Principles of Operation
The basic construction of turbine flow meters includes a bladed turbine rotor which is axially suspended in the pipe. As the fluid flows through the pipe, it causes the rotor to spin on its axis at a speed which is proportional to the velocity of the fluid. The passage of each rotor is sensed by the turbine meter using gears, photoelectric cell or magnetic pickup installed on the outside of the flow tube or the meter body, adjacent to the perimeter of the rotor.
The turbine meter is a popular displacement flow measuring device, which can be used in a wide range of industries for both liquids and gases. Turbine flow meters have the ability to measure wide flow ranges with good accuracy and at an economic price; their application is restricted only by the fact that they must be used with clean, non-corrosive fluids.
Turbine Meter Advantages
• Wide flow rangeability including low flow rates
• Turndown ratio is up to 35:1
• Good level of accuracy at an economic price
• Simple, durable construction
• Easy to install and maintain
• Flexible connection to flow instruments for flow control
• Wide variety of process connections
• Turbine meters can operate over a wide range of temperatures and pressures
• Low pressure drop across the turbine
• Provides a convenient signal output
Turbine Meter Limitations
• Requires constant backpressure to prevent cavitation
• Accuracy adversely affected by bubbles in liquids
• Turbine meters can be used with clean liquids and gases only (may need to install a strainer upstream to prevent damage from particulates)
• Not applicable for measuring corrosive fluids
• Requires a turbulent flow profile (consistent fluid velocity across the pipe diameter) for accuracy
• Sensitive to changes in fluid viscosity
• Require a straight run of pipe before and after the turbine meter to allow swirl patterns in the flow stream to dissipate
• May not function properly with high viscosity fluids where the flow profile is laminar
Turbine meters operate most effectively in applications with steady, high-speed flows.
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