A portable online calibration device for small-diameter water meters

Abstract

This utility model discloses a portable online calibration device for small-diameter water meters, comprising a rigid pipe, a standard meter module, a sensing module, and an intelligent processing system. The rigid pipe is an S-shaped rigid pipe, with an air vent valve installed at the second vertical upward bend. A quick-connect interface is provided at the water inlet end of the pipe, enabling rapid connection of the pipe via a snap-fit ​​mechanism. An upstream and downstream rigid pipe section are respectively provided before and after the standard meter. The sensing module includes a first pressure transmitter, a second pressure transmitter, and a temperature sensor installed before and after the standard meter. The intelligent processing system is connected to the standard meter and integrates a pressure compensation calculation module and a temperature compensation calculation module.

Description

Technical Field

[0001] This utility model relates to the field of flow measurement technology, and in particular to a portable online calibration device for water meters with a diameter of DN15-DN25. Background Technology

[0002] Existing water meter calibration devices are measuring equipment that uses water as a medium to provide water flow values ​​with definite accuracy, ultimately traceable to national standards for the basic quantity. Water meter standard devices can be classified in various ways: by calibration method (dynamic and static methods); by standard type (mass method, volumetric method, and standard meter method); and by working medium (water flow standard devices, gas flow standard devices, and oil flow standard devices, etc.). Currently, the most widely used and technologically mature flow standard devices in my country include the static mass method, static volumetric method, and standard meter method.

[0003] Statistics show that residential water meters (DN15~DN25) account for approximately 96% of all water meters, while other types account for about 4%. In field use, the metering accuracy of water meters is affected not only by their inherent characteristics but also by actual water quality and installation environment conditions such as large diameter, low flow rate, inclined installation, and insufficient straight pipe length. These conditions can lead to changes in the metering performance, resulting in discrepancies between the total meter reading and the sum of the individual meter readings. Since volumetric and weighing methods require specific measuring instruments, offline verification or calibration of the flowmeter is primarily performed in laboratories or metering stations. However, most water meters in residential areas are installed by water companies for trade settlements, making disassembly or disconnection for verification difficult. Therefore, online testing of water meter performance is essential. Thus, online calibration of water meters under actual usage conditions, evaluation of the meter's indication error, analysis of the causes affecting the field metering accuracy, and proposal of improvement measures are crucial for improving the accuracy of water meters in actual use and achieving precise water flow measurement.

[0004] Among existing methods for calibrating water meters, the standard meter method is best suited for online metering scenarios. The standard meter method is based on the principles of fluid mechanics: within the same time interval, the cumulative flow through flowmeters connected in series on the same pipe is equal. Therefore, when the flow rate is stable, comparing the flow rate values ​​of the standard meter and the meter under test allows determination of the metering parameters of the flowmeter under test.

[0005] During water meter calibration, firstly, determine one or more standard flow meters based on the diameter and flow range of the water meter under test, ensuring that both the device and the water meter are functioning correctly. Turn on the water pump and adjust the flow regulating valve to the flow point to be calibrated. After the temperature, pressure, and flow rate stabilize, simultaneously record the indicated flow rates of both the tested flow meter and the standard flow meters, along with the corresponding calibration time. By comparing the indicated flow rates, mathematical calculations can be performed to obtain the various performance parameters of the tested flow meter.

[0006] Existing water meter calibration devices are mostly fixed structures (such as those using the mass method or volumetric method), which are bulky and require disassembly of the water meter for inspection. Although online calibration technology using standard meter methods exists, large-diameter ultrasonic flow meters are expensive and cannot be adapted to small-diameter (DN15-DN25) water meters. Small-diameter water meters account for 96% of all residential water meters, and their on-site installation environment (such as insufficient straight pipe sections or inclined installation) can easily lead to measurement errors. Therefore, there is an urgent need for portable online calibration devices to solve the problem of uninterrupted water supply testing. Summary of the Invention

[0007] To address the aforementioned technical problems, the purpose of this utility model is to provide a portable, low-cost online calibration device for small-diameter water meters. This device achieves high-precision calibration through structural innovation, solving the problems of low accuracy, high cost, and inability to adapt to small-diameter water meters in existing on-site calibration.

