Variable Area & Rotameters
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Variable area flow meters are used in pipelines to determine the flow of liquids or gases within. The flow meter consists of a conical measuring tube with a float inside it.
The measuring principle is based on the body being vertically deflected through the flowing medium. Various forces act on the float - the flow resistance, the buoyant force, as well as the weight force of the body. In summary, if the volume flow rises, the float is lifted. The current flow is indicated on the scale at the top of the float. We are able to supply variable area flow meters other than our standard range. If you require a glass tube, steel frame or any other variation then please let us know and we will be able to quote. |
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Typical Application for variable area flow meters:
Key Points for variable area flow meters:
Advantages for variable area flow meters:
Disadvantages for variable area flow meters:
- Liquid flow meter or gas flow meter where high accuracy is not required
- Measuring water and gas flow in plants or labs
- Monitoring chemical lines
- Purging instrument air lines (i.e. lines that use a valved meter)
- Monitoring filtration loading
- Monitoring flow in material-blending applications (i.e. lines that use a valved meter)
- Monitor water for food & beverage plants
Key Points for variable area flow meters:
- Variable area flow meters operate on the principle that the flow of the media will alter the position of a float in a tapered tube. The position of the float in the tapered tube is proportional to the volumetric flow rate
- Typical accuracy of variable area flow meters is ±3% full scale
- A variable area flow meter normally has a turn down ratio in the region of 10:1
- A variable area flow meter normally requires vertical installation and a straight pipe run (minimum length of five times the diameter of the pipe) before the flow meters inlet
Advantages for variable area flow meters:
- Low cost
- Simple to install
- Easy to use and virtually maintenance free
- Wide choice of materials including all PTFE for aggressive fluids
- Many control options including control valves, set-point switches and analogue outputs
Disadvantages for variable area flow meters:
- Lower accuracy compared to many other flow meter technologies
- Affected by pulsation
- Sensitive to fluid changes such as viscosity, density and temperature
