Closed flow calibration system

Abstract

The invention belongs to the technical field of fluid measurement, and particularly relates to a closed flow calibration system. According to the device, a first inlet is formed in the side wall of a high-position liquid storage device, and an outlet of a circulating pump is connected with the first inlet; an inlet of the circulating pump is connected with the low-position liquid storage device, a second inlet is formed in the top end of the high-position liquid storage device, the gas cylinder is connected with the second inlet through a first pipeline, the low-position liquid storage device is connected to the first pipeline through a second pipeline, and a bottom outlet of the high-position liquid storage device is connected with the flowmeter to be detected. The other end of the flowmeter to be detected is connected to a top inlet of the calibration tank through a quick reversing valve, a first outlet end of the quick reversing valve is connected to the calibration tank through a pipeline, and a second outlet end of the quick reversing valve is connected to the low-level liquid storage device through a backflow pipeline; and the quick reversing valve is used for quickly switching the liquid metal flow to the calibration tank or the backflow pipeline. The method has the advantages of being safe, reliable and high in precision, and can be used for high-precision flow calibration of high-temperature, easily-oxidized and corrosive liquid metal.

Description

Technical Field

[0001] This invention belongs to the field of fluid measurement technology, specifically relating to a closed-loop flow calibration system. Background Technology

[0002] Liquid metals are widely used as coolants in fourth-generation nuclear reactors, fusion reactors, and certain specialty chemical industries. Accurate flow measurement is crucial for system safety and control. However, the calibration of liquid metal flow meters faces significant challenges:

[0003] Easily oxidized: Liquid metals exposed to air will rapidly oxidize, generating solid impurities that can clog pipes and contaminate the system. Therefore, the entire calibration system must be completely sealed and isolated from the atmosphere.

[0004] Its physical properties are unique: it is subject to high temperatures and has a certain degree of corrosiveness, and its viscosity differs greatly from that of water, making it impossible to directly apply traditional calibration devices and techniques based on water media.

[0005] The challenge of reversing flow: In classic volumetric / gravimetric calibration, a reversing device is needed to direct fluid flow to the calibration container or return tank. For liquid metals, this reversing device must meet the following requirements: a) rapid action to reduce reversing errors; b) reliable sealing to prevent leakage of highly toxic / hazardous liquid metals; c) corrosion resistance and high temperature resistance; d) avoidance of water hammer effects, as rapid switching can easily generate pressure surges in the pipeline, causing damage to pipelines and equipment.

[0006] The metrological challenge: Level measurement in calibration containers (calibration tanks) is crucial. Traditional glass tube level gauges are unsuitable. High-temperature resistant, sealed electrical contact level gauges are required. However, these gauges suffer from zero drift and accuracy degradation at high temperatures, and disassembling them for inspection is extremely inconvenient and compromises the system's airtightness.

[0007] Current technology lacks a comprehensive flow calibration device that can simultaneously solve all the above problems. Therefore, there is an urgent need for an integrated closed-loop solution. Summary of the Invention

[0008] The technical problem solved by this invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a closed-loop flow calibration system with the advantages of safety, reliability and high precision. It can be used for high-precision flow calibration of high-temperature, easily oxidized and corrosive liquid metals (such as sodium, sodium-potassium alloy, lead, lead-bismuth alloy, etc.).

[0009] The technical solution adopted in this invention is as follows:

[0010] A closed-loop flow calibration system includes a high-level liquid reservoir, a calibration tank, a low-level liquid reservoir, a gas cylinder, and a circulating pump. The high-level liquid reservoir has a first inlet on its side wall, and the outlet of the circulating pump is connected to the first inlet. The inlet of the circulating pump is connected to the low-level liquid reservoir. The top of the high-level liquid reservoir has a second inlet, and the gas cylinder is connected to the second inlet via a first pipeline. The low-level liquid reservoir is connected to the first pipeline via a second pipeline. The bottom outlet of the high-level liquid reservoir is connected to a flow meter under test. The other end of the flow meter under test is connected to the top inlet of the calibration tank via a quick-reversing valve. The calibration tank is used to receive and accurately measure the volume of flowing liquid metal. The first outlet of the quick-reversing valve is connected to the calibration tank via a pipeline, and its second outlet is connected to the low-level liquid reservoir via a return pipeline. The quick-reversing valve is used to quickly switch the liquid metal flow to the calibration tank or the return pipeline.

