Are balance flowmeters special orifice plate flowmeters?

Project Overview

　　Orifice plate flowmeter, also known as differential pressure flowmeter, consists of a primary detecting member (throttling member) and a secondary device (differential pressure transmitter and flow indicator). Its working principle is based on the fluid continuity equation and Bernoulli's equation, when the fluid flows through the throttle device in the pipeline, it will cause a local contraction near the throttle member, the flow velocity increases, thus generating a static pressure difference between the upstream and downstream sides of the throttle member. There is a certain relationship between this pressure difference and the flow rate, by measuring this pressure difference, you can calculate the flow rate of the fluid. Orifice plate flowmeter is widely used in petroleum, chemical, metallurgy, electric power, heating, water supply and other fields because of its simple structure, easy maintenance, stable performance and other characteristics.

　　However, with the continuous development of industrial technology, the requirements for flowmeters are getting higher and higher. The traditional orifice plate flowmeter in some aspects has been unable to meet the needs of modern industry, such as in high precision, high stability, wide range ratio and adapt to complex fluid media and so on. Therefore, a new flowmeter - balance flowmeter came into being.

　　Balance flowmeter, is a revolutionary differential pressure flow meter, which originated from the 2003 U.S. Space Shuttle main engine measurement of liquid oxygen flowmeter, designed and developed by the U.S. NASA using flow simulation technology. The Balance Flow Meter adopts a unique equal Reynolds number design, which increases the thickness and machining precision of the throttle member, making its flow performance close to that of a venturi, but the structure is still simple and safe. Its clever structural design can be in the shortest straight pipe section requirements, with a relatively small permanent pressure loss in exchange for a larger stable differential pressure, so as to achieve high precision and long-term stability of measurement.

　　The core component of the Balance Flow Meter is a multi-hole disc throttling rectifier mounted in the cross-section of the pipe. The size and distribution of each hole is customised based on special formulas and test data, called function holes. As the fluid passes through the function holes of the disc, the fluid is rectified in a balanced manner and vortices are minimised, creating an approximate ideal fluid. Through the pressure taking device, a stable differential pressure signal can be obtained, and the volume flow rate and mass flow rate can be calculated according to Bernoulli's equation.

　　Compared with the orifice plate flowmeter, the balance flowmeter has the following significant advantages:

　　First, high measurement accuracy. Balance flowmeter using multi-hole symmetrical balance design, reducing the formation of vortex and turbulence friction, reducing the loss of kinetic energy. Under the same working conditions, compared with the traditional throttling device, the pressure loss is reduced by 70%, close to the venturi. At the same time, due to the characteristics of its porous structure, it can balance the flow field, reduce vortex, vibration and signal noise, and the stability of the flow field is greatly improved. Therefore, the balance of the flowmeter measurement accuracy than the traditional orifice plate flowmeter to enhance the 5-10 times, after the real flow calibration, the sensor accuracy of up to ± 0.5%, suitable for trade measurement occasions.

　　Second, the range ratio is wide. Balance flowmeter greatly improves the measurement range ratio, research results show that the Reynolds number is greater than 50000, select the appropriate aperture parameters, balance flowmeter without upper limit. According to the needs of industrial measurement of practical applications, the conventional measurement range ratio of 10:1, choose the right parameters can be done 30:1 or higher. This means that the balance flowmeter can maintain high accuracy measurement in a wider flow range.

　　Third, adaptability. The balanced flowmeter can measure bi-directional flow and is suitable for gas, liquid, gas-liquid two-phase, liquid gas, dirty media, slurry measurement. Its multi-hole symmetrical design reduces turbulent shear and vortex formation, greatly reducing the formation of dead zones, to ensure that dirty media smoothly through multiple holes, reducing the chance of fluid holes are blocked. At the same time, the balance of the flowmeter's working pressure and working temperature range is very wide, the highest working pressure up to 42MPa, the highest working temperature up to 850 ℃, suitable for extremely low-temperature fluids such as LNG, liquid air, liquid nitrogen, liquid oxygen, liquid argon, liquefied ethylene, liquid hydrogen, liquid chlorine, etc., measurement, which can effectively prevent the gasification, the measurement of the best results.

　　Fourthly, it is easy to install. Balance flowmeter left and right completely symmetrical, so it can be very convenient to measure bidirectional flow. At the same time, its lower requirements for straight pipe section, in most cases straight pipe section can be as small as 0.5D ~ 2D (D for the diameter of the pipe), especially for special or expensive pipelines, the use of balanced flowmeter can save a large number of straight pipe section.

　　Fifth, long service life. Balance flowmeter multiple flow holes dispersed force, no sharp wear, its β value remains unchanged for a long time, long-term stability is very good. The whole instrument has no moving parts, service life than the traditional throttle device extended 5-10 times.