in the meter, it is advantageously possible to cover a wide range of desired flow rates.

Since it is possible to utilize the characteristics of smaller capacity sensors, the use of these sensors is also convenient in industrial meters, in terms of immunity to contaminants (dust) and also in terms of gas recognition, and there is no need to adapt the sensors to the much larger flows found in meters for high flow rates. Economies of scale can also be achieved in respect of the sensors, owing to the fact that a common type of sensor can be used in a wide range of meters, from the smallest domestic models to the larger ones for industrial use.

The invention also enables greater robustness and reliability of measurement to be achieved when there are perturbations in the flow, since a sensor designed to measure only a proportion of the total flow will only be affected by a corresponding proportion of the energy of the flow.

A further important advantage is that the ratio between pressure drop and flow rate can be utilized more efficiently in a sensor of this type which is affected by only a proportion of the total main flow.

The meter apparatus according to the invention thus achieves the proposed objects, overcomes the drawbacks of the known solutions, and yields the benefits stated above.

Claims

A gas meter apparatus, particularly for high flow rates, comprising a boxlike casing (2) having an inlet section (3) and an outlet section (4) for the flow of gas, and comprising a device (5) for measuring the flow of gas supplied through the meter, characterized in that the measuring device (5) comprises a mass flow sensor (6) placed inside the casing (2), through which flows a predetermined part (P) of the total flow (Q) supplied to the outlet section (4) of the meter, this predetermined part of the flow being correlated with the total flow in such a way that the total flow supplied, which is indicative of the consumption of gas, is determined from the measurement made by the mass flow sensor (6), on the basis of the correlation present between the predetermined part (P) of the flow and the total flow (Q).

A meter apparatus according to Claim 1, wherein the mass flow sensor (6) is provided with an auxiliary conduit (8) through which the predetermined part of the total flow passes, this conduit (8) extending inside the casing (2) between a first end (8b) of the conduit opening into the outlet section (4) of the meter and a second, opposite, end (8a) of the conduit placed in a position remote from the outlet section (4) of the meter, the mass flow sensor (6) being placed in the proximity of the second end (8a) of the conduit.

A meter apparatus according to Claim 2, wherein the size of the passage cross section of the first end (8b) of the conduit (8) is correlated with the total size of the outlet section (4) of the meter, in accordance with the correlation ratio between the predetermined part of the flow and the total flow.

4. An apparatus according to Claim 3, wherein the auxiliary conduit (8) is placed coaxially within the outlet section (4) of the meter, thus forming an annular passage section for the passage of the part of the total flow of gas which is not conveyed by the auxiliary conduit (8).

5. An apparatus according to any one of the preceding claims, wherein a bypass conduit (12) is provided on the auxiliary conduit (8) and extends between a first and a second connecting section (12a, 12b) connected to the auxiliary conduit (8), and the mass flow sensor (6) operates in the by-pass conduit portion to measure the flow passing through the auxiliary conduit

(8).