[0011] The high-level liquid reservoir is located at the top of the device, and an electric heating element is installed inside the high-level liquid reservoir.

[0012] The circulation pump is provided with a circulation pump inlet shut-off valve at the front end of the inlet; the circulation pump and the circulation pump inlet shut-off valve are connected in parallel by a bypass pipeline, and the bypass pipeline is provided with a circulation pump bypass shut-off valve.

[0013] The first pipeline is equipped with a gas pipeline shut-off valve, and the second pipeline is equipped with a gas pipeline shut-off valve.

[0014] The calibration tank integrates a high-precision electric contact level gauge, which includes one or more vertically arranged electrode rods and a signal transmitter; the calibration tank is also equipped with a built-in standard volume scale with precise graduations, and / or multiple temperature sensors distributed along the height direction and a high-temperature viewing window.

[0015] It also includes a control system, which uses data measured by the standard volume scale and temperature sensor to perform temperature expansion compensation and online calibration on the measured value of the electric contact level gauge; controls the switching timing of the quick-reversing valve; records the pulse signal emitted by the flow meter under test; records the standard volume value calculated from the liquid level change in the calibration tank; and calculates the instrument coefficient and accuracy of the flow meter under test based on the pulse signal and the standard volume value.

[0016] The quick-reversing valve is a quick-switching ball valve, including an actuator, a valve stem, a ball valve core, and a valve seat. The actuator is connected to the valve stem, and the other end of the valve stem passes through the valve seat and is connected to the ball valve core. The actuator drives the valve stem to drive the ball valve core to rotate rapidly within a 180-degree angle stroke.

[0017] The valve stem is provided with an extension tube assembly on its exterior. The valve stem's sealing structure includes a first-stage seal and a second-stage seal. The first-stage seal is a metal bellows seal, with one end welded to the valve stem and the other end welded to the valve seat, achieving absolute isolation of the dynamic seal. The second-stage seal is a stuffing box located above the bellows seal and inside the extension tube assembly, filled with high-temperature resistant graphite or flexible graphite packing. The stuffing box is sealed by a packing gland.

[0018] The quick-reversing valve includes flow channel A, flow channel B, and flow channel C, wherein flow channel C is connected to the flow meter to be tested, flow channel A is connected to the calibration tank, and flow channel B is connected to the low-level liquid reservoir.

[0019] The spherical valve core and the valve seat that mate with it are provided with liquid metal self-lubricating guide grooves and coatings; the coating is a soft metal plating or an oxide ceramic composite coating formed on a base material.

[0020] The beneficial effects of this invention are:

[0021] (1) The present invention provides a closed flow calibration system with a fully enclosed design: which fundamentally eliminates the oxidation of liquid metal and environmental pollution, and ensures operational safety.

[0022] (2) The closed flow calibration system provided by the present invention has high performance of the commutator: the self-lubricating coating solves the problem of high temperature jamming; the fast ball valve structure avoids water hammer; the bellows seal ensures zero leakage of the valve stem and has extremely high reliability.

[0023] (3) The closed-loop flow calibration system provided by the present invention has high measurement accuracy: the self-calibration system integrated in the calibration tank eliminates the system error of the level gauge and ensures the long-term accuracy of volume measurement.

[0024] (4) The closed-loop flow calibration system provided by the present invention has a high degree of automation: the entire calibration process, including reversal, data acquisition, calculation and self-calibration, is automatically completed by the control system, which is highly efficient and has little human error.

[0025] (5) The closed flow calibration system provided by the present invention uses a specially designed ball valve for the commutator. The contact surface between the valve core and the valve seat is provided with a liquid metal self-lubricating coating to ensure that it can switch flexibly and quickly under high temperature and corrosive media, and avoid water hammer effect.

[0026] (6) The closed flow calibration system provided by the present invention adopts a special structure of bellows mechanical seal combined with packing seal for valve stem, which fundamentally eliminates the leakage of liquid metal.

[0027] (7) The present invention provides a closed flow calibration system, wherein the calibration tank integrates a high-precision electric contact level gauge, and performs online self-calibration through a temperature sensor and a standard volume scale, without the need for disassembly and inspection.

