Looking for recommendations for steam flow meters used in trade settlement

When the flow rate remains relatively stable, I think a vortex flow meter will work fine

For DN400, it’s better to use an orifice plate with temperature and pressure compensation – it’s more cost-effective.

Thank you everyone. The accuracy of the vortex flowmeter is not high enough; currently, an A+k balanced flowmeter is being used, which also relies on orifice plates along with temperature and pressure compensation!

Personally, I recommend using a vortex flow meter with temperature compensation............

This post was last edited by yunrun on 2017-12-22 at 18:38. Traditional steam flow measurement typically relies on differential pressure flow meters (composed of orifice plates or nozzles along with differential pressure transmitters). Vortex flow meters, on the other hand, offer advantages such as low pressure loss, reliability over long periods of operation, high accuracy, simple installation, and easy maintenance; as a result, they are increasingly used by users to measure saturated steam flow and for purposes related to steam trade accounting. This post provides a detailed overview of the use of vortex flow meters in steam trade accounting. In steam trade settlements, both steam suppliers and consumers desire steam flow measurement systems that are \"high-precision, reliable, stable, fair, and easy to use\"; this helps to better protect everyone’s interests and reduce disputes related to steam trade settlements. It is particularly important to choose the appropriate vortex flowmeter for measuring steam. Vortex flow meters: yunrun.com.cn/product/175.html. Common difficulties associated with steam vortex flow meters: 1. When there is no flow, the vortex flow meter still shows a reading, and this reading is relatively high; this leads the steam consumers to question the accuracy and reliability of the vortex flow meter. Vortex flow meters obtain flow signals by detecting the frequency of fluid oscillations, and the intensity of these signals is proportional to the square of the flow rate. To enable the vortex flow meter to measure low flow rates, it is necessary to amplify the flow signals by several thousand times. This is why mechanical vibrations can interfere with the accuracy of vortex flow meter measurements. When there is no flow in the pipeline, the reading of the vortex flow meter is actually a vibration interference signal; mechanical vibration interference is the biggest problem encountered in the practical use of vortex flow meters ； The high temperature of steam can damage the electronic components and circuits of vortex flowmeters. Some manufacturers of vortex flowmeters use a design in which the sensor and the electronic circuits are installed separately, which leads to the introduction of electromagnetic interference; when there is no flow, the reading on the vortex flowmeter is actually due to electromagnetic interference signals (typically 50Hz power frequency interference). 2. The vortex flow meter does not display any reading when there is a low flow rate; it only shows a reading when the flow rate reaches a certain level, which results in losses for the steam supplier. The vortex flow meter gives a zero reading when the flow rate is below the minimum measurement threshold, and it only displays a reading when the flow rate exceeds that threshold. Currently, the minimum flow rate that can be measured by imported vortex flow meters is generally 5.5 m/s, while domestic products typically have a minimum flow rate of around 7.0 m/s. Most vortex flowmeter manufacturers achieve resistance to mechanical vibration interference by discarding lower flow rates, which results in the measurement values of these flowmeters being **lower than the actual steam flow rate** ； In steam metering, due to various technical and human factors, the diameter of the steam pipes and the range of the vortex flowmeter used often deviate significantly from the original design, which may result in lower readings of the flow rate indicated by the meter. Under such circumstances, it can cause significant economic losses for the supplier. 3. The service life of vortex flowmeters is shorter than that of orifice plates and nozzles, and their failure rate is relatively high. Source address: yunrun.com.cn/tech/1115.html. Vortex flowmeter sensors mainly come in stress-type, differential capacitive-type, and magnetosensitive-type variants; moreover, since these sensors need to be able to detect the tiny lift forces generated by vortices at low flow rates, this imposes constraints on their structural design. In comparison, the stress-type sensor structure has no moving parts and requires no mechanical deformation, making it more reliable. The main cause of failure in such sensors is damage to the piezoelectric crystal, particularly cracking of the crystal due to high temperatures, a decrease in sensitivity, or even a complete loss of the piezoelectric effect. Therefore, in the production process of vortex flowmeters, it is crucial to use high-quality piezoelectric crystals, ensure sufficient temperature headroom, and employ packaging techniques that can withstand high temperatures and temperature shocks. 