Positive Displacement Flow Meter – Vane-Type Flowmeter

There are numerous methods and types of instruments for measuring flow, and accordingly, many ways to classify them. To date, over 60 different types of flow meters are available for industrial applications. The wide variety stems from the fact that no single flow meter has yet been developed that can reliably measure any fluid, across all ranges, under every flow condition, or in response to every set of operating conditions. Among these, the commonly used scraper-type flow meter enjoys particularly broad application.

A positive-displacement flowmeter functions like a standard-volume container, continuously measuring the flowing medium as it passes through. The higher the flow rate, the more frequently the measurement occurs—and thus, the higher the output frequency. This type of flowmeter operates on a straightforward principle, making it particularly well-suited for measuring highly viscous fluids or those with low Reynolds numbers. Depending on the shape of the rotating element, current products include: oval gear flowmeters and lobe (Roots) flowmeters—both ideal for liquid flow measurement—as well as rotary piston and scraper-type flowmeters; meanwhile, for gas flow applications, you’ll find servo-type volumetric flowmeters, diaphragm flowmeters, and rotary vane flowmeters, among others.

The scraper flowmeter is a positive-displacement flowmeter, primarily used for measuring the total volume of liquids flowing through closed pipelines. It boasts high measurement accuracy, a wide flow range, excellent repeatability, and minimal sensitivity to changes in the viscosity of the fluid being measured. Additionally, it can be equipped with various counters and transmitters as needed, enabling either local indication or remote transmission of electrical signals. One of its key advantages is smooth rotation, ensuring stable fluid flow within the pipeline without pressure fluctuations or vibrations. Moreover, the fluid’s physical state has no impact on measurement accuracy, and the flowmeter doesn’t require straight pipe sections before or after installation. The single-shell design is simple, compact, lightweight, and easy to handle. Meanwhile, the dual-shell configuration prevents deformation of the metering chamber caused by high pressure, thereby maintaining precise measurement performance. Lastly, the scraper flowmeter allows the inner shell assembly to be easily removed for maintenance, as well as for tasks such as pipeline flushing, purging, or pressure testing.

Different types of orifice plates serve various purposes. Today, we’ll focus on analyzing the key differences between several commonly used orifice plate flowmeters.

Orifice flowmeters can be used to measure the flow rates of various media, such as gases and liquids. Today, to meet the diverse needs of different industries, many different types of orifice flowmeters have emerged in the market. However, standard orifice flowmeters are prone to fouling and erosion during operation, which can alter the discharge coefficient of the medium and potentially introduce measurement errors. To minimize these errors, it’s essential to address edge wear on the throttling element and ensure regular cleaning of the device.

Suitable for measuring fluids containing solid particles or entrained air, such as wet steam, producer gas, blast furnace gas, mixed gases, and water-containing liquid droplets. The segmental orifice plate is designed exclusively for installation in horizontal or inclined pipelines and must not be used in vertical pipes. Meanwhile, the scraper flowmeter automatically compensates for upstream flow disturbances during operation and effectively prevents non-axisymmetric flow distributions around the meter, eliminating concerns about fouling buildup on the throttling element. This ensures smooth passage of even highly contaminated media without any risk of stagnation before or after the throttling device. The eccentric orifice plate is particularly well-suited for applications involving wet steam, flue gas, coke oven gas, and similar media.