[0008] The objective of this utility model is achieved through the following technical solution:

[0009] A portable online calibration device for small-diameter water meters includes a rigid pipe, a standard meter module, a sensing module, and an intelligent processing system;

[0010] The rigid pipe is an S-shaped rigid pipe. An air vent valve is installed at the second vertical upward bend of the S-shaped rigid pipe, and a quick-connect interface is installed at the water inlet end of the pipe. The pipe can be quickly connected by a snap-fit ​​mechanism.

[0011] The standard table specifies upstream and downstream rigid pipe sections, respectively.

[0012] The sensing module includes a first pressure transmitter, a second pressure transmitter, and a temperature sensor disposed before and after the standard gauge.

[0013] The intelligent processing system is connected to the standard meter and integrates a pressure compensation calculation module and a temperature compensation calculation module.

[0014] Furthermore, the standard meter is a DN25 ultrasonic water meter with a range ratio of R400 and an accuracy class of 1.

[0015] The upstream rigid pipe section length before the standard table is 10DN, and the downstream rigid pipe section length after the standard table is 5DN.

[0016] Furthermore, the quick-connect interface achieves a mechanically sealed connection through a snap-fit ​​mechanism, allowing for insertion and rotation.

[0017] Furthermore, the exhaust valve is a shut-off valve, and its installation position is ≤10mm vertically from the top of the S-shaped rigid pipe.

[0018] Furthermore, the device also includes an instantaneous flow indicator and an electronic timer integrated into the housing, both of which are connected to the intelligent processing system.

[0019] Furthermore, the temperature sensor is located upstream of the standard meter and connected to the upstream rigid pipe section of the standard meter to monitor the water temperature in real time.

[0020] Furthermore, the first pressure transmitter located in front of the standard gauge is connected to a hose, one end of which is connected to a switch valve and connected to the gauge under test through the switch valve, and the other end is connected to the inlet of the rigid pipe.

[0021] The second pressure transmitter is installed on the upstream rigid pipe section before the standard gauge and is connected to the temperature sensor and the instantaneous flow indicator respectively to detect the water pressure at the standard gauge.

[0022] Furthermore, the downstream rigid pipe section located after the standard meter is connected to the drain hose, and a flow regulating valve is installed at the connection with the drain hose.

[0023] Furthermore, the intelligent processing system also includes a data acquisition module, a central control module, and a touch and digital display module.

[0024] Furthermore, the pressure compensation calculation module is based on the Darcy-Weisbach equation:

[0025]

[0026] And output compensation factor K , where Δ P It's a pressure difference. f It is the friction factor. L It is the length of the pipe. D It is the pipe diameter. ρ It is the fluid density. v It's the flow rate.

[0027] Compared with the prior art, one or more embodiments of this utility model may have the following advantages:

[0028] This device uses an S-shaped pipe and a high-position exhaust valve to exhaust air by utilizing gravity and pressure gradient in a coordinated manner, thereby reducing bubble error.

[0029] By using 10DN and 5DN rigid pipe sections, flow stability is ensured with an accuracy of ±1%.

[0030] The DN25 standard table covers all diameters from DN15 to DN25 through a compensation algorithm;

[0031] The quick-connect interface completes pipe connection within 3 seconds, making it suitable for narrow spaces on site. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the pipeline structure;

[0033] Figure 2 It is a schematic diagram of the device system;

[0034] Figure 3 This is a schematic diagram of the device's external structure. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0036] like Figure 1 As shown, the S-shaped pipe structure of this utility model includes: a rigid pipe, a standard meter module, a sensor module, and an intelligent processing system;

[0037] The rigid pipe is an S-shaped rigid pipe, with an air vent valve 3 installed at the second vertical upward bend. A quick-connect interface is installed at the pipe inlet, enabling rapid pipe connection via a snap-fit ​​mechanism. An upstream and downstream rigid pipe section are installed before and after the standard meter, respectively. The sensing module includes a first pressure transmitter, a second pressure transmitter, and a temperature sensor installed before and after the standard meter. The intelligent processing system is connected to the standard meter and integrates a pressure compensation calculation module and a temperature compensation calculation module.