[0028] (8) The closed-loop flow calibration system provided by the present invention realizes the closed, safe, high-precision and automated process of liquid metal flow calibration, and solves the problems of oxidation, jamming, leakage and inaccurate measurement in the prior art. Attached Figure Description

[0029] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in describing the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments recorded in the present invention. Those skilled in the art can derive other drawings from the following drawings without any creative effort.

[0030] Figure 1 This invention provides a schematic diagram of a closed-loop flow calibration system.

[0031] Figure 2 A cross-sectional view of a fast reversing valve provided by the present invention;

[0032] Figure 3 This is a top view of a fast reversing valve provided by the present invention.

[0033] In the diagram: 1. High-level liquid reservoir; 2. Calibration tank; 3. Low-level liquid reservoir; 4. Gas cylinder; 5. Circulation pump; 6. Flow meter to be tested; 7. Control valve; 8. Quick-reversing valve; 9. Discharge line shut-off valve; 10. Circulation pump inlet shut-off valve; 11. Circulation pump bypass shut-off valve; 12. Gas line shut-off valve; 13. Actuator; 14. Packing gland; 15. Stuffing box; 16. Valve stem; 17. Extended pipe assembly; 18. Flow channel B; 19. Bottom drain pipe; 20. Ball valve core; 21. Flow channel A; 22. Metal bellows; 23. Valve seat. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] like Figure 1 As shown, the present invention provides a closed-loop flow calibration system for calibrating the flow rate of liquid metals, comprising a high-level reservoir 1, a calibration tank 2, a low-level reservoir 3, a gas cylinder 4, and a circulation pump 5.

[0038] The high-level liquid reservoir 1 is located above the device and is used to absorb thermal expansion and provide covering gas for the device; the high-level liquid reservoir is equipped with an electric heating element to heat the liquid metal to the temperature required for the calibration of the flow meter under test.

[0039] The high-level liquid reservoir 1 has a first inlet on its side wall, and the outlet of the circulating pump 5 is connected to the first inlet; the inlet of the circulating pump 5 is connected to the low-level liquid reservoir 3, and the front end of the inlet of the circulating pump 5 is provided with a circulating pump inlet shut-off valve 10; the circulating pump 5 and the circulating pump inlet shut-off valve 10 are connected in parallel to a bypass pipeline, and the bypass pipeline is provided with a circulating pump bypass shut-off valve 11.

[0040] The high-level liquid storage device 1 is provided with a second inlet at its top. The gas cylinder 4 is connected to the second inlet through a first pipeline. A gas pipeline shut-off valve 12 is provided on the first pipeline. The low-level liquid storage device 3 is connected to the first pipeline through a second pipeline. A gas pipeline shut-off valve 12 is provided on the second pipeline.

[0041] The bottom outlet of the high-level liquid reservoir 1 is connected to the flow meter 6 to be tested. The flow meter 6 to be tested is equipped with a regulating valve 7. Preferably, the flow meter 6 to be tested and the regulating valve 7 comprise two sets, which are connected in parallel. This can be used to calibrate flow meters with different flow ranges.

[0042] The other end of the flow meter 6 under test is connected to the top inlet of the calibration tank 2 via a quick reversing valve 8. The calibration tank 2 is used to receive and accurately measure the volume of the flowing liquid metal.

[0043] The first outlet of the quick-reversing valve 8 is connected to the calibration tank 2 via a pipeline, and its second outlet is connected to the low-level liquid reservoir 3 via a return pipeline; the quick-reversing valve 8 is used to quickly switch the liquid metal flow to the calibration tank 2 or the return pipeline.

[0044] The high-level liquid reservoir 1 can provide pressure head for fluid circulation through the high-low pressure difference when the circulation pump 5 is not running, thereby achieving the ability to make the fluid flow in the device without relying on the pump.

[0045] The low-level liquid reservoir 3 is used to store liquid metal and contains a heating device that can melt the liquid metal.

[0046] The circulating pump 5 is used to circulate pressure head for the test apparatus.

[0047] The regulating valve 7 is used to regulate the flow rate of the flow meter 6 under test.

[0048] The calibration tank 2 is integrated with a high-precision electric contact level gauge, which includes one or more vertically arranged electrode rods and a signal transmitter.

[0049] The calibration tank 2 is also equipped with a built-in standard volume scale with precise graduations, and / or multiple temperature sensors distributed along the height direction, as well as a high-temperature viewing window.

