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Your number one source for flow, level, pressure and temperature instruments and accessories |
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Progressive Instruments located at 1737 Stebbins Drive, Suite 240 B, Houston, Texas 77043 866/350-1351 |
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Segmental Wedge Meters |
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The segmental wedge element is a device, specifically designed for use on slurries, corrosive/ erosive fluids, viscous liquids and high temperature applications. In is available for pipe sizes > ˝ in. The unique flow restriction is designed to last the life of the installation, without requiring repair or replacement, and without experiencing any degradation in accuracy. The segmental wedge is used with a remote seal DP transmitter, eliminating the need for lead lines, and eliminating any dead zones or spaces inside the element for a secondary phase to build up. It will rarely require cleaning, demonstrated in over 30 years history on fluids like dewatered sludge, black liquor, coal slurry, fly ash slurry, taconite, and crude oil. The segmental wedge has a discharge coefficient that is stable for Reynolds numbers > 500. The segmental wedge discharge coefficient is also highly insensitive to velocity profile distortion and swirl, requiring just 5 pipe diameters of relaxation piping upstream of the meter for most common combinations of fittings and valves. Testing has shown the value of the discharge coefficient is biased by < ˝% when this rule of thumb is followed. Segmental wedge meters have a high initial cost compared to most other flow devices. Their use has been restricted to difficult fluids, where a low cost of ownership is still possible due to dramatic savings in maintenance and installation costs. The segmental wedge has a V shaped restriction cast or welded into a flanged meter body. The restriction is characterized by the H/D ratio, where H is the height of the opening below the restriction. The H/D can be varied, like b on an orifice, to create a specific differential pressure for any flow rate. The V restriction has no critical dimensions, and can withstand significant erosion/corrosion without biasing the value of the discharge coefficient. The slanting of the upstream face to oncoming flow creates a sweeping action through the meter than has a scouring effect that helps to keep it clean and free of build up. The meter body allows direct connection of a remote seal DP transmitter having 3 in. diaphragm seals. The seals attach to the meter body immediately upstream and downstream of the restriction. The ability to use large 3 in. diaphragm seals makes the DP transmitter much less susceptible to error due to ambient temperature variations. Segmental wedges can measure flow bi-directionally but either the DP transmitter must be calibrated for a split range, or the primary element ordered with connections for 2 DP transmitters (one for forward flow and one for reverse flow). The discharge coefficient of a segmental wedge can only be determined by a water calibration. An uncalibrated element will have a discharge coefficient uncertainty of 2% to 5%. A calibrated element will have a discharge coefficient uncertainty of ˝%. The largest source of measurement error is generally from the density term in the flow equation. Density is not typically measured on such difficult fluids and an assumed “normal” value used in the flow equation. Slurry density does not generally remain constant, and may not be highly predictable. For this reason, typical accuracy may be in the 3% to 5% range. |
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We sell Wedge Meters for all types of applications across many industries. Please contact one of our customer service representatives for part numbers, pricing, availability, and applications assistance. |
