When we are monitoring the oil transport process, the flow rate of oil will change; we use the ultrasonic flow meter to understand the flow rate of oil between stations. We can calculate the pipeline oil monitoring simulation and mixing oil volume primary data by ultrasonic flowmeter measurement. We can also analyze the monitoring data to determine whether there is a leak in the pipeline and the leak’s location. The economic losses caused in the event of a pipeline leak will be reduced. Therefore, it is essential to monitor the flow rate of oil in the pipeline.
1. Testing instruments for oil transport flow
There are many different types of flow sensors in use by various companies, and their detection methods are different. Suppose classified from the detection principle, including “sound, light, heat, force, electricity,” and other academic principles. According to the standard classification method in the industry can be divided into volumetric, differential pressure, float, turbine, electromagnetic, vortex, insertion, external clamping, pipe section type, portable, and so on. Different kinds of flowmeter adapted to the fluid medium is different. The liquid medium measurement conductivity is better, and it is suitable for the use of an electromagnetic flowmeter. The ultrasonic flowmeter is most commonly used for meeting the large diameter, large flow, high density, high speed, and long-distance transmission requirements of the flowmeter.
2. The evolution of ultrasonic flowmeters
The world’s first ultrasonic flowmeter was born in Germany in the 19th world, more than 80 years of development history. Although the rapid development of science and technology in recent years, high-speed digital signal processing technology for ultrasonic flowmeter technology upgrades injected vitality, the rapid growth of microprocessing technology has also accelerated the pace of ultrasonic, electromagnetic flowmeters. In addition, the emergence of new materials and new processing processes for flowmeter probes and advances in technology such as sound channel configuration has made the technical advantages of ultrasonic flowmeters even more robust and more rapid development.
3. Selection of oil transfer flow monitoring instruments
Ultrasonic flowmeter system composition including power supply, transducer, junction box, converter. The transducer is also the sensor, according to the different installation methods of the sensor, and the ultrasonic flowmeter can be divided into external clamp type, pipe section type, and insertion type ultrasonic flowmeter.
3.1 External clamp-on ultrasonic flowmeter
External clip type also known as external paste type ultrasonic flowmeter, it is the earliest, the user is most familiar with and the most widely used ultrasonic flowmeter, it is characterized by the use of the measured medium will not be in contact with, it is also suitable for measuring the fluid not easy to contact and observation and large diameter flow, only not installed in the pipeline instrument will not change the flow state of the medium and produce additional resistance. Because the ultrasonic flowmeter is a non-contact instrument, its installation and maintenance will not affect the regular operation of the production pipeline. External clamping type ultrasonic flowmeter is the best choice of oil conveying process flow monitoring instrument type.3.2 Pipe section ultrasonic flowmeter
Production enterprises in certain pipelines due to loose material, poor sound transmission, or pipeline wall corrosion, lining and other reasons, resulting in the sound signal in the transmission process attenuation serious, with external clamping type ultrasonic flowmeter, can not be measured normally, thus giving rise to the pipe section type ultrasonic flowmeter.
As shown in Figure 2, the tube section ultrasonic flowmeter is the transducer and measuring tube connected into a whole. Then it is installed in the middle of the pipe for the ultrasonic detection of fluid flow. Thus, it has the advantage of high measurement accuracy, and the disadvantage is that the installation and maintenance must stop fluid delivery.
The pipeline ultrasonic flowmeter in its internal several sound channel for high-frequency time difference measurement, due to the instability of the fluid flow exists, any slight flow disturbance and pulsation will be detected by the flowmeter, which resulting in the flowmeter producing variable pulse output, and this information is another traditional mechanical flowmeter response does not come out. Furthermore, piston volumetric tubes cannot be used directly for the calibration of liquid ultrasonic flow meters due to the volume’s maximum size and the fact that the emission and recovery of the volumetric piston tube during operation can cause significant disturbances in the flow.
3.3 Insertion type ultrasonic flowmeter
The insertion type ultrasonic flowmeter is used between the media external clamping type and the pipe section type. Installation generally requires a break in the flow of the building. Suppose the special tools can also be achieved through the non-break in the flow of the structure, installation schematic, as shown in Figure 3. Its measurement accuracy is better than the external clamping type ultrasonic flowmeter, which is slightly worse than the tube section type ultrasonic flowmeter.
4. Detection principle of ultrasonic flowmeters
Closed pipeline with ultrasonic flowmeter measurement principle there are five, now the most used is the propagation time method and Doppler method two categories.
4.1 Propagation time method —- Ultrasonic flowmeter testing principle
Propagation time method of measurement principle: when the sound wave propagates in the fluid, the fluid flow in the downstream and countercurrent directions is affected. Differently, the transducer receives different sound waves. The received signal is converted into an electrical signal representing the flow rate through the converter to be supplied to the display and calculation instrument for display and calculation.
External clamp-on ultrasonic flowmeter mainly uses the transmission time difference method to measure flow. The ultrasonic wave through the fluid downstream and countercurrent time is different. The time difference ΔT and fluid velocity FV is proportional to the faster the medium flow rate, “ΔT” is more considerable.
4.2 Doppler method ultrasonic flowmeter detection principle
When the sound wave propagates in the fluid medium, the frequency reflected in the transducer by the particles in the fluid varies, a phenomenon known as the Doppler effect. The so-called Doppler measurement principle is based on the Doppler effect of acoustic waves p (4) Press the button to enter No. The window instrument displays the outer diameter of the tube.
Liquid ultrasonic flowmeter calibration by the above, according to the API standard available spherical volume tube, according to the specification recommended volume to choose the direct calibration of the liquid ultrasonic flowmeter. However, not every project and application has enough space for a spherical volume tube due to offshore conditions. Therefore, to seek updates and developments in CNOOC’s business, there must be a way to address this issue.