JPH068501Y2 - Electromagnetic flowmeter earth ring - Google Patents

Description

TECHNICAL FIELD The present invention relates to an earth ring of an electromagnetic flowmeter.

2. Description of the Related Art As is well known, an electromagnetic flowmeter measures the flow rate of a conductive fluid flowing in a measuring tube by using Faraday's law of electromagnetic induction. That is, a coil that generates a magnetic field orthogonal to the flow of the measuring tube is arranged, and the minute electromotive force generated in the conductive fluid flowing in the magnetic field is insulated on the inner surface of the measuring tube orthogonal to the flow and the magnetic field. It outputs as an electric signal through a pair of electrodes arranged, and the micro electromotive force between the electrodes is measured with reference to the potential of the earth ring pressed against the end face of the measuring tube. Therefore, the potential of the earth ring must be reliable and stable.

As shown in FIG. 3, the electromagnetic flowmeter has a lining 2 made of an insulating material such as resin on the inner wall of a measuring tube 1 made of a non-magnetic material.
A pair of electrodes 4 are embedded on the diameter of the measuring tube 1 in contact with the fluid and insulated from the measuring tube 1. A main part 11 such as a coil for generating orthogonal magnetic fields is housed and fixed in the measuring tube 1. When the fluid is a relatively weakly active fluid such as water, as shown in FIG. 3 (a), the end face of the measuring tube 1 is provided with a corrosion-resistant conductive annular earth ring substrate 7 such as stainless steel.
Is attached, the conductor bar 3 is welded, and the other end of the conductor bar 3 is connected to the measuring tube 1 with a screw 5 to securely hold the earth potential. However, since corrosive liquids such as strongly active acids and alkalis are corroded, it is possible to ground the measuring tube 1 to the same potential as the fluid through the conductive pin 6 made of platinum or a noble metal such as tantalum or zirconium. It was done. 3 (b) and 3 (c) are views showing an example in that case. In FIG. 3 (b), the conductive pin 6 penetrates the surface of the lining 2 and is implanted in the measuring pipe 1, In the figure,
(A) and (b) are combined, that is, the earth ring substrate 7 is insulated with the resin lining 8 and the conductive pin 6 is implanted on the inner peripheral surface of the ring. As described above, the outer peripheral surface of the earth ring is connected to the measuring tube 1 through the conductor bar 3.

However, the conductive pin 6 in the above-mentioned conventional technique is not only extremely expensive, but even if the conductive pin 6 is implanted in the measuring tube 1 by penetrating the resin coating lined, the conductive pin 6 and the conductive line 6 are electrically conductive. A slight gap may occur due to creep or the like between the pin 6 and the corrosive liquid from this gap penetrates into the inner surface of the measuring tube 1, so that it cannot be said that it is always stable over a long period of time. there were.

Means for Solving Problems The present invention has been made in order to solve the problems of the above-mentioned conventional techniques, and an object thereof is to provide an earth ring which is inexpensive and can secure a stable earth potential for a long period of time.
That is, the earth ring is a ring-shaped metal ring, and a conductive resin ring made of carbon resin or the like covering the inner peripheral portion of the earth ring from one surface of the metal ring to the inner peripheral surface to the other surface. The plurality of earth rings are welded at one end at a plurality of positions on the outer circumference of the metal ring, the other end is fixed to the outer peripheral surface of the measuring tube, and the conductive holding spring that expands and contracts in the flow direction is applied to the end surface of the electromagnetic flowmeter. It can be pressed coaxially.

