in today's industrial production application is more and more widely, involving the industrial application of type also more and more rich, we noticed that especially gas pipeline ultrasonic flowmeter in gas pipeline has been more and more widely used in measurement, because ultrasonic measuring principle is the use of the characteristics of the ultrasonic transmission work, in other words, the pipeline ultrasonic flowmeter is actually in use sound waves to carry on the work, because in the process of gas production will produce unnecessary ultrasonic noise, it will directly affect the normal operation of the pipeline ultrasonic flowmeter, for pipeline ultrasonic flowmeter accurately measuring adverse impact.
Natural gas flow meter
ing as part of the natural gas pipeline industry is extremely important, its measurement data is accurate or not directly affects the production enterprise's economic efficiency and user interests.
In recent years, many users start using multichannel pipeline as a gas ultrasonic flowmeter measurement instrument, principle of propagation time difference method is used to measure gas flow rate, it has been recognised by natural gas industry is more and more widely, the future pipeline of the use of ultrasonic flowmeter will become more extensive.
Propagation time difference method of pipeline working principle of ultrasonic flowmeter is the use of ultrasonic transducer two-way alternate (
Or at the same time)
To send and receive ultrasonic pulse, by measuring and calculating the pulse downstream and upstream transmission time lag in the medium to indirectly measure the fluid velocity, by an indirect method for measuring flow rate to calculate the flow.
Therefore, in order to get the travel time, requires flowmeter receiving transducer can correctly detect the issue of the ultrasonic pulse transmitting transducer, but if the ultrasonic noise existing in the medium and then will make the transducer to detect unit cannot detect and distinguish the normal work of the pulse signal, lead to stop or flow meter reading error measurement.
Pipeline gas production, noise sources of ultrasonic noise is the main control valve, throttle valve, relief valve, pump and other equipment.
China's national standard 'the gas ultrasonic flowmeter was used to measure gas flow,' noted & other
From the internal noise measured medium could lead to adverse effect on accurate measurement of the flow meter, flow meter should be made in the process of design and installation far from noise sources as possible or take measures to eliminate noise interference.
However, the above problems in some natural gas metering projects and didn't get the attention they deserve, lead to pipeline after ultrasonic flowmeter production affect measurement accuracy, even stop measurement fault.
About how to reduce or even eliminate the noise effect on the pipeline of the ultrasonic flowmeter, concrete has the following measures can be implemented: 1 regulator and noise reduction measures, regulating valve, A noise in the process of natural gas pipeline gas production, regulating valve is commonly used to the pressure regulating device.
When regulator for regulating, can produce a very wide frequency range of noise, including ultrasonic frequency range of ultrasonic noise.
The noise with the physical properties of sound waves from the essence, its size and the type of valve, gas flow rate and pressure regulating pressure factors, noise is generated to the regulating valve upstream and downstream transmission at the same time.
But due to the effect of differential pressure of the regulating valve, gas was downstream compressed tightly in throttling mouth, make the noise of the main energy in the form of shock wave propagation to downstream, a relatively small number of upstream noise energy transmission.
For pipeline ultrasonic flowmeter, the ultrasonic pulse transducer has a specific working frequency, used in the measurement of pipeline gas ultrasonic flowmeter its pulse frequency all above 120 KHZ.
Transducer only on the working frequency of the pulse signal response, if the valve regulating the noise frequency transducer working frequency, and spreads through the air medium to pipeline ultrasonic flow timing, will make the transducer to detect and distinguish the pulse signals, resulting in failure of measurement.
B, noise reduction measures in the operation condition of the regulating valve design using pipeline ultrasonic flowmeter, we must give full consideration to the noise reduction measures.
Due to the noise of the regulating valve upstream energy is far less than to the spread of the noise energy downstream, so should first consider regulating valve installed in the pipeline ultrasonic flowmeter downstream, and make sure they have installed distance as large as possible.
Through the pipeline between the ultrasonic flow meter and control valve installed a certain number of pipe fittings can achieve the purpose of different degree of attenuation of ultrasonic noise , different pipe noise reduction ability are shown in table 1.
Different pipe fittings of noise reduction ability fitting name noise reduction ability,
100 m straight section 590 degrees bend 5!
6 t tube 10 two plane bend 14 bundles (
20 perforated plate muffler 24 bundle muffler 33 as shown in table 1, the pipeline between the ultrasonic flow meter and control valve installed straight section of 100 m and 90 degree Angle noise reduction capability are equal, but the straight pipe installed in the application of 100 m is simply unrealistic.
Is common and effective way is in the pipeline between ultrasonic flow meter and control valve using tee pipe or two plane bend to noise attenuation regulator.
In the actual design, using the number of tee pipe, depends on many factors, when the valve regulating pressure difference is greater than 2.
067 mpa should be considered when using two or more than two T tube
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