RU2710007C1 - Bypass level gauge - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: bypass level gauge for measuring level of liquid in vessels and reservoirs with aggressive and explosive liquids, with high pressure and operating in a wide temperature range using a bypass, comprising a float located in the bypass pipe, a magnetostrictive transducer located outside the reservoir next to the bypass pipe, wherein the float in the bypass pipe comprises antifriction elements in the upper and lower parts of the float, wherein the antifriction elements can be sliding elements or rolling elements in any combinations, the magnetostrictive converter additionally includes information on temperature and density of the liquid in the reservoir for correcting the value of the level to the true value. When measuring level of explosive liquids one or both antifriction elements are made of antistatic material.EFFECT: development of a new device for measurement of liquid level in vessels and tanks with aggressive liquids and explosive liquids, with high pressure and operating in a wide range of temperatures, having continuous level measurement with high accuracy.1 cl, 2 dwg

Description

The invention relates to the field of measuring technology and can be used in systems for measuring the level of aggressive liquids, including explosive ones, located in vessels or tanks with high pressure and in a wide temperature range using bypass.

Bypass level meters (level indicators) are used for continuous measurement and display of the liquid level in tanks. The principle of operation is based on the law on communicating vessels - the level in the bypass chamber is equal to the level of the measured liquid inside the tank. The level indication is provided by a system of two-color roller magnets such as red and white, mounted on the surface of the bypass chamber, in which the white color of the roller corresponds to the absence of liquid in the vessel, and red to the filling of the vessel. A float with a built-in magnet installed in the chamber is located on the surface of the liquid. Rising and falling along with the liquid level in the vessel, the float rotates the roller by 180 ° with the magnetic field, provides a visual indication of the level in the vessel.

Such level gauges are described in the patent of Germany No. 969753, CL. 42е 31/03, 1960, a.s. of the USSR No. 807065 M.C. G01F 23/12 1979, A.S. USSR No. 934231 M.C. G01F 23/12 1980 and others.

Due to the use of corrosion-resistant float materials (corrosion-resistant steel, titanium, etc.), bypass level meters can operate in vessels with aggressive liquids, vessels with high pressure and in a wide temperature range.

Instead of or in addition to level indicators, level converters can be installed. The installation of level converters allows you to convert the position of the magnetic float into an electrical signal corresponding to the current liquid level in the tank. As level converters, reed switch lines or magnetostrictive sensors are used.

An ultrasonic level gauge operating according to the magnetostrictive principle is described in RF Patent RU 2298154 M.Kl. G01F 23/28 2005 and is the closest in technical essence to the claimed device.

The ultrasonic level gauge contains a straight-line sound duct made of magnetostrictive material with a reflective load at one end and an electro-acoustic transducer at the other and a float element with a magnet located in the reservoir with the working medium, the output of the electro-acoustic transducer through a readout amplifier is connected to the information input of the coding and computation unit, a recording generator connected to the sound duct, a second electro-acoustic transducer located on the sound duct reference distance from the first electro-acoustic transducer and connected to another signal input of the reading amplifier, an indication unit connected by information inputs to the outputs of the coding and computing unit, another signal input of which is connected to the output of the recording generator of the same name connected to the control bus, the second magnet is fixed in the float element at a reference distance from the first magnet and moving inside the tank at the level of the boundary of the working medium along the sound duct within d the action of the movement limiter, and the sound pipe is fixed on the outside of the tank near its working wall made of non-magnetic material.

The proposed technical solution provides increased reliability of the conversion of the level of liquid media in tanks compared with previously known technical solutions and the expansion of functionality.

However, as in other bypass level gauges, the indicated device has a very significant drawback, which leads to large dimensions of measurement error. It consists in the fact that the measuring float located in the bypass has poor stability due to the displacement of the center of the buoyancy force relative to the center of gravity of the float. The impact of forces on the float is schematically shown in Figure 1. The displacement of the center of gravity relative to the center of the buoyant force leads to the formation of a torque M that tries to overturn the float, but this does not happen because the float is in the bypass pipe. But the forces arising from this lead to a large value of the friction force of the float on the wall of the bypass pipe. This design of the float is forced due to the need to install a magnet in the upper part of the float to align the magnet with the liquid level. As tests carried out at the enterprise showed, the float moves jerkily when filling or emptying the tank, and the float does not respond to small changes of the level of the order of 1-3 mm, and jumps have a value of 3-20 mm. This is due solely to the frictional forces of the float on the bypass pipe wall.

In addition, the immersion value of the float depends on the density and temperature of the liquid. This factor is also not taken into account. The measurement error is especially noticeable in the case of a deviation of the liquid density from the value for which the float is designed. The result is a large additional error.

The problem to which the invention is directed is the creation of a device for measuring the liquid level in vessels and reservoirs with aggressive liquids, with high pressure and operating in a wide temperature range, which provides high level measurement accuracy using bypass.

This object is achieved in that the bypass level gauge for measuring the liquid level in vessels and reservoirs with aggressive liquids, with high pressure and operating in a wide temperature range using bypass contains a float located in the bypass pipe, a magnetostrictive transducer located outside the tank near the bypass pipe, and the float in the bypass pipe contains anti-friction elements in the upper and lower parts of the float, while the anti-friction elements can be cleaved By using pressure gauges or rolling elements in any combination, information on the temperature and density of the liquid in the tank is additionally entered into the magnetostrictive transducer to adjust the level to the true value, when measuring the level and density of explosive liquids, one or both antifriction elements are made of antistatic material.

