WO2018109675A1

WO2018109675A1 - An electromagnetic flowmeter

Info

Publication number: WO2018109675A1
Application number: PCT/IB2017/057863
Authority: WO
Inventors: Ravikumar KANDASAMY; Subhashish Dasgupta; Philipp Nenninger; Frank Gotthardt; Ralf Baecker; Rostyslav TYKHONYUK; Nizar AOUNI
Original assignee: Abb Schweiz Ag
Priority date: 2016-12-14
Filing date: 2017-12-13
Publication date: 2018-06-21

Abstract

Electromagnetic flowmeter for measuring flow of fluid in a conduit of the electromagnetic flowmeter. The electromagnetic flowmeter comprises a coil mounted on a surface of the conduit and excited by an excitation unit for generating an electromagnetic field; a pair of electrodes mounted on the conduit for measuring potential difference generated by the interaction of electromagnetic field in the fluid to determine the flow of fluid in the electromagnetic flowmeter; the coil is supported with a support element of non- magnetic material for holding the mounting of the at least one coil; wherein the coil has a first surface area that is overlaid on the support element, and has a second surface area that overhangs on a side from any of the edges of the support element; and wherein the support element is mounted on the coil such that the second surface area is less than the first surface area.

Description

AN ELECTROMAGNETIC FLOWMETER

FIELD OF THE INVENTION

The present invention relates generally to an electromagnetic flowmeter for measuring flow of fluid and more particularly to an electromagnetic flowmeter with coils to maximize electromagnetic field and minimize coil overhanging.

BACKGROUND OF THE INVENTION

Measurement of flow of fluids through a conduit or pipe can be done by numerous ways like using electromagnetic flowmeters. A typical electromagnetic flowmeter works on Faraday's law of electromagnetic induction. An electromagnetic field is imposed within a flow pipe having a flow of fluid with a certain level of conductivity. Electromotive force (EMF) induced as a result of the interaction of the electromagnetic field with fluid molecules (ions in the fluid), is measured using electrodes provided at the pipe side walls. The measured EMF is proportional to the flowrate and thus used to measure flowrate. While electromagnetic flowmeters are attractive given that they have high accuracy and simplistic in construction, it is desirable to reduce the material cost and/or weight of the flowmeters, especially for application in large diameter flow pipes.

The imposition of magnetic field is done using copper coils by electrically exciting the copper coils. The magnetic fields produced by the copper coils are enhanced with use of magnetic inserts, referred simply as inserts or magnetic cores. The sensitivity of the electromagnetic flowmeter is directly influenced by placement of these copper coils and inserts. Also, the shape of coils play an important role in the performance (e.g. sensitivity, accuracy, linearity) of the electromagnetic flow meter. Most electromagnetic flowmeters conventionally use saddle shaped coils for magnetic field generation. Saddle shaped coils have been generally found to be suitable in terms of shape, accuracy, sensitivity and other related parameters, however other shapes of coil such as diamond shaped coils are also popular.

These coils, whatever be the shape, needs to be mounted on the surface within the electromagnetic flowmeter and be closer to the fluid passing through the electromagnetic flowmeter. A steel or metallic corset (supporting element for the coils) is provided around the rubber or non-metallic liner of the Electromagnetic (EM) flow meter. The coils are then attached to the corset using a glue or adhesive. Next, the assembly is inserted in a cover of carbon steel or a suitable magnetic material which acts as a magnetic shield and also as a housing for the internal components. The space between the carbon steel cover and the internal components is filled using a potting material like resin which hardens with time. The potting material ensures electrical insulation and support to the internal components.

Conventionally, assembling of coils in the electromagnetic flowmeter comprises mounting the coils for magnetic field generation along with cylindrical stainless supports (corsets) which are in turn mounted on rubber or non-magnetic liners to support the coils. However, considerable area of the coils for magnetic field generation may extend or overhang beyond the corset and can affect quality of support to the coil. For reasons such as their design, manufacturability, use of one design of corsets in manufacturing of varied size flowmeters, and cost, corsets can be limited in length and contribute to the problem of overhanging of coils beyond the corsets and consequently leading to structural and performance issues in the electromagnetic flowmeter. These limitations relating to corsets and coil shapes for improving electromagnetic flow meter performance need to be improved upon.

