GB2410555A

GB2410555A - Electromagnetic flow meter

Info

Publication number: GB2410555A
Application number: GB0402112A
Authority: GB
Inventors: Nigel Langham
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-01-30
Filing date: 2004-01-30
Publication date: 2005-08-03
Also published as: GB0402112D0; WO2005073675A2; WO2005073675A3

Abstract

An electrode (1) for an electromagnetic flowmeter comprises a body having a threaded portion (5) for securing the body, in use, within one of a pair of threaded radial through openings (9) formed in a collar (6) at diametrically opposite sides thereof. The electrode further includes an electrical terminal (3), and a self piercing electrode tip (4) in electrical contact with the terminal, which electrode tip, upon screwing the body into the housing (9), pierces the skin of a conduit so as to extend into the conduit and into electrical contact with a medium flowing therein whilst maintaining a medium tight seal with the walls of the conduit so as to prevent leakage of the media therefrom. The collar has magnets (12) for creating a magnetic field across the conduit. The flowmeter assembly (6,1) is easily fitted to existing pipes and conduits.

Description

24 1 0555 Electromagnetic Flowmeters The present invention relates to

electromagnetic flow meter assemblies and electrodes for use therewith.

Electromagnetic Dowmcters are known in the art which use Faraday's law of electromagnetic induction to measure the flow rate of a conducting medium flowing within a conduit. Faraday's law of electromagnetic induction states that voltage will be induced in a conductor moving through a magnetic field. If, then, a magnetic field is induced across a conduit through which a conducting medium is flowing, for example by positioning magnets on opposites sides of the conduit, a voltage will be induced across the flowing medium in a direction perpendicular to the magnetic field. This voltage can be measured by electrodes located in the conduit, spaced apart in the direction perpendicular to the magnetic field and in electrical contact with the medium. The magnitude of the induced voltage will be directly proportional to the velocity of the flowing medium, the distance between the electrodes, and the strength of the magnetic field, knowledge of the latter two parameters enabling the flow rate to be calculated once the system is calibrated.

The magnets do not need to be in electrical contact with the conducting medium in order to induce the required magnetic field, and hence can very easily be mounted outside of the conduit without compromising the integrity of the conduit. However, in order to be effective, the electrodes must be in electrical contact with the conducting medium, and, since modern water pipes are typically made of non-conducting plastics material, this means the electrodes must be positioned inside the apertures of the conduit, typically at diametrically opposite sides thereof. Conventionally, this is achieved by removing a section of the conduit and mounting a pre-formed flow meter in line in the conduit between the ends of the cut section. This has the drawback, however, that since the conduit is cut during the installation process, it is necessary to cut off the supply of the medium to the conduit to prevent leakage of media whilst the installation operation is performed. This is clearly undesirable where the conduit is supplying essential services such as domestic and business water supplies.

According to one aspect of the present invention there is provided an electrode for an electromagnetic flowmeter comprising a body have mounting means for securing the body, in use, within a housing, an electrical terminal and a self piercing electrode tip in electrical contact with the terminal, which electrode tip, upon mounting the assembly within the housing in use, pieces the skin of a conduit so as to extend into the conduit and into electrical contact with a medium flowing therein whilst maintaining a medium tight seal with the walls of the conduit so as to prevent leakage of media therefrom.

An electrode assembly in accordance with the invention has the advantage that the electrode can be installed within a conduit without compromising the media tight integrity of the conduit, and therefore can be installed without necessitating cutting off of the supply of the media to the conduit. This will, in turn, facilitate quick installation of the flowmeter, saving both time and money.

Preferably, the mounting means of the body takes the form of a thread formed on the outer surface thereof, by means of which the assembly may be screw mounted within the housing. Rotation of the body during mounting of the assembly within the housing results in the self piercing tip drilling through the walls of the conduit, which is particularly advantageous since a particularly smooth hole in the wall of the conduit is thereby produced which facilitates scaling of the electrode tip therein. However, the mounting means may alternatively take the form of a tapering friction fit surface on the body which is a press fit within the housing, the piercing tip then simply being pressed through the wall of the conduit upon inserting the body into the housing. A securing collar may also then be used to further secure the body within the housing.

The piercing tip is advantageously formed with a sealing coating on its sides which forms an effective seal with the material of the conduit upon installation whilst keeping the very tip of the electrode exposed to the medium as so as ensure effective electrical contact between the electrode and the conducting medium. Alternatively or additionally, the electrode may be sealed with the pierced conduit by provision of sealing means between the body and the housing.

According to another aspect of the present invention, there is provided an electromagnetic flowmeter assembly comprising an electrode according to the first aspect of the invention, a housing having at least one through opening therein for receiving the electrode, electrode mounting means associated with the or each through opening which complements the mounting means of the electrode so as, in use, to secure the electrode within the housing, and anchoring means for securing the housing to a conduit.

