SU1096533A1 - Vibration-type density meter - Google Patents

Abstract

VIBRATION PLOTNOMER, containing a sensor, made in the form of two tubular resonators fastened by peremes as a twin tuning fork, installed in a housing and equipped with a device for supplying and discharging a controlled medium, an oscillation excitation system, as well as a measuring device that differs in that measurements by reducing the error of the change in the velocity of the flow of the controlled medium, the output ends of the resonators, performing for the jumper, are bent at a right angle to their longitudinal was m

Description

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The invention relates to the field of instrumentation and can be used to control the density of petroleum products transported through high-pressure pipelines.

Known vibrating densitometer, the sensor of which is made in the form of a flow-type tubular resonator tuning fork type 1.

The drawback of the densitometer is the measurement error due to the dependence of the oscillation frequency of the tubular resonator of the sensor on the velocity of the medium through the sensor,

The closest to the invention is a resonant densitometer, with a sensor, made in the form of two tubular resonators, fastened with bridges like a twin tuning fork, installed in a housing and equipped with a device for supplying and discharging a controlled medium, an oscillation excitation system, and a measuring device. Tubes at both ends are connected to the hydraulic system through which the test fluid flows 2.

A disadvantage of the known densitometer is the presence of an additional measurement error due to the dependence of the oscillation frequency of the tubular resonators on the speed of the flow through the controlled medium through them. This error becomes significant at speeds of medium movement of 3-8 m / s and can reach 2 g3 kg / m for each m / s,

The aim of the invention is to improve the measurement accuracy by reducing the error of the change in the flow rate of the controlled medium.

The goal is achieved by the fact that in a vibrating densitometer, there is a sensor made in the form of two tubular resonators, connected by bridges like a twin tuning fork, installed in a housing and equipped with a device for supplying and discharging a controlled medium, an oscillation excitation system, and also a measuring device, output ends resonators protruding beyond the jumper are bent at an angle to their longitudinal axis,

The drawing schematically shows a device, a density meter,

The densitometer sensor contains two tubular resonators 1 and 2, connected by bridges 3 and 4 in the form of a twin tuning fork, installed in a housing (not shown) equipped with an input and output device 5 of the controlled medium. The resonator oscillation excitation system includes a receiver 7 oscillations, an amplifier 8, a pathogen 9 oscillations switched on according to the electromechanical scheme

auto generator. A frequency meter 10 is provided for recording the density. One pair of ends of the resonators 11 and 12 protruding beyond the exit bar is bent at a right angle to their longitudinal axes 13 and 14.

Densitometer works as follows

Kontro,;: the simulated medium with velocity V enters the densitometer sensor through the input device 5. The fluid moves along the straight pipe sections of the tubular :: resonators 1 and 2, at the output of which, behind support 4 (jumper), the flow of the controlled medium turns at a right angle in the bent parts 11 and 12 of the resonators and through the output device 6 the fluid flows into the technological pipeline. When the jet leaves the parts of the resonators 1 and 2, the reaction force of the jet N arises at a right angle, which in the general case is equal to

rJ mV (i-cosoLl,

where m is the linear mass of the fluid.

The projection of the N reaction force of the jet onto the longitudinal axes 13 and 14 of the resonators 1 and 2 at a 90 ° C angle is V, which reduces the effect; flow rates V of the controlled medium at the oscillation frequency f and the error due to a change in the velocity of the medium. The regions of the resonators 1 and 2 are driven into self-oscillation mode by means of the receiver 7, amplifier 8, exciter, 9 at a frequency f close to the natural frequency; resonators, which depends on the mass of the resonators r and, consequently, on the density of the controlled medium and does not depend on its flow rate. The natural frequency of the resonator is

, e (N-T)

± 4ft4pf Ed4H-M

I l

Тг Л ,,: (.tT4-0- frequency fluctuating

 about i scientific research institute of an empty tube;

DJ; d - outer and inner tube diameter, m;

pm) P is the density of the tube and fluid material, kg / cm; (vf-}.) the resonator constant, kg / m;

and

-the relative wall thickness of the tube;

- tube length, m;

N, T

- axial forces of stretching and compressing the tube;

a., b V

- coefficients depending on the type of tube attachment;

- the speed of the controlled fluid

Substituted in the relation for f N mV (l-cosoi) and taking into account that

Tt 2, m - d p, we get

I,

MiTpT T yp;)

From the obtained ratio, it can be seen that the error due to the change in the flow velocity is zero when the condition

(1 - cosoL) b.

from where

ot arccos (1 - -;:;).

II a

0965334

For attaching the ends of the support-support type, 064, 621, i5 3.1416.

c6 f arccos About 90 °.

5 For fastening end fittings, 970,, 762

ot arccos С 0.0002, t 90 °

Thus, in the proposed 10 design, the right angle between the longitudinal axis of the rectilinear part of the resonator and the axis of the end of the resonator rotated beyond the support is optimal.

5 In comparison with the known, the proposed density meter reduces the error in measuring the density due to the influence of the flow rate of the test liquid by an average of 75%.

Claims (1)

VIBRATION DENSITY METER, comprising a sensor made in the form of two tubular resonators, fastened with jumpers of the type of a double tuning fork, installed in the housing and equipped with a device for supplying and removing a controlled medium, an oscillation excitation system, and a measuring device, characterized in that, in order to increase measurement accuracy by reducing the error from changes in the flow rate of the controlled medium, the output ends of the resonators protruding beyond the jumper are bent at right angles to their longitudinal axes. 1. About 9 6 5 3 3 g