SU1525469A1 - Method of measuring consumption of raw gas - Google Patents

Abstract

The invention relates to the control and measurement of parameters of controlled media in the case of automatic control of technological processes and can be used in the gas industry. The purpose of the invention is to improve the measurement accuracy. A differential Pitot tube is placed in the pipeline, the channels of which are supplied with an intermediate medium, which is a hydrate inhibitor, and the flow rate of this medium is stabilized and divided into two equal flows, the pressure drop in the channels after the divider is measured. . 1 il.

Description

The invention relates to the control and measurement of parameters of controlled media in the case of automatic control of technological processes, for example, production and preparation of natural gas, and can be used in the gas industry.

The purpose of the invention is to increase the accuracy of gas flow measurements.

The essence of the method of measuring gas flow rate in a pipeline using a Pitot tube is that the working flow medium is fed into the channels of the pitot tube, the parameters of which are controlled, while the flow rate of the auxiliary medium, which uses a hydrate formation inhibitor, is stabilized and, after dividing it into equal flows, measure the pressure difference in the channels of the tube after the divider, on which the flow is judged. As a working

mediums use a hydrate formation inhibitor.

In this case, the flow rate of the raw gas is determined not by the measured flow rate of the working medium flowing in the tube channels, but by the measured differential pressure of the fluid in the tube channels, proportional to the flow rate of the raw gas,

V

(one)

where K is the coefficient of the pitot tube,

dependent on its design; UP - measured pressure drop

in the channels of the tube; Р - density of the measured flow

gas in the pipeline. The coefficient of tube K is almost equal to unity, provided that the Reynolds number, related to the diameter d of the tube, is Rej 500

If, when measuring gas flow, an increased accuracy of the results is required, then when using the method for accurate measurements of gas flow, it is necessary to meet the requirements for measuring pipeline sections when installing standard tapering devices in accordance with the guidelines of RD 50-411-83, in order to ensure stationary gas flow with a velocity profile over a cross section of the flow that is close to rectangular.

In this case, the measured gas flow rate is uniquely determined by the equation

0 V.Q, (2)

where V is the gas flow rate, defined by the equation CO 03 - the cross-sectional area of the measuring section of the pipeline.

In addition, when using a liquid as a working medium, it is necessary to make an amendment to the hydraulic resistance of the channels of the tube, causing an additional error in the measurements.

To account for the error of local resistance as defined by the equation

R

.-J where} coefficient of hydraulic resistance;

1 - the length of the tube channels;

d is the diameter of the channels; it is necessary to introduce a KU- correction factor, which is determined when calibrating the tube before installing it on the pipeline. Calibration consists in measuring the pressure drop in the channels of the tube, which is formed due to their hydraulic resistance at

0

five

0

five

0

five

0

V K, K)

(3)

five

flow of the working fluid and in the absence of a measurable gas flow in the pipeline. With this correction, the flow velocity equation (1) is written as

2 & P

The drawing shows a diagram of the device that implements the method.

In the pipeline 1, in which the flow rate of the raw gas is measured, a Pitot tube 2 is placed, the openings 3 and 4 for the selection of pressures of which are connected to channels 5 and 6, respectively. The channels 5 and 6 of the tube are connected to the chambers of the choke divider 7 of the flow, to which the flow of the hydrate inhibitor inhibitor is fed through the flow regulator 8 (stabilizer) from the pump J9.

The inhibitor flow is divided by throttles 10 into two equal flows and enters the channels 5 and 6 of the Pitot tube 2. The pressure drop in the chambers of the flow divider 7 is measured by a differential pressure meter 11, the output signal of which is proportional to the flow rate or flow rate.

Claims (1)

Invention Formula A method for measuring the flow of syphonic gas in a pipeline, including filling the channels of the differential Pitot tube placed in the pipeline with equal flows of the working medium and measuring the pressure difference between these flows, characterized in that, in order to improve the measurement accuracy, the filling of the channels of the tube is performed continuously, the flow rate The working medium is pre-stabilized, and a hydrate inhibitor is used as the working medium. natural gas Hhzufumop eleven