JP5271552B2 - Electromagnetic flow meter - Google Patents

Abstract

Provided is an electromagnetic flow meter in which the portions of a lining (12) provided on the inner surface of a measurement pipe (1) which are easily scraped by particularly solid matters mixed in a liquid (4), i.e., lining portions (12B-1) near the inner peripheral surface opening parts of the measurement pipe (1) can be surely protected, and a measurement error is small, and accordingly, the reliability and durability of which can be improved. An earth ring (15) fixed to the pipe connection end surface (3a) of a measurement pipe (2) comprises a disk-like ring body (15A) and a cylindrical part (15B) so integrally provided as to be projected from the inner peripheral edge of the ring body (15A). The lining portion (12B-1) near the inner peripheral surface opening part of the measurement pipe (2) is covered by the cylindrical part (15B), thereby protecting the lining portion from solid matters such as slurry.

Description

  The present invention relates to an electromagnetic flow meter used for measuring a flow rate of a conductive fluid.

  There are two types of electromagnetic flowmeters: a flange type in which a measurement pipe made of a straight pipe is provided, and flanges for pipe connection are integrally provided at both ends, and a wafer type in which no flange is provided. In the case of the flange type, the lining material is coated on the inner peripheral surface of the measurement tube and the surface of the flange (piping connection end surface). In the case of the wafer type, the inner surface and end surface (piping connection end surface) of the measurement tube are also coated. By coating the lining material, the measurement tube and the fluid to be measured having a conductivity flowing in the measurement tube are electrically insulated. In addition, a pair of exciting coils are arranged on the outer peripheral surface of the measuring tube so as to face each other with the measuring tube interposed therebetween, and a pair of electrodes whose axis is orthogonal to the magnetic field generated by the exciting coil are provided through the tube wall of the measuring tube. In addition, an earth ring is attached to the pipe connection end face.

  The earth ring grounds the fluid to be measured flowing through the measuring tube and the same potential by grounding it, and detects the reference potential of the measurement, thereby detecting noise generated when the potential of the fluid to be measured becomes unstable. It has a function to erase and a function to protect the lining material coated on the pipe connection end face. Such an earth ring is usually made of stainless steel 316 or the like, but is formed of a noble metal such as platinum, titanium, monel, or hastelloy when corrosion resistance and wear resistance are required. For example, it may be formed by baking a platinum paste (see, for example, Patent Documents 1 to 5).

Japanese Utility Model Publication No. 7-12927 Japanese Patent Laid-Open No. 10-38648 JP 2002-277299 A Japanese Patent Laid-Open No. 2005-084040 Publication No. 58-501552

  By the way, especially when measuring the flow rate of a process fluid with an electromagnetic flow meter in a paper / pulp paper factory, if solids (wood, nails, metal pieces, etc.) are mixed in the process fluid, Because the lining material coated on the inner peripheral surface of the measuring tube, especially near the opening on the inner peripheral surface, is scraped off, the fluid flow is disturbed, resulting in a large measurement error, and the durability of the electromagnetic flow meter is remarkably increased. There was a problem of lowering.

  The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to reliably protect the lining portion that is easily scraped by the solid matter mixed in the liquid. An object of the present invention is to provide an electromagnetic flow meter with small errors and improved reliability and durability.

In order to achieve the above object, the present invention provides an electromagnetic flowmeter in which a lining material is coated on an inner peripheral surface of a measurement tube and a pipe connection end surface, and an earth ring is disposed on the pipe connection end surface via the lining material. the projected cylindrical portion which is inserted into the measuring pipe to the inner periphery of the ground ring, not covering the lining material in the vicinity of the inner peripheral surface opening of the measuring tube by the cylindrical portion, the thickness of the cylindrical portion group A tapered hole is formed which gradually decreases from the end toward the tip and whose inner surface increases in diameter from the base end toward the tip .

  In the present invention, the lining material in the vicinity of the opening on the inner peripheral surface of the measuring tube is covered as far as the range in which the cylindrical portion does not affect the magnetic field generated by the exciting coil.

In the present invention, since the lining material in the vicinity of the inner peripheral surface opening of the measuring tube is covered by the cylindrical portion provided in the earth ring, the solid material in which the lining material in the vicinity of the inner peripheral surface opening is mixed in the liquid Can be prevented from being scraped off, and the measurement error can be reduced. Since the lining material is most easily scraped off by the solid material in the vicinity of the opening on the inner peripheral surface of the measurement tube, it is extremely effective to protect the lining material near the opening on the inner peripheral surface with a cylindrical portion.
In the present invention, since the thickness of the cylindrical portion is gradually reduced from the base end toward the tip, the surface of the lining material coated on the inner peripheral surface of the measurement tube and the inner peripheral surface of the tip of the cylindrical portion The step formed between them can be reduced. Thereby, generation | occurrence | production of the turbulent flow which affects a measurement can be decreased.

