JP2794146B2 - Electromagnetic flowmeter electrode mounting structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode mounting structure for an electromagnetic flowmeter for electrically measuring the flow rate of a measuring fluid flowing in a measuring tube.

[0002]

2. Description of the Related Art Various types of electrode mounting structures for this type of electromagnetic flowmeter for electrically measuring the flow rate of a conductive fluid by utilizing an electromagnetic induction phenomenon have been proposed in the past. An extrapolation type electrode structure disclosed in Japanese Patent Publication No. Hei 3-51707 and the like is known. As shown in FIG. 2, the electrode structure has a large-diameter flange portion 3A provided at the outer end of the electrode 3 by inserting the electrode 3 into the electrode mounting hole 2 formed in the tube wall of the measurement tube 1 from the outside. Is fixed to the outer wall of the measurement tube by a spring mechanism 4 via a sealing member 5, and one end of a signal lead wire 6 is connected and fixed to an outer end of the electrode 3 by a set screw 7.

[0003] The measuring tube 1 is formed of a stainless steel or the like into a cylindrical body having both ends open, and a lining 8 made of an insulating material such as a fluororesin is provided on the inner peripheral surface. The protruding dimension of the electrode 3 from the lining surface varies depending on the properties of the measurement fluid. That is, if the nature of the fluid is adhesive or the deposit is electrically insulating,
During use, the liquid contact end surface 3a of the electrode 3 is covered with an insulating substance, the impedance between the fluid and the electrode increases, the signal electromotive force attenuates, and the output decreases. Therefore, in this case, the electrode liquid contact end surface 3a is protruded from the lining surface to the inside of the measurement tube by a required size, and the adherent is washed away by the flow of the fluid itself, thereby performing self-cleaning. In the case of a slurry fluid, the solid matter contained in the fluid collides with the electrode 3 to change the surface state of the electrode material, and an electrochemical potential is generated. The output becomes noisy and becomes unstable. For this reason, the electrode 3 is depressed, that is, the electrode contact surface 3a is positioned in the hole 8a of the lining 8, thereby reducing the number or frequency of the solids colliding with the electrode 3 and stabilizing the output. In the case of a normal fluid, the liquid contact end surface 3a is flush with the lining surface. In addition,
In FIG. 2, the protrusion amount L2 of the electrode is ± 0.

[0004]

When the measurement fluid is a slurry fluid, as described above, the electrode contact surface 3a is recessed from the lining surface to reduce noise. In this case, however, a recess is formed in the lining surface. As a result, insulators such as solids and oils, bubbles, and the like easily accumulate in the recesses or adhere to the end surfaces of the electrodes in contact with the electrodes, resulting in a problem that the output is reduced or hunting occurs. Therefore, conventionally, as a method for solving such a problem, the electrode 3 is removed from the measuring tube 1 periodically or as necessary to remove deposits.
The self-cleaning is performed by cleanly cleaning the electrode contact surface 3a or replacing the electrode itself, or by protruding the electrode contact surface 3a from the lining surface to wash off the deposits by the flow of the fluid itself. However, the former method of removing and cleaning the electrode has a problem that the operation is troublesome and time-consuming, and that the fluid in the pipe needs to be emptied and the installation place of the detector is restricted. On the other hand, the latter method of self-cleaning by the flow of fluid has the advantage that it can be performed easily and in a short time, but has the problem that the electrode mounting structure is significantly limited. That is, in the mounting structure in which the flange 3A of the electrode 3 is pressed against the outer wall of the measurement tube by the above-described spring mechanism 4, it is impossible to move the electrode 3 inward of the measurement tube. Therefore, a mounting structure (eg, Japanese Utility Model Publication No. Sho 55-5928) which is configured to be movable is also known. However, the mounting structure is complicated in that a pair of setscrews are pressed against the electrode from both sides and fixed. Not only is it difficult to adjust the dimensions, but if the tightening force is weak, return the electrode to its original position, and then connect the signal lead wire to the outer end surface of the electrode with a set screw. The electrode rotates and moves forward, and the size of the recess changes. As a result, noise increases, and the distance between the electrodes changes, so that the span fluctuates and the measurement accuracy decreases.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to simplify the structure and to surely return the electrode to its original position after self-cleaning with a fluid. It is another object of the present invention to provide an electrode structure of an electromagnetic flowmeter in which an electrode does not move even when a signal lead wire is connected, and a dent amount of a liquid contact surface of an electrode can be constantly set.