The technical result is the creation of a new device for measuring the liquid level in vessels and tanks with aggressive liquids and explosive liquids, with high pressure and operating in a wide temperature range, with continuous level measurement with high accuracy.

In FIG. 2 schematically shows a bypass level gauge.

The numbers in the figures indicate:

1 - reservoir;

2 - bypass pipe;

3 - float;

4 - magnetostrictive converter

5 - anti-friction element

6 - magnet float;

7 - roller magnetic indicator.

The bypass level gauge contains a float 3 located in the bypass pipe 2, a magnetostrictive transducer 4 located outside the tank 1 near the bypass pipe 2. The antifriction elements 5 are installed on the float above and below, and the magnet of the float 6 is located inside it. At the request of the operating organization, it can additionally be installed roller magnetic indicator 7 with two-color magnetic plates for visual level control.

Bypass level gauge works as follows.

The reservoir 1 and the bypass pipe 2 are interconnected vessels - the level in the bypass pipe 2 is equal to the level of the measured liquid inside the tank 1, so the float 3 monitors the liquid level in the tank 1 during its movement in the bypass pipe 2. Permanent magnet 6 is installed inside the float 3. C using magnetostrictive transducer 4 determines the position of the float 3. This happens as follows.

Level measurement is based on measurements of the propagation time of ultrasound in a magnetostrictive waveguide. The propagation velocity of ultrasound in the waveguide is practically independent of pressure and humidity. The influence of temperature is automatically compensated using a special algorithm for processing time intervals of ultrasound propagation.

At the command of the magnetostrictive transducer control unit, an ultrasonic wave is generated according to the magnetostriction principle directly in the waveguide made of a special steel wire with magnetostrictive properties and located inside the body of non-magnetic material.

When the alternating magnetic field created by the current pulse in the waveguide and the field of the permanent magnet 6 located inside the float 3 interact, the crystal structure of the waveguide is deformed, which creates a mechanical wave propagating with ultrasonic speed. An ultrasonic wave arising at the location of the magnet propagates along the waveguide in both directions from the place of occurrence. In the upper part of the waveguide, the ultrasonic wave is converted into electrical impulses due to the inverse magnetostrictive effect and then damped. These pulses are converted into a rectangular shape and then fed to the control unit of the magnetostrictive transducer. The time interval between the moment of generation of the ultrasonic wave and its conversion into electrical pulses is proportional to the measured distance, i.e. float position.

Antifriction elements 5 are located in the upper and lower parts of the float 3. The antifriction elements on the float can be made both sliding elements and rolling elements in any combination. As a sliding element, a ring made of a material with a low coefficient of friction, for example, fluoroplastic, can be used, and cages with balls or rollers rotating on an axis can be used as rolling elements. In the process of prototyping, both options were tested. Best results are obtained with rolling elements. However, the design with rolling elements is more complex, and in cases where high measurement accuracy is not required, sliding elements or combinations of these options can be used.

The temperature and density of the liquid may vary, but the electronic system of the magnetostrictive sensor provides for the introduction of appropriate correction, which allows without replacing the float to obtain reliable information about the level of liquid in the tank. Temperature correction is carried out automatically from temperature sensors in the tank, and the density value is entered according to the results of laboratory measurements of liquid samples or using automatic densitometers.

The depth of immersion of the float in the bypass is adjusted when the temperature and density change according to the formula:

Where:

h is the immersion depth of the float;

M is the mass of the float;

ρ is the fluid density;

α is the temperature coefficient of density change;

t is the current fluid temperature.

During the tests, a magnetostrictive sensor of the measuring system “STRUNA +” КШЮЕ.421451.002ТУ was used as a magnetostrictive converter.

When operating at high temperatures, the magnetostrictive converter can be protected from the bypass pipe using thermal insulation.

Near the magnetostrictive transducer 4, a classic roller magnetic indicator 7 with two-color magnetic plates described above can be installed.

It should be noted that the use of the proposed technical solution in terms of floats will improve the accuracy of measurement of almost all known indicators and level meters operating on a bypass pipe. The choice of a magnetostrictive transducer as a level meter is explained solely by its high metrological characteristics compared to other level measurement methods.

Another advantage of using a magnetostrictive transducer is the ability to move the magnet to the bottom of the float to improve its stability with appropriate correction of the measured value, however, this is unacceptable for other types of sensors due to the impossibility of correction and in the case of simultaneous use of two types of sensors, for example roller magnetic and magnetostrictive .

It should also be noted that due to the use of low operating voltages and low current consumption in magnetostrictive sensors, the described level measuring device is easily implemented in an explosion-proof version, which allows it to be used in measurements in explosive atmospheres. In this case, one or both of the anti-friction elements 5 are made of antistatic material to remove static charges from the float.

At the applicant plant, a prototype was made, and then a prototype of a bypass level gauge, and tests were carried out that fully confirmed the correctness of the proposed solution.

Claims (2)

1. Bypass level meter for measuring liquid level in vessels and reservoirs with aggressive liquids, with high pressure and operating in a wide temperature range using bypass, containing a float located in the bypass pipe, a magnetostrictive transducer located outside the tank next to the bypass pipe, characterized in that the float in the bypass pipe contains antifriction elements in the upper and lower parts of the float, and the antifriction elements may be sliding elements or elements to In any combination, information on the temperature and density of the liquid in the tank is additionally entered into the magnetostrictive transducer to adjust the level to the true value. 2. Bypass level gauge according to claim 1, characterized in that one or both antifriction elements are made of antistatic material when measuring the level of explosive liquids.

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