JPS6152921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reference volume tubular meter prover.

Generally, the one shown in FIG. 1 is known as this type of reference volume tube type meter prover. In FIG. 1, 1 is a pipeline (tube) to which magnetic sensors 2a and 2b are attached. The outputs of these magnetic sensors 2a, 2b are sent to amplifiers 3a,
3b and are each amplified and input to the summing amplifier 4. The output of this summing amplifier 4 is sent to the zero potential detector 5.
is input.

A pig (not shown) is inserted into the pipeline 1, and when the pig comes to the position of the sensors 2a and 2b, its output is obtained. 4 and is input to the zero potential detector 5. This detector 5 detects the moment the pig passes directly under the sensors 2a and 2b. Furthermore, since the sensors 2a and 2b are installed at a predetermined distance, it is possible to measure the flow rate when the pig passes between the sensors 2a and 2b (see Japanese Patent Application No. 118011/1982).

By the way, the one shown in Figure 1 had the following drawbacks (a) and (b).

(a) Since the pipeline that constitutes the reference volume pipe is made of steel pipes, residual magnetism exists in the longitudinal and circumferential directions of the pipe, which deteriorates the detection accuracy of the pig. Therefore, before starting the test, it is necessary to demagnetize the location where the magnetic sensor is installed.

(b) During the test, leakage occurs through the pig while it passes, reducing measurement accuracy.

The present invention provides a reference volume tube type meter prover that eliminates the above-mentioned drawbacks and has high detection accuracy and measurement accuracy.

An embodiment of the present invention will be described in detail below with reference to FIGS. 2 to 4.

FIG. 2 shows a pig, which is composed of rubbers 6a, 6b, magnetic rubber 7, a metal fitting 8 for holding the magnetic rubber, washers 9a, 9b, a shaft 10, and nuts 11a, 11b. has been done. The above metal fittings 8, washers 9a, 9b, shaft 10
The nuts 11a and 11b are made of non-magnetic material. A shaft 10 is inserted through the rubbers 6a, 6b, the metal fittings 8, and the washers 9a, 9b, and is secured by nuts 11a, 11b. The rubbers 6a, 6b have internal cuts 12a, 12b.
By tightening the nuts 11a and 11b, the outer peripheral surface is raised as shown by the chain line, and the diameter of the pig can be adjusted. A metal fitting 8 having magnetic rubber 7 disposed on its circumferential surface is disposed in the center of the pig. This magnetic rubber 7 is detected from outside the pipeline as the position of the pig by a magnetic sensor, which will be described later. Even if the diameter of the pig is changed as described above, the diameter of the magnetic rubber 7 does not change, so the distance from the magnetic sensor does not change.

The pig shown in FIG. 2 is inserted into the pipeline 1 and moved, as indicated by the reference numeral 13 in FIG.
As described above, by adjusting the diameter of the pig 13 to match the inner diameter of the pipeline 1, leakage can be prevented. In FIG. 3, magnetic sensors 14a and 14b are arranged as a pair in the axial direction outside the pipeline 1. 15a, 15
b is also a magnetic sensor, and magnetic sensors 14a,
Similarly to 14b, it is installed at a predetermined position apart from the magnetic sensor in the axial direction. 16,
17 is a differential amplifier, 4 is the above-mentioned summing amplifier, 5
is the zero potential detector described above.

The pig 13 moves through the pipeline 1,
Magnetic sensors 14a, 14b (or 15a, 15
b) When passing directly under the magnetic sensor 14a
The output signal shown in FIG. 4A is obtained from the magnetic sensor 14b (or 15a), and the output signal shown in FIG. 4B is obtained from the magnetic sensor 14b (or 15b). These pair of output signals A and B are input to the differential amplifier 16 (or 17), and the combined output voltage shown in FIG. 4C is obtained at its output terminal. The differential amplifier 16,1
The output voltage from 7 is applied to the zero potential detector 5 via the summing amplifier 4, and the zero potential (point a) of the waveform shown at C in FIG. 4 is detected. The flow rate can be measured by the output voltage of this zero potential detector 5.

The present invention is as described above, and has the following features (a) to (d).

(b) The residual magnetism present in the pipeline is detected by a magnetic sensor, but since the outputs of the pair of magnetic sensors are supplied to a differential amplifier, the influence of the residual magnetism is removed by the differential amplifier. . FIG. 5 shows an example of the measurement accuracy when the magnetic sensor was changed seven times in the axial direction of the pipeline, and the solid line is the one according to the present invention;
The broken line is the characteristic explained in FIG. According to the present invention, measurement accuracy can be improved regardless of the installation position of the magnetic sensor, and the measurement error is 0.0002 or less.

(b) Since there is no effect of residual magnetism, there is no need to erase the residual magnetism of the pipeline as in the past.

(c) Even if an external noise magnetic field is applied, this is a common magnetic field, so it is canceled out by taking out the difference between the magnetic sensors, and is not affected by the external noise magnetic field.

(d) The diameter of the pig can be adjusted using the nut.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a side view of a pig which is an embodiment of the present invention, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 5 is a waveform diagram explaining the operation shown in FIG. 5, and FIG. 5 is a characteristic diagram showing a comparison of measurement accuracy between the conventional example and the present invention. 1: Pipeline, 6a, 6b: Rubber, 7: Magnetic rubber, 10: Shaft, 11a, 11b: Nut, 13: Pig, 14a, 14b, 15a, 15
b: Magnetic sensor, 16, 17: Differential amplifier.

Claims (1)

[Claims] 1. In a reference volume tube type meter prover using a pig, the diameter of the pig is adjusted by tightening the rubber constituting the pig with a bolt and nut arranged at the center of the pig, and Magnetic rubber is installed at the reference position on the outer periphery of the
In addition, a pair of magnetic sensors are installed adjacent to each other in the axial direction outside the tube at the reference point of the tube, and another pair of magnetic sensors are placed at a certain measurement interval, and the outputs of these pair of magnetic sensors are A reference volume tube type meter prover, characterized in that it detects passing of the pig through a reference point by differentially synthesizing.