[0038] The standard meter 5 is a DN25 ultrasonic water meter with a range ratio of R400 and accuracy class 1. Its measurement range fully covers user meters of DN15-DN25 R160 class 2 in the user's field. It has built-in temperature and cumulative flow calculation functions, a communication interface, and an external button. Enabling the external button resets the cumulative data to zero, facilitating data comparison.

[0039] The length of the rigid pipe section is set with the standard table as the dividing line. The length of the rigid pipe in the first half of the standard table is 10 times the nominal diameter (10DN), and the length of the rigid pipe in the second half of the standard table is 5 times the nominal diameter (5DN). That is, the upstream rigid pipe section length before the standard table is 10DN, and the downstream rigid pipe section length after the standard table is 5DN.

[0040] The quick-connect interface achieves a mechanical seal connection through a snap-fit ​​mechanism; the quick-connect water pipe interface is a device that allows for rapid connection and disconnection of water pipes without tools. The core principle is to achieve sealing and locking through a mechanical structure.

[0041] In a vertically installed S-shaped pipe section, gravity further accelerates the bubbles to the top of the pipe. An exhaust valve or exhaust pipe is installed at the highest point of the S-shaped pipe section to discharge the gas by utilizing the natural upward floating characteristic of the bubbles. The pressure gradient change at the bend causes the bubbles to migrate to the low-pressure area (top of the pipe), creating conditions for subsequent discharge. Therefore, the drain valve is designed at the vertical rise of the second bend in the S-shaped pipe section.

[0042] The exhaust valve is a shut-off valve, and its installation position is ≤10mm from the top of the S-shaped rigid pipe.

[0043] An effective bend and venting design is adopted to reduce the impact of incomplete pipe / bubbles on the error of the standard gauge.

[0044] The device also includes an instantaneous flow indicator and an electronic timer integrated into the housing, both of which are connected to the intelligent processing system. The instantaneous flow indicator displays the instantaneous flow rate to help verify flow stability, while the electronic timer helps calculate the cumulative flow rate by setting a water flow reference time.

[0045] The temperature sensor is located upstream of the standard meter and connected to the upstream rigid pipe section of the standard meter. It monitors the water temperature in real time and inputs the temperature data into the temperature compensation calculation module.

[0046] The first pressure transmitter located before the standard meter is connected to a hose. One end of the hose is connected to a switch valve 1, which is connected to the meter under test 2 through the switch valve. The other end is connected to the inlet 23 of the rigid pipe. After water enters, the entire pipe section is rigid to ensure stable water pressure and reduce flow error. The first pressure transmitter acts as a pressure sensor, detects the water pressure at the inlet, and converts the pressure signal into an electrical signal, which is then input into the pressure compensation calculation module.

[0047] The second pressure transmitter is installed on the upstream rigid pipe section before the standard gauge and is connected to both a temperature sensor and an instantaneous flow indicator to detect the water pressure at the standard gauge. The second pressure transmitter acts as a pressure sensor, detecting the water pressure at the standard gauge and converting the pressure signal into an electrical signal, which is then input into the pressure compensation calculation module.

[0048] The downstream rigid pipe section, located after the standard meter, is connected to the drain hose 25, and a flow regulating valve 6 is installed at the connection point to the drain hose to control the water flow rate. The drain hose connection facilitates water intake into the inlet in various scenarios, reducing water pressure errors.

