STAUFF flowmeter performance requirements

STAUFF was founded in Werdohl in the Sauerland region of Germany. Under the STAUF brand, we have become a major manufacturer and supplier in the field of upper pipeline components and hydraulic accessories. STAUF has more than 50 years of advanced industry experience, rich business experience and a highly enterprising staff team, and forward-looking management of the production process. These make us a Competitive partners. We conduct various routine tests and experiments in the company's own laboratory to ensure that all STAUF products meet the standards. In order to make products comply with ISO9001:2000 certification standards, STAF's quality assurance system continuously strives to improve product quality. We have good warehouses and flexible production lines, which ensures our quick response and fast delivery. We have a close distributor network, wholly-owned production bases, distribution bases and warehouses in *14 countries, and we are closely connected with our customers. Our various branches also provide retail products required by local hydraulic preliminaries for advanced industries, so as to be able to provide customers with almost complete flow measurement, system monitoring, chemical agent proportioning, paint film thickness control, and other major industrial products. Hydraulic series, process control, connection/break loop control, printing and dyeing agent measurement and control; suitable for various industries, such as: plastics, chemicals, pharmaceuticals, hydraulics, printing and dyeing, paints, coatings, automobiles/vehicles Preparatory industries such as manufacturing and food must be advanced in advance.

STAUFF flow meter selection principles

STAUFF flow meter selection principles The first step in selecting a flow meter is to have a deep understanding of the structural principles and fluid characteristics of various flow meters. knowledge, and at the same time, the selection must be made in advance based on the specific conditions of the site and the investigation of the surrounding environmental conditions. Economic factors must also be taken into consideration. Under normal circumstances, the selection should be made from the following five aspects: ① Performance requirements of the flow meter; ② Fluid characteristics; ③ Installation requirements; ④ Environmental conditions; ⑤ Price of the flow meter. 1. Performance requirements of the STAUFF flow meter. The performance aspects of the flow meter mainly include: measuring flow (instantaneous flow) or total flow (cumulative flow); accuracy requirements; repeatability; linearity; flow range and range; pressure loss; output Signal characteristics and flow meter response time, etc. (1) Flow measurement or total flow measurement includes two types, namely instantaneous flow and cumulative flow. For example, if the crude oil in the distribution station pipeline belongs to the transfer of trade or the petrochemical pipeline is pre-prepared, continuous proportioning production must be carried out first. Or the process control of the production process requires total measurement, sometimes supplemented by the observation of instantaneous flow. In some workplaces, if the flow rate needs to be controlled in advance, instantaneous flow measurement is required. Therefore, the selection must be made in advance according to the needs of on-site measurement. Some flow meters such as positive displacement flow meters, turbine flow metersThe measuring principle is to obtain the total amount directly by mechanical counting or pulse frequency output. It has high accuracy and is suitable for measuring the total amount. If equipped with a corresponding signaling device, it can also output the flow rate. Electromagnetic flowmeters, ultrasonic flowmeters, etc. derive the flow rate by measuring the fluid flow rate. They have fast response and are suitable for process control. If equipped with an accumulation function, the total amount can also be obtained. (2) Accuracy The accuracy level of the STAUFF flowmeter is specified within a certain flow range. If it is used under certain conditions or within a relatively narrow flow range, for example, it only changes within a small range, this The measurement accuracy will be higher than the specified accuracy level. If a turbine flowmeter is used to measure oil products and distribute them in barrels, and when the valve is fully open, the flow rate will be basically constant, and its accuracy may be improved from 0.5 to 0.25. Used for trade accounting, storage and transportation handover and material balancing. If high measurement accuracy is required, the durability of the accuracy measurement should be considered. Generally used for flow meters in the above situations, the accuracy level requirement is 0.2. In such a workplace, measurement standard equipment (such as volume tubes) is usually equipped on site, and the flowmeter used must be pre-prepared and tested online first. In recent years, due to the increasing tightness of crude oil and the high requirements of various units for crude oil measurement, practical * requirements * advance advance requirements for crude oil measurement must be carried out first, such as coefficient handover, that is, in addition to the advance * requirements * advance requirements for flow meters every six months After a periodic inspection, both parties to the custody transfer will negotiate to pre-qualify the flow meter every 1 or 2 months. The flow meter must be calibrated to determine the flow coefficient. Calculate the flow coefficient based on the data measured by the flow meter every day. The handover must be carried out before the data enters and exits, in order to improve the accuracy of the flow meter, which is also called handover. The accuracy level is generally determined based on the maximum allowable error