SU1427236A1 - Method of measuring density of liquid and loose materials - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the density of bulk materials in the construction industry. The goal is to improve the accuracy of determination and ensure the possibility of determining the volume of the material under study after determining its density. The method is based on using the maximum value of the period of natural oscillations of a container with the material under study, suspended as a physical master, when the volume of the material in the container varies from the density of the material to be filled. The height of the suspension and the geometrical dimensions of the capacitance are chosen so as to ensure, in the range of measured densities and load levels, an increase in the natural oscillation period from the initial value with an empty capacitance to the maximum value and a subsequent decrease in the period. An arbitrary amount of material is produced in discrete portions, the period of oscillation of an empty tank n is measured after loading each portion, the value of the maximum period is determined, and the bulk density is determined from it according to the calibration curve. With this density value and the value of the current period of oscillation of the capacitance, the volume of the material is determined at the time of reaching the maximum of the oscillation period and after loading subsequent batches. In the process of determining, the calibration dependence is measured according to the measured value of the period of natural oscillations of an empty tank 1. 3. sv f-ly, 2 silt, 2 tab. WITH

Description

The invention relates to a measurement technique and can be used to measure the bulk density of bulk materials in the construction industry.

The purpose of the invention is to improve the accuracy of determination and to make it possible to determine the volume of the material under study after determining its density.

Figures 1 and 2 show diagrams explaining the theoretical foundations of the method; Fig. 3 schematically shows a device for implementing the proposed method.

The method is based on using the dependence of the maximum value of the period of natural oscillations Tm of the container with the material under study, suspended as a physical case, when the volume of the material in the vessel varies with the density of the material to be filled.

The method is carried out as follows.

The container for the material under investigation is suspended as a physical man, the height of the suspension and the geometrical dimensions of the container are selected, providing a range of measured values and loading levels, the period of its natural oscillations T from the initial value To

The test material is loaded into the container in discrete portions, the volume of which is determined by the measurement accuracy requirement. The dosage is as follows. At an eternal maximum intensity of a continuous flow of material, the interval At is determined, over which

The value of T „and the subsequent decrease does not exceed the permissible period with an increase in the volume V of the material dose. After the interval At ends, the material supply is stopped. After each portion is loaded, the period of natural oscillations of capacity with material T is measured. When the period of oscillation reaches its maximum value T | the calibration dependence (3) determines the desired

the rial in the tank, i.e. extreme dependence of iid) period T on the volume V of the material filled into the container at any load level in a given range (figure 1).

The dependence of the oscillation period T of a cylindrical capacity of radius r with the material under study with a density f of its volume is

-TTJ-jT -; v

. gpv (e - 2

where S is the cross-sectional area

containers;

 - distance from the oscillation axis to the bottom of the tank;

50 determine the volume of the material in the tank 1G and its mass M «« P V.

Example. Measurements were made of the bulk density of gravel and crust sands of known density — the acceleration of free fall; nosti (kg / m).

MO is the mass of an empty container;

do is the distance from the oscillation axis to the center of mass of the empty tank;

The sand was loaded into a 5-liter mercury cylindrical vessel of the MP type, suspended at a distance of 0.1215 m from the upper edge of the vessel by means of

0

five

g

to is the moment of inertia of an empty capacitive, relative to the axis of oscillation. Mo-r2.

Calculate the calibration dependence of P (T "). Equating to zero the partial derivative d (T2) / dV-0, we obtain the dependence of the material density of its volume V in the container, at which the maximum of the period of the corresponding oscillations T of the container with the material is reached:

.l (-. I J. 1. Л. U «, lr V

(2)

p bi3zt + VMi2 / e;: 2 t2 if.t :: kr

ez4lf-2kzV + y, ak -Yav) 5 where z is A / 3r; oC 4) k "gt {

ft + r2 / 4); 1G-C 4TG .0 g / 25rr; t gModo. From here, graphically get the inverse relationship (/). Substituting this dependence in (1), we obtain the desired calibration dependence

P (T „). (3)

The period of natural oscillations of an empty tank is measured. Substituted the value in (2), specify the calibration dependence (3).

