JP2854887B2 - Flow meter difference test equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter instrument difference test apparatus, and more particularly to a flow meter instrument difference test apparatus that automatically measures instrument instrument characteristics using a reference tank.

2. Description of the Related Art For example, in a factory or the like where a flow meter is assembled, a correction operation is performed in which an instrumental difference is obtained for each flowmeter and a measurement value of the flowmeter is corrected based on the instrumental error. There is a flow meter instrument difference test apparatus as an apparatus for obtaining such instrumental errors unique to each flow meter. A conventional flow meter instrument difference test apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 60-7832.
As described in the section of the prior art of Japanese Patent Publication No. 4 (1999), comparing the measured flow rate of the flow meter as the device under test with the actual flow rate flowing into the reference tank using the reference tank, Devices for determining instrumental differences are known.

When measuring instrumental differences with such a flowmeter instrumental difference test device, a flowmeter is installed in the middle of the pipe upstream of the reference tank, and the liquid pumped by the pump flows into the reference tank through the flowmeter. I do. The reference tank is provided with a liquid level detector that detects the liquid level at a height position corresponding to a predetermined flow rate, and the liquid level detector detects the liquid level when a predetermined flow rate of liquid flows into the reference tank. And outputs the signal. Accordingly, the liquid level measurement value of the flow meter when there is a detection signal from the liquid level detector is read, and the actual flow value is compared with the flow measurement value to determine the instrument difference of the flow meter. Thereafter, based on the instrumental error, a correction constant setting switch or the like provided in the flow rate indicator of the flowmeter is operated to correct a constant unique to the flowmeter so that the instrumental error of the flowmeter becomes zero.

Problems to be Solved by the Invention When the liquid that has passed through the flow meter flows into the reference tank at a high flow rate, the liquid surface is likely to wave and move up and down. Other possible causes for the liquid level in the tank to fluctuate up and down include, for example, that the flow velocity of the liquid discharged from the pump fluctuates irregularly due to irregular rotation of the pump or the rotor of the flow meter. Can be Therefore, when detecting the liquid level of the actual flow rate in the reference tank in the conventional apparatus, there is a problem that the liquid level detector cannot accurately detect the liquid level, and the instrumental difference cannot be obtained accurately.

Therefore, an object of the present invention is to provide a flow meter instrument difference test apparatus that solves the above-mentioned problems.

Means for Solving the Problems The present invention relates to a flowmeter disposed in the middle of a pipe as a device under test, a reference tank provided downstream of the flowmeter and storing a fluid passing through the flowmeter, and a reference tank. A liquid level detector disposed at a predetermined height of the reference tank and detecting a liquid level in the reference tank; a flow control valve provided in the middle of the pipe upstream of the reference tank to adjust a flow rate flowing into the reference tank; Flow rate adjusting means for closing a flow rate adjusting valve when a liquid level in the tank reaches a position immediately before a predetermined height position detected by the liquid level detector.

When the liquid level of the liquid that has flowed into the reference tank reaches a straight position at a predetermined height position detected by the liquid level detector, the valve opening of the flow control valve is reduced to reduce the flow velocity flowing into the reference tank. To suppress the vertical fluctuation of the liquid level. Thereby, the liquid level in the reference tank is stabilized, the liquid level detection accuracy is improved, and the instrumental error measurement accuracy is increased.

Embodiment FIG. 1 shows an embodiment of a flow meter difference test apparatus according to the present invention.

In FIG. 1, a flow meter instrument difference test apparatus 1 is configured to supply a liquid (test water) stored in a liquid supply tank 2 to a pipe 3 to perform an instrument difference test. In the pipe 3, a pump 4 for pumping the liquid in the liquid supply tank 2, a flow meter 5 as a device under test, a flow regulating valve 6 for adjusting the flow rate in the pipe 3, an inflow opening / closing valve 7, a reference tank 8, A drain-side on-off valve 9, a drain pump 10, and the like are provided.

A pressure gauge 11 measures the pressure of the liquid that has passed through the flow meter 5. A thermometer 12 measures the temperature of the liquid that has passed through the flow meter 5.

During the instrumental difference test, the inflow-side on-off valve 7 is open, and the drain-side on-off valve 9 is closed. Therefore, the liquid in the liquid supply tank 2 pumped by the pump 4 passes through the flow meter 5 via the pipe 3 and flows into the reference tank 8. In addition, the flow control valve 6 is controlled to a valve opening degree which becomes a set flow rate.

The reference tank 8 is a small diameter portion 8a, 8b where the liquid level is detected.
And an intermediate large-diameter portion 8c. Liquid level detectors 13 and 14 are provided in the small diameter portions 8a and 8b. The liquid level detectors 13 and 14 are provided in the small diameter portions 8a and 8b because the liquid level rises faster than the large diameter portion 8c and the liquid level is easily detected. The lower liquid level detector 13 detects that the liquid level has reached the actual flow rate measurement start position, and the upper liquid level detector 14 detects that a predetermined actual flow rate has flowed into the reference tank 4. That is, with the liquid level detector 13
Numeral 14 is provided at a position where an interval capable of measuring the actual flow rate of a predetermined amount (for example, 2 _Kl ) is maintained.