Hence there is a need for an improvement in electromagnetic flowmeter with minimized overhanging of coils and maximum generation of electromagnetic field. In particular, the corset being expensive, it is desired to limit the length of the corset (avoiding covering of the entire liner length). However, a substantial portion of the coil overhangs resulting in air gap between the coil and rubber liner. This causes structural weakness during operation (high pipe pressure)

and possible failure. Hence it is proposed to develop other coil shapes with substantial reduction in overhanging portion while maintaining sufficient signal strength.

SUMMARY

The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.

In one aspect, the present invention provides an electromagnetic flowmeter for measuring flow of fluid flowing in a conduit of the electromagnetic flowmeter. The electromagnetic flowmeter comprises a coil provisioned and excited by an excitation unit. The coil provides for generating an electromagnetic field and is mounted on a surface of the conduit. The electromagnetic flowmeter comprises a pair of electrodes which are mounted on the conduit for measuring potential difference generated by the interaction of electromagnetic field in the fluid to determine the flow of fluid in the electromagnetic flowmeter. The coil which is mounted on the surface of the conduit is supported with a support element of a non-magnetic material. The support element helps in holding the mounting of the coil. The coil has a first surface area from a total surface area of the coil that is overlaid on the support element, and has a second surface area from the total surface area of the coil that overhangs on a side from any of the edges of the support element. Finally, the support element is mounted on the coil such that the second surface area is less than the first surface area.

In an embodiment of the present invention, the electromagnetic flowmeter comprising the coil is provisioned with an insert and the shape of the insert corresponds to the shape of the coil. In an embodiment of the present invention, the support element of a non-magnetic material for holding the mounting of the coil is made of steel.

In an embodiment of the present invention, the electromagnetic flowmeter comprising the coil is a diamond shaped coil.

In an embodiment of the present invention, the electromagnetic flowmeter comprising the coil is hexagonal shaped coil.

In an embodiment of the present invention, the coil is wound as a two-layered coil. In an embodiment of the present invention, the measured flow of fluid in the conduit is transmitted to a remote control center of the electromagnetic flowmeter for storage or analysis.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts hexagonal-shaped coils along with support element mounted on the conduit of the electromagnetic flowmeter.

Figure 2 depicts a saddle shaped coil mounted on the conduit of the electromagnetic flowmeter.

Figure 3a depicts a diamond shaped coil mounted on the conduit of the electromagnetic flowmeter.

Figure 3b depicts a diamond shaped sheet of metal or insert to be mounted on the electromagnetic flowmeter.

Figure 4 depicts a hexagonal shaped coil along with insert or coil mounted on the conduit of the electromagnetic flowmeter.

Figure 5 depicts a stepped coil mounted on the conduit of the electromagnetic flowmeter.

Figure 6a depicts sheet of high permeable material for mounting on the electromagnetic flowmeter.

Figure 6b depicts a graph of magnetic flux density versus electromagnetic flowmeter conduit diameter.

Figure 7a illustrates a graph of percentage of error versus percentage of flowrate in an electromagnetic flowmeter without using sheet of metal or inserts attached to the coils.

Figure 7b illustrates a graph of percentage of error versus percentage of flowrate while using sheet of metal or inserts attached to the coils.

