RU2273838C1 - Density meter - Google Patents

Abstract

FIELD: the invention refers to arrangements for measuring density of liquids and may be used in systems of measuring density of oil products and other liquids including explosive at their outletting, getting and storing with measuring density on various levels.

SUBSTANCE: the density meter has a converter of displacement in the shape of a magnetostriction waveguide placed inside the body of nonmagnetic material on which n toroidal floats with counter-balancing chains are located on different altitude. With its one end it is fastened to a float and with the other end to locators firmly fastened on the body of the converter of displacement and with the magnets inside the floats. On the magnetostriction waveguide there is a reading bobbin connected to an amplifier-former and the magnetostriction waveguide itself is switched to a former of impulses. The output of the amplifier-former is switched to the input of a signal processing block whose output is connected with the input of the former of impulses.

EFFECT: possibility of measuring density at various levels without tying to the boundary of conditional division of mediums, high sensitiveness and wide range of working temperatures.

2 dwg

Description

The invention relates to devices for measuring the density of liquids, including stratified in height, for example, petroleum products.

There are many devices of a float type for measuring the density of liquids, an overview of which is well presented in the book of S. S. Kivilis "Density" ed. Energia, Moscow, 1980. All these densitometers are classified according to two functional principles - with partial immersion of the float and with full immersion of the float.

Readings of densitometers with partial immersion of the float, i.e. located on the surface, depend on the surface tension of the liquid, which, in turn, is determined by a number of factors (such as pressure, temperature, wettability) and, as a rule, is a variable. This leads to a decrease in measurement accuracy.

To exclude the influence of surface tension allow densitometers with floaters full immersion (float-weight densitometers). Density meters of complete immersion include the so-called chain densitometers, the principle of operation of which is described in the book by S. S. Kivilis "Density meters". Using chains allows you to balance the float in a wide range of density.

A technical description of a submersible densitometer is presented in GB Patent GB No. 20133900 A, G 01 N 9/18, publ. 08/15/1979, the Density Meter contains a float with a chain and an electrode system associated with a bridge circuit to assess the electrical conductivity of the liquid and determine the position of the float by measuring the resistance of the liquid zones. However, this device is only suitable for measuring the density of electrically conductive liquids, such as electrolytes, and does not allow measuring the density of non-conductive liquids, such as petroleum products.

An interesting technical solution is the device for measuring the level and density according to the patent RU 2188400, G 01 N 9/10, only 14 pages, published. August 27, 2002). The device comprises a converter unit, including an amplifier driver, a pulse generator, a counter, a memory register, a register with parallel input and sequential shift of information, two start pulse shapers, an address decoder, a ready signal shaper, a lock shaper, two keys, an exchange bus, four multiplexers , encoder address decoder and k level and density sensors. Each of the sensors contains a sound duct installed in a protective casing in the form of a string of magnetostrictive material, a read coil and two floats with magnets located on them. The sensors are installed in two rows and are offset in height relative to each other to ensure overlap of the working areas. In the upper part of all sensors, except for the upper one, there are installed rigidly attached and hermetically closed in the upper part shrouds of non-magnetic material in the form of a bell, inside of which, from the lower side, during the operation, floats of sensors with magnets fixed to them can enter. The device allows you to measure the density at different levels in the tank, but it has several disadvantages:

1. Density measurement is carried out under the hood where the interface between the media (air-liquid) is artificially created. The densitometer floats operate at this interface, and in this connection there are additional errors that depend on the surface tension of the liquid, which in turn is determined by a number of factors (wettability of the floats, meniscus, pressure, temperature, etc.) and is usually a variable.

2. The presence of a cap with an air cushion limits the pressure at which density can be measured (for example, it is completely unsuitable for liquefied gas);

3. The displacement transducer measures the relative distance between the floats (level and density), and not the position of one float, which leads to additional errors.

The closest in technical essence to the proposed densitometer is the densitometer described in the USSR author's certificate No. 397813, G 01 N 9/10, only 2 pages, publ. 09/17/1972 The specified densitometer contains a balanced immersed vertically moving float with a magnet installed on it, means for balancing the float, for example a chain, a transducer for moving the float into an electric signal, the float being made in the form of a toroid enclosing a nonmagnetic enclosed in a tubular body material, a float displacement transducer made in the form of a ferrite-semiconductor distributor connected to the output of a clock pulse generator.