[0050] It also includes a control system, which uses data measured by the standard volume scale and temperature sensor to perform temperature expansion compensation and online calibration on the measured value of the electrical contact level gauge; controls the switching timing of the commutator; records the pulse signal emitted by the flow meter under test 6; records the standard volume value calculated from the liquid level change in the calibration tank 2; and calculates the instrument coefficient and accuracy of the flow meter under test 6 based on the pulse signal and the standard volume value.

[0051] Electric heat tracing devices are installed on the high-level liquid storage tank 1, calibration tank 2, low-level liquid storage tank 3, gas cylinder 4, circulation pump 5, quick reversing valve 8, flow meter to be tested 6, as well as valves and pipelines through which the liquid metal flows. The electric heat tracing devices are covered with heat insulation material.

[0052] The self-calibration process of calibration tank 2 is as follows: The external laser instrument can read the scale of the standard volume scale through the high-temperature window on calibration tank 2 and compare it with the reading of the electrical contact level gauge on the control system screen. The built-in algorithm of the control system can perform expansion compensation according to the temperature difference and allows manual or automatic input of offset to correct the measured value of the level gauge, thereby achieving high-precision calibration without offline operation.

[0053] The quick-response valve 8 is a quick-switching ball valve, such as... Figure 2 As shown, it includes an actuator 13, a valve stem 16, an extension tube assembly 17; flow channels (18, 22), a ball valve core 20, and a valve seat 23; the actuator 13 is preferably a pneumatic or hydraulic actuator, configured to drive the valve stem to drive the ball valve core to rotate rapidly within a 180-degree angular stroke.

[0054] The spherical valve core 20 and the valve seat 23 that cooperate with it are provided with liquid metal self-lubricating guide grooves and coatings; the coating is a soft metal plating or an oxide ceramic composite coating formed on a base material.

[0055] The soft metal coating is a gold, silver, lead, or tin coating; the oxide ceramic composite coating is an alumina-titanium oxide composite coating.

[0056] The sealing structure of the valve stem 16 includes a first-stage seal and a second-stage seal. The first-stage seal is a metal bellows 22 seal, one end of which is welded to the valve stem and the other end is welded to the valve seat 23, achieving absolute isolation of the dynamic seal. The second-stage seal is a stuffing box 15 located above the bellows seal, filled with high-temperature resistant graphite or flexible graphite packing. The stuffing box 15 is sealed by a packing gland 14.

[0057] The valve seat 23 has a drain pipe 19 at the bottom, and a drain valve is provided on the drain pipe to drain the liquid metal remaining in the valve seat.

[0058] The quick-reversing valve 8 includes flow channels A, B, and C, such as... Figure 3 As shown in the diagram. Flow channel C is connected to the flow meter under test, flow channel A is connected to the calibration tank 2, and flow channel B is connected to the low-level liquid reservoir 3.

[0059] The working principle of this invention is as follows:

[0060] In the non-calibration state, liquid at a certain temperature flows out from the high-level reservoir 1, passes through the flow meter under test, and is then guided by the quick-reversing valve 8 to the return pipe, returning to the low-level reservoir 3, forming a cycle. At the start of calibration, the control system issues a command to drive the actuator (such as a pneumatic head) of the quick-reversing valve 8, rapidly rotating the ball valve core 180 degrees within 100-200ms. The flow path is switched to the pipe leading to the calibration tank 2, and liquid metal is injected into the calibration tank 2. The integrated high-precision electrical contact level gauge in the calibration tank 2 measures the rate of liquid level rise in real time. Simultaneously, the control system rapidly acquires the linear signal emitted by the flow meter under test 6. After reaching the predetermined volume or time, the quick-reversing valve 8 quickly switches back to the return position. After injection stops, the control system calculates the flow meter coefficient based on the acquired linear signal and the precise volume measured in the calibration tank 2. After calibration is complete, valves 9, 10, and 11, as well as the valve on the drain pipe at the bottom of the quick-reversing valve, are opened, and the liquid metal flows back to the low-level reservoir 3 by gravity.

