JP2689163B2 - Double pipe sorting type electromagnetic flow meter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a measuring instrument for measuring a flow rate of a liquid.

(Prior Art) When a high-temperature liquid such as liquid metal is flowing in a double pipe, it is necessary to separate the flow rate of the inner pipe from the flow amount of the outer pipe in order to expose the detector to the high-temperature liquid. The accuracy of measurement deteriorates significantly due to the influence of temperature changes, and even in the case of a low-temperature liquid, the detector protruding into the flow path of the outer tube causes turbulence in the flow inside the outer tube, so it is sufficiently separated in the axial direction of the tube. There has been a problem that the distances have to be measured at each position and the measurement distances between them are necessary.

(Problems to be Solved by the Invention) An object of the present invention is to provide a flowmeter which measures the flow rates of an inner pipe and an outer pipe of a double pipe separately in a short measurement distance and has a high measurement accuracy even in a high temperature liquid. To do.

(Means for Solving Problems) The flowmeter of the present invention uses a set of two electromagnetic flowmeters,
One flowmeter measures the total flow rate of the outer tube and the inner tube, the other flowmeter measures the flow rate of the outer tube, but the inner tube is magnetically shielded so that the flow rate is not measured. The flow rate of the inner pipe is calculated by subtracting the flow rate of both flow meters. In this case, if two electromagnetic flowmeters are placed close to each other in the tube axis direction and arranged in the same direction, the electromotive forces interfere with each other, so that the straight lines connecting the electrode pairs of the respective electromagnetic flowmeters are at right angles to each other. To eliminate interference.

(Operation) In the electromagnetic flowmeter of the present invention, since the two electromagnetic flowmeters can be arranged relatively close to each other, the measurement distance is short, and the electromagnetic measurement is performed. There is no turbulence, and the change in the flow rate can be measured separately for the outer pipe and the inner pipe with a fast response speed.

(Examples) The present invention will be specifically described with reference to Examples.

FIG. 1 shows an arrangement relationship of two electromagnetic flow meters of the present invention, and a double pipe is seen through. FIG. 2 is a top view of each of the two electromagnetic flow meters, showing the arrangement of the magnetic poles and electrodes and the electrical relationship.

The outer pipe 1 and the inner pipe 2 of the double pipe are concentric circles and are made of a magnetically permeable material.

One of the two flowmeters (upper side in the figure) is provided with a magnetic tube on the inner surface of the inner tube by a required length. The magnetically shielded tube 3 magnetically shields the inside of the tube and does not penetrate the lines of magnetic force. A permanent magnet 4 having an appropriate thickness is arranged outside the double tube so that the N pole and the S pole face each other through the tube.

When a conductive fluid flows in the double pipe, the flow rate of the outer pipe F ₂
With respect to (2), since the electromotive force flows in the direction crossing the magnetic force line, an electromotive force corresponding to the flow rate is generated by the Fleming's law in a direction orthogonal to the magnetic force line and each direction of the flow. Therefore, the electromotive force is measured by the electrode 5. This electromotive force is the flow rate of the inner tube because the magnetic field lines are blocked by the magnetically shielded tube in the inner tube.
It becomes zero regardless of the magnitude of F ₁ , and the electromotive force between the electrodes is measured by the voltmeter 6 as a magnitude V ₀ proportional to only the flow rate F _{2 of the} outer tube.

If the other flowmeter (the lower side in the figure) is not equipped with a magnetic shield tube and the other structures are the same, the electromotive force generated in the electrode 5 depends on the flow rate F _{1 of the} inner tube. It is measured by the voltmeter 6 as the sum V _t of the generated amount. Therefore, the flow rate of the outer pipe is known from V _0, and the flow rate of the inner pipe is known from V _t −V _0. Therefore, if this calculation is performed by the arithmetic circuit 7, the flow rates of both pipes can be always separated and obtained.

By the way, in the two electromagnetic flowmeters, when the material of the double pipe or the fluid is conductive, the electromotive force between the electrodes may interfere with each other. Therefore, the straight lines connecting the electrode pairs are arranged at right angles to each other (therefore, the magnetic pole pairs are at right angles to each other). The two pairs of permanent magnets are placed at a distance such that the magnetic field lines do not affect each other. As a result, the potential of the other electrode pair is neutral with respect to the voltage between the other electrode pair, and it is possible to avoid mutual potential interference.

The proportional constant of each flow rate and voltage is obtained by calibration by flowing a predetermined flow rate to only one of the outer tube and the inner tube, and if these are used for calculation, the flow rates of both tubes can be obtained independently.

(Effects of the Invention) In the differential measurement of the flow rate of the double pipes by the pair of electromagnetic flow meters of the present invention, the negative electromotive force is positive even if the flow directions of the inner pipe and the outer pipe are opposite to each other. Since it is measured and calculated as the difference in which the electromotive force is canceled, it is separately measured regardless of the flow direction. Further, although the case where the flow direction is vertical is shown in the embodiment, the flow rate of the double pipe can be separately measured without losing any effect even in the case where the flow direction is horizontal or inclined in principle. Moreover, since the flow rate to be measured is the volume flow rate, the volume flow rate is always correctly and separately measured even if the temperature or density of the fluid changes.

[Brief description of the drawings]

The figure shows a specific example of the double-tube separation type electromagnetic flow meter of the present invention,
FIG. 1 is an arrangement perspective view, and FIG. 2 is a set of top views. In the drawings: 1 outer tube 2 inner tube 3 shield tube 4 permanent magnets (N, S magnetic poles) 5 electrode pairs 6 voltmeter 7 calculation circuit

Claims (1)

(57) [Claims] 1. An electromagnetic flowmeter comprising two electromagnetic flowmeters arranged in the axial direction of the double pipe.
Place them so that the straight lines connecting the respective electrode pairs are at right angles to each other, and only for one of the electromagnetic flow meters, attach a magnetic tube to the inner surface of the inner tube of the double tube and A dual pipe fractionation type electromagnetic flowmeter consisting of a pair of magnetically shielded structures.