The segmental wedge element is a proprietary device for slurry, corrosion, erosion, viscous or high-temperature applications. It is relatively expensive and is mostly used in hard fluids, where dramatic maintenance savings can justify the initial cost. The unique flow limitation is designed to last the installation of life without deterioration.
Construction:
Wedge elements are used with chemical seals of 3-in diameter, eliminating the lead lines as well as any dead-end cavities. The seals instantly attach upstream and downstream of the restriction to the meter body.
Even in services such as dewatered sludge, black liquor, coal slurry, fly ash slurry, taconite, and crude oil, they rarely require cleaning.
Working:
The functional principle is based on the principle of Bernoulli (continuity and energy balance equations). Differential pressure is generated using a wedge that can be equated with the flow rate of mass or volume. The range of flow is determined by the H/D ratio.
The oncoming flow creates through the meter a sweeping action. This provides a scouring effect on both sides of the restriction, helping to keep the restriction clean and free of buildup.
Segmental wedges can measure flow in both directions, but the d/p transmitter has to be calibrated for a split range, or two sets of connections for two d/p transmitters have to be provided to the flow element (one for forward and one for reverse flow).
Benefits of segmental wedge flowmeter:
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Pressure drop is about half of conventional orifice flowmeter
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Ability to measure low Reynolds flows
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Useful for measuring highly viscous fluids, slurries, and dirty fluids.
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Can be used for bi-directional flow