Embodiment FIG. 1 is a schematic view for explaining an embodiment of the present invention. In the figure, parts having the same functions as those of the prior art shown in FIG. 3 are the same as those in FIG. The reference number is attached and the description is omitted. In FIG. 1 (a), a flangeless electromagnetic flowmeter is clamped by a flange 9 (the other flange is not shown),
It is arranged coaxially with the flow pipe 92, and after being inserted between the flow pipe 92 and a flange of another flow pipe (not shown) coaxial therewith, the bolt hole 9
It is clamped to 1 through a bolt. The earth ring substrate 7 is an annular stainless steel, and as shown in detail in FIG. 1 (b) and FIG. 1 (c) which is a plan view of FIG. 1 (b),
One surface 71 and the other surface 72, inner peripheral surface 73, outer peripheral surface 74
have. Reference numeral 32 denotes a conductive resin ring, which has a double structure in which a conductive resin, for example, carbon tetrafluoride ethylene is used alone or is adhered or closely adhered to a wire mesh. The shape of the conductive resin ring 32 is a ring shape having a concave cross section, and the recess covers the earth ring substrate 7 over one surface of the earth ring substrate 7 and the inner peripheral surface 73 and the other surface. It is inserted so as to cover it. The conductive holding springs 31 are welded to the outer peripheral surface 74 of the earth ring 7 at a plurality of locations. The conductive holding spring 31 is composed of an arc-shaped spring 311 that expands and contracts in the flow axis direction and a flat portion 313 at the other end, and the screw 5 is inserted into a screw hole 312 provided in the flat portion 313 so that the measuring tube 1 has a Screw on the end face.

The earth ring described above includes the end face 2 of the electromagnetic flowmeter and the flange 9
Since they are pressed against each other by sandwiching, the contact resistance between the earth ring substrate 7, the flange 9 and the conductive resin ring 32 is lowered, and the ground resistance can be made sufficiently small. Further, the spring 311 can prevent the conductive resin ring 32 and the creep from affecting. FIG. 1D shows a structure in which a through hole 75 is formed in a part of the earth ring substrate 7 and the conductive resin ring 32 is integrally brought into close contact with the earth ring substrate 7. Further, it is also possible to fix an annular pressing ring 35 having an L-shaped cross section to the conductive holding spring 31 and press the open end of the lining 2 by the pressing ring 35.

The electromagnetic flowmeter shown in FIG. 2 shows a case where the electromagnetic flowmeter has a flange structure, and shows a state in which the earth ring of the present invention having the same structure as that of FIG. 1 is pressed. Shows.

Effect As described above, according to the earth ring of the present invention, the earth ring substrate 7 is liquid-tightly sealed by covering the inexpensive earth ring substrate 7 made of conventional stainless steel with the conductive resin ring made of resin containing carbon, The contact surface can be grounded with a low contact resistance value by press contact, and the conductive holding spring 31 allows the conductive resin ring 32 to be grounded.
The effect of creep deformation can be prevented, and a long-term stable earth ring can be provided with the same or better effect without using a conventional expensive metal such as platinum.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view for explaining an example of an electromagnetic flowmeter equipped with an earth ring of the present invention, FIG. 1 (b),
(C) is a detailed explanation view of the earth ring of the present invention, FIG. 1 (d) is a view showing another earth ring structure of the present invention, and FIG. 2 is an earth ring of the present invention for a flange type electromagnetic flowmeter. Fig. 3 (a), which shows an example of the case where the
(B), (c) is a figure for demonstrating a prior art. 1 ... Measuring tube, 2 ... Lining, 4 ... Electrode, 7 ...
Earth ring substrate, 31 ... Conductive holding spring, 32 ... Conductive resin ring.

Claims (1)

[Scope of utility model registration request] 1. A non-magnetic measuring tube having an insulated inner surface sandwiched by a flow tube through which a fluid flows through an earth ring, and a pair of electrodes arranged to face each other on the diameter of the measuring tube. An electromagnetic flowmeter comprising magnetic field generating means for applying a magnetic field orthogonal to a flow and a diameter including electrodes, and for determining the flow rate from an electric signal output between a pair of electrodes with reference to the potential of the earth ring. A ring-shaped metal ring, and a conductive resin ring made of carbon resin or the like covering the inner peripheral portion of the earth ring from one surface of the metal ring through the inner peripheral surface to the other surface. The earth ring is welded at one end at a plurality of positions on the outer circumference of the metal ring, the other end is fixed to the outer peripheral surface of the measuring pipe, and is coaxially pressed onto the end surface of the electromagnetic flowmeter by a conductive holding spring that expands and contracts in the flow direction. Made possible Earth ring of the electromagnetic flowmeter according to claim.