Advantages and disadvantages of elbow flowmeter

   1. No additional pressure loss. The primary sensing element of the elbow flowmeter is just a 90-degree right-angle elbow, without inserts and throttling parts, so there is no additional pressure loss. However, the pressure loss of the orifice plate is relatively large, generally 70% of its differential pressure value. The energy loss caused by the orifice plate is huge every year, which should be given enough attention. The orifice plate pressure loss causes the steam quality to decline, and also brings inconvenience to the user's production. For example, Tai'an Paper Mill uses the second-stage steam extraction of the thermal power plant turbine as the production heat source. In the early days, the orifice flowmeter was used for measurement. Due to the large pressure loss, the steam quality could not meet the normal production, resulting in a decrease in production efficiency.

   2. Large range ratio, high accuracy, and good performance at small flow rate. The range ratio of elbow flowmeter is 1:10, while that of orifice flowmeter is only 1:3. In the case of large flow fluctuation, elbow flowmeter has a greater advantage. In steam flow measurement, the measurement range of elbow flowmeter is 5m/s-120m/s. Elbow flowmeter has outstanding advantages in measuring flow range and small flow measurement. Regarding the accuracy problem, the elbow flowmeter is calibrated by steam condensation weight method at the flow calibration station of the State Administration of Technical Supervision, and the maximum error of system accuracy is 1.14%. It is well known that the accuracy of orifice flowmeter is 1-1.5, but the error caused by installation is often much higher than 1.5. For example, the frequent occurrence of boiler degassing flow rate higher than water inlet is caused by the above reasons. For vortex flowmeter, its accuracy is generally 1-1.5, which can be achieved for pipeline vortex flowmeter without external interference (such as vibration, straight pipe section). However, for the insertion vortex flowmeter, due to its installation error and the inability to accurately determine the cross-sectional area of ​​the fluid, the flow measurement accuracy is uncertain, and the error is much higher than 1.5%, so it is not suitable for metering settlement.
    3. Wear-resistant, maintenance-free, and long life. The measurement principle of the elbow flowmeter is: when the medium flows through the bend of the pipeline, it must make a circular motion, generating inertial centrifugal force. The centrifugal force can be measured to calculate the fluid flow rate, thereby further obtaining the flow rate. Based on this principle, it can be seen from the actual flow calibration that wear only causes a slight change in the caliber of the elbow flowmeter, and ultimately has little effect on the flow measurement value, so the elbow sensor does not need regular maintenance. The welding installation will not cause leakage, and there is no maintenance, and its service life is equivalent to that of industrial pipelines. The orifice flowmeter uses throttling to generate a pressure difference for flow measurement. In order to match the mathematical model of the orifice plate, the edge of the orifice plate inlet is required to be sharp, but the sharp edge quickly becomes blunt under the scouring of the fluid, which is the fluid flow state deviating from the original mathematical model requirements, resulting in a large measurement error. In order to ensure the measurement accuracy, the orifice plate is connected by flanges, and the orifice plate must be inspected once a year, which greatly increases the maintenance and repair costs. When the flange is in the process of steam stopping and delivering, it is very easy to cause leakage due to the thermal stress of the pipeline, which causes unnecessary steam loss and affects production.
    4. Good high temperature resistance, pressure resistance and vibration resistance. The elbow flowmeter and the orifice flowmeter can operate stably all year round under high temperature and pressure (the elbow flowmeter has been applied to 5.2Mpa, 500℃ medium temperature and medium pressure conditions on site, and has been running without trouble for more than three years). Under high temperature and pressure, the orifice plate of the orifice flowmeter has large deformation on the plane, and needs to be replaced regularly, otherwise it will cause large errors; the vortex flowmeter is generally used at a temperature below 300℃, and the upper limit of the working temperature of the poor quality one is only 180℃, and most instruments have poor long-term stable performance under high temperature. After installation, some instruments cannot work normally and need to be replaced with other types of instruments. Since elbow flowmeter and orifice flowmeter are both differential pressure flowmeters, vibration and impact do not affect their normal operation; while vortex flowmeter measures frequency signals, pipeline vibration will be added as a frequency signal to the real fluid vortex frequency signal, resulting in untrue measurement values ​​and large field errors. Vortex flowmeters should not be used for occasions with large field vibrations.
    5. The sensor has a wide range of calibers, and the requirements for the front and rear straight pipe sections are not strict. The minimum diameter of elbow flowmeter is DN10, while that of orifice is DN50; the maximum diameter of elbow flowmeter is over DN1200, and orifice can be made with large diameter but it is expensive; in terms of the requirements for the front and rear straight pipe sections, elbow flowmeter has greater advantages, and only 5 (D) in the front and 2 (D) in the rear are required; while the orifice flowmeter requires at least 10 (D) in the front and 5 (D) in the rear, and if there are throttling parts in the pipeline, the straight pipe section needs to be lengthened, with a maximum of 40 (D) in the front and 10 (D) in the rear, making it difficult to find a suitable installation location. Sometimes, in order to obtain a longer straight pipe section, it is necessary to change the pipeline process or increase the plant area, increasing investment.