[0049] The intelligent processing system also includes a data acquisition module, a central control module, and a touch and digital display module. The data acquisition module acquires temperature and cumulative flow data from the ultrasonic water meter; acquires pressure data from the first pressure transmitter 21 and the second pressure transmitter 22; and acquires water temperature data from the temperature sensor. The touch and digital display module sets the flow point and displays the actual flow rate after flow point compensation. The central control module calculates the compensated actual cumulative flow rate based on the acquired cumulative flow data and the compensation data from the pressure compensation calculation module and the temperature compensation calculation module, and outputs it to the digital display module for display.

[0050] Calibration procedure during use:

[0051] Connect the quick-connect connector to the drain port 26 of the meter under test, turn on the water flow until the pipe is full, the S-shaped pipe will automatically release air, and the intelligent system will collect the pressure difference Δ. P Water temperature T It automatically calculates the compensation flow rate and compares it with the standard meter reading, displaying the error value via the touchscreen. Specifically:

[0052] Open the outlet valve of the meter under test, connect the drain hose to the outlet valve of the meter under test, fill the entire pipeline with clean water, and let the water flow into the rigid pipe section, then pass through the temperature sensor and the instantaneous flow indicator to display the test environment, and then into the standard ultrasonic water meter, and then through the flow regulating valve and the drain pipe (inlet) Figure 2 (As shown). During use, the device can be easily moved using the bottom casters 34 and the top handle 31. The exterior features a flow display instrument window 32 and a standard gauge indicator window 33. A flow regulating valve 6 is located on the side, and an inlet and outlet are located at the bottom (e.g., ...). Figure 3 (As shown).

[0053] During testing, the online calibration device for the water meter should be placed in parallel as much as possible to avoid deviations in water pressure between the tested meter and the standard meter due to gravity. Two pressure transmitters measure the water pressure at both the tested and standard meters, and the pressure compensation factor is confirmed by the compensation calculation module. Furthermore, by observing pressure changes, it can be ensured that the pipeline is completely filled with liquid during calibration. The standard meter is installed in series downstream of the water meter in a rigid pipe section 10 times the nominal diameter (10DN) from any upstream component and 5 times the nominal diameter (5DN) from any downstream disturbance component, ensuring the accuracy and stability of the water meter's measurements. A temperature sensor and an instantaneous flow indicator reflect the water flow during measurement, and a timer module is added for significant convenience.

[0054] The device uses the standard meter method (cumulative flow rate) for measurement. The principle is that the cumulative flow rate of flow meters connected in series on the same pipe is equal within the same time interval. Flow velocity will change to maintain flow conservation. Pressure will change, typically corresponding to changes in pipe diameter.

[0055] Pressure compensation module:

[0056] Neglecting pipe losses and assuming the medium is water, the entire process can be explained using Bernoulli's equation in fluid dynamics. Bernoulli's equation, also known as the steady flow energy equation, is the dynamic equation for steady flow of an ideal fluid. It means that in fluid flow where viscous losses are neglected, the sum of pressure potential energy, kinetic energy, and potential energy at any two points on a streamline remains constant.

[0057]

[0058] in, P This represents the pressure at a point in the fluid. The velocity of the fluid at that point. For fluid density, It is the acceleration due to gravity. The altitude of that point. It is a constant.

[0059] When using the standard gauge method for measurement, ideally, the sum of the pressure potential energy, kinetic energy, and potential energy of the measured gauge and the standard gauge remains constant. This can be derived from Bernoulli's equation:

[0060]

[0061] in, P 1 represents the pressure in the gauge being measured. Let be the fluid velocity at the location of the meter being measured. For fluid density, g It is the acceleration due to gravity. h 1 represents the height of the meter being measured. P 2 represents the pressure in the standard table. Let be the fluid velocity at the standard gauge position. h 2 represents the height of the standard table.

[0062] As shown in the above formula, when the water meter diameters are the same, the main factors affecting measurement accuracy are the pressures of the meter being measured and the standard meter. However, when the water meter diameters are different, the flow rate and velocity formulas need to be considered.

