JP2010002249A - Magnetic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a lining and a porous plate from being deformed, and ensure the accuracy of a flow rate measurement. <P>SOLUTION: A through-hole (a ventilation hole) 2c is provided in a position corresponding to a joint 3d of the porous plate (a reinforcement member) 3 in a pipe 2. A fluid passing through the lining 4 and entering between the lining 4 and an inner circumference 2a of the pipe 2 is collected in a gap h of the joint 3d of the porous plate 3, discharged to the outside through the ventilation hole 2c of the pipe 2 provided to correspond to the position, and prevented from being accumulated between the lining 4 and the inner circumference 2a of the pipe 2. A volume change due to a thermal expansion and a thermal contraction is hardly generated, and the lining 4 and the porous plate 3 are prevented from being deformed even if the fluid is used for a black liquor line in a paper-pulp factory. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic flow meter provided with a measuring tube whose inner peripheral surface is lined with an insulating resin.

  Conventionally, this type of electromagnetic flowmeter has an excitation coil that creates a magnetic field in a direction perpendicular to the flow direction of the fluid flowing in the measurement tube, and a measurement tube that faces the direction perpendicular to the magnetic field created by the excitation coil. And an electromotive force generated in the fluid flowing in the measurement tube by the magnetic field generated by the exciting coil.

  Generally, a lining made of a soft elastic insulating material such as a fluororesin is applied to the inner peripheral surface of a measurement tube of an electromagnetic flow meter. This type of lining may be peeled off from the pipe due to an external pressure applied when the inside of the pipe is at a low pressure, particularly below atmospheric pressure during use. In order to prevent such peeling, a cylindrically wound porous plate is used as a reinforcing member, and the porous plate is fixed to the inner peripheral surface of a nonmagnetic metal pipe and then lining is performed by molding. (For example, refer to Patent Document 1).

  FIG. 5 shows a main part of the conventional electromagnetic flow meter described above. In the figure, reference numeral 1 denotes a measuring tube, and a porous plate 3 wound in a cylindrical shape is fixed as a reinforcing member on an inner peripheral surface 2a of a pipe 2 made of nonmagnetic metal, and is molded so as to cover the porous plate 3 Thus, a fluororesin lining 4 is applied.

  A large number of holes 3a are formed on the peripheral surface of the perforated plate 3 (see FIG. 6). This perforated plate 3 is obtained by winding a plate (punching plate) P having a large number of holes H formed in a rectangular shape as shown in FIG. 7 into a cylindrical shape, and aligning the edge surfaces 3b and 3c on both sides. It has eyes 3d on its peripheral surface.

  Although not shown in FIG. 5, an exciting coil for creating a magnetic field is provided in a direction orthogonal to the flow direction of the fluid flowing in the measuring tube 1, and the direction orthogonal to the magnetic field created by this exciting coil. The signal electrode 5 is provided on the inner peripheral surface of the measuring tube 1.

JP-A-3-124 JP 2007-70784 A

  However, in the electromagnetic flow meter described above, the fluid flowing through the measuring tube 1 may pass through the fluororesin lining 4 and enter between the lining 4 and the inner peripheral surface 2 a of the pipe 2. In particular, in a paper / pulp factory, black liquor flowing through the measuring tube 1 enters between the lining 4 and the inner peripheral surface 2 a of the pipe 2.

  Black liquor in paper and pulp mills includes hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl dioxide produced by hydrolysis of sodium sulfide, as well as lignin, and alkalinity that also contains carbohydrates, organic acids, and resins. It is a liquid material (see, for example, Patent Document 2).

  The black liquor line of paper and pulp mills is often high temperature and high pressure. In addition, the black liquor line is stopped or flows depending on the operation status of the factory, and the temperature and pressure in the piping repeatedly increase and decrease accordingly.

  Due to the change in temperature and pressure, the black liquor that has entered between the lining 4 and the inner peripheral surface 2a of the pipe 2 thermally expands or contracts, and the lining 4 flows due to the volume change due to the thermal expansion or contraction. It swells to the roadside, and the perforated plate 3 is deformed together with the lining 4 to cause a problem of adversely affecting the flow rate measurement.