19 is a bypass pipe, which is connected to the upstream side of the flow control valve 7 and the pump.
It communicates with 10 downstream. An on-off valve 20 that opens during the preliminary operation is provided in the bypass pipe 19 as described later.

Reference numeral 16 denotes a control device, which is an input / output interface 16A, a CPU 16B,
It has a memory 16C and the like. The input / output interface 16A includes a drive motor 4a for the pump 4, a transmitter 5a for the flow meter 5, a flow control valve 6, an inflow-side on-off valve 7, an outflow-side on-off valve 9, a drive motor 10a for the discharge pump 10, a pressure gauge 11 , Thermometer 12, liquid level detector 13, 14, thermometer
15, connected to on-off valve 20 and the like. Reference numeral 17 denotes an auxiliary storage device composed of a magnetic disk device or the like, which stores, for example, data measured by various sensors and parameters (liquid expansion correction coefficient and the like) necessary for calculating an instrumental error. A printer 18 prints measurement data, test results, and the like. The auxiliary storage device 17 and the printer 18 are connected to the control device 16 and connected to the CPU 16B.
It operates based on the output signal from.

The height positions of the liquid level detectors 13 and 14 are input to the CPU 16B as described later. When the liquid level reaches a position immediately before the liquid level detectors 13 and 14 detect the liquid level, the flow control valve 6 A flow rate adjustment program for reducing the valve opening degree and reducing the inflow amount into the reference tank 8 is input.

Here, the operation of the flow meter instrument difference test apparatus 1 having the above configuration will be described.

The control device 1 executes the processing shown in FIG. 2 during the instrumental difference test. 2, the control device 1 reads data stored in the auxiliary storage device 17 in step S1. Each test flow rate (for example, 50.0, 25.0,
…), The number of tests (for example, N times) for each test flow rate, a correction coefficient required to calculate the instrumental error, the pulse rate of the flow meter 5, the flow rate control valve 6 and the like, and a series of instrumental error tests. The data required for the processing of
In S1, the various data are read.

In the present embodiment, data is read from the auxiliary storage device 17, but data may be input using an input device such as a keyboard (not shown).

In step S2, a start command is awaited. For example, when the flowmeter 5 as a device under test is connected to the pipe 3 and the transmitter 5a is connected to the control device 16 and preparation is completed, an external switch (not shown) is used. A start signal is input. Preliminary operation is performed by inputting a start signal (step S
3). The preliminary operation is a process for stably obtaining test results. The preliminary operation is performed for a predetermined time (for example, 10 minutes) by driving the pump 4 and opening the on-off valve 20 provided in the bypass pipe 19. A first process of pumping the liquid to the pipe 3 at the maximum flow rate (50 m ² / h in the case of this embodiment) for testing only, and then stopping the pump 4 and opening the on-off valve 20 provided in the bypass pipe 19. After that, the pump 4 is driven again, and the inflow-side on-off valve 7 is opened in the future to open the reference tank 8.
When the reference tank 8 is filled with the liquid, the pump 4 is stopped and the inflow-side on-off valve 7
After the stool is closed, the drain pump 10 is driven and the outflow-side on-off valve 9 is opened to discharge the liquid filled in the reference tank 8, and when the liquid is discharged from the reference tank 8, the drain pump is Stop 10 and outlet valve 9
And a second process of repeating closing the valve a predetermined number of times.

In step S4, the flow rate is set. This flow setting is
The fine adjustment correction is performed on the valve opening control data corresponding to each test flow rate of the flow control valve 6 which is previously obtained experimentally as data and is stored as data in the data file read in step S1. And set. That is, at the time of the preliminary operation, the flow control valve 6 is adjusted based on the valve opening control data, and at this time, a master (not shown) provided between the pump 4 and the flow meter 5 as a device under test, for example. Based on the correction data obtained by calculation based on the difference from the actual flow rate measured by the flow meter, the valve opening control data for each test flow rate is finely adjusted and set.

Then, as the valve opening of the flow control valve 6, the valve opening control data subjected to the fine adjustment corresponding to the current test flow (in this case, 50.0) is stored, and the counter n is reset to zero (step S5). .

In the next step S6, the valve opening of the flow regulating valve 6 is set to a valve opening smaller than a preset test flow, and is reduced to a predetermined small flow. This is to prevent the liquid level in the reference tank 8 from fluctuating due to the force of the liquid flowing into the reference tank 8 and to stabilize the liquid level. That is, the lower liquid level detector 13 can detect the liquid level with higher accuracy.

In step S7, the pump motor 4a is started to drive the pump 4. Then, the inflow-side on-off valve 7 is opened (step S8). As a result, the liquid pumped by the pump 4 passes through the flow meter 5 and flows into the reference tank 8 from below at a flow rate set by the flow control valve 6.