of the flow meter. It will be given in the flow meter instructions provided by each manufacturer. Be sure to pay attention to whether the percentage error refers to relative error or reference error. The relative error is the percentage of the measured value, often expressed as "% R". The quoted error refers to the measurement upper limit value or the percentage of the measuring range, commonly used as "% FS". Many manufacturers do not indicate this in their instructions. For example, float flowmeters generally use reference errors, and some models of electromagnetic flowmeters also use reference errors. If the STAUFF flowmeter does not simply measure the total amount, but is used in a flow control system, the accuracy of the flowmeter must be determined based on the control accuracy requirements of the entire system. Because the entire system not only has flow detection errors, but also contains errors and various influencing factors in signal transmission, control and adjustment, operation execution, etc. For example, there is a hysteresis of about 2% in the operating system. It is uneconomical and unreasonable to determine too high an accuracy (above 0.5) for the measuring instrument used. As far as the instrument itself is concerned, the accuracy between the sensor and the secondary instrument should also be appropriately matched. For example, the error of the velocity averaging tube designed without actual calibration should be ±2.Between 5% and ±4%, it makes little sense to use a differential pressure gauge with a high accuracy of 0.2% to 0.5%. Another problem is that the accuracy level specified for the flowmeter in the calibration procedures or the manufacturer's instructions refers to the maximum allowable error of the flowmeter. However, due to the influence of changes in environmental conditions, fluid flow conditions and dynamic conditions when the flow meter is used on site, some additional errors will occur. Therefore, the flow meter used on site should be a combination of the maximum allowable error of the instrument itself and the additional error. This issue must be fully considered. Sometimes the error within the scope of the on-site use environment may exceed the maximum allowable error of the flow meter. (3) Repeatability Repeatability is determined by the principle of the flow meter itself and the manufacturing quality. It is an important technical indicator during the use of the flow meter and is closely related to the accuracy of the flow meter. Generally, in the measurement performance requirements in the calibration regulations, there are not only accuracy level regulations for flow meters, but also pre-requisites for repeatability. The general regulations are: the repeatability of the STAUFF flow meter shall not exceed 1/3 to 1/5 of the maximum allowable error specified by the corresponding accuracy level. Repeatability is generally defined as the consistency of multiple measurements of a certain flow value in the same direction within a short period of time when the environmental conditions and medium parameters remain unchanged. However, in practical applications, the repeatability of the flow meter will often be affected by changes in fluid viscosity and density parameters. Sometimes these parameter changes have not reached the level that requires special correction, which may cause errors. It is thought that the repeatability of the flow meter is not good. In view of this situation, a flowmeter that is not sensitive to changes in this parameter should be selected. For example, the float flowmeter is easily affected by the density of the fluid. The small-diameter flowmeter is not only affected by the density of the fluid, but may also be affected by the viscosity of the fluid; if the turbine flowmeter is used in the high viscosity range, it will be affected by the viscosity; some are not corrected Processed ultrasonic flow meters are affected by fluid temperature and more. This effect may be more pronounced if the flow meter output is non-linear. (4) Linearity The output of STAUFF flow meter mainly includes linear and nonlinear square root. Generally speaking, the nonlinear error of the flow meter is not listed separately, but is included in the error of the flow meter. For flowmeters that generally have a wide flow range, whose output signal is pulse, and are used for total volume accumulation, linearity is an important technical indicator. If a single instrument coefficient is used within its flow range, the linearity difference will be Will reduce the accuracy of the flow meter. For example, a turbine flowmeter uses an instrument coefficient in the flow range of 10:1. When the linearity is poor, its accuracy will be lower. With the development of computer technology, its flow range can be segmented and fitted using the small square method. The flow rate-instrument coefficient curve must be corrected before the flow meter is entered, thereby improving the accuracy of the flow meter and expanding the flow range. (5) Upper limit flow rate and flow range The upper limit flow rate is also called the full scale flow rate or maximum flow rate of the flow meter. When we select the diameter of the flow meter, we should press the diameter of the pipe under testThe flow range used by the channel and the upper limit flow rate and lower limit flow rate of the selected flow meter must be configured first. You cannot simply enter the preset flow rate according to the diameter of the pipeline and configure it first. Generally speaking, the maximum flow rate of fluid in a designed pipeline is determined based on the economic flow rate. If the choice is too low, the pipe diameter will be thick, and the investment will be large; if it is too high, the transmission power will be large, and additional transportation costs will be incurred in advance. For example, the economic flow rate