[0061] While those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention, the embodiments should be considered illustrative and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and therefore all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0062] Furthermore, it should be understood that although the present invention is described according to embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A closed-loop flow calibration system, characterized in that, The system includes a high-level reservoir (1), a calibration tank (2), a low-level reservoir (3), a gas cylinder (4), and a circulation pump (5). The high-level reservoir (1) has a first inlet on its side wall, and the outlet of the circulation pump (5) is connected to the first inlet. The inlet of the circulation pump (5) is connected to the low-level reservoir (3). The top of the high-level reservoir (1) has a second inlet. The gas cylinder (4) is connected to the second inlet via a first pipeline. The low-level reservoir (3) is connected to the first pipeline via a second pipeline. The bottom of the high-level reservoir (1)... The outlet is connected to the flow meter (6) to be tested, and the other end of the flow meter (6) to be tested is connected to the top inlet of the calibration tank (2) through a quick reversing valve (8). The calibration tank (2) is used to receive and accurately measure the volume of the flowing liquid metal. The first outlet end of the quick reversing valve (8) is connected to the calibration tank (2) through a pipe, and its second outlet end is connected to the low-level liquid reservoir (3) through a return pipe. The quick reversing valve (8) is used to quickly switch the liquid metal flow to the calibration tank (2) or the return pipe.

2. The closed-loop flow calibration system according to claim 1, characterized in that, The high-level liquid reservoir (1) is located above the device, and the high-level liquid reservoir (1) is equipped with an electric heating element.

3. The closed-loop flow calibration system according to claim 2, characterized in that, The circulation pump (5) is provided with a circulation pump inlet shut-off valve (10) at the front end of the inlet; the circulation pump (5) and the circulation pump inlet shut-off valve (10) are connected in parallel by a bypass pipeline, and the bypass pipeline is provided with a circulation pump bypass shut-off valve (11).

4. The closed-loop flow calibration system according to claim 3, characterized in that, The first pipeline is equipped with a gas pipeline shut-off valve (12), and the second pipeline is equipped with a gas pipeline shut-off valve (12).

5. The closed-loop flow calibration system according to claim 4, characterized in that, The calibration tank (2) integrates a high-precision electric contact level gauge, which includes one or more vertically arranged electrode rods and a signal transmitter; the calibration tank (2) is also equipped with a built-in standard volume scale with precise graduations, and / or multiple temperature sensors distributed along the height direction and a high-temperature window.

6. The closed-loop flow calibration system according to claim 5, characterized in that, It also includes a control system, which uses data measured by the standard volume scale and temperature sensor to perform temperature expansion compensation and online calibration on the measured value of the electric contact level gauge; controls the switching timing of the quick reversing valve (8); records the pulse signal emitted by the flow meter under test (6); records the standard volume value calculated from the liquid level change in the calibration tank (2); and calculates the instrument coefficient and accuracy of the flow meter under test (6) based on the pulse signal and the standard volume value.

7. The closed-loop flow calibration system according to claim 6, characterized in that, The quick-reversing valve (8) is a quick-switching ball valve, including an actuator (13), a valve stem (16), a ball valve core (20), and a valve seat (23). The actuator (13) is connected to the valve stem (16), and the other end of the valve stem (16) passes through the valve seat (23) and is connected to the ball valve core (20). The actuator (13) drives the valve stem (16) to drive the ball valve core (20) to rotate quickly within a 180-degree angle stroke.

8. The closed-loop flow calibration system according to claim 7, characterized in that, The valve stem (16) is provided with an extension tube assembly (17) on the outside. The sealing structure of the valve stem (16) includes a first-stage seal and a second-stage seal. The first-stage seal is a metal bellows (22) seal, one end of which is welded to the valve stem (16) and the other end is welded to the valve seat (23) to achieve absolute isolation of dynamic sealing. The second-stage seal is a stuffing box (15) located above the bellows seal and inside the extension tube assembly (17), which is filled with high-temperature resistant graphite or flexible graphite packing. The stuffing box (15) is sealed by a packing gland (14).

9. The closed-loop flow calibration system according to claim 8, characterized in that, The quick-reversing valve (8) includes flow channel A, flow channel B and flow channel C, wherein flow channel C is connected to the flow meter to be tested, flow channel A is connected to the calibration tank (2) and flow channel B is connected to the low-level liquid reservoir (3).

10. The closed-loop flow calibration system according to claim 9, characterized in that, The spherical valve core (20) and the valve seat (23) that cooperate with it are provided with liquid metal self-lubricating guide grooves and coatings; the coating is a soft metal plating or an oxide ceramic composite coating formed on the base material.

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