Principle and Features of Scraper Flow Meters

The scraper flowmeter is a volumetric measuring instrument used to determine the volume of fluids flowing through closed pipelines, primarily designed for heavy oils such as crude oil. It features on-site display of totalized flow and includes a remote transmission output interface. When paired with a compatible photoelectric pulse converter and flow totalizer, the device can be integrated with a computer system, enabling remote measurement, display, and control functions.

Features of Scraper Flow Meters

1. High measurement accuracy—basic errors typically range from ±0.2% to ±0.5%, with special requirements allowing for as low as ±0.1%. The characteristics of scraper flowmeters are generally unaffected by fluid conditions and are not limited by the magnitude of the Reynolds number.

2. Scraper flowmeters can measure fluids with higher viscosity, and changes in fluid viscosity have minimal impact on the indicated value.

3. The wheel counter features cumulative total measurement and requires no external power source—it’s simple and easy to use. Additionally, one of the counters can be reset to zero, making it convenient for users who don’t need continuous measurement.

4. The bearings are made from cemented carbide material, offering excellent wear resistance, corrosion resistance, sandproof properties, and superior stability.

5. Differential Regulator: The stepless speed-regulating differential regulator from domestic manufacturers of scraper flow meters offers convenient adjustment. When the displayed value of the scraper flow meter deviates from the verified value and needs adjustment, simply use a screwdriver to rotate the adjustment rod directly until the desired correction is achieved—no replacement of parts required.

6. The scraper flowmeter features an optoelectronic output shaft, which can be paired with an optoelectronic pulse converter to transmit pulse signals or 4-20mA signals over long distances. Additionally, the scraper flowmeter offers an optional electronic head that enables RS485-based remote communication, allowing direct reading of both instantaneous and cumulative flow rates—even over significantly greater distances.

7. The scraper flowmeter follows the verification procedure JJG667-2010 for liquid volumetric flowmeters.

Scraper-style Flow Meter Operating Principle

The scraper flowmeter operates by using the fluid to drive the rotor in rotation. As the rotor spins, the scrapers—guided by a fixed cam—alternately extend and retract, creating discrete metering chambers. Since the volume of each metering chamber remains constant, the number of rotor rotations directly corresponds to the volume of fluid flowing through the meter. Finally, a reduction mechanism translates these rotations into a precise flow measurement displayed on the counter.

The metal vane flowmeter operates on the principle of a rotating shaft that sequentially drives four vanes to extend and retract, creating distinct chambers within the housing. As the liquid flows through the device, it fills each of the four vane-defined chambers—each containing an identical volume—before being transferred via a gear mechanism. This mechanism converts the volume into a measurable output, which is then displayed on the meter’s dial. The dial’s counter subsequently translates the number of rotations into the actual volume of fluid being measured, enabling highly accurate quantification of the medium under test. The device comprises several key components, including the main chamber, gear assembly, precision corrector, and dial unit. The main chamber features a circular, hollow cylindrical design, with the rotor—a thin, hollow cylinder that rotates freely inside—as its central element. Two pairs of vanes, totaling four in all, are arranged in a cross-shaped configuration around the rotating shaft. Each pair of vanes is connected to a linkage system that includes connecting rods, rollers, and cover plates, while the entire assembly is securely housed within the robust outer casing.