Flow meter selection

GE has a natural gas ultrasonic flowmeter that can be used

Without considering the specific components of the natural gas, the selection of a flow meter for this gas supply pipeline primarily depends on the following factors: 1. **Operating pressure range**: 0.8 MPa to 1.2 MPa; the flow meter must be able to withstand such pressure levels and function stably over the long term. 2. **Medium temperature range**: -5°C to 40°C. The material and design of the flow meter must be capable of withstanding such temperature variations in order to ensure accurate measurement and good corrosion resistance of the equipment. 3. **Flow rate range**: 3000~10000 Nm?/h. The flow meter’s range should cover this flow rate interval while maintaining good measurement accuracy. Based on the above requirements, the following types of flow meters can be considered: 1. **Orifice plate flow meter**: A traditional differential pressure flow meter that is suitable for various operating conditions; however, it requires specific pipeline specifications, including long straight sections, and it also results in certain energy consumption. 2. **Turbine flowmeter**: Suitable for measuring the flow rate of natural gas in medium and low-pressure pipelines, featuring high accuracy and repeatability. The medium is required to be relatively clean; gases containing a large amount of impurities are not suitable. 3. **Eddy current vortex flowmeter** (an optimized version of the turbine flowmeter): It can maintain high measurement accuracy over a wide range of flow rates, and is not sensitive to fluid disturbances or pressure fluctuations. 4. **Ultrasonic flowmeter**: It does not come into contact with the fluid, making it suitable for applications where pressure losses in the pipeline are required to be very low. It offers the advantages of low maintenance costs and no disruption to fluid flow. 5. **Mass flow meters** (such as thermal mass flow meters or Coriolis mass flow meters): They directly measure mass flow rate and are not affected by changes in fluid density, making them suitable for applications that require high precision measurements. For this application, ultrasonic flowmeters or Coriolis mass flowmeters are the preferred options, taking into account the advantage of ultrasonic flowmeters in terms of non-contact interaction with the medium as well as their lower maintenance costs. The Coriolis mass flow meter is suitable for high-precision measurements, and it is also a good option if the project budget permits it. When selecting a flow meter, factors such as its compatibility with the installation site (such as connection methods and power requirements), budget costs, and long-term maintenance costs should also be taken into consideration. When appropriate, you can consult the manufacturer or a professional flow meter supplier for specific model and parameter recommendations. .

It’s quite good. I’m thinking about whether a thermal mass flow meter could be used?

That was the consideration when making the initial selection.

This post was last edited by zhoudingshengs on 2023-11-23 at 16:56. In general, when making a selection, the flow rate under standard conditions is first converted to the flow rate under actual operating conditions using the gas equation, and then an appropriate diameter is chosen. The gas equation is as follows: Qb = Q × PTb / PbT × Zb / Zg = QCF2 (where: C is the conversion factor) ； F is the gas compressibility factor). Calculation: ① When the medium pressure is at its lowest and the temperature is at its highest, the maximum standard conditions volumetric flow rate should be achieved. That is, Qb=Q×PTb/PbT×Zb/Zg=QCF2=1200.87 m3/h. ② When the medium pressure is at its highest and the temperature is at its lowest, the standard condition volume flow rate should be at its minimum. That is, Qmin = 213.51 m3/h. From the above calculations, it can be seen that the flow rate range for the flow meter to be selected should be (214–1200) m3/h. Based on the calculated flow range, select a flow meter that meets the requirements of the operating conditions.

