Process Engineering Division – Instrumentation and Automation Section – Daily Topics – Topic No. 2021-01-26

The balanced flow meter is a new type of throttling flow instrument; its working principle is the same as that of a differential pressure flow meter. It consists of a porous disc-shaped throttling and straightening element that is installed in the pipe cross-section, and the flow rate is proportional to the square root of the differential pressure. Balance flow meters have the advantages of a simple and reliable structure, easy manufacturing, low requirements for straight pipe sections before and after use, and the ability to maintain high precision. The balanced flow meter features a symmetric porous structure; as the fluid passes through these pores, it is evenly directed, minimizing vortices and resulting in behavior similar to that of an ideal fluid, which in turn reduces vibrations and signal noise. Compared with traditional throttling devices, it features: (1) a measurement accuracy that is 5 to 10 times higher; at a 1:10 range, the accuracy can reach +-1.0%. (2) The flow noise is reduced to 1/15, and the permanent pressure loss is about 1/3, resulting in low pressure loss. (3) Due to the stable flow field, low requirements are placed on the straight pipe section; generally, 3D length in front and 1D length at the back is sufficient. However, manufacturers claim that the minimum required straight pipe section can be reduced to 0.5D, but there is a lack of appropriate test data to verify this claim. (4) It can directly replace orifice plates, making it suitable for replacing orifice plate flow meters with balanced flow meters during energy metering upgrades across the entire plant. Balance flow meters have no moving parts, making them very simple to install and use; they also eliminate the need for long straight sections of pipe, **reducing the energy consumption associated with fluid flow. Used for measuring the flow rate of single-phase fluids (liquids, gases, or vapors) in enclosed pipelines. The balanced flow meter inherits all the advantages of traditional throttling devices, while avoiding most of their disadvantages such as a low measurement accuracy and high requirements for straight pipe sections, thereby **improving its measurement performance. In recent years, balanced flowmeters have seen rapid development as a result of widespread adoption, and coupled with marketing efforts by manufacturers, they seem poised to replace standard throttling instruments. However, their high cost makes them less economical from a financial perspective.

Advantages of balanced flow meters: 1. Good long-term stability; 2. Low requirements for straight pipe sections; 3. High linearity and good repeatability; 4. Reduced pressure loss; 5. Resistant to dirt and less prone to clogging. Advantages of orifice flow meters: 1. The standard throttling elements are universally used and recognized by international standard organizations, allowing them to be put into use without the need for calibration using actual flow rates – they are also unique among flow sensors；  2. The structure is easy to replicate, simple and sturdy, with stable and reliable performance at a low cost ； 3. It has a wide range of applications, covering all single-phase fluids (liquids, gases, steam) as well as some mixed-phase flows; it can measure the pipe diameter and operating conditions (temperature, pressure) in various production processes ；  4. The test piece and the differential pressure display instrument can be manufactured by different manufacturers, facilitating specialized mass production. Balance flowmeters are suitable for almost all fluid measurement applications, representing a revolution in fluid measurement technology. Today, they are widely used in industries such as petroleum, chemicals, metallurgy, power generation, natural gas, and water treatment.

Low pressure loss, with fewer requirements for straight sections before and after.

Low pressure loss, with fewer requirements for straight sections before and after.

Balanced flow meters utilize a symmetric porous structure to balance the flow field, reducing eddies, vibrations, and signal noise. This greatly improves the stability of the flow field, resulting in a linearity that is 5 to 10 times higher than that of orifice plates, as well as a repeatability that has increased by 54%, reaching 0.15%. Due to the stable flow field, the pressure recovery speed of balanced flow sensors is twice as fast as that of those with openings; this reduces the requirements regarding straight pipe sections – the straight pipe sections before and after such sensors are generally 3D in length on the front side and 1D on the back side, with a minimum length of 0.5D. As a result, a large amount of straight pipe section is eliminated, especially those made from particularly expensive materials. It adopts a hole-symmetric balance design to reduce turbulent shear forces and the formation of vortices, thereby minimizing kinetic energy losses. Under the same measurement conditions, it can reduce pressure loss by 2.5 times compared to orifice plates, making it an energy-saving instrument. By adopting a balanced design with symmetrical pores, turbulent shear forces and the formation of vortices can be reduced, thereby **decreasing the formation of stagnant zones and allowing dirt and debris to pass through the various pores easily, thus reducing the likelihood of blockages in those pores. It has the same usage method and shape as orifice plates, so it can be replaced directly without the need to change the piping or related instruments; it is highly suitable for replacing orifice plates with balanced flow meters during the EMS upgrade of electricity meters across an entire plant. The flow measurement range is larger than that of orifice plate flow meters.