[0006]

According to the present invention, an electrode mounting hole is formed in a tube wall of a measuring tube, and a screw hole and a protrusion amount regulating stopper portion are formed to penetrate the electrode so as to move forward and backward. A holder to be measured is disposed on the outer wall of the measuring tube coaxially with the electrode mounting hole, a stopper for limiting the amount of dent made of an insulating material is fitted around the outer periphery of the holder, and a nut member is fitted around the outer periphery of the holder. By screwing and fixing the nut to the nut mounting portion provided on the outer wall of the holder, the stopper is pressed against the holder to fix the holder to the measuring tube, and the outer end of the electrode is projected outward from the stopper and the nut member. One end of the signal lead wire is connected by screwing a set screw into a screw hole provided on the outer end surface, and the electrode has a small diameter portion at both ends and a central portion having a diameter larger than both ends and a screw of the holder. Male thread to be screwed into the hole The screw hole of the holder and the screw hole formed in the outer end surface of the electrode are opposite threads to each other. The end face is recessed by a predetermined dimension from the inner peripheral surface of the measuring tube, and when the end surface is abutted and engaged with the protrusion amount regulating stopper portion, the electrode liquid contact end surface is projected from the inner peripheral surface of the measuring tube.

[0007]

[Function] When the electrode threaded through the holder moves forward and backward by rotation, and the male screw portion comes into contact with the dent amount regulating stopper,
The liquid contact end surface of the electrode is recessed from the inner peripheral surface of the measurement tube by a predetermined amount, and the liquid contact end surface protrudes from the inner peripheral surface of the measurement tube when it comes into contact with the protrusion amount regulating stopper. Since the screw hole on the outer end face of the electrode and the screw hole on the holder are opposite threads, even when the signal lead wire is connected and fixed to the outer end face of the electrode, even if the set screw is tightened, the electrode does not rotate and move forward.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 electrode mounting structure for an electromagnetic flowmeter according to the present invention. Reference numeral 1 denotes a cylindrical measuring tube made of stainless steel or the like. An electrode mounting hole 2 is formed at the center of the tube wall of the measuring tube 1, and a cylindrical shape having an internal thread 11 formed on the inner peripheral surface of the outer wall. The nut mounting portions 12 are integrally formed so as to surround the periphery of the electrode mounting hole 2 so as to be aligned with their axes. A lining 8 made of an insulating material such as a fluororesin is applied to the entire inner peripheral surface of the measuring tube 1. The lining 8 is also provided on the inner peripheral surface of the electrode mounting hole 2 and the outer peripheral edge of the electrode mounting hole 2. Therefore, the hole 8a of the lining 8 forms a substantial electrode mounting hole. Inside the nut mounting portion 12, a cylindrical holder 13 having both ends open is provided coaxially with an electrode mounting hole 8 a via an O-ring 14, and the electrode 3 passes through the holder 13. The O-ring 15 is inserted into the electrode mounting hole 8a. The center hole 16 of the holder 13 is the small-diameter hole 1 on the lower end side.
6a and a large-diameter hole 16b on the upper end side are formed, and a part of the large-diameter hole 16b is a screw hole 17 formed by a left-hand thread. The provided step forms a stopper 18 that regulates the amount of protrusion of the electrode 3. A recessed amount limiting stopper 19 formed of a cup-shaped insulating material is fitted on the outer peripheral surface of the upper end of the electrode 3, and a cap nut (nut member) 20 is further fitted on the outer periphery of the stopper 19. I have. The cap nut 20 is screwed into the female screw 11 of the nut mounting portion 12 to press the dent amount stopper 19 against the distal end surface of the holder 13, thereby fixing the holder 13 to the pipe wall of the measuring pipe 1 by pressing. doing.