If high precision is required, just choose a mass flow meter

When selecting a flow meter for use on-site, it is necessary to take into account the actual operating conditions there in order to choose the most suitable measuring instrument. Generally, the following points can be considered: 1. Determine the type and specifications of the flow meter based on the properties and flow conditions of the fluid being measured. (1) When selecting a type, several key physical and chemical properties of the fluid must be considered: the fluid’s state (solid, gas, liquid), its electrical conductivity, corrosiveness, and viscosity. (2) It is necessary to fully understand the application ranges of various types of flow meters. When selecting a model, the properties of the fluid should be considered comprehensively. - Fluids in a solid state are generally in the form of dust or lumps; therefore, the only flow meters that can be used are impulse flow meters, belt scales, and rail scales. -There are various types of flow meters for fluids in liquid and gas states. Common flow meters used for measuring gases include vortex flow meters, rotameter flow meters, vortex street flow meters, and others. In situations where the liquid conditions are poor, such as corrosion, conductivity, or the presence of solid particles, an electromagnetic flowmeter is the best choice. -Flowmeters suitable for high-viscosity fluids include elliptical gear flowmeters, gear pumps, scraper flowmeters, target flowmeters, wedge flowmeters, etc.; the specific choice depends on requirements regarding accuracy, cost-effectiveness, and other practical operating conditions. -When selecting flowmeters for use with corrosive fluids, it is essential to pay attention to the material used for the parts that come into contact with the fluid. For example, when an electromagnetic flowmeter is used to measure hydrochloric acid, tantalum electrodes must be used; otherwise, the electrodes will corrode very easily. 2. The selection of the flow meter must take into full account the conditions provided by the process. (1) The static pressure and temperature of the medium must be taken into consideration. The static pressure and temperature resistance of the flowmeter are also important factors in ensuring the instrument’s service life and accuracy. The static pressure of the instrument, that is, its pressure resistance, should be slightly higher than the operating pressure of the medium being measured; generally, 1.25 times that value is used to prevent leaks or other issues. Choose turbine flowmeters whenever possible to minimize pressure loss. Because the pressure loss of the fluid as it passes through the turbine flow meter is the smaller, the less energy is consumed by the fluid as it moves from the inlet pipe to the outlet pipe; in other words, the total power required is reduced. This allows for **energy savings, lower transportation costs, and improved efficiency**. The main component that affects pressure loss is the pilot nozzle of the turbine flow meter; compared to a conical pilot nozzle, using a semi-elliptical pilot nozzle can significantly reduce the pressure loss in the turbine flow meter. (2) Flow range, mainly the selection of the upper limit of the instrument scale. Choosing a too small size can lead to overload and damage to the instruments ； Choosing a too large size hinders the accuracy of the measurement. **The standard specifies that the maximum flow rate should not exceed 70% to 30% of the full scale. It is recommended that the lower flow limit for the instrument be set at 0.8 times the minimum flow rate actually used. (3) Process pipe diameter: The selection of the flow meter diameter is also determined by the flow range. Some flowmeters do not come in particularly large diameters, and those with large diameters are very expensive. Currently, the flowmeters that are more suitable for large diameters include electromagnetic flowmeters, ultrasonic flowmeters, insert-type vortex flowmeters, insert-type turbine flowmeters, and venturi tubes. 3. Consider the accuracy class and cost-effectiveness of the flow meter. Areas where high precision is generally required include the measurement of raw materials entering the plant and production units, the measurement of finished products leaving these units and being sold, the measurement of ingredients used in manufacturing processes, and the measurement of expensive substances. However, the higher the accuracy of the flow meter, the more sensitive it is to changes in field operating conditions. Therefore, careful consideration must be given to the choice of instrument accuracy, taking economic factors into account. For flow rates that are used only for general reference in production facilities, flow meters such as ultrasonic flow meters, which are relatively inexpensive, are usually chosen. In production, vortex flowmeters are typically used for gases in utility systems (air, nitrogen, steam), while electromagnetic flowmeters are mainly used for various types of water. 4. Consider the safety of the measurement. (1) The measurement method is reliable, meaning that the sampling device will not experience mechanical strength or electrical circuit failures during operation that could lead to accidents ； (2) The measuring instruments shall not affect the safety of the production system, whether under normal operation or in case of faults. For example, in the measurement of the high-temperature and high-pressure main steam flow in power plants, the primary measuring element installed in the pipeline must be robust to prevent mechanical damage caused by the impact of high-speed steam streams. In fuel-fired power plants and areas with flammable gases, explosion-proof instruments should be used.

It can be used, provided that the composition of natural gas remains stable and known. Additionally, calibration is necessary to ensure a certain level of accuracy; flow calibration is preferred.