[0063] The flow rate and velocity formulas are formulas used in physics to describe the characteristics of fluid flow, describing the relationship between flow rate, velocity, and cross-sectional area:

[0064]

[0065] in, Q Represents traffic; V This represents the flow velocity, which is the average velocity of a fluid over a specific cross-section. SIt represents the cross-sectional area, which is the area of ​​a section perpendicular to the flow direction through which the fluid flows.

[0066] When measuring cumulative flow under full water conditions, without additional conditions (such as pressure changes, pipe length changes, fluid property changes, etc.), only the change in pipe diameter is considered. As the pipe diameter increases (from small to large), the flow velocity decreases. When the pipe diameter increases, the pipe cross-sectional area increases, and the flow velocity decreases proportionally to the inverse of the square of the diameter. Furthermore, according to Bernoulli's equation, there must be a pressure difference between the measured gauge and the standard gauge, which can be used to compensate for the cumulative flow.

[0067] Pressure compensation is required whenever a pressure difference exists between the standard meter and the meter being measured. The compensation process is as follows: This invention uses two pressure sensors to measure the pressure difference between the two water meters. Since the pressure difference is along the length of the pipe, the Darcy-Weisbach equation can be used to estimate the effect of the pressure difference on the flow velocity. The Darcy-Weisbach equation is as follows:

[0068]

[0069] Where Δ P It's a pressure difference. f It is the friction factor. L It is the length of the pipe. D It is the pipe diameter. ρ It is the fluid density. v It refers to the flow velocity. The calculated flow velocity is then substituted into the flow rate-velocity formula to determine the flow rate change. This change is the compensated cumulative flow rate. Simultaneously, based on the influence of pressure difference on flow velocity, under known pressure difference conditions, the actual flow rate can be measured using standard equipment or methods to determine a compensation factor. K Then measure the flow rate of the water meter on the tested object. Q 1 The compensated result can be obtained by multiplying the result by the compensation factor. The compensated flow rate value. Q n for:

[0070]

[0071] The measurement process is as follows: If the water meter being measured and the standard meter are of the same diameter, connect the water directly to the inlet through the outlet valve, and let the water flow through the various sensors via the pipe until the standard meter reading changes. Once the water pipe is full, close the flow valve and record the reading of the water meter being measured. Q 1 and the current reading of the standard meter Q2 is used as the initial value. Open the flow valve and set the water flow time according to the actual situation. After the set time, close the flow valve and record the readings of both the measured and standard meters as the end value. Repeat this process three times, recording the readings of both the measured and standard meters. Calculate the difference in readings between the measured and standard meters during the flow valve opening and closing process, and then calculate the average value to obtain the error data. If the measured and standard meters are of different diameters, compare the compensation flow values. Q n Compared with standard values Q 2. Calculate the indication error.

[0072] Temperature compensation module:

[0073] The propagation speed of ultrasound in fluids is significantly affected by temperature. Temperature changes cause changes in the speed of sound, which in turn affects the measurement accuracy of flow velocity and flow rate. Therefore, temperature compensation is necessary to ensure the measurement accuracy of ultrasonic water meters as standard meters.

[0074] The temperature compensation formula is as follows:

[0075]

[0076] in: v Speed ​​of sound at temperature T; Reference temperature The speed of sound at a given temperature; α: the temperature coefficient of the speed of sound, for example, α = 2.5 m / (s·℃) for water.

[0077] The formula for calculating the flow velocity of an ultrasonic water meter is as follows:

[0078]

[0079] in: Difference in water flow velocity L : Spacing between ultrasonic transducers; θ Δ: The angle between the ultrasonic wave path and the water flow direction; t : Time difference of ultrasonic wave propagation; v :temperature T The speed of sound at that point; Reference temperature The speed of sound below.