The above densitometer has a high noise immunity. However, its resolution is determined by the size of one element of the ferrite-semiconductor distributor and the distance between adjacent elements, i.e. its readings are discrete in nature, and an increase in its accuracy and sensitivity requires an increase in the number of ferrite-semiconductor elements and a decrease in their geometric dimensions (for example, for a relative error of 0.1% and movement of a float of 10 cm, 1000 pieces of ferrite-semiconductor elements are needed, and the size they should be 0.1 mm, in practice now such ferrite-semiconductor distributors are not feasible). In addition, with the help of one densitometer it is impossible to make simultaneous measurements at different levels, which is a necessary requirement when measuring the density of stratified liquids, for example, petroleum products. Therefore, the solution of the problem of measuring density at different levels requires the installation of several densitometers, and this, when using a ferrite-semiconductor distributor, directly increases the cost of the measuring system, which will consist of several densitometers. Attention is also drawn to the design feature of fastening chains in a known densitometer: with one end they are attached to the float from below, and with the other end they are fixed at the base of the pipe, i.e. at the conditional boundary of the interface of the media (air - liquid), while the measurement at great depth is not feasible due to the too long chains. In addition, it should be noted that the disadvantage of this densitometer, as well as other known chain densitometers, is the limited working area determined by the length of the measuring element (in this case, ferrite-semiconductor). This, in turn, imposes certain requirements on chains and floats, which have to be made either large-sized with a large number of chains or chains must be made of heavy metals, for example platinum-iridium alloys, which makes them very expensive. But the most serious drawback of a ferrite-semiconductor converter is the narrow temperature range associated with the loss of magnetic properties of the materials used both at low (below -60 °) and at high temperatures (above 100 ° C). This significantly limits the scope of use of these densitometers, for example for measuring the density of liquefied gases and high-temperature melts (in the chemical industry).

The subject of the invention is a liquid densitometer, comprising a balanced vertically moving float immersed in a liquid in the form of a toroid with magnets placed in it, means for balancing the float, for example a chain, a transducer for moving the float into an electrical signal, placed in a tubular body made of non-magnetic material, covered by a toroidal float wherein the float displacement transducer is made in the form of a magnetostrictive waveguide with a read coil located on it I and the pulse shaper connected to it, the read coil is connected to the input of the driver-amplifier, the output of which is connected to the input of the signal processing unit, the output of which is connected to the input of the pulse shaper, the balancing chains of the floats are attached at one end to the float, and at the other end to the latch, rigidly mounted on the housing of the displacement transducer, and the number of floats and their fastening elements is n pieces with their location at different heights depending on the required number of measurement points Grain density fluid.

The technical result is the creation of a new liquid densitometer with continuous measurement with a high threshold of sensitivity, a wide range of operating temperatures and good temperature stability, the ability to measure density at different levels without reference to the boundary of the medium, without increasing the complexity of the meter for displacing the float at a sufficiently long length densitometer (several meters), the ability to use a variety of materials for balancing chains, which makes it possible You can get cheap multi-channel densitometers.

These properties are obtained due to the use of a magnetostrictive waveguide as a displacement transducer located inside a body made of non-magnetic material, on which n toroidal floats with magnets located inside them and with balancing chains attached to them, the second ends of which are attached to latches, are fixed at different heights on the housing of the displacement transducer at various heights. On the magnetostrictive waveguide is a read coil connected to the driver amplifier, and the magnetostrictive waveguide is connected to the pulse former. The output of the amplifier-driver is connected to the input of the signal processing unit, the output of which is connected to the input of the pulse shaper.

Structurally, the holders of the floats can be located both below the floats and above the floats. Such design options are necessary to provide a wider range of measurement of fluid density without changing the design of the floats.

Figure 1 schematically shows the device of the densitometer with the location of the latches below the floats.

The numbers in the drawing indicate:

1 - the first float;

2 - the second float;

3 - n-th float;

4 - a permanent magnet inside the float;

5 - magnetostrictive waveguide;

6 - read coil;

7 - case of non-magnetic material;

8 - pulse shaper;

9 - amplifier-driver;

10 - signal processing unit;

11 - balancing chains;

12 - clamps for floats.

