SU1744484A1 - Flowmeter - Google Patents

Abstract

Use: measurement of temperature difference makes it possible to judge the amount of scale deposits, to conduct calibration of flow meters, thereby increasing the measurement accuracy without disassembling. SUMMARY OF THE INVENTION: Along with a pressure differential between positive 1 and negative 2 chambers, a temperature differential also occurs, which is measured by a thermocouple formed by a diaphragm with ring axes of metal deposited on it. The readings are corrected for the temperature difference, which improves the accuracy of the flow meter. 3 il. 2 bo x | 4 b t

Description

The invention relates to the measurement, namely to the measurement of the flow rates of gases and liquids by restricting devices and can be used in pipelines with a diameter of 50 mm and above and the nominal pressure of the medium transported through the pipelines within 10 MPa.

A flow meter is known that includes annular chambers and a diaphragm in which pressure is drawn through an annular gap between the cheek of the chamber and the diaphragm. However, this flow meter has a relatively low measurement accuracy due to the formation of scale on the walls of the diaphragm and annular chamber. In addition, for these flow meters, it is necessary to have a thickened diffraction in order to avoid the occurrence of vibrations at high pressures.

Closest to the invention is the apertured BCS. In this device, the annular chambers have grooves for the passage of fluid, evenly spaced around the circumference. The diaphragm is clamped by annular chambers from two sides due to the protrusions between the grooves, and sealing of the chambers is achieved by installing a gasket.

A disadvantage of this device is a decrease in the accuracy of flow measurement due to the lack of control over the presence and size of scale deposits. Periodically conducted metrological examinations quite often fix measurement errors that go beyond permissible limits.

The aim of the invention is to improve the measurement accuracy.

This goal is achieved by the fact that in a flow meter for liquids and gases, containing positive and negative chambers, between which a diaphragm and a sealing gasket are installed, the diaphragm on both sides is provided with annular layers of metal forming a thermocouple with the diaphragm metal and radial slots for placing current collectors and tokovodov , and tokovods are passed out through the sealing gasket.

The presence of thermocouples, current collectors and tokodov allows measuring the change in thermoEMF, and judging by it about changes in heat transfer and, without disturbing, not changing the design of the flow meter, amend the measurement, thereby increasing the accuracy of the flow meter, and if possible, replace the sensitive element (diaphragm) or flush it without disassembling.

FIG. 1 shows a schematic of the proposed flow meter;

-

FIG. 2 - qualitative dependence of the temperature difference on the thickness of the layer of sediments (scale); in fig. 3 shows the calculated dependence of the change in the relative gradient of the flow meter on the scale I thickness.

The flow meter consists of positive 1 and negative 2 chambers, a sealing gasket 3 between them and diaphragm 4, on

10 of which are coated on both sides with a thin layer of metal 5 and 6, the enclosures of chambers 1 and 2 are provided with radial grooves 7 for placing current collectors 8 in them, the current leads 9 from which are passed through a hermetic gauge 3 (pipeline not shown).

The device works as follows.

Measured medium with temperature TCP

20 passes the plus chamber 1, through the opening of the diaphragm 4 and the minus chamber 2. In addition to this, the pressure drop between the plus 1 and the minus cameras results in a temperature difference caused by the thickness of the diaphragm Td. temperature difference along the working medium due to heat losses along the TCP line length, temperature difference due to expansion of the medium at the orifice of the diaphragm Tr and temperature difference between the temperature meter and the measured medium Ti. The greatest influence on deposits (scale) is exposed to the drop of Ti. During long-term operation, this component of the differential varies significantly within the range of

T T h T

wed

Tr + Ti

At the beginning of operation, when the surface of the diaphragm is a cheat, Ti is positive. With an increase in the thickness of the deposit layer (Fig. 2), the temperature difference decreases and may even change sign. In a very short time of operation, the error in measuring the flow rate can go beyond the permissible limits due to a change in diameter due to deposits.

To the main forum, determine flow rate Q ,, 5.9736

50 No. V / fiKi kRcdao

.Afi P

(SI)

the diameter of the hole aperture d20 is included in the 2nd degree. Even with a high degree of water purification, for example, in the water treatment system of power plants, permanently adhered to the metal surface of the pipes up to a thickness of 20 mm and more accumulate during the inter-overhaul period (i.e. 3-4 years),

having low thermal conductivity (the latter circumstance is useful in the proposed solution). Take as an example a fragment from the real calculation and give a check on the calculation of the diaphragm, where the measured medium is water. Dao 150; O0 150 m3 / h; Pu 4 kgf / cm2; t 35 ° C; pipeline material - article 20

Q0 159.96074.

The relative deviation of Q0 from a given value of Qnp d 0,025%.

In order to go beyond the tolerance of 0.2%, it is necessary to change the diameter of the diaphragm from 71.40 to 71.3 mm, i.e. only 0.1 mm, then Q0 159.513, and the relative deviation d -0.3 ; c5 | 2, the most reliable method of correction is the method based on preliminary calibration of a measuring diaphragm with different scale thickness formed by a particular medium being measured to determine the d20 f (AT) quantitative dependence. When a deviation of d20 is found from the limits at which dK 0 2% It is possible to recalculate readings based on actual pressure drops P in diameters if the measuring unit cannot be replaced or washed.

FIG. 3 shows the effect of the thickness of the scale I on the cylindrical part of the

i

i

g,

the aperture cross section of the d20 diaphragm (for the given example) by the relative deviation idl,

Thus, measuring the temperature drop T can be judged on the amount of scale deposits, to carry out the calibration of flow meters without disassembling them, and not disturbing the size of the gauges.

The use of the proposed device, instead of the known ones, makes it possible to significantly improve the metrological assurance and determine the reliable operation time of the flowmeters, which improves accuracy, reduces operating costs and gives significant

economic effect in the national economy

Claims (1)

Invention Formula A flow meter for liquids and gases containing a plus and a minus chamber between which a diaphragm and a sealing gasket are installed, characterized in that, in order to increase accuracy of measurement, the diaphragm on both sides is provided with annular layers of metal forming a thermocouple with metal of the thermocouple with radial grooves for placement of current collectors and tokovodov, and current leads passed out through the sealing gasket I with: Ј P Layer thickness g and 2 % d 0.2 ABOUT J О, - / 0,2 0,5 0,4 0,4 mm Tolerance  significant deviation J FIG. J.