In step S9, the pressure of the liquid passing through the flow meter 5 and the liquid temperature measured by the pressure gauge 11 and the thermometer 12 are stored. In the next step S10, it is confirmed that the lower liquid level detector 13 has detected the liquid level. In step S10, when the liquid level detector 13 outputs a liquid level detection signal,
The flow control valve control data stored in S5 is output to the flow control valve 6, and the valve is opened to the valve opening corresponding to the current test flow stored in step S5 so that a predetermined set flow flows ( Step S11).

At the same time as the liquid level detector 13 outputs the liquid level detection signal, the count value of the pulse output from the transmitter 5a of the flow meter 5 is read (step S12).

In the next step S13, it is checked whether or not the pulse counter value has reached a predetermined amount. That is, the process of step S12 is repeated until the pulse counter value reaches the predetermined amount.

As the flow rate to the reference tank 8 continues, the liquid level gradually rises and soon approaches the upper liquid level detector 14.
In step S13, when the pulse counter value reaches a predetermined value, that is, when the liquid level reaches a position immediately before the liquid level is detected by the liquid level detector 14, the process proceeds to step S14, in which the valve opening of the flow control valve 6 is reduced, and The amount is reduced so that the liquid level does not fluctuate up and down so that the liquid level can be detected accurately.

The predetermined amount of the pulse counter used as the criterion in step S13 and the flow rate adjusted in step S14 are arbitrary values experimentally obtained in advance so as not to affect the test accuracy.

In this way, with the flow meter into the reference tank 8 adjusted to a small flow rate, in step S15, the upper liquid level detector 14
To see if it has detected the liquid level. The liquid level in the reference tank 8 further rises, the liquid level is detected by the liquid level detector 14, and at the same time, the pulse counter of the flow meter 5 is stopped (step S16). Subsequently, the liquid temperature in the reference tank 8 (the thermometer 1
5) and the temperature of the liquid that has passed through the flow meter 5 is measured and stored in the auxiliary storage device 17 (step S17).
Further, after closing the inflow-side on-off valve 7 in step S18, the pump is stopped (step S19), the count value of the held pulse counter is stored in the auxiliary storage device 17, and the value of the counter n is stored in the auxiliary storage device 17. Increment by 1 (step S20). In step S21, the outflow side opening / closing valve 9 is opened to drive the drain pump 10, and the liquid flowing into the reference tank 8 is discharged and returned to the liquid storage tank 2.
In this drainage treatment, when the lower liquid level detector 13 stops detecting the liquid level, the drainage pump 10 is stopped and the outflow side on-off valve 9 is closed.

In the next step S22, in order to obtain an average value at an arbitrary reference flow rate, whether or not the above test is performed N times is confirmed by the value of the counter n. In step S22, the instrumental difference test (the processing in steps S6 to S21) is repeated N times. When the instrumental error test has been performed N times, the process proceeds to step S23, and it is confirmed whether or not the instrumental error test has been performed for all the flow rates specified in advance, that is, for each test flow rate.
If the measurement has not been performed for all the flow rates, step S4
The process from step S22 is repeated from the flow rate setting process for the next test flow rate. The number of tests N in step S22 and the respective flow rates in step S23 are included in the data read in step S1. In step S24, the data measured in the instrumental error test for each flow rate, that is, the flow meter 5
The instrumental difference is calculated from the pulse counter value of the reference tank 8, the pulse counter value of the reference tank 8, the liquid temperature in the reference tank 8, the liquid temperature at the time of passing through the flowmeter 5, and the set correction value. FIG. 4 and FIG.
Print out the test results as shown in (B).

Effect of the Invention As described above, the flowmeter difference test apparatus according to the present invention reduces the flow rate immediately before the liquid level in the reference tank is detected by the liquid level detector, and suppresses the vertical fluctuation of the liquid level in the reference tank. Since the liquid level can be stabilized, the liquid level detector can detect the liquid level more accurately. Therefore, it has features that the measured value of the flow meter and the actual flow value can be measured with high accuracy, a more accurate instrumental difference can be obtained, and the instrumental difference unique to each flowmeter can be appropriately calibrated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a flow meter difference test apparatus according to the present invention, FIG. 2 is a flowchart for explaining processing executed by a control device, FIG. 3, FIG.
(B) is a diagram of an instrumental difference test result printed out by a printer. 1 ... flow meter instrument difference test device 2 ... liquid supply tank 4 ...
Pump 5, Flow meter 6, Flow regulating valve 7, Inlet on-off valve 8, Reference tank 13, 13, Liquid level detector 1,
6 ... Control device.

Claims (1)

(57) [Claims] 1. A flowmeter disposed in the middle of a pipe as a device under test, a reference tank provided downstream of the flowmeter and storing a fluid passing through the flowmeter, and a predetermined height of the reference tank A liquid level detector disposed at a predetermined position and detecting a liquid level in a reference tank; a flow control valve provided in the middle of a pipe on an upstream side of the reference tank to adjust a flow rate flowing into the reference tank; A flow rate adjusting device that throttles the flow rate adjusting valve when the liquid level in the tank reaches a position immediately before a predetermined height position detected by the liquid level detector.