The first, second, and nth floats 1, 2, and 3 are toroidal in shape with magnets 4 located inside them and counterbalancing chains 11 attached to them; the second ends of the balancing chains are attached to the latches 12, which are rigidly fixed to the housing of non-magnetic material 7 of the displacement transducer, the floats They are located outside the casing of non-magnetic material 7, inside of which there is a magnetostrictive waveguide 5 and a read coil 6. The entire structure is placed in the reservoir with the test liquid. The pulse shaper 8 is configured to generate rectangular ultrasonic pulses with a duration of not more than 10 μs, an amplitude of 12 V and a frequency of 10 Hz, necessary to create an ultrasonic wave around the waveguide 5. The amplifier-shaper 8 is configured to amplify a signal taken from the read coil 6 and the formation of single rectangular pulses with a duration of not more than 10 μs and an amplitude of 5 V, necessary for subsequent processing of the signal in the signal processing unit 10, configured to lease time intervals between the pulses in the incoming pulse shaper 8 and the pulses arriving from the amplifier-shaper 9, followed by conversion of information received in the digital value sample liquid density.

Figure 2 schematically shows the device densitometer with the location of the latches above the floats.

The designations and purpose of all the elements of this design are fully consistent with the above description of figure 1 and differ only in the ability to measure lower density values, for example the density of liquefied gases.

The operation of the densitometer is as follows.

The density 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 signal processing unit 10 using the pulse shaper 8, the ultrasonic wave is generated by the principle of magnetostriction directly in the waveguide 5, made of a special steel wire with magnetostrictive properties and located inside the body of non-magnetic material 7.

When the alternating magnetic field generated by the current pulse in the waveguide 5 and the field of permanent magnets 4 interact, the crystal structure of the waveguide deforms, which creates a mechanical wave propagating with ultrasonic speed. An ultrasonic wave arising at the locations of the magnets 4 propagates along the waveguide 5 in both directions from the place of occurrence. In the upper part of the waveguide, ultrasonic waves are converted by a read coil 6 into electrical pulses due to the inverse magnetostrictive effect and then are damped by a damper. These pulses are fed to an amplifier-shaper 9, where they are converted into a rectangular shape, and then fed to a signal processing unit 10. The time interval between the moment of generation of an ultrasonic wave and its conversion into electric pulses is proportional to the measured distance, i.e., the position of the float 1, 2 or 3, and, accordingly, the density of the liquid at a given level. In the presence of several floats with magnets placed in them, several ultrasonic waves arise, equal to the number of floats. At the same time, the moments of the conversion of ultrasonic waves into electric pulses are spaced in time, and an analysis of the number of pulses and the corresponding time intervals will determine the position of each float and thus measure the density of the liquid at the appropriate level. It should be noted that due to the use of a magnetostrictive waveguide as a displacement sensor, it is possible to use steel balancing chains, abandoning heavier and more expensive materials, because There are no stringent requirements for restricting float movements during density measurement. When the float leaves the working area due to a decrease in the liquid level in the tank, the float rests on the retainer 12 in the constructive arrangement of the retainer from below the float, which eliminates tangling of the balancing chains, and in the constructive arrangement of the retainer on the top of the float, the latter hangs on the balancing chains, which also eliminates entanglement of balancing chains.

It should also be noted that due to the use of low operating voltages and low currents, the described densitometer is easily implemented in explosion-proof design, which allows it to be used when measuring density in explosive atmospheres, for example, when working with oil products or liquefied gases.

At the applicant enterprise, a prototype was made, and then a prototype of the described densitometer was described, and tests were carried out that fully confirmed the correctness of the proposed solution.

Claims (1)

A liquid densitometer containing a balanced vertically moving float immersed in a liquid in the form of a toroid with magnets placed in it, means for balancing the float, for example a chain, a transducer for moving the float into an electrical signal placed in a tubular body made of non-magnetic material, covered by a toroidal float, characterized in that the float displacement transducer is made in the form of a magnetostrictive waveguide with a read coil located on it and connected to to it by the pulse shaper, the read coil is connected to the input of the driver-amplifier, the output of which is connected to the input of the signal processing unit, the output of which is connected to the input of the pulse shaper, the balancing chains of the floats are attached at one end to the float, and at the other end to a latch rigidly fixed to the converter housing displacement, and the number of floats and their fastening elements is n pieces with their location at different heights depending on the required number of density measuring points dkosti.

Images