Preferably, the electrode mounting means associated with the or each through opening comprises a thread formed within the opening which complements a thread formed on the outer surface of body of the electrode. The electrode is then screwed into the opening of the housing, securing it in place whilst at the same time driving the piercing tip of the electrode through the wall of the conduit and into electrical contact with the fluid flowing there through by a drilling action. Alternatively, the electrode may be a slide fit within the or each through opening, which may, in turn, a clip or the like associated with it for retaining the electrode within the through opening.

The assembly further preferably includes sealing means which seals the electrode to the conduit to prevent escape of fluid through the pierced hole in the conduit. In one embodiment, the seal may take the form of a seal washer which engages between the body of the electrode and the housing, in particular the through opening therein.

However, other sealing means are possible, such as a self-sealing coating applied to the piercing tip of the electrode, a sealing material such as PTFE provided between the through opening and the body of the electrodes, in particular on thread formed therein, or the like.

Preferably the housing takes the form of a collar, such as a split collar, which is clampable around the conduit to secure the assembly thereto. The housing then preferably has a pair of through openings on diametrically opposite sides thereof for mounting electrodes at diametrically opposite sides of the conduits. The housing further, then preferably includes mounting means for attaching magnet means at diametrically opposite sides of the housing, preferably so that the magnetic field therebetween is perpendicular to the diameter upon which the pair of through openings are located. The magnets may be permanent magnets or electromagnets.

It will, of course, be understood that in practice, two electrodes are required for operation of an electromagnetic flowmeter.

The present invention still further provides a method of installing an electromagnetic flow meter assembly according to the second aspect of the invention, comprising the steps of attaching the housing to a conduit, inserting an electrode into a through opening formed therein such that the piercing tip thereof pierces the wall of the conduit and extends therethrough into electrical contact with a conducting medium flowing therethrough,, and engaging the electrode with mounting means associated with the through opening securing to retain it therein.

In the preferred embodiment, the mounting means is a screw thread which is engaged by a complementary thread formed on the body of the electrode during insertion of the electrode into the through opening, the thread being tightened to retain the electrode in position.

In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawing, in which: Figure I is a side view of an electrode according to the invention; and Figure 2 is a sectional view through a conduit having an electromagnetic flow meter assembly according to the invention mounted thereon.

Referring first to Figure 1, there is shown an electrode 1 formed with a main body 2 having a contact 3 formed on one end and an electrode tip 4 formed on the other, the tip 4 being in electrical contact with the contact 3. The body 2 also has a threaded portion 5 extending partially along its outer surface for securing the electrode I with a mounting collar 6 as described hereinafter. The electrode tip 4 is formed with a pointed end 5, which, upon being pressed again the surface of a conduit, operates to pierce the wall of the conduit and thereby allow the electrode tip 4 to be pressed through the wall of the conduit and into electrical contact with medium flowing therethrough.

The mounting collar 6 is formed from in two halves 6a, 6b which are connected together at diametrically opposite sides by means of bolts 7 which extend through flanges 8 so as to enable the collar to be positioned around a pipe and securing clamped in position. In the illustrated embodiment, the collar is circular for use with circular pipes, but it will be understood that it may be configured for use with pipes of any cross-sectional shape within the scope of the invention. Each half 6a, 6b of the collar has as a radial through opening 11 formed therein, from which an annular electrode housing 9 extends radially outwardly. The inner annular surface of each housing 9 is formed with a thread 10 which complements the threaded portion 5 of the body 2 of the electrode, and the housings are configured on the collar halves 6a, 6b such that, when clamped onto a pipe, they are positioned diametrically opposite each other as shown in Figure 2.

Each collar half 6a, 6b also has attached thereto an electromagnet 12a, 12b. The skilled reader will understand that any suitable and conventional means may be used for attached the magnets 12a, 12b to the collar halves 6a, 6b, and further details will not, therefore, be provided herein. The magnets 12a, 12b are positioned on the collar halves 6a, 6b so that the field generated therebetween through the pipe is substantially perpendicular to the diameter upon which the electrode housings 9 are formed.

The flow meter is installed as follows: The collar halves 6a, 6b are positioned at the required point along the pipe and are clamped together by means of the bolts 7 so as to secure the collar in position. An electrode I is then inserted into each electrode housing 9 with its piercing tip 5 directed toward the outer surface of the pipe and its threaded portion engaged with the thread of the housing 9. The electrode is then screwed into housing 9, the rotation of which causing the tip 5 to be driven through the wall of the pipe in a drilling action so as to extend into the aperture of the pipe and hence into electrical contact with the fluid flowing therethrough. A flange 13 on the body of the electrode 1 provides a screw stop against which the electrode can be tightened and also provides a depth gauge which ensures that each tip is located at a pre-defined radial position within the conduit and hence that the separation between the electrode tips is known, which parameter is required for calculation of the liquid flow rate. The magnets 12a, 12b may be attached to the collar either prior to or following clamping of the collar halves on to the pipe.