  The present invention has been made in order to solve such problems, and an object of the present invention is to provide an electromagnetic flow meter capable of preventing the lining and the deformation of the perforated plate and ensuring the accuracy of the flow measurement. There is to do.

In order to achieve such an object, according to the present invention, in the above-described electromagnetic flow meter, a through hole is provided at a position corresponding to the joint between the end portions of the perforated plate of the pipe made of nonmagnetic metal.
According to the present invention, the fluid that has passed through the lining and has entered between the lining and the inner peripheral surface of the pipe gathers in the gap between the joints of the perforated plate and penetrates the pipe provided corresponding to this position. It is discharged to the outside through the hole.

  In the present invention, it is desirable that the diameter of the through-hole is a value within a range defined by the minimum value and the maximum value, with the minimum value being 2 mm and the maximum value being one third of the inner diameter of the pipe. In the present invention, it is better to form the through hole in the pipe before the lining than in the pipe after the lining.

  According to the present invention, since the through-hole is provided at a position corresponding to the joint of the perforated plate of the pipe made of nonmagnetic metal, the fluid that permeates through the lining and enters between the lining and the inner peripheral surface of the pipe. It gathers in the gap of the joint of the perforated plate and is discharged to the outside through the through hole of the pipe provided corresponding to this position. As a result, fluid does not accumulate between the lining and the inner peripheral surface of the pipe, and even when used in the black liquor line of a paper / pulp factory, the volume change due to thermal expansion and contraction hardly occurs. The deformation of the plate can be prevented and the accuracy of the flow rate measurement can be ensured.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view showing a main part of an embodiment of an electromagnetic flow meter according to the present invention. 5, the same reference numerals as those in FIG. 5 denote the same or equivalent components as those described with reference to FIG. 5, and the description thereof will be omitted.

  In this electromagnetic flow meter, through holes (hereinafter referred to as vent holes) 2c and 2c that reach the inner peripheral surface 2b from the outer peripheral surface 2a of the pipe 2 are provided at positions corresponding to the joints 3d of the perforated plate 3 of the pipe 2. ing. FIG. 2 shows a side view of the electromagnetic flow meter. FIG. 3 is a sectional view taken along line III-III in FIG.

  FIG. 4 shows a cross-sectional view of the portion where the vent hole 2c is formed as viewed from the pipe line direction (the direction of arrow A shown in FIG. 1). Since the joint 3d of the perforated plate 3 is merely abutting the edge surfaces (end portions) 3b and 3c on both sides thereof, a slight gap h exists between the edge surfaces 3b and 3c. The vent hole 2c is provided at a position corresponding to the joint 3d of the porous plate 3 with a diameter larger than the gap h of the joint 3d of the porous plate 3.

In this embodiment, the vent hole 2 c needs to be formed only in the pipe 2. In this case, the following methods (1) and (2) can be considered as a method of forming the vent hole 2c.
(1) After forming the lining 4 on the inner peripheral surface 2a of the pipe 2 through the perforated plate 3, a hole is drilled from the outside of the pipe 2 with a drill or the like so as not to damage the perforated plate 3 and the lining 4. A vent hole 2c is obtained.
(2) First, a hole is formed in the pipe 2 by forming a vent hole 2 c, and then the vent hole 2 c is closed and a lining 4 is applied through the perforated plate 3.

  In the above method (1), for example, when a hole is drilled from the outside of the pipe 2, resistance suddenly disappears when the drill exits the pipe 2, and the perforated plate 3 opens a hole to the lining 4 at once. There is a possibility that. On the other hand, if the method (2) is adopted, the lining 4 is applied after the vent hole 2c is formed in the pipe 2, so that there is no possibility of damaging the porous plate 3 or the lining 4.

