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Impact of noise on ultrasonic flowmeter Analysis

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Impact of noise on ultrasonic flowmeter Analysis

Release date:2015-07-23 00:00 Source:http://www.yinhuanchina.com Click:

   

    Ultrasonic flowmeter has high accuracy, low repair and maintenance costs, with a self-diagnostic function and many other advantages, multi-channel ultrasonic flowmeter measurement in the gas sector more widely used. Currently, for the technical standards and reporting ultrasonic flowmeter are:

GB / T 18604-2014 "gas ultrasonic flowmeter gas flow" (hereinafter referred to GB / T 18604), IS0 17089-2-2012 "Measurement of fluid flow in closed conduits inside - gas ultrasonic flowmeter - Part 1: in trade metering and distribution metering meter "(hereinafter referred to IS0 17089) and the United States AGA released in 1998 AGA9 Report" with a multi-channel ultrasonic flowmeter gas flow "(hereinafter referred to as the number AGA9 report). These standards, reports on the use of an ultrasonic flowmeter play a great role in promoting, but the lack of foreign fine and strict installation instructions, can not guide the engineering staff for field instruments were designed and installed.

 

   Factors affecting ultrasonic flowmeter flow measurement Uncertainty many, such as the flow meter straight pipe upstream wall roughness, gas components, upstream straight pipe length, flow meters upstream fluid flow patterns, noise, air pulsation. The operator, the most common pipe noise may interfere with the work of the ultrasonic flowmeter, thereby affecting the performance of the instrument. This noise produces the most typical part of it is the pressure drop of place, such as flow control valve.

 

    This article focuses on the impact of noise on ultrasonic flowmeter and the elimination or reduction of noise measures. At the beginning of a project, if the project designers to recognize these factors and take appropriate action, you can largely reduce engineering costs, and once all devices are installed, we found the problem and then take measures generally have to pay a high price. So, to understand the impact of these measures to reduce noise is very necessary, it can instruct the user to the proper application of ultrasonic flowmeter.

 

    2 noise on ultrasonic flowmeter [1].

    Process plant operation will generate noise, such as high-speed gas through pipes, pipe fittings, projecting the temperature sensor, control valve. . The study found that the maximum noise is large pressure drop regulator valve, such noise if not addressed, it would interfere with the work of the flowmeter signal detecting system, and cause transmission errors detected. The size and nature of the noise generated by the control valve and control valve design. Some regulating valve to achieve "low-noise" characteristics, specifically the noise frequency increases, but the high frequency of the operating frequency range ultrasonic flowmeter, seriously affect the normal operation of ultrasonic flowmeter. Although the valve can be reduced by the noise signal cage design and other means, but the valve characteristics also determine any valve with throttle characteristic is a potential source of ultrasonic noise. Research shows that the body of energy loss and pressure drop through the valve body and the flow rate is proportional to the actual operating conditions, and the noise with the loss of energy through the body to improve and increase.

P = qvDp

Where P-- energy loss, W

qv-- traffic conditions, m3 / s

Dp-- valve pressure drop, Pa

 

     For example a nominal diameter of 200mm gas pipeline, the gas flow velocity through the valve of 20m / s, can be derived flow 0.628m3 / s, if the pressure drop is about 10kPa, the energy loss 6.28kW, noise level, and the energy loss proportional. For general ultrasonic flow meter, if the choice of intrinsically safe instrumentation, energy electrical circuit will be limited to less than 2W, and energy loss compared to the much smaller, and therefore, to get the instrument signal resistant to noise interference must take measures .

 

     Noise, once produced, will be in the upstream and downstream propagation regulating valve, so only the ultrasonic flowmeter installed before the valve and the valve can not guarantee that interference noise meter unregulated. Experimental results show that the control valve is installed downstream of the flowmeter, from the regulating valve near the sensor noise ratio by the valve away from the noise of the sensor by 2 to 4 times larger.


Related Tags:ElectromagneticFlowmeter

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