JPS5975116A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To improve a wear resistance and to eliminate a measurement error by providing a sintered hard alloy or a wear resistant alloy to a liquid contacting part of an inner circumferential surface of a liningless pipe body of an electromagnetic flowmeter. CONSTITUTION:A nonmagnetic sintered hard alloy or a wear resistant nonmagnetic alloy 12b is provided to the liquid contacting part where a fluid 1 to be measured is broght into contact with the inner circumferential surface of the pipe body 12. In case the wear occurs, a sectional area of the body 12 is varied and the measurement error is caused. But in this method, the measurement error can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic flowmeter, and particularly to an improved tube body of a liningless electromagnetic flowmeter.

The tubular body of a conventional electromagnetic flowmeter usually consists of a non-magnetic, electrically conductive cylindrical conduit, and a lining lined on the inner peripheral surface of the conduit. The lining, which is in contact with the conductive fluid to be measured, is attached to the pipe and connects between the conduit and an electrode that is attached to the pipe body and simultaneously contacts the fluid to be measured to extract an induced electromotive force generated in the fluid to be measured. It is insulated and usually uses an insulating material such as rubber or Teflon. Therefore, when measuring mortar or the like as a fluid to be measured using this type of electromagnetic flow needle, the lining is severely worn, which not only causes a situation where measurement becomes impossible in a short period of time, but also results in large losses. However, in conventional electromagnetic flowmeters that require an insulating lining, the materials for the lining are limited, and there is a limit to the ability to improve wear resistance.

On the other hand, recently, an electromagnetic flowmeter has been announced that does not require a lining to insulate the circumferential surface of the tube. This liningless electromagnetic flowmeter is shown in Figure 1. As shown in the figure, measurement poles 3 and 3a are provided at positions orthogonal to a magnetic field B on a non-magnetic and conductive tube body 2 through which a fluid to be measured whose flow rate is to be measured flows. . Furthermore, measurement electrode 3.
3a' (i7 Surrounding ring-shaped power supply terminals 4, 4a are provided. Measurement electrodes a, AAH are attached to the tube body 2 through insulating materials 6, 6af such as epoxy resin. Amplifiers 5 and 5a with a gain of 1 are connected to measuring electrodes 3 and 5a, respectively.
The induced voltage detected by 3a is applied to power supply terminals 4, 4a. For this reason, the power supply terminals 4, 4a are not at the same potential as the measuring electrodes 3, 3a, and a large current flows between them, causing a potential drop on the tube wall. If the wall thickness of the tube body 2 is uniform, the potential distribution between the power supply terminals 4.4a will be linear with respect to the length of the inner circumference of the tube. It is known that the distribution of the induced voltage near the inner wall of the pipe of fluid L is uniform regardless of the location of the magnetic field B, and that when the flow is uniform across the cross section of the pipe, it becomes sinusoidal over the inner circumference length. ing.

Therefore, if the positions of the power supply terminals 4 and 4a are appropriately selected, the potential distribution on the tube wall and the measured fluid l at all points on the inner circumference of the tube body 2 can be adjusted.
It is possible to make the distribution of the induced voltage in the inside approximately equal. Therefore, even if the inner wall of the tube body 2 is conductive, there is no current flowing between the tube body 2 and the fluid to be measured.
The voltage obtained from the terminals 6, 6a via the output amplifiers 5, 5a by 3a is the same induced voltage as in the case with a normal lining.

In this way, if there is no need for a lining to provide insulation to the inner wall of the pipe, troubles such as deformation and damage of the lining can be prevented and the reliability of the electromagnetic flowmeter can be increased, but in the above case Also, stainless steel is usually used as the material for the tube body 2, and there remains a problem in terms of wear resistance.

In view of the above-mentioned prior art, the present invention provides a liningless electromagnetic flowmeter with improved wear resistance.
Our aim is to provide a complete range of flowmeters. The present invention, which achieves the above object, is a liningless electromagnetic flowmeter, in which a non-magnetic cemented carbide or a non-magnetic wear-resistant alloy is used on the inner peripheral surface of the tube, which is the surface that comes into contact with the fluid to be measured. This approach is the basis of its technical philosophy.

Embodiments of the present invention will be described in detail below based on the drawings. Note that parts that are the same as those in the prior art are given the same numbers and redundant explanations will be omitted. Moreover, all of FIGS. 2 to 6 show a tube body of a liningless electromagnetic flowmeter similar to that shown in FIG. 1.