The electrode 3 is formed into two parts in the axial direction, so that the first electrode piece 2 is inserted into the small-diameter hole 16a of the holder 13 and the electrode mounting hole 8a via the O-ring 15.
1 and a second electrode piece 2 connected to the outer end of the first electrode piece 21
And 2. The first electrode piece 21 is a straight rod-like body, the inner end face of which forms a liquid contact end face 3a, and a fitting recess 23 is formed in the center of the outer end face. The second electrode piece 22
A male screw portion 22a, which is formed with a left-hand thread and is screwed into the screw hole 17 of the holder 13, and a small-diameter portion 22b connected to one end of the male screw portion 22a. A fitting projection 24 press-fitted into the recess 23 of the electrode piece 21 is integrally formed to protrude. The small-diameter portion 22b of the second electrode piece 22 penetrates through the hole 25 of the dent amount regulating stopper 19 and protrudes above the cap nut 20, and has a screw hole 26 formed of a right-hand thread on the protruding end face and a screw hole 26 for rotating the electrode 3. A minus groove 27 is formed as a rotation operation part. A set screw 7 for connecting and fixing a terminal 28 attached to one end of the signal lead wire 6 to the electrode 3 is screwed into the screw hole 26. In the present embodiment, the electrode 3 is composed of two members, the first electrode piece 21 and the second electrode piece 22. However, the electrode 3 is formed by a single rod having a diameter different from that at both ends. As a matter of course, a left-handed screw that is screwed into the screw hole 17 of the holder 13 may be formed on the peripheral surface of the large diameter portion. In addition, a minus groove 29 as a rotation operation part is also formed on the tip end surface of the cap nut 20.

In such a configuration, when attaching the electrode 3 to the measuring tube 1, the electrode 3 is attached to the center hole 16 of the holder 13.
When the screw portion 22a is screwed into the screw hole 17 of the holder 13, the tip of the first electrode piece 21 is inserted into the electrode mounting hole 8a. Next, the dent amount regulating stopper 19 is attached to the holder 1.
3 and abuts against the distal end surface of the holder 13, and further, the cap nut 20 is fitted into the recess amount control stopper 19 and screwed into the female screw 11 of the nut mounting portion 12, and the recess amount control stopper 1
9 is pressed and fixed to the holder 13, and the holder 13 is firmly fixed to the tube wall of the measuring tube 1. Next, the electrode 3 is rotated in the loosening direction (rightward), and the screw portion 22a is brought into contact with the inner surface of the dent amount regulating stopper 19 as shown in the figure, so that the liquid contact end surface 3a of the electrode 3 is in the electrode mounting hole 8a. The required dimension (d) can be recessed. The recess size d is determined in consideration of noise at the time of measurement. Then, the set screw 7 is screwed into the screw hole 26 to connect and fix the terminal 28 to the outer end face of the electrode 3.
At this time, if the external thread portion 22a of the electrode 3 is the same right-hand thread as the set screw 7, the electrode 3 also rotates integrally with the set screw 7 and moves forward to change the recess dimension d of the liquid contact end face 3a. ,
Since the external thread portion 22a is a left-hand thread, the moving direction of the electrode 3 is the backward direction. Since the backward movement is prevented by the recess amount regulating stopper 19, the recess dimension d of the liquid contact end surface 3a does not change. . In this state, the flow rate of the slurry fluid is measured. In the case where solid matter accumulates in the electrode mounting hole 8a or adheres to the liquid contact end surface 3a during the flow rate measurement and the output decreases or hunting occurs, the set screw 7 is removed and the terminal 28 is removed from the electrode 3. Then, tighten the electrode 3 in the direction of tightening (left direction)
Then, the male screw portion 22a may be moved forward to bring the male screw portion 22a into contact with the protrusion amount regulating stopper portion 18. Then, the liquid contact end face 3a protrudes into the measuring tube 1 by a required dimension from the electrode mounting hole 8a, and the solid substance is washed away by the flow of the fluid itself, and self-cleaning is performed. After the self-cleaning, when the electrode 3 is rotated in the loosening direction and the screw portion 22a again comes into contact with the dent amount regulating stopper 19, the dent size d before cleaning can be secured. Then, the terminal 28 may be connected to the electrode 3 again by the set screw 7. At this time, of course, the recess dimension d does not change.

