Thread Content
The technical specialist from my manufacturer explained that when measuring compressed air, the selection of the flow meter plays a crucial role in ensuring accurate measurement. However, due to the complex nature of the substance being measured, as well as the wide variety of instruments available and the difficulty in assessing their quality, it becomes very challenging to choose the right instrument. Today, our technical editor will analyze in detail what factors need to be considered when selecting a compressed air flow meter. (1) Meeting the process requirements regarding pressure loss: It is necessary to determine whether the permanent pressure loss after passing through the flow meter affects production. (2) Properties of the fluid under test: fluid composition, density, viscosity, compressibility and their variations, as well as temperature, pressure, humidity and their ranges of variation. (3) Uncertainty of the selected instrument: The accuracy of the instrument chosen should be determined based on the level of measurement required, in order to avoid waste. (4) Whether the instrument can meet the on-site installation requirements: To enable the flow meter to perform accurate measurements, it is necessary to meet the specified length of straight pipes, and considerations must also be given to factors such as temperature resistance, pressure resistance, vibration resistance, and safety protection. (5) Environmental conditions around the instrument after use: Consideration should be given to the convenience of daily maintenance and replacement of the instrument. The impact of ambient temperature, humidity, and electromagnetic interference on instruments, as well as the safety performance of the environment. (6) Cost of instrument investment: Sometimes, the funds required to install the instrument system as specified by the measurement department differ from the actual amount available; in such cases, it is necessary to choose the most suitable instruments based on the available funds. Below is a brief summary by technicians on the flow meters commonly used for measuring compressed air flow. I hope it can help a wide range of users. Differential pressure flow meters: Differential pressure flow meters are a type of flow measurement instrument that is widely used, accounting for approximately 60% to 70% of all flow measurement instruments. It consists of a throttling device, a pressure guide tube, and a differential pressure gauge, and is suitable for measuring most gas and liquid media, but not for media that are highly viscous, corrosive, prone to crystallization, or prone to scaling. The advantages of such instruments include a robust structure and a long service life; mass production results in relatively low prices and easy adjustment. The disadvantages are also quite obvious: the measurement accuracy is low and the range is limited, usually only 3:1 to 4:1; the requirements for on-site installation are high; some throttling elements such as orifice plates and nozzles incur high pressure losses. These factors must be fully considered when selecting a design. Vortex flow meter: A vortex flow meter consists of a non-streamlined vortex generator placed in the fluid; as the fluid flows past this generator, it separates alternately on either side, resulting in two sequences of vortices that are arranged in a regular, interlaced pattern. Within a certain range of Reynolds numbers, the vortex separation frequency is proportional to the average flow velocity in the pipe, and various types of detectors can be used to detect the vortex frequency. So what are the advantages of vortex flowmeters? (1) Advantages ① Simple and robust structure, with no moving parts; ② Very easy to maintain, and low installation costs; ③ High accuracy; ④ Wide measurement range, with a ratio of up to 1:10; ⑤ Low pressure loss; ⑥ Low operating costs; ⑦ Wide range of applications, capable of measuring the flow rate of both gases and liquids. Flow metering is one of the components of metrological science and technology, and it is closely related to the national economy, national defense construction, and scientific research. Doing this job well plays an important role in ensuring product quality, improving production efficiency, and promoting the development of science and technology. Especially in today’s era of energy crises and an increasing degree of automation in industrial production, the significance and role of flow meters in the national economy have become even more evident.