  Further, in the present invention, since the lining material near the inner peripheral surface opening of the measuring tube is covered to the extent that the cylindrical portion does not affect the magnetic field generated by the exciting coil, measurement is not affected.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a sectional view showing an embodiment of an electromagnetic flowmeter according to the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG. In these drawings, the present embodiment shows an example applied to an electromagnetic flow meter 1 provided with a flange-type measuring tube 2.

  The measuring tube 2 is a straight tube with both ends open made of a nonmagnetic material such as SUS, and flanges 3 are joined to both ends of the outer peripheral surface 2a by TIG welding or the like. The flange 3 is formed of the same material as that of the measurement tube 2 or a different material, and the surface 3a forms a connection end face (pipe connection end face) of the pipe. A pair of exciting coils 5 for generating a magnetic field H in a direction perpendicular to the flow direction of the fluid 4 to be measured flowing in the measurement tube 2 in the center in the axial direction on the outer peripheral surface 2a of the measurement tube 2 are vertically oriented. Are provided so as to face each other. These exciting coils 5 are connected to a power source.

  A pair of electrodes 7 whose axis is orthogonal to both the magnetic field H of the exciting coil 5 and the flow direction of the fluid 4 to be measured are attached to the center of the tube wall of the measuring tube 2 in the axial direction. These electrodes 7 are inserted into through-holes 8 formed in the tube wall of the measurement tube 2 so that the inner end is exposed in the measurement tube 2 to form a liquid contact surface 7a with the fluid 4 to be measured. The outer ends are connected to conversion units 9 provided on the upper part of the measuring tube 2 via signal lines 10 respectively.

  Further, the inner peripheral surface 2b of the measuring tube 2 and the pipe connection end surface 3a of each flange 3 are coated with a lining material 12 to prevent a short circuit between the measuring tube 2 and the electromotive force generated in the fluid 4 to be measured. In addition, a reinforcing pipe 13 is embedded in the interior thereof. As the lining material 12, an electrically insulating material having excellent heat resistance, corrosion resistance, and insulation, such as a fluororesin, is used, and is formed by injection molding or rotational molding.

  The reinforcing tube 13 increases the mechanical coupling strength between the measuring tube 2 and the lining material 12, prevents the lining material 12 from peeling from the measuring tube 2, and linings due to temperature changes and pressure changes of the fluid 4 to be measured. It is embedded in order to prevent deformation of the material 12. The reinforcing tube 13 is formed in a cylindrical shape by a perforated plate usually called a punching plate, and is fixed to the inner peripheral surface 2 b of the measuring tube 2 via a ring-shaped spacer 14.

  Furthermore, earth rings 15 formed of SUS, platinum, titanium, monel, hastelloy, or the like are fixed to the pipe connection end face 3a of each flange 3 of the measuring pipe 2 by a plurality of set screws 16, respectively. The earth ring 15 includes a disc-shaped ring main body 15A having a center hole 17, a cylindrical portion 15B integrally projecting on the inner peripheral edge of the ring main body 15A, and a circumferential direction on the outer peripheral edge of the ring main body 15A. It is composed of a plurality of, for example, four fixing portions 15C that are bent and formed in a J shape on the back side at intervals. The ring main body 15 </ b> A has an outer diameter substantially equal to that of the flange 3 and is in close contact with the lining portion 12 </ b> A coated on the pipe connection end surface 3 a of the flange 3. In addition, you may shape | mold the reinforcement pipe | tube 13 and the spacer 14 integrally.

  The cylindrical portion 15B protrudes from the inner peripheral edge of the back surface of the ring main body 15A, that is, from the peripheral edge of the center hole 17, and is inserted into the inner peripheral surface 2b from the opening of the measuring tube 2. A part of the coated lining portion 12B, that is, the surface of the lining portion 12B-1 covering the vicinity of the opening of the inner peripheral surface 2b of the measuring tube 2 is in close contact with the solid matter mixed in the liquid. doing. Of the lining portion 12B that covers the inner peripheral surface 2b of the measuring tube 2, the lining portion 12B-1 that particularly covers the vicinity of the opening of the measuring tube 2 is a portion that is most easily scraped by the solid matter in the liquid. It is very effective to cover and protect this portion with the cylindrical portion 15B.

  As the cylindrical portion 15B, it is desirable to cover the lining portion 12B-1 in the vicinity of the opening on the inner peripheral surface of the measuring tube 2 within a range that does not affect the magnetic field H by the excitation coil 5. Specifically, the length of the cylindrical portion 15B is about several millimeters to several tens of millimeters, and when the inner diameter of the lining portion 12B coated on the inner peripheral surface 2b is D, from the tip of the cylindrical portion 15B to the electrode 7 It is desirable that the distance E be approximately 0.65D.

