The turbine flow meter is a speed-type instrument, it has the advantages of high accuracy, good repeatability, simple structure, high-pressure resistance, wide measuring range, small size, light weight, small pressure loss, long life, simple operation, easy maintenance, etc. It can be widely used in the chemical industry, metallurgy, petroleum, organic liquids, inorganic liquids, liquefied natural gas, city gas pipeline network, pharmaceuticals, food, paper making, and other industries. Turbine flow meter can be divided into liquid turbine flow meter and gas turbine flow meter according to the different measurement media.
The turbine flow meter belongs to the velocity type flow meter, using a turbine for measurement. It first converts the flow rate into the rotational speed of the turbine and then converts the rotational speed into an electrical signal that is proportional to the flow rate. This type of flow meter is used to detect instantaneous flow and total cumulative flow, and its output signal is frequency, which is easy to digitize. The induction coil is fixed to the housing along with a permanent magnet. When a ferromagnetic turbine blade passes over the magnet, the magnetic resistance of the magnetic circuit changes, resulting in an inductive signal. The signal is amplified and shaped by an amplifier and sent to a counter or frequency meter, which displays the total accrued flow. The pulse frequency is also frequency-to-voltage converted to indicate the instantaneous flow rate. The rotational speed of the impeller is proportional to the flow rate, and the number of revolutions of the impeller is proportional to the total amount of flow through it. The output of the turbine flow meter is a frequency-modulated signal, which not only improves the anti-interference of the detection circuit but also simplifies the flow detection system. Its range ratio of up to 10:1, with accuracy within ± 0.2%. Inertia and small size of the turbine flow meter time constant of up to 0.01 seconds.
Since the principle is the same, then what are the differences between the two types of flow meters? In this paper, we will introduce the difference between liquid turbine flow meter and gas turbine flow meter from four aspects.
1. Measurement Medium
The measuring medium is a liquid turbine flow meter and a gas turbine flow meter of the essential difference. Liquid turbine flow meter is generally only used to measure high cleanliness, low viscosity single-phase fluid. Liquid turbine flow meters to measure the liquid medium mainly can measure edible oil, alcohol, methanol, etc., and can be widely used in petroleum, chemical, metallurgy, paper, and otherindustries to measure the volume of liquid volume instantaneous flow and total volume. Gas turbine flow meter can mainly measure gas media such as natural gas, air, and other gases, gas turbine flow meter is mainly used in industrial pipelines for air, nitrogen, oxygen, hydrogen, methane, natural gas, steam, and other media fluid flow measurement, in the measurement of the volume of flow in the measurement of the condition of almost independent of the fluid density, pressure, temperature, viscosity and other parameters of the impact.
2. Application Field
The liquid turbine flow meter is a precision flow measurement instrument, and the corresponding flow accumulation instrument can be used to measure the flow of liquid and the total amount. Liquid turbine flow meter is widely used in petroleum, chemical, metallurgy, scientific research, and other fields of measurement, and control systems. Liquid turbine flow meters equipped with sanitary connectors can be used in the pharmaceutical industry.
The gas turbine flow meter is suitable for natural gas, nitrogen, compressed air, and other clean gases with low and medium flow rates. It is not suitable for liquids or high-temperature vapors and wet gases. Gas turbine flow meter also applies to power generation and cogeneration, heating industry; aviation, aerospace, shipbuilding, nuclear energy and weapons industry; machinery, metallurgy, coal mining and automobile manufacturing industry; petroleum, chemical industry; medicine, food and tobacco sprinkler manufacturing industry; forest industry, agricultural reclamation and light industry.
3. Impeller Structure
The liquid turbine flow meter movement structure is relatively simple, has no bearing system, suitable for low-flow media, impeller speed speed is low, and the conventional flow rate of liquid media for 0.5-3m/s.
The gas turbine flow meter movement structure is complex, the requirements are relatively high, with a bearing system, applicable to low flow rate media, the impeller speed is high, and the gas medium conventional flow rate of 5-40m/s.
Both at the same time with different infusion systems, if the liquid turbine flow meter is used to measure the gas medium, maybe in the high-speed rotation, resulting in impeller wear.
4. Sensor
The density of gas by the temperature and pressure changes have a greater impact, so in the gas volume flow measurement, generally more temperature and pressure compensation function of the gas turbine flow meter, in order to achieve accurate measurement of the purpose of the gas medium, and in the process of measurement, to track the temperature and pressure of the gas medium, and will be converted to different conditions of the gas volume flow rate of the volume flow rate of the standard state. These liquid turbine flow meters do not need to consider the temperature, pressure changes, and other factors.
Because the gas turbine flow meter in the measurement of gas media, the measurement results will also be affected by atmospheric pressure, so the choice of sensor is very important. Different media products use the appropriate sensor technology, in order to play the expected results.
5. Summary
In summary, the liquid turbine flow meter and gas turbine flow meter in the measurement medium, application areas, impeller structure, sensors, and other aspects of the existence of major differences. In the actual use of the process, choosing the right type of turbine flow meter and parameters has an important impact on the stability and accuracy of measuring.