DETAILED DESCRIPTION

The present invention provides an electromagnetic flowmeter for measuring flow of fluid and more particularly provides for an improved electromagnetic flowmeter with better accuracy when concerning linearity of the flowmeter. As mentioned earlier, coils are used for inducing an electromagnetic field which in turn leads to measurement of flowrate of fluid passing through a conduit or flow pipe of the electromagnetic flowmeter. These coils can influence performance and sensitivity of the electromagnetic flowmeter as inducing a strong electromagnetic field for accurate results is dependent on the coils. And the coils are often supported by support elements or corsets. The corsets for supporting the coils are usually made of non-magnetic material like steel and used along with rubber liners. However as mentioned earlier, due to limitations at times in using corsets of a lesser dimensions, there can be structural issues in electromagnetic flowmeters concerning support to the coil. The present invention provides for improving electromagnetic flowmeter performance by overcoming such limitations. The present invention also provides for electromagnetic flowmeters with coils that can perform better than the currently popular saddle shaped coils, in terms of magnetic field generation and hence improve sensitivity of the electromagnetic flowmeter, achieved by increasing electromagnetic fields to interact with the fluid flowing through the electromagnetic flowmeter.

Accuracy (i.e. error observed in the range of the flowmeter) and sensitivity of electromagnetic flowmeters are directly impacted by the uniformity and intensity of the generated magnetic field. In order to achieve better performance, the present invention provides for alternative shapes for coils. And the coils are provided with attachments of sheets (magnetic inserts) made of high permeability metals where shape of these high permeability sheets of metal are taken into consideration to improve performance and achieve the desired accuracy and sensitivity of the electromagnetic flowmeters. In general copper coils are used but one may also use cost-effective materials like aluminum instead of copper for the coils and achieve similar performance standards (relating to electromagnetics and thermal).

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized. The following detailed description is, therefore, not to be taken in a limiting sense.

Figure 1 shows an electromagnetic flowmeter (100) for measuring flow of fluid flowing in a conduit (110). Electromagnetic flowmeters can measure flowrate for fluids with some amount of conductivity. As shown in Figure 1, the electromagnetic flowmeter (100) is provided with a coil (120) attached with an insert (130). It may be known to the person skilled in the art that there can be two sets of coil, a top coil and a bottom coil in an electromagnetic flowmeter. The coils of an electromagnetic flowmeter are electrically excited for generation of an electromagnetic field by an excitation unit, so that the electromagnetic filed interacts with the fluid passing through the conduit (100).

Figure 1 shows an electrode (140) mounted on the conduit (110) for measuring potential difference generated by the interaction of electromagnetic field in the fluid. Figure 1 only shows one of the electrodes (140) from a pair of electrodes wherein the other electrode is present on the opposite side of the conduit (not shown). The potential difference measured by the pair of electrodes (140) eventually determines the rate of flow of fluid in the electromagnetic flowmeter (100).

As shown in Figure 1, the coil (120) and the insert (130) are symmetrically mounted on the surface of the conduit around an axis (150). As shown in Figure 1, the coil (120) is a hexagonal shaped coil is said to be among most suitable for improving electromagnetic field and to minimize overhanging of the coils. The figure also depicts an axis of symmetry (central axis) which is perpendicular to the direction of flow of fluid. The figure also depicts the coils supported with a support element (160) of a non-magnetic material, also referred as corsets in this description. Though, the Figure 1 illustrates a central axis (as an axis for symmetry), for the purpose of the invention, the axis can be any axis perpendicular to the flow of the fluid and passing through the coil (i.e. also perpendicular to the surface of the coil). Also, it is possible to have non symmetrical assembly across the central axis. The support element (160) provides for securely mounting (holding) of the coil (120) and the insert (130).

Figure 1 also shows that the coil (120) has a first surface area (170) that is well supported by the support element (160) i.e. overlaid on the surface of the support element (160). In the invention, the support element (corset) being of a smaller dimension in comparison with the spread of the coil, there is an overhanging portion of the coil beyond the corset. As mentioned earlier, for cost reasons (material cost and manufacturing cost), one may use a slightly smaller size corset. It is also possible to have a design where multiple corsets of smaller size corsets may be used at different locations (can be symmetrical around an axis and each of the smaller size corsets separated uniformly along the span (distance between the two peripheral/outer points on a coil) of the coil. The effectiveness of support to the coil may be determined by the surface area of the coil that is supported by the corsets used for mounting. Therefore, out of the total surface area of the coil (120), one can define a surface area (170), also referred as a first surface area, that is supported by the corset. In the figure, the first surface area is depicted as a cylindrical area covering the corset around the conduit i.e. this portion of the coil is supported by the support element, (corset, 160). In view of the overhang and other surface of the coil that is not supported by the support element, one may have a second surface area ( 180) that is a portion of the total surface area of the coil (120) which lies exposed without the support from the support element (160). This second surface area (180) or exposed area is for example the portion of the coil that extends beyond the corset or support element and is the overhanging area of the coil. This exposed area (180), as shown in Figure 1, can lay on either (two) side of the corset or support element (160) and in the invention defined to lay on a side from any of edges of the support element (160) which is parallel to the axis of the support element (160). As it may be known to a person skilled in the art, the overhang area (180, though the Figure 1 shows only two sides) can lay on any side of the corset or support element (160), that is the overhang area (180) can lay on any of the sides from any of the edges of the support element (160).