Advantages of orifice plate flow meters: The throttling element has a structure that is easy to replicate; it is simple and robust, offers stable and reliable performance, and has a long service life； Suitable for measuring larger-diameter pipelines (currently, for flowmeters with diameters greater than DN 600 mm, orifice plates are generally the only option available) ； Durable ； Comprehensive calibration ； It’s cheap. Disadvantages of orifice plate flowmeters: High requirements are placed on the installation of the throttling device, pressure tapping pipes, and condensation tank, making the installation process relatively complex ； It is relatively difficult to perform a comprehensive calibration of orifice plate flowmeters; currently, only the differential pressure sensor, pressure sensor, and temperature sensor can be calibrated individually, making it hard to ensure the overall accuracy ； The structure of the orifice plate causes the static pressure of the fluid as it flows through it to decrease significantly, while the flow velocity increases markedly. This results in the fluid eroding the orifice plate severely, wearing away the sharp metal edges at its center, and thus leading to a continuous decline in the accuracy of the orifice plate. In the flow measurement of easily vaporizable liquids such as liquefied gas and propylene, changes in the physical state of the fluid lead to more severe erosion of the orifice plate ； The structure of the orifice plate results in significant static pressure losses as the fluid flows through it. Overall, an orifice plate flow meter is a device that consumes a lot of energy, which increases the mechanical power loss of pumps and motors; this is not conducive to improving the energy efficiency of the system. It represents a disadvantage in light of the increasingly strict energy-saving requirements.

Advantages of balanced flow meters: 1. Good long-term stability 2. Low requirements for straight pipe sections 3. High linearity and good repeatability 4. Reduced pressure loss 5. Resistant to dirt and less prone to clogging

Balanced flow meters utilize a symmetric porous structure to balance the flow field, reducing eddies, vibrations, and signal noise. This greatly improves the stability of the flow field, resulting in a linearity that is 5 to 10 times higher than that of orifice plates, as well as a repeatability that has increased by 54%, reaching 0.15%. Due to the stable flow field, the pressure recovery speed of balanced flow sensors is twice as fast as that of those with openings; this reduces the requirements regarding straight pipe sections – the straight pipe sections before and after such sensors are generally 3D in length on the front side and 1D on the back side, with a minimum length of 0.5D. As a result, a large amount of straight pipe section is eliminated, especially those made from particularly expensive materials. It adopts a hole-symmetric balance design to reduce turbulent shear forces and the formation of vortices, thereby minimizing kinetic energy losses. Under the same measurement conditions, it can reduce pressure loss by 2.5 times compared to orifice plates, making it an energy-saving instrument. By adopting a balanced design with symmetrical pores, turbulent shear forces and the formation of vortices can be reduced, thereby **decreasing the formation of stagnant zones and allowing dirt and debris to pass through the various pores easily, thus reducing the likelihood of blockages in those pores. It has the same usage method and shape as orifice plates, so it can be replaced directly without the need to change the piping or related instruments; it is highly suitable for replacing orifice plates with balanced flow meters during the EMS upgrade of electricity meters across an entire plant. The flow measurement range is larger than that of orifice plate flow meters.

Advantages of balanced flow meters: 1. Good long-term stability; 2. Low requirements for straight pipe sections; 3. High linearity and good repeatability; 4. Reduced pressure loss; 5. Resistant to dirt and less prone to clogging. Advantages of orifice plate flow meters: 1. The standard throttling element is widely used and recognized by international standard organizations, allowing them to be put into use without the need for actual flow calibration. It is also the only type of flow sensor whose structure is easy to replicate, offering simplicity, durability, stable and reliable performance, as well as low cost； 3. Wide range of applications

The balanced flow meter is a new type of throttling flow instrument; its working principle is the same as that of a differential pressure flow meter. It consists of a porous disc-shaped throttling and straightening element that is installed in the pipe cross-section, and the flow rate is proportional to the square root of the differential pressure. Balance flow meters have the advantages of a simple and reliable structure, easy manufacturing, low requirements for straight pipe sections before and after use, and the ability to maintain high precision. The balanced flow meter features a symmetric porous structure; as the fluid passes through these pores, it is evenly directed, minimizing vortices and resulting in behavior similar to that of an ideal fluid, which in turn reduces vibrations and signal noise. Compared with traditional throttling devices, it features: (1) a measurement accuracy that is 5 to 10 times higher; at a 1:10 range, the accuracy can reach +-1.0%. (2) The flow noise is reduced to 1/15, and the permanent pressure loss is about 1/3, resulting in low pressure loss. (3) Due to the stable flow field, low requirements are placed on the straight pipe section; generally, 3D length in front and 1D length at the back is sufficient. However, manufacturers claim that the minimum required straight pipe section can be reduced to 0.5D, but there is a lack of appropriate test data to verify this claim. (4) It can directly replace orifice plates, making it suitable for replacing orifice plate flow meters with balanced flow meters during energy metering upgrades across the entire plant. Balance flow meters have no moving parts, making them very simple to install and use; they also eliminate the need for long straight sections of pipe, **reducing the energy consumption associated with fluid flow. Used for measuring the flow rate of single-phase fluids (liquids, gases, or vapors) in enclosed pipelines. The balanced flow meter inherits all the advantages of traditional throttling devices, while avoiding most of their disadvantages such as a low measurement accuracy and high requirements for straight pipe sections, thereby **improving its measurement performance. In recent years, balanced flowmeters have seen rapid development as a result of widespread adoption, and coupled with marketing efforts by manufacturers, they seem poised to replace standard throttling instruments. However, their high cost makes them less economical from a financial perspective.