As shown in FIG. 2, the tubular body 12 of this embodiment includes a non-magnetic and conductive cylindrical conduit 12a made of stainless steel or the like, and a non-magnetic and conductive cylindrical conduit inserted into the conduit 12a. The sleeve 12b is made of a cemented carbide (a sintered alloy of tungsten carbide and cobalt). At this time, since the end of the cemented carbide sleeve 12b is easily chipped, the left end in the figure is a protrusion 12c protruding from the inner peripheral surface of the left end of the conduit 12a.
A removable ring 12eKfi is in contact with and is protected from the left side in the figure, and the right end in the figure is in contact with a removable ring 12eKfi that is inserted and fitted from the right side in the figure into a recess 12d carved in the right end of the conduit 12H. protected. Therefore, during assembly, the cemented carbide sleeve 12b' is inserted into the conduit 12a from the right side of the conduit 12a until it abuts the protrusion 12c, and then the ring 12eji is fitted into the concave part 12d.

FIG. 3 shows a second embodiment of the invention. As shown in the figure, the tube body 22 may be formed by fitting flanges 22b and 22c onto both ends of a non-magnetic and conductive superalloy sleeve 22a and brazing the boundaries between the two. The conduit 12a in the previous embodiment can be omitted. At this time, as shown in FIG. 4, flange portions 32b and 32C'e may be formed integrally with the cemented carbide sleeve 32a. In this case, ring-shaped corner abutments may be formed on the end surfaces of the flange portions 32b and 32c. The tube body 32 is formed by abutting and fixing protective plates 32d and 32e for preventing damage. In FIG. 5, a sealed space 43 is formed between the outer peripheral surface of the cemented carbide sleeve 42b, and this sealed space 43
In this embodiment, the tube body 42 is formed by inserting the cemented carbide sleeve 42b into a conduit 42a having all four parts 42C and brazing or fixing both ends to accommodate the excitation coil 44 therein.

In four such embodiments, a number n of cemented carbide sleeves 12b
, 22, 32, and 42b are used, but a wear-resistant alloy may be used for these. FIG. 6 shows a tube body 52 according to this embodiment, in which the inner circumferential surface of a non-magnetic and conductive cylindrical conduit 52a is coated with Stellai l- (trade name; wear-resistant material mainly made of cobalt, chromium, and tungsten). Alloy) 52
b is welded.

The surfaces in contact with the fluid to be measured 1 in the five diagonal embodiments are the cemented carbide sleeves 12b and 22.

32 and 42b or the inner circumferential surface of stellite 52b.

respectively, the cemented carbide sleeves 12b, 22a*
The needles 32a and 42b may be inserted into the inner peripheral surface of a plastic conduit, and in this case, the weight of the tube body can be reduced.

As specifically explained above in conjunction with the embodiments, according to the present invention, the cemented carbide or the abrasive alloy on the swing side faces the liquid-contacted part of the inner peripheral surface of the liningless electromagnetic flow pipe. Therefore, wear resistance can be improved. Therefore, when wear occurs, the cross-sectional area of the tube changes, resulting in a 6111 fixed error, but this measurement error 'fr,
Can be removed. In the past, when the fluid to be measured was under high pressure, the tube expanded and the cross-sectional area of the tube changed, resulting in a measurement error of 7n, but cemented carbide and abrasive alloys are hard, so they expand. The amount can also be reduced, and measurement errors can be reduced accordingly. Furthermore, cemented carbide and wear-resistant alloy! −
Because it is thin and strong, it is suitable for measuring high-pressure fluids. Incidentally, when conventional stainless steel is used to hold high-pressure fluid, the wall thickness of the tube becomes thicker, and electromagnetic flowmeters apply a magnetic field around the outer circumference of the tube due to the measurement principle, but thicker tubes cause eddy currents. The power consumption increases and the loss of excitation current for generating the magnetic field increases. Furthermore,
Foreign matter tends to adhere to the liquid-contact surface of the pipe body, and in this case, it is scraped off with a screwdriver, but in the case of the present invention, the above work can be done without damaging the liquid-contact surface of the pipe body. can be done.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing a liningless electromagnetic flow arrangement;
2 to 6 are longitudinal sectional views showing tube bodies according to first to fifth embodiments of the present invention, respectively. In the drawing, l is the fluid to be measured, 2.12, 22, 32, 42.52 are tube bodies, 3.3a is a measurement electrode, 4.4a is a power supply terminal, 12b, 22a, 32a, 42b are cemented carbide The sleeve 52b is Stellite (a wear-resistant alloy). Patent Applicant Hokushin Electric Manufacturing Co., Ltd. Representative, Patent Attorney Shibe Mitsuishi (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] A conductive tube for flowing the fluid to be measured, a magnetic field generating means for applying a magnetic field to the tube, and a magnetic field generator provided in the tube for extracting the induced electromotive force generated in the fluid to be measured. In the electromagnetic flow needle, the electromagnetic flow needle is equipped with a measuring electrode, and a power feeding means that forms a potential distribution substantially equal to the induced electromotive force in the tubular body at least in the vicinity of the measuring electrode. An electromagnetic flowmeter characterized in that a non-magnetic cemented carbide or a non-magnetic wear-resistant alloy faces the surface that comes into contact with the fluid to be measured.