As shown in Figure 1, 160a and 160b are the two edges that form sides of the support element (160), and the second surface area (180) that is overhanging i.e. not supported can lie on either side of the edges. For effective support, the support element (160) is mounted on the coil (120) such that the second surface area (180) is less than the first surface area (170), and accordingly the coil shape can be adjusted or developed.

Development of the hexagonal shape of the coil (120), as shown Figure 1, the area overhanging of the coils in greatly reduced in comparison to conventional saddle shaped coils. Figure 2, shows an electromagnetic flowmeter with conventional saddle shaped coil where the second surface area (180) can be much larger than the first surface area (170) and thereby may be limited in structural support provided by the corset (of similar dimension) to the coil though the saddle shaped coil may provide equivalent electromagnetic field as that of the hexagonal shaped coil. Hence for coil shapes such as hexagonal shaped coil as shown in Figure 1 , the overhanging area is reduced without affecting the coil performance.

Figure 3 a shows diamond shaped coil 300 with core or inserts 310. A coil and core combination is the diamond shaped coil with specially shaped core or insert attached below the coil. The net effect i.e. enhancement in EMF signal and improvement in accuracy over the saddle shaped coil with a similar core to the tune of 20% can be observed. Figure 3b shows the specially shaped core 310 below the coil. It is to be noted that the diamond coil without the core doesn't perform better than the saddle shaped coil with the core. It is the combination of both the coil and core that performs better as the inserts help in achieving a higher and more uniform electromagnetic field distribution across the pipe. In the diamond shaped coil as well, the overhanging area (second surface area) is less and EM field equivalent of that provided by hexagonal shaped coil or saddle shaped coil can be created. Though, the invention is illustrated with shapes of the coil that are well known (e.g. saddle shaped coil, diamond shaped coil), it is to be understood that shapes other than hexagonal or these well-known shapes of the coil can be developed to provide the required EM field intensity and required level of structural support by ensuring the surface area (second surface area) of the overhanging (unsupported) portion is less than the supported portion (first surface area).

Figure 4 shows an embodiment of the present invention with the hexagonal shaped coil 400 attached to specially shaped insert underneath. The combination of such specially shaped core with the hexagonal shaped coil contributes to better performance of the electromagnetic flowmeter.

Figure 5 shows another coil modification which is a stepped coil 500 that provides a higher electromotive force signal strength and accuracy than the saddle shaped coil without a change to the basic saddle shape. Figure 5 shows a modified coil 500 where it can be observed that a smaller or mini coil is attached atop the main coil. The electromagnetic flowmeter shown in Figure 5 uses a coil wherein one coil is wound as a two-layered coil. The amount of copper used is the same as the conventional saddle shaped coil, since the inner dimension of the coil was reduced and the removed copper was used to form the mini coil. Thus, such modification can result in reducing the overhanging portion (second surface area) and provide for better support to the coils with the corset without significantly affecting the EM field intensity requirement.