4. Sensor failure poses a threat to the safe operation of the equipment. Sensor failures often occur in vortex flowmeters with an external separate detection mechanism used in China; if the sensor components are carried by steam to other operating devices, it is very likely that those devices will face safety risks. The main reasons for the failure of vortex flowmeter sensors are an unreasonable structure of the separation detection element and material defects. Since the sensor is exposed to fluids with high flow velocities and frequencies reaching several thousand hertz, this leads to fatigue fracture and resonance fracture of the sensor’s metal material. 5. Vortex flowmeters have large errors. Based on the principle of vortex flowmeters, within a certain range of Reynolds numbers, the frequency of the output signal is not affected by the physical properties or composition of the fluid; the meter coefficient depends only on the shape and size of the vortex generator. No compensation is required when measuring the volumetric flow rate of the fluid, and generally no re-calibration of the meter coefficient is needed after replacing the components. As a result, some vortex flowmeter manufacturers ship products without carrying out basic calibration; in particular, the deviations in the meter coefficients caused by machining are not corrected, leading to significant variations in the performance of these devices. The meter coefficients indicated on the products are determined based on prototype units, which in turn results in substantial measurement errors ； Some vortex flowmeter manufacturers use water to calibrate steam flowmeter sensors, but in reality, the flow rates of liquids and steam fall within substantially different measurement ranges, resulting in an actual error in the instrument coefficient of up to 5%. To address the challenges associated with using vortex flowmeters for steam measurement, Changhui Instruments, drawing on extensive experience in the application of steam vortex flowmeters among its peers, developed the YR-VF11 vortex flowmeter to overcome these practical issues. This development significantly improved the overall performance of vortex flowmeters, which is why the vibration-resistant vortex flowmeter has earned a good reputation for use in steam trade settlements. http://yunrun.com.cn/upload/201611/03/201611031545461028.jpg Features of seismic vortex flow meters: 1. Innovative sensor structure and signal processing methods. The YR-VF11 vortex flow meter has made significant advances in resisting vibration interference; it offers clear advantages in terms of accurate measurement at low flow rates. Even when the vibration interference level is 1g, the YR-VF11 vortex flow meter can still maintain a minimum measurement rate of 2 m/s, ensuring accurate measurement of steam flow even when the actual steam consumption is lower than the designed flow rate. A vortex flow meter obtains the flow signal by detecting the oscillation frequency of the fluid, and the intensity of this flow signal is proportional to the square of the flow rate. At low flow rates, the fluid oscillation frequency is very low, which imposes high requirements on the technical specifications regarding the lower measurement limit of vortex flow meters (for example, at flow rates of 2 m/s compared to 60 m/s, the fluid oscillation frequency in the former case is only one percent of that in the latter case). If the minimum flow velocity that can be measured by a vortex flow meter is increased to 4 m/s, vibrations in the pipeline that are perceptible to the human hand (with an intensity of around 0.1g) will cause interference with conventional vortex flow meters. Vibrational disturbances cause vortex flow meters to indicate a flow rate of zero even when there is no actual flow. A common practice among many manufacturers today is to reduce the amplification factor of the circuit, thereby making the vortex flow meter less sensitive to small forces (including the forces generated by low flow rates and minor vibrations). This allows the vortex flow meter to detect lower flow rates; it is no longer unable to measure small flow amounts ； As the vibration intensity increases, the interference received by the sensor increases proportionally; to ensure accurate measurements, it is necessary to raise the lower measurement limit further. Once the vibration intensity exceeds 0.5g, to ensure no indication when there is no flow, it may be necessary to discard all flow rates below 20 m/s, which results in a significant reduction in the measurement accuracy of the vortex flow meter and causes substantial losses for the steam supplier. On the contrary, if the lower measurement limit is not increased and flow rates with signal amplitudes lower than those of vibration interference are discarded, it will cause the vortex flow meter to indicate a value even when there is no flow, which is unacceptable to steam consumers and leads to measurement disputes. For these reasons, users often find that vortex flowmeters are significantly inaccurate in actual use, but accurate when sent to a metrology testing institute for calibration. The reason for this common phenomenon is that the calibration equipment at the metrology testing institute is free from vibration interference. The vibration-resistant technology for vortex flowmeters aims to address the issue of readings appearing even when there is no flow, as well as the accuracy problems in measuring low flow rates. 