Any conventional materials may be used for the various components of the system, although preferably at least one of the threads of the electrode and the threads of the housings 9 are formed from a fluid sealing material such as PTFE or have a coating of such material provided on the surface thereof so as to prevent leakage of liquid through the threads. Alternatively or additionally, a seal washer can be provided on the body of the electrode l which is compressed between the flange 13 and the outer end of the housing 9 so as seal the threads. Each collar half 6a, 6b may also be provided with circumferentially extending seals on their inner circumferential surface, spaced axially on either side of the through opening 11 so as to prevent the escape of liquid from the pipe between the outer surface of the pipe and the inner surface of the collar 6.

The flow meter according to the invention can be operated in a conventional manner by attachment of suitable voltage measuring means across the contacts 3 of the two electrodes 1, and details will not, therefore, be provided herein.

It will be understood that, although the above described embodiment employs bolts 7 to clamp the halves of the mounting collar 6 around a pipe, spring clips or other releasable fastening means may instead be used for this purpose. Furthermore, the halves of the collar 6 may be fastened to the pipe using more permanent fastening means such as adhesive, by welding, by electrofusion or the like depending upon the application requirements and the materials involved.

Claims

Claims 1. An electrode for an electromagnetic flowmeter comprising a body

having mounting means for securing the body, in use, within a housing, an electrical terminal, and a self piercing electrode tip in electrical contact with the terminal, which electrode tip, upon mounting the assembly within the housing in use, pierces the skin of a conduit so as to extend into the conduit and into electrical contact with a medium flowing therein whilst maintaining a medium tight seal with the walls of the conduit so as to prevent leakage of the media therefrom.
2. An electrode according to claim 1, wherein said mounting means comprises a thread formed on an outer surface of the body which engages with a complementary thread formed in the housing, screwing of the electrode, in use, into the housing resulting in the electrode tip piercing through the skin of the conduit.
3. An electrode according to claim 1, wherein said mounting means is a tapering friction surface formed on the body which is of complementary size and shape to a friction surface formed on housing.
4. An electrode according to claim 3, further including a securing collar which, in use, operates to further secure the body within the housing.
5. An electrode according to any of the preceding claims, wherein the piercing tip has a sealing coating applied on the sides thereof, which, in use, provides a seal between the tip and the walls of the conduit.
6. An electrode according to any of the preceding claims, wherein seal means is provided on the body which engages, in use, with the conduit so as to sealing engage the electrode with the conduit.
7. An electromagnetic flow meter assembly comprising an electrode according to any of the preceding claims, a housing having at least one through opening therein for receiving the electrode, electrode mounting means associated with the or each through opening which complement the mounting means of the electrode so as, in use, to secure the electrode within the housing, and anchoring means operable, in use, to secure the housing to a conduit.
8. An electromagnetic flow meter assembly according to claim 7, wherein said electrode mounting means comprises a thread associated with the or each through opening, preferably formed on the inner wall of the or each through opening.
9. An electromagnetic flow meter assembly according to claim 7, wherein the or each electrode mounting means is a clip which retains the electrode in said opening.
10. An electromagnetic flow meter assembly according to any of claims 7 to 9, further including sealing means provided between the housing and the electrode so as, in use, to prevent escape of fluid from the conduit between said electrode and said housing.
11. An electromagnetic flow meter assembly according to claim, wherein said sealing means include a seal washer which engages between the body of the electrode and the walls of the associated through opening.
12. An electromagnetic flow meter assembly according to claim 10 or claim 11, wherein said sealing means include sealing material applied to at least one of the piercing tip (4) of the or each electrode, the electrode mounting means and the body of the electrode.
13. An electromagnetic flow meter assembly according to any of claims 7 to 12, wherein the housing takes the form of a collar which, in use, is positioned on the conduit so as to extend around the periphery thereof.
14. An electromagnetic flow meter assembly according to claim 13, wherein the collar is a split collar which is clampable around the conduit so as to secure the assembly thereto.
15. An electromagnetic flow meter assembly according to claim 13 or claim 14, wherein the collar has a pair of through openings at diametrically opposite sides thereof for mounting electrodes at diametrically opposite sides of the conduits.
16. An electromagnetic flow meter assembly according to any of claims 13 to 15, wherein the collar further includes mounting means offset from said through openings for attaching magnet means at diametrically opposite sides of the collar, in particular so that the magnetic field therebetween is perpendicular to the diameter upon which the pair of through openings are located.
17. An electromagnetic flow meter assembly according to any of claims 13 to 16, wherein said collar is formed of two collar halves which are connected together at diametrically opposing sides by said anchor means in the form of bolts so as, in use, to clamp the collar around the conduit.
18. A method of installing an electromagnetic flow meter assembly according to any of claims 7 to 17, comprising the steps of attaching the housing to a conduit, inserting an electrode into a through opening formed therein such that the piercing tip thereof pierces the wall of the conduit and extends therethrough into electrical contact with a conducting medium flowing therethrough, and engaging the electrode with mounting means associated with the through opening so as securely to retain it therein.
19. An electromagnetic flow meter substantially as herein described with reference to the accompanying drawings.
20. A method of installing an electromagnetic flow meter substantially as herein described with reference to the accompanying drawings.