Figure 6a shows an embodiment of the present invention wherein thin sheets of high permeability metals (inserts) 600 are available for attaching below the coils and these inserts may also be made as per the shape of the coil to have well supported coil and insert assembly on the corset i.e. have similar first surface area (supported coil and insert assembly with the corset) and second surface area (overhanging/unsupported coil and insert assembly). As mentioned before, these inserts or core enhances magnetic field strength near the walls of the conduit and promote uniformity of magnetic field strength and enhanced performance of the coil (for various shape the coil is developed) can be achieved. Figure 6b shows a comparison between the magnetic field strength with and without the inserts. As observed in Figure 6b, the magnetic flux density versus pipe diameter plot shows that the decrease in magnetic field at the center has negligible effect on signal strength. The net effect is enhancement of signal by 20% and high measurement accuracy.

Figure 7a and Figure 7b show Test and Model results where improvement in accuracy or linearity with flowrate is observed. As observed in figure 7a and 7b, comparison between the % error versus % flowrate plots for Test and Model shows an improvement in accuracy and linearity in case of coils with inserts.

The electromagnetic flowmeter are provided with suitable power source and electronics circuitries for exciting the coils for producing electromagnetic fields for making potential difference measurements and display/transmitting the measured values. In an embodiment, the electromagnetic flowmeter can comprise a display for indicating the determined flow of fluid in the flow pipe.

In an embodiment, the electromagnetic flowmeter wherein the determined flow of fluid in the flow pipe (measured potential difference between the electrodes) is transmitted to a remote control center of the electromagnetic flowmeter for further analysis.

In an embodiment, the electromagnetic flowmeter is Internet of Things (IOT) enabled for providing remote controlling, better visibility of the working of the electromagnetic flowmeter, providing real time information to software systems and other surrounding IOT enabled systems.

The electromagnetic flowmeter described herein above comprises a processing device, an excitation unit, potential sensing electrodes, coils and a flow pipe or conduit through which fluids to be measured flow. The excitation unit is controlled by the processing device wherein the processing device is used for taking measurements from potential sensing electrodes. The coils are excited by the excitation unit wherein the power of excitation is controlled by the processing device. It may be known to the person skilled in the art that the processing device can internally calibrate the rate of flow of the fluid corresponding to the measured potential difference and results can be displayed or transmitted to a remote control centre for further analysis.

This written description uses examples to describe the subject matter herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. An electromagnetic flowmeter (100) for measuring flow of fluid flowing in a conduit (110) of the electromagnetic flowmeter, wherein the electromagnetic flowmeter (100) comprises: at least one coil (120) mounted on a surface of the conduit (110) and excited by an excitation unit for generating an electromagnetic field; a pair of electrodes (140) mounted on the conduit (110) for measuring potential difference generated by the interaction of electromagnetic field in the fluid to determine the flow of fluid in the electromagnetic flowmeter (100); wherein the at least one coil (120) is mounted on the surface of the conduit and supported with at least one support element (160) of a non-magnetic material for holding the mounting of the at least one coil (120); wherein the at least one coil (120) has a first surface area (170) from a total surface area of the at least one coil that is overlaid on the at least one support element (160), and has a second surface area (180) from the total surface area of the at least one coil that overhangs on a side from at least one edge (160a, 160b) of the at least one support element (160); and wherein the at least one support element (160) is mounted on the coil (120) such that the second surface area ( 180) is less than the first surface area.

2. The electromagnetic flowmeter as claimed in claim 1, wherein the at least one coil is provisioned with at least one insert and the shape of the at least one insert corresponds to the shape of the at least one coil.

3. The electromagnetic flowmeter as claimed in claim 1, wherein the at least one support element of a non-magnetic material for holding the mounting of the at least one coil is made of steel.

4. The electromagnetic flowmeter as claimed in claim 1, wherein the at least one coil is a diamond shaped coil.

5. The electromagnetic flowmeter as claimed in claim 1, wherein the at least one coil is a hexagonal shaped coil.

6. The electromagnetic flowmeter as claimed in claim 1 , wherein the at least one coil is wound as a two-layered coil.

7. The electromagnetic flowmeter as claimed in claim 1, wherein the measured flow of fluid in the conduit is transmitted to a remote control center of the electromagnetic flowmeter for storage or analysis.