  In this embodiment, the fluid that passes through the lining 4 and enters between the lining 4 and the inner peripheral surface 2a of the pipe 2 gathers in the gap h of the joint 3d of the perforated plate 3, and corresponds to this position. It is discharged to the outside through the vent hole 2c of the pipe 2 provided.

  Thereby, in this Embodiment, even if it uses in the black liquor line of a paper and pulp factory, a fluid does not accumulate between the lining 4 and the internal peripheral surface 2a of the pipe 2, but by thermal expansion and contraction. Volume change hardly occurs, deformation of the lining 4 and the perforated plate 3 can be prevented, and accuracy of flow rate measurement can be ensured.

  In the above-described embodiment, the number of vent holes 2c provided in the pipe 2 is two, but the number is not limited to two and may be one. Since the vent holes 2c are intended to allow the fluid inside to escape, the larger the number of vent holes 2c, the more effective, and the number may be determined according to the process conditions.

  In the present embodiment, since the vent hole 2c is provided at a position corresponding to the joint 3d of the perforated plate 3 of the pipe 2, the fluid between the lining 4 and the inner peripheral surface 2a of the pipe 2 can be effectively and It can be discharged smoothly. For this reason, compared with the case where the vent hole 2c is provided in positions other than the position corresponding to the joint 3d of the perforated plate 3, the number of the vent holes 2c can be reduced. Further, it is possible to make the diameter of the vent hole 2 small and not noticeable.

  As a result of repeated tests with an actual machine, it was found that the diameter of the vent hole 2c needs to be 2 mm or more for the effect of discharging the fluid. Also, it should be less than 1/3 of the inner diameter of the pipe 2 that can be ignored in calculating the strength of the measuring tube 1. The minimum value is 2mm and the maximum value is 1/3 of the inner diameter of the pipe 2. It was found that the fluid discharge effect is good and the strength of the pipe 2 is not affected.

It is a sectional side view which shows the principal part of one Embodiment of the electromagnetic flowmeter which concerns on this invention. It is a side view of this electromagnetic flowmeter. It is the III-III sectional view taken on the line in FIG. It is sectional drawing which looked at the part in which the vent hole of this electromagnetic flowmeter was formed from the pipe line direction. It is a sectional side view which shows the principal part of the conventional electromagnetic flowmeter. It is a perspective view which shows the perforated plate wound by the cylindrical shape. It is a top view which shows the plate (punching plate) before winding this porous plate cylindrically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Measuring tube, 2 ... Pipe, 2a ... Inner peripheral surface, 2b ... Outer peripheral surface, 2c ... Through-hole (vent hole), 3 ... Perforated plate, 3a ... Hole, 3b, 3c ... Edge end surface (end part), 3d ... seam, 4 ... lining, 5 ... signal electrode, P ... plate (punching plate), H ... hole.

Claims (3)

Measuring tube with inner resin lined with insulating resin, exciting coil that creates a magnetic field in a direction perpendicular to the flow direction of fluid flowing in the measuring tube, and perpendicular to the magnetic field created by this exciting coil In an electromagnetic flowmeter comprising a signal electrode provided on an inner peripheral surface of the measurement tube opposite to a direction, and taking out an electromotive force generated in a fluid flowing in the measurement tube by a magnetic field generated by the excitation coil from the signal electrode ,
The measuring tube is
A pipe made of non-magnetic metal,
A reinforcing member provided between the inner peripheral surface of the pipe and the lining;
The reinforcing member is
It consists of a perforated plate wound in a cylindrical shape,
The pipe is
The electromagnetic flowmeter characterized by having a through-hole in the position corresponding to the joint of the edge parts of the perforated plate wound by the said cylindrical shape. The electromagnetic flow meter according to claim 1,
The diameter of the through hole is
An electromagnetic flow meter characterized in that a minimum value is 2 mm and a maximum value is one third of the inner diameter of the pipe, and the value is within a range defined by the minimum value and the maximum value. In the electromagnetic flowmeter according to claim 1 or 2,
The through hole is
An electromagnetic flowmeter formed on the pipe before the lining is applied.

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