Crude oil flow meter must consider the factors that need to be considered when using crude oil flow meter
Flowmeters are the most commonly used instruments for oil extraction companies. The flowmeters used in many fields of oil fields are not reasonably configurable, and some have installation errors, causing measurement errors that are too large, and some fail to meet the needs of production or crude oil handover measurement. General high pressure electromagnetic flowmeters are used in oil fields. Many types of flowmeters can measure crude oil, but choosing only to rely on experience and simply consider the purchase cost for selection, may lose the opportunity to choose the most suitable instrument. For example, the flow range of the instrument does not match with the actual flow rate, and instruments with high precision are used in places where the measurement requirements are not high. This shows that the correct choice and use of flowmeters is not easy. To properly and effectively select crude oil flow meters, the following five factors must be considered: performance requirements, crude oil properties, installation requirements, environmental conditions, and costs. Due to the large amount of content, Huijiajie has divided into two chapters for sharing. Share the first two points today. Friends who are interested in this article should continue to pay attention tomorrow.
Flowmeter performance requirements
Select the flow meter to consider in the performance requirements include: instantaneous flow, cumulative flow, accuracy, repeatability, linearity, flow range and range, pressure loss, output signal characteristics and response time. For different measurement purposes, there are different options for flow meter performance. Such as crude oil trade settlement measurement requires higher accuracy; continuous measurement process control usually requires good reliability and repeatability, sometimes also requires a wide range of degrees, the measurement accuracy requirements should be placed on a secondary position; oil field production site is not The flowmeter is required to have too high accuracy, but it has better adaptability to the physical properties and working conditions of the crude oil.
Volumetric flowmeters are usually output at mechanical or pulsed frequencies to obtain a cumulative flow rate directly. They have a high degree of accuracy and are suitable for the measurement of total volume. If an instantaneous flow rate is to be output, a corresponding signaling device must be provided. Electromagnetic flowmeters, ultrasonic flowmeters, etc., in principle, are based on measuring the flow rate of media to derive flow, fast response, suitable for process control (such as leak alarm), the total flow can also be obtained after totalization.
In the selection of the flowmeter, the measurement accuracy required by the production process, the fluctuation range of the flow at the production site, the accuracy of the measurement range, the verification cycle of the flowmeter required for production or management, and the on-site on-line liquid verification should be considered. , flow meter pressure rating, explosion-proof rating.
If it is necessary to measure the total flow, but also used in the flow control system, such as the flowmeter is used as a crude oil delivery metering port, but also to consider the crude oil pipeline leakage alarm signal acquisition, the accuracy of the flowmeter to determine the accuracy of the entire system control Under the requirements, because the entire system not only has the error of flow detection, it also contains errors and various influencing factors such as signal transmission and control adjustment. If the operation execution link often has certain errors, the measurement instrument is determined to be overly accurate. Degree is unreasonable and uneconomical. The accuracy level determined by the flowmeter specification is within a certain flow range. If used within the specified range, the general accuracy is guaranteed, exceeds the specified flow range, the actual accuracy is lower than the nominal value, and the measured flow rate is lower than the flowmeter. When the minimum measurement value is used, the flow meter may not start. Generally, the use range of the flow meter should be within 30% to 80% of the nominal range. For trade settlement requires a higher accuracy, generally should not be less than 0.2, but also consider the relationship between the accuracy of the durability and the verification cycle, whether it can guarantee that the entire test cycle is qualified. The pressure rating of the flowmeter should be one order of magnitude greater than the pressure rating required by the process. For example, the process flow rate is 4 MPa, and the selected flowmeter should generally be 6.4 MPa. Crude oil flowmeters should have explosion-proof functions, and the explosion-proof grades should meet the design requirements of the oil and gas stations and warehouses and safety requirements.
Repeatability is an important indicator in process control applications. It is determined by the principle of the flowmeter itself and the quality of manufacturing. However, in practical applications, the repeatability of the flowmeter is affected by many factors such as crude oil viscosity, density, and interference from surrounding electromagnetic fields. Therefore, a site that requires good repeatability should not be selected to affect sensitive flow meters due to environmental, media, and operating conditions.
The diameter of the selected flowmeter should be selected according to the flow range used by the pipeline under test and the upper and lower flow rates of the selected flowmeter instead of simply selecting the path of the pipeline. The maximum flow rate of a pipe fluid is usually designed according to the economic flow rate. Because the flow rate selection is too low, the diameter of the pipe is large and the investment is large; if the flow rate is too high, the transmission power is large and the operation cost is increased. The flow rate of most of the flowmeter's upper flow rate is close to or slightly higher than the economic flow rate of the pipeline. Therefore, the possibility that the flowmeter path is the same as the pipe diameter is relatively large, and the installation is convenient. If it is not the same, it should not be too different from each other. File specifications, use reducer connection.
The range of the flow meter is the ratio of the upper limit flow to the lower limit flow. The larger the value is, the wider the flow range is. Linear instruments have a larger range, 0.5 volume flowmeter is generally 10:1; 0.2 volumetric flowmeter is generally 5:1; nonlinear instrument is smaller, usually only 3:1, the higher the flowmeter accuracy The smaller the range, the greater the range. When choosing, you should reasonably consider the relationship between the two.
Consideration of crude oil properties and oil conditions
The operating conditions of crude oil flowmeters are affected by factors such as crude oil temperature, oil pressure, crude oil density, crude oil viscosity, and flow rate. The physical properties of crude oil change with temperature and pressure. When crude oil is metered by a flow meter, changes in temperature, pressure, viscosity, and other factors can affect the volume of crude oil. The temperature is one of the most influential parameters in the flowmeter metering. Changes in temperature will cause a series of parameters to change, which changes the volume, density, viscosity of the crude oil, and the gap between the flow meter housing and the internal components, thus causing a change in the leakage flow. If the temperature decreases, paraffin and coke matter in the crude oil adhere to the inner wall of the housing and components, which changes the volume of the metering chamber of the flow meter and directly affects the metering accuracy of the flow meter. In the measurement of crude oil, volumetric flowmeter is the most commonly used, and its measurement principle is that there is an accurate measurement chamber in the flowmeter housing. The flowmeter measures the volume of crude oil delivered by recording the number of times the crude oil fills the measurement chamber. . Because there is a certain gap between the rotor of the flowmeter and the wall of the metering chamber, and the machining error of the rotor and the metering chamber, it will inevitably cause leakage of the measured medium, but generally it is within the allowable range of the design, thus causing additional errors in the flowmeter. Caused by flow, viscosity, temperature, pressure, and operating time.
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