[0080] Cumulative traffic compensation formula:

[0081]

[0082] in, Represents traffic; This represents the velocity difference, which is the average velocity of the fluid at a specific cross-section. SIt represents the cross-sectional area, which is the area of ​​a section perpendicular to the flow direction through which the fluid flows.

[0083] The online water meter calibration device provided in the above embodiments has the advantages of high precision, low cost, and wide application scenarios. Using an ultrasonic water meter as the standard, it is more cost-effective than ultrasonic flow meters commonly used for online water meter calibration. By adding a pressure transmitter, temperature sensor, and instantaneous flow indicator, and equipping it with an intelligent processing system to achieve pressure-flow compensation and temperature-flow compensation, and by incorporating a unique S-shaped pipe design, quick-connect interface design, a rigid pipe of corresponding length and diameter to ensure stable water pressure, and a unique air vent valve position, flow errors are reduced, fully meeting the needs of online calibration of small-diameter water meters.

[0084] Although the embodiments disclosed in this utility model are as described above, the content described is merely for the purpose of facilitating understanding of this utility model and is not intended to limit this utility model. Any person skilled in the art to which this utility model pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this utility model, but the patent protection scope of this utility model shall still be determined by the scope defined in the appended claims.

Claims

1. A portable small-bore water meter online calibration device, characterized in that, Includes rigid pipes, standard meter modules, sensor modules, and intelligent processing systems; The rigid pipe is an S-shaped rigid pipe. An air vent valve is installed at the second vertical upward bend of the S-shaped rigid pipe, and a quick-connect interface is installed at the water inlet end of the pipe. The pipe can be quickly connected by a snap-fit ​​mechanism. The standard table specifies upstream and downstream rigid pipe sections, respectively. The sensing module includes a first pressure transmitter, a second pressure transmitter, and a temperature sensor disposed before and after the standard gauge. The intelligent processing system is connected to the standard meter and integrates a pressure compensation calculation module and a temperature compensation calculation module.

2. The portable small-diameter water meter online calibration device according to claim 1, characterized in that, The standard meter is a DN25 ultrasonic water meter with a range ratio of R400 and an accuracy class 1. The upstream rigid pipe section length before the standard table is 10DN, and the downstream rigid pipe section length after the standard table is 5DN.

3. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The quick-connect interface achieves a mechanically sealed connection through a snap-fit ​​mechanism, allowing for one-insertion and one-turn rotation.

4. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The exhaust valve is a shut-off valve, and its installation position is ≤10mm from the top of the S-shaped rigid pipe.

5. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The device also includes an instantaneous flow indicator and an electronic timer integrated into the housing, both of which are electrically connected to the intelligent processing system.

6. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The temperature sensor is located upstream of the standard meter and connected to the upstream rigid pipe section of the standard meter to monitor the water temperature in real time.

7. The portable small-diameter water meter online calibration device according to claim 1, characterized in that, The first pressure transmitter located in front of the standard gauge is connected to a hose. One end of the hose is connected to a switch valve and is connected to the gauge under test through the switch valve. The other end is connected to the inlet of the rigid pipe. The second pressure transmitter is installed on the upstream rigid pipe section before the standard gauge and is connected to the temperature sensor and the instantaneous flow indicator respectively to detect the water pressure at the standard gauge.

8. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The downstream rigid pipe section, located after the standard meter, is connected to the drainage hose, and a flow regulating valve is installed at the connection point with the drainage hose.

9. The portable small-diameter water meter online calibration device according to claim 1, characterized in that, The intelligent processing system also includes a data acquisition module, a central control module, and a touch and digital display module.

10. The portable online calibration device for small-bore water meters according to claim 1, characterized in that The pressure compensation calculation module is based on the Darcy-Weisbach equation: ； And output compensation factor K , where Δ P It's a pressure difference. f It is the friction factor. L It is the length of the pipe. D It is the pipe diameter. ρ It is the fluid density. v It's the flow rate.

Images