The rotor flowmeter is a high-precision volumetric flow measurement instrument that measures the volume of fluid by the cooperation of the rotor and the metering chamber.

Inside a circular cavity, there is an eccentrically installed rotor (cam). Several radial slots (usually two pairs or more) are opened on the rotor, and a freely sliding scraper is installed in each slot.

1. High Precision: It features extremely high precision, generally reaching ±0.2% to ±0.5%, making it a trade settlement-level metering instrument. It operates very smoothly with minimal vibration and noise: The scraper's movement is a continuous sliding without the impact meshing like that of elliptical gears, thus ensuring very smooth operation and low noise.
2. Wide Range Ratio: Typically, it can reach 10:1, and high-performance models can achieve 20:1 or higher, capable of measuring both large and small flow rates.
3. Insensitive to Viscosity Changes: Inheriting the advantages of positive displacement flowmeters, it is highly suitable for measuring high-viscosity fluids such as crude oil and fuel oil.
4. Low Pressure Drop: Due to its streamlined design, the pressure loss when the fluid passes through is relatively small.
5. Good Repeatability: With a stable mechanical structure, it offers excellent measurement repeatability.

We can compare the paddle flowmeter with the several types introduced earlier:

The scraper flowmeter is often used for liquids of high value and requiring precise measurement due to its high accuracy and stability, especially in the petrochemical industry.

1. Natural Gas:
   • Trade handover of crude oil (very common), it is a key metering device for oil pipelines and loading and unloading at ports.
   • Precise measurement of refined oil products (gasoline, diesel, aviation kerosene).
   • Measurement of liquefied petroleum gas (LPG).
2. Chemical Industry: Various chemical raw materials, solvents, additives, etc.
3. Food and Pharmaceutical: Hygienic-level metering occasions such as edible oil, syrup, chocolate, cosmetic raw materials, etc. (with hygienic design).
4. Ships: Used for precise fueling of ships.

The scraper flowmeter is an outstanding representative of volumetric flowmeters that pursue high precision and stable operation. Through the ingenious design of eccentric rotors and sliding scrapers, it achieves continuous, gentle and precise measurement of fluids. Although its structure is relatively complex and the cost is high, it remains a trusted core device in fields with extremely high requirements for data accuracy and equipment reliability, such as crude oil trade and refined oil product measurement. Its stability makes it stand out in advanced application scenarios that require low noise and low vibration.