The test material is loaded into the container in discrete portions, the volume of which is determined by the measurement accuracy requirement. The dosage is carried out as follows. With a known maximum intensity of a continuous flow of material, the interval At is determined, for which it gets no more than permissible, no more than permissible

doses of material. At the end of the interval At stop the flow of material. After each batch is loaded, the period of natural oscillations of capacity with material T is measured. When the magnitude of the oscillation period reaches its maximum value T | the calibration dependence (3) determines the desired

R. density

45 Continue to fill the container with subsequent portions of the material and measure the current period of oscillation of capacity T. According to relationship (1) with already known material density p, the volume of material in tank 1G and its mass M «« P V are additionally determined.

Example. The bulk density of gravel and expanded clay sands of known density (kg / m) was measured.

The sand was loaded into a 5-liter volumetric cylindrical vessel of the MP type, suspended at a distance of 0.1215 m from the upper edge of the vessel by means of

two inelastic inextensible metal bonds to the oscillation axis, fixed horizontally in two instrument bearings (Fig. 2), the vessel was reported to have small oscillations around the axis of suspension, the period of which was measured by an electron-counting frequency meter 43-33, Magnetic reed switch type SCH1U2-AO with contact bounce circuit was used.

At the same time, the suspension height of the container as a physical model, as well as its geometrical dimensions were chosen such that they increase the period of capacitance oscillations as the material is filled from the initial value with an empty container. To a maximum value when loading no more than 26% of the capacity (see Table .1) and the subsequent reduction of the period. The sand was loaded into the container in portions, the size of which was limited to the volume of the measuring cup arbitrarily by volume. After filling each portion, the period of natural oscillations of the capacitance T was measured and the maximum of the measured periods of oscillation was checked (see Table 2). The maximum value of the oscillation period T was determined (in table 2 it is highlighted with a line). According to the initial parameters of the meter shown in table 1, the calibration dependence Tn, f (p) -V was obtained.

The bulk density was determined according to this calibration dependence (presented in Table 1) and the measured value of the maximum period of capacitance oscillations (see Table 2).

The volume of the material at the time of the maximum period of oscillation was determined from the dependence (1) from the value of the bulk density and the value of the current period of oscillation of the capacitance, and the mass of the loaded material from the found bulk density and volume values.

In addition, before the measurements, the calibration dependence was measured by the measured period of the natural oscillations of the empty capacitance by determining the refined coefficient. T | where is the constant meter.

The results of measurements and calculations are given in table 2.

The periods of oscillations were measured with an accuracy of 10 s. Maximum values

0

five

0

five

0

five

0

five

0

five

measured periods in the table are highlighted. As can be seen from Table 2, the error in determining the density when tested on two materials was 1.41–5%, and that of the volume determination was 1–3%.

A further increase in the measurement accuracy of the proposed method can be achieved due to the special design of the suspension, reducing the attenuation coefficient of oscillations and exceeding-. overall period measurement accuracy.

The proposed method can be applied in devices for controlling bulk density and volume-weight dosing in the production of expanded clay concrete, as well as in construction laboratories.

Claims (2)

1. Method of determining the density of liquid and bulk materials, including the loading of the material under study in a container suspended as a physical tick, the excitation of capacitance oscillations, measuring the period of its natural oscillations around a fixed axis, characterized in that, in order to determine the accuracy of the determination and ensure the possibility of determining the volume of the material after determining its density, choose the height and the geometrical dimensions capacitances, which in the range of measured densities and load levels increase the period of natural oscillations from the initial value when the capacitance is empty to the maximum value and The following reduction of the period,: load an arbitrary amount of material in discrete portions, measure the period of oscillations of the empty tank, and after loading each portion, determine the magnitude of the maximal period, find the bulk density from it according to the calibration dependence and the value of the current period of capacitance oscillations is determined by the volume of the material at the time of reaching the maximum of the oscillation period and after loading subsequent batches. 2. Method POP1, characterized in that, in the process of determining, the calibration dependence is refined according to the measured value of the period of natural oscillations of an empty capacitance. Calibration dependencies Table 1 T "4lktsa2 RvAutAtI emvrvkni Oscillations M1 GMG Tmz GAG fi) (v) №f / r wme- rial t Ung Fi. 2 i-i I diiO4Lb. -J: (:); - th About -i) .-. ag .; :; $. . QacmomoMCf) ShoShGShShShShSh liiiii iinin Fi. H