In the above embodiment, the screw hole 1 of the holder 13 is used.
7 and the external thread portion 22a of the electrode 3 are left-handed, and the screw hole 26 of the electrode 3 is right-handed. Also,
In the above embodiment, the measuring tube 1 is made of stainless steel and the lining 8 is applied to the inner peripheral surface. However, a measuring tube made of ceramic may be used, and in this case, the lining process is not required.

[0012]

As described above, in the electrode mounting structure of the electromagnetic flow meter according to the present invention, when the signal lead wire is connected to the electrode with the set screw, the electrode does not rotate integrally with the set screw. The dent dimension of the electrode contact surface can be kept constant, and the original dent size can be maintained even when the contact surface protrudes into the measuring tube and is self-cleaned and then dents from the inner surface of the measuring tube. Therefore, the distance between the electrodes can be kept constant. Therefore, there is no fluctuation of the output, and stable measurement accuracy can be secured. In addition, the structure is simple, and during electrode cleaning maintenance, there is no need to remove the detector and remove the fluid in the piping, which can reduce maintenance time and improve workability.
Particularly, it is suitable for measurement of a slurry fluid.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an electrode mounting structure of an electromagnetic flow meter according to the present invention.

FIG. 2 is a sectional view showing a conventional example of an electrode mounting structure.

FIG. 3 is a diagram showing a relationship between a protrusion dimension of an electrode contact surface and noise.

[Description of Signs] 1 Measuring tube 3 Electrode 3a Wetted end face 7 Set screw 8 Lining 8a Electrode mounting hole 11 Female screw 12 Nut mounting part 13 Holder 17 Screw hole 18 Protrusion limit stopper 19 Depression limit stopper 20 Cap nut 22a Male thread part 26 Screw hole 26 Signal lead wire 28 Terminal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-66122 (JP, A) JP-A-59-64529 (JP, U) JP-A-5-64718 (JP, U) JP-A 55-64 101312 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01F 1/58

Claims (1)

(57) [Claims] An electrode mounting hole is formed in a tube wall of a measuring tube, and a holder through which a screw hole and a protrusion amount regulating stopper are formed and through which an electrode can move forward and backward can be provided coaxially with the electrode mounting hole on an outer wall of the measuring tube. It is arranged, and a dent amount regulating stopper made of an insulating material is fitted around the outer periphery of the holder, and a nut member is fitted around the stopper and screwed and fixed to a nut attaching portion provided on the outer wall of the measuring tube. By pressing the stopper against the holder, the holder is fixed to the measuring tube, the outer end of the electrode is projected outside from the stopper and the nut member, and a set screw is screwed into a screw hole provided on the outer end surface. One end of the signal lead wire is connected to both ends of the electrode to form a small-diameter portion, and the center portion has a larger-diameter portion than both ends to form a male screw portion to be screwed into the screw hole of the holder. Formed in the screw hole and the outer end face of the electrode The screw hole is a reverse screw to each other, and the external thread portion of the electrode is normally abutted and locked by the recess amount regulating stopper, so that the electrode liquid contact end surface is depressed by a required dimension from the inner peripheral surface of the measuring tube, and protrudes. An electrode mounting structure for an electromagnetic flowmeter, wherein the liquid contact end surface of the electrode protrudes from the inner peripheral surface of the measuring tube when the electrode liquid contacting stopper is engaged with the amount regulating stopper portion.