Such a handy metal scraper flowmeter

The metal vane flowmeter is a type of positive-displacement flowmeter, consisting of a main chamber, a gear assembly, a precision corrector, and a meter head. The main chamber is primarily composed of a rotor, cams, a camshaft, vanes, connecting rods, rollers, a cover plate, and the housing. Inside the housing, the inner cavity forms a circular hollow cylinder, while the rotor itself is a rotating, hollow, slender cylindrical component. The design incorporates two or four pairs of vanes, with the rotating shaft shaped in a cross configuration.

This flowmeter requires no straight pipe sections, flow conditioners, or other auxiliary equipment for installation, and is unaffected by pipe fittings such as elbows, tees, and valves. It operates smoothly, with zero vibration and minimal noise, delivering highly accurate measurements—up to 0.2% accuracy. Even in cases involving complex crude oil compositions or media containing solid particle impurities like water and sand, the flowmeter continues to perform flawlessly without any measurement interference. Additionally, it features very low pressure loss, with pressure drop not exceeding 0.06 MPa.

What are the advantages and features of metal vane flowmeters?

　1. Accuracy: System accuracy must be determined based on application conditions and the accuracy of the secondary instrument, with tolerances of 0.5%, 1.0%, and 1.5%.

　2. Excellent repeatability: Better than 0.1%

　3. Wide measurement range: Typically 10:1, but can be increased if necessary.

4. Low straight pipe requirements: A straight pipe section of 0–3D upstream and 0–1D downstream of the flowmeter is sufficient to ensure measurement accuracy. Experiments have shown that the V-cone flowmeter can closely mimic the effects of a single bend or even a dual-bend configuration in different planes, with minimal impact on accuracy.

5. Excellent Long-Term Stability: The conical shape design ensures that flow through the cone occurs gradually, without any abrupt changes, allowing numerical values to remain consistently stable over time. As a result, the instrument can be used continuously for extended periods without requiring calibration. 
 

6. Signal Stability: All metal vane flowmeters experience signal fluctuations—meaning that even when the fluid flow is highly stable, the signal generated by the primary throttling element will still vary. In the case of orifice plates, the long vortices formed downstream of the restriction create high-amplitude, low-frequency pulsating signals, which can interfere with the accuracy of differential pressure gauges. In contrast, cone flowmeters generate a small vortex downstream, producing low-amplitude, high-frequency fluctuating signals instead.

The elastic scraper flowmeter, a measurement technology introduced from abroad in the 1980s, offers three key advantages. First, since the scraper is made of rubber—a material that ensures a seamless fit with the outer housing and provides excellent elastic sealing—any sand particles or impurities present in the measured medium are effectively scraped away, preventing them from interfering with the rotor inside the flowmeter. As a result, its sand-handling capability is remarkably robust. Second, the rubber scrapers used in these devices are manufactured via mold casting, allowing for easy replacement if issues arise. Third, the rubber material performs well even in high-water-content crude oils, as it resists scaling on the scraper surface. While the flowmeter boasts numerous benefits, its drawbacks cannot be overlooked. For instance, it generates relatively high pressure during normal operation, which can lead to challenges in separator drainage, particularly in oilfields with lower production rates. In severe cases, this issue may even compromise the overall quality of the crude oil.