2. Reliable high-flow detection: An innovative sensor design with a resonance frequency of over 6000 Hz, which is **above the vortex street frequency; this helps to prevent resonance from occurring, ensuring structural safety even when measuring high flow rates of up to 90 m/s. Together with a patented signal amplifier, this enables accurate and reliable measurement of high flow rates. Combined with excellent interference suppression capabilities and intelligent error correction, the actual range ratio of the vibration-resistant vortex flow meter is increased to over 45:1, **which is better than the 10:1 or 20:1 range ratios of similar products, thus enabling the wide-range characteristics inherent in the vortex flow meter principle to be utilized to a greater extent. 3. Improved reliability of sensors at high temperatures: The innovative glue-free, semi-free-degree crystal packaging process ensures that the crystal remains undamaged under large temperature differences ； By restricting the use of piezoelectric crystals with a Curie point as high as 680°C to temperatures below 320°C, sufficient high-temperature tolerance is provided for the sensors, thereby significantly extending their lifespan. 4. Reliable factory testing: Each vortex flow meter is subjected to routine calibration using a flow calibration device. In addition, its interference resistance is tested and adjusted, ensuring that it can operate without any further tuning on-site once powered on. 5. Designed specifically for trade settlement: reliable power-on/power-off logging, protection against unauthorized changes to meter coefficients, and prevention of artificial interruptions in measurement. 6. Easy to integrate: It features high-precision signal processing circuits that generate 4-20mA output signals with an accuracy of up to 6 parts per ten thousand, allowing it to be used in conjunction with any relevant flow totalizers or DCS systems. 7. Wide operating range: Advanced temperature drift correction ensures long-term, reliable, and stable operation in ambient temperatures ranging from -40°C to +80°C. 8. Lower maintenance requirements: With no moving parts and no pressure guide holes, steam vortex flow meters require virtually no maintenance for steam measurement. 9. Eliminate electromagnetic interference: An integrated design with isolated signal transduction ensures complete elimination of electromagnetic interference. 10. Reliable electronic circuitry: SMC (surface-mounted electronic components) and four-layer printed circuit boards (PCBs) are used throughout, with all electronic components being imported industrial-grade ones, ensuring the reliability of the electronic circuitry. How can a high-precision steam metering system be obtained? A common control strategy is to use vortex flow meters and flow integrators to form a steam metering system. The accuracy, stability, and reliability of this entire steam flow metering system are directly related to whether disputes may arise in future collaborations between the parties involved in steam trade, due to significant discrepancies in the steam measurement results. When building a high-precision steam metering system, attention should be paid to the following five aspects: 1. Choose a true vibration-resistant vortex flowmeter, which offers better measurement accuracy, reliability, and stability. 2. When measuring the flow rate of saturated steam, it is advisable to use high-precision pressure transmitters for pressure compensation; the reasons for this can be found in the technical article titled \"Pressure compensation provides higher accuracy than temperature compensation in saturated steam flow measurement.\" 3. For steam trade settlement, it is best to use a flow accumulation meter for trade settlement in order to obtain more accurate flow measurement results. 4. Install the on-site vortex flow meter and pressure transmitter correctly in strict accordance with the installation specifications and the technical requirements for flowmeter installation. 5. If conditions permit, it is best to send the vortex flow meter, flow integrator, and pressure transmitter to a metrology institution to obtain a calibration certificate before installing them. The relatively authoritative testing institution in China is the Shanghai Institute of Metrology and Testing.