![]() Type of measurement: Industrial flow measurements fall under one of two categories: mass or volumetric. Consequently, any change that involves significant pressure variations is generally accompanied by much larger changes in mass density in the case of a gas than a liquid. The most important difference between these two types of fluid lies in their relative compressibility (i.e., gases can be compressed much more easily than liquids). Process media: Fluids are conventionally classified as either liquids or gases. Additional considerations such as mechanical restrictions and output-connectivity options impact the user’s choice.įor plant operations, the key factors in meter selection include: In a typical industrial facility, fluid characteristics, flow profile, flow range and accuracy requirements are important for determining the best flow meter for a particular measurement task. Meters made with aluminum or bronze discs can meter hot oil and chemicals. Nutating disc: Nutating disc meters have a reputation for high accuracy and repeatability, but viscosities below their designated threshold adversely affect performance. This design offers easy installation and high accuracy, and measures high temperature, viscous and caustic liquids with simple calibration. ![]() It features a wide flow range, minimal pressure drop and extended viscosity range. Oval gear: The latest breed of oval gear meters directly measures actual volume. Vortex meters may introduce pressure drop due to obstructions in the flow path. Vortex: Vortex meters have no moving parts that are subject to wear, so regular maintenance is not necessary. They also need to be calibrated for viscous liquids and compressed gases. Be advised most of these meters must be mounted perfectly vertical. Variable area: Simple, inexpensive and reliable, variable area meters provide practical flow measurement solutions for many applications. Clamp-on ultrasonic flow meters can be used for troubleshooting a wide range of flow issues, from verifying the reading of another meter to monitoring flow systems over an extended time period. Clamp-on ultrasonic meters can be used for troubleshooting a wide range of flow issues (see Image 2). Ultrasonic: Ultrasonic flow meters have no moving or wetted parts, suffer no pressure loss, offer a large turndown ratio, and provide maintenance-free operation. Their performance suffers in applications with low fluid velocity. ![]() Their attributes include direct volumetric flow measurement (often with visual indication) universal mounting fast response with good repeatability and relatively low cost. Impeller: Impeller meters are frequently used in large diameter water distribution systems. Turbine meters are limited to use with only clean fluids, and they require periodic recalibration and service. ![]() They produce a high-resolution pulse rate output signal proportional to fluid velocity and, hence, to volumetric flow rate. ![]() Turbine: Turbine meters are known for high accuracy, wide turndown and repeatable measurements. They are designed to work with clean gases of known heat capacity, as well as some low-pressure gases not dense enough for Coriolis meters to measure. Thermal mass: Thermal mass meters carry a relatively low purchase price. There is no need for straight pipe lengths as with other metering approaches. These devices have only one or two moving parts, making them easy to maintain. Positive displacement: Positive displacement meters are highly accurate (especially at low flows) and have large turndown ratios. The meters have no moving parts or flow obstructions, and are relatively unaffected by viscosity, temperature and pressure when correctly specified. They provide low pressure drop, high accuracy, high turndown ratio and excellent repeatability. DP meters are not greatly affected by viscosity changes.Įlectromagnetic: Electromagnetic meters measure virtually any conductive fluid or slurry. (Images courtesy or Badger Meter)ĭifferential pressure: Differential pressure (DP) meters employ a proven, well-understood measuring technology that does not require moving parts in the flow stream. Coriolis flow meters are designed to directly measure fluid mass over a wide range of temperatures with very high accuracy. ![]()
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