  Further, the cylindrical portion 15B is formed so that the wall thickness gradually decreases toward the tip at the maximum on the base end side, that is, the ring main body 15A side. For this reason, the tip of the cylindrical portion 15B forms a knife edge. In addition, the inner surface of the cylindrical portion 15B forms a tapered hole whose diameter increases toward the tip.

  The fixing portion 15 </ b> C is fixed to the outer periphery of the pipe connection end surface 3 a of the flange 3 by the set screw 16. For this reason, a screw mounting hole 22 through which the set screw 16 is inserted is formed in the fixing portion 15C. Further, a screw hole 23 through which the set screw 16 is inserted is formed at a position corresponding to the screw mounting hole 22 of the fixing portion 15C near the outer periphery of the ring main body 15A.

  When such a ground ring 15 is fixed to the pipe connection end surface 3a of the flange 3 by the set screw 16, the ring main body 15A covers the lining portion 12B, and the cylindrical portion 15B attaches the lining portion 12B-1 which is the end portion of the lining portion 12B. Cover the measurement tube 2 and the potential of the fluid 4 to be measured flowing in the measurement tube 2 to be equal. The earth ring 15 is electrically connected to the arithmetic processing circuit in the converter 9 to guide the potential of the fluid 4 to be measured as a reference potential.

  In the electromagnetic flow meter 1 having such a structure, of the lining portion 12B that covers the inner peripheral surface 2b of the measuring tube 2 by the cylindrical portion 15B that protrudes integrally with the inner peripheral edge of the earth ring 15, particularly the measuring tube 2 Since the lining portion 12B-1 covering the vicinity of the opening is protected, there is no possibility that the lining portion 12B-1 is scraped off by the solid matter mixed in the liquid, and the durability of the electromagnetic flow meter 1 is improved. Can be improved. If the lining portion 12B-1 is not cut off, the measurement error is small and the measurement accuracy can be improved.

  Further, the cylindrical portion 15B covers the lining portion 12B-1 in the vicinity of the opening on the inner peripheral surface of the measuring tube 2 to the extent that the magnetic field H by the exciting coil 5 is not affected. It can measure well without having.

  Moreover, since the front end is formed in an edge shape by gradually decreasing the plate thickness of the cylindrical portion 15B from the base end toward the front end, generation of turbulent flow can be prevented. That is, when the cylindrical portion 15B having a constant plate thickness is inserted into the measuring tube 2 to cover the lining portion 12B-1, the cylindrical portion 15B becomes a step with respect to the lining portion 12B-1, and thus the fluid to be measured 4 is disturbed and the measurement is adversely affected. On the other hand, if the plate thickness of the cylindrical portion 15B is decreased for a while from the base end toward the tip and the tip is formed in an edge shape, a step is generated between the lining portion 12B-1 and the cylinder 15B. Therefore, there is no possibility of disturbing the flow of the fluid 4 to be measured, and measurement is not affected.

  In the above-described embodiment, the example applied to the flange type electromagnetic flow meter 1 is shown. However, the present invention is not limited to this, and can be applied to a wafer type electromagnetic flow meter. Is possible.

It is sectional drawing which shows one Embodiment of the electromagnetic flowmeter which concerns on this invention. It is the II-II sectional view taken on the line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electromagnetic flowmeter, 2 ... Measuring pipe, 3 ... Flange, 3a ... Pipe connection end surface, 4 ... Fluid to be measured, 5 ... Excitation coil, 7 ... Electrode, 12 ... Lining material, 12A, 12B ... Lining part, 15 ... Earth ring, 15A ... ring body, 15B ... cylindrical part.

Claims (2)

In the electromagnetic flowmeter in which the inner peripheral surface of the measurement pipe and the pipe connection end surface are coated with a lining material, and an earth ring is disposed on the pipe connection end surface via the lining material,
The projected cylindrical portion which is inserted into the measuring pipe to the inner periphery of the ground ring, not covering the lining material in the vicinity of the inner peripheral surface opening of the measuring tube by the cylindrical portion,
2. The electromagnetic flowmeter according to claim 1, wherein the cylindrical portion is formed with a tapered hole in which a wall thickness gradually decreases from the base end to the tip, and an inner surface increases in diameter from the base end to the tip . The electromagnetic flowmeter according to claim 1,
The electromagnetic flowmeter according to claim 1, wherein the cylindrical portion covers a lining material in the vicinity of the opening on the inner peripheral surface of the measurement tube, up to a range that does not affect the magnetic field generated by the exciting coil.

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