of low-viscosity liquids such as water is 1.5 to 3 m/s, and that of high-viscosity liquids is 0.2 to 1 m/s. The upper flow rate of most flow meters is close to or higher than the economic flow rate of pipelines. Therefore, when selecting a flowmeter, its diameter is usually the same as that of the pipe, and installation is more convenient. If they are not the same, there will not be much difference. Generally, the specifications of the upper and lower adjacent gears can be connected by reducing pipes. When selecting a STAUFF flowmeter, attention should be paid to different types of flowmeters. The upper limit flow rate or upper limit flow rate is greatly different due to the limitations of the measurement principle and structure of the respective flowmeter. Taking a liquid flowmeter as an example, the upper flow rate of a glass float flowmeter is lower, generally between 0.5 and 1.5m/s, a volumetric flowmeter is between 2.5 and 3.5m/s, and a vortex flowmeter is higher. Between 5.5~7.5m/s, the electromagnetic flowmeter is between 1~7m/s, or even between 0.5~10m/s. The upper limit flow rate of the liquid also needs to be considered so that cavitation does not occur due to excessive flow rate. The location where cavitation occurs is generally at a location with high flow rate and low static pressure. In order to prevent the formation of cavitation, it is often necessary to control the size of the flow meter. Back pressure (large flow). It should also be noted that the upper limit value of the flow meter cannot be changed after ordering, such as a positive displacement flow meter or a float flow meter. Once the design of a differential pressure flowmeter, such as the orifice plate of the throttling device, is determined, its lower flow limit cannot be changed. Changes in the upper limit flow rate can be changed by adjusting the differential pressure transmitter or replacing the differential pressure transmitter. For example, for some types of electromagnetic flowmeters or ultrasonic flowmeters, some users can reset the upper limit of the flow rate by themselves. (6) Range The range is the ratio of the upper limit flow and the lower limit flow of the STAUFF flowmeter. The larger the value, the wider the flow range. Linear meters have a wider range, generally 1:10. The range of nonlinear flowmeter is as small as 1:3. Flow meters are generally used for process control or custody transfer accounting. If a wide flow range is required, do not choose a flow meter with a small range. At present, in order to promote the wide flow range of their flow meters, some manufacturers have raised the upper limit flow rate very high in the instruction manual, for example, for liquids, it has been raised to 7 to 10 m/s (usually 6 m/s); for gases, it has been raised to 50 to 50 m/s. 75m/s (usually 40~50) m/s); in fact, such a high flow rate is not used. In fact, the key to a wide range is to have a lower lower limit flow rate to meet the measurement needs. Therefore, a wide-range flowmeter with a low lower limit flow rate is more practical. (7) Pressure loss Pressure loss generally refers to the flow sensor due to static or movable detection components or changes in the flow channel.The flow direction results in an irrecoverable pressure loss that changes with the flow rate, and its value can sometimes reach tens of kilopascals. Therefore, the flowmeter should be selected based on the pumping capacity of the pipeline system and the inlet pressure of the flowmeter to determine the allowable pressure loss for large flow rates. Improper selection will restrict the fluid flow and cause excessive pressure loss, which will affect the circulation efficiency. For some liquids (high vapor pressure hydrocarbon liquids), it should also be noted that excessive pressure drop may cause cavitation and liquid phase vaporization, reduce measurement accuracy and even damage the flow meter. For example, for flowmeters used for water delivery with pipe diameters greater than 500mm, the increased pumping costs due to excessive energy loss caused by pressure loss should be considered. According to relevant reports, the pumping costs paid for measurement by flow meters with large pressure losses in recent years often exceed the purchase cost of more expensive flow meters with low pressure losses. (8) Output signal characteristics The output and display quantities of the STAUFF flow meter can be divided into: ① Flow (volume flow or mass flow); ② Total quantity; ③ Average flow rate; ④ Point flow rate. Some flowmeters output analog quantities (current or voltage), others output pulse quantities. Analog output is generally considered suitable for process control and is more suitable for coupling with control loop units such as regulating valves; pulse output is more suitable for total volume and high-accuracy flow measurement. Long-distance signal transmission pulse output has higher transmission accuracy than analog output. The mode and amplitude of the output signal should also be compatible with other equipment, such as control interfaces, data processors, alarm devices, circuit breaker protection circuits and data transmission systems. (9) Response time When used in pulsating flow situations, attention should be paid to the response of the flow meter to step changes in flow. Some applications require the flowmeter output to follow the fluid flow, while others require a slower response output to obtain a comprehensive average. Instantaneous response is often expressed in terms of time constant or response frequency, the former ranging from a few milliseconds to a few seconds, and the latter below hundreds of Hz. The use of a display instrument may significantly extend the response time. It is generally believed that when the flow rate of a flow meter increases or decreases, the asymmetric dynamic response will accelerate the flow measurement error.