A rotameter, also known as a float flowmeter, is a device that consists of a conically tapered tube, which gradually expands from the bottom to the top. Inside this tube, a rotor is placed and allowed to move freely along the central axis. The working principle of a rotameter is based on variable area measurement—when fluid flows through the annular gap between the rotor and the tube wall, the rotor rises or falls depending on the flow rate. This movement allows for the determination of the flow rate by measuring the position of the rotor.
Rotameters are commonly categorized into two main types: glass-tube and metal-tube models. While glass rotameters are often used for corrosive or sensitive fluids due to their transparency and chemical resistance, metal rotameters are more widely used in industrial applications such as petrochemical, textile, and metallurgical processes. In recent years, advanced materials like all-titanium and high-quality glass have become popular choices, especially in environments where durability and precision are essential.
Nanjing Dasman Machinery Co., Ltd. has developed rotameters that have performed well in both professional testing and long-term stability assessments. The company's design process involves a deep understanding of how the rotameter functions. The basic principle is straightforward: as the fluid passes through the annular space between the rotor and the tube, it exits at the top, causing the rotor to rise. The higher the flow rate, the higher the rotor will float.
When reading a rotameter, the displayed value represents the instantaneous flow rate, which can be either volumetric or mass flow. If the measurement is in mass flow, it must first be converted to volumetric flow (in m³/s) before determining the actual flow rate. Once converted, the volume flow rate is calculated using the cross-sectional area of the rotor, allowing for accurate measurement of the fluid's movement through the system.
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