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Piping Change Nearly Leaves Engineer Up the River Without a Paddle
DP Flow Meter Solves The Problem at Eastman Chemical Plant
By Mike Dyer
Applications Engineer, McCrometer
A short straight pipe run between a river water pumping station and a valve at the Eastman Chemical Company’s plant in Kingsport, TN, caused critical water flow measurement accuracy problems for the company. The piping configuration left the company’s Utility Division engineer with only a straight pipe run of 15 feet, which was insufficient in length for accurate water flow measurement with the existing orifice plate flow meter already in place.
To solve the flow measurement accuracy problem, Eastman staff contacted applications engineers at McCrometer and asked them to review the situation. They suggested that a differential pressure flow meter, such as the company’s V-Cone, would be compatible with the 15-foot straight pipe run because of the built-in flow conditioning that is inherent within its flow meter's design.
The Eastman personnel agreed with the application’s engineering assessment. They installed a 30-inch McCrometer V-Cone Differential Pressure Flow Meter to support one of their large river water pumps. The V-Cone’s compatibility with shorter straight pipe runs not only provides excellent measurement accuracy, but also meant the Eastman personnel could avoid making more costly changes to their pump station and plant piping configuration.
“Our plant’s minimal straight pipe run of only about 15 feet between pump and valve required a flow meter that offered extensive installation flexibility, said Allen Clem, project engineer at Eastman Chemical. “The V-Cone, with its small-space installation ability, increased accuracy and large turndown ratio, enabled us to replace the orifice plate and gain immediate results. We are pleased so far with the flow indication. The V-Cone is performing well.”
The V-Cone Flow Meter accurately measures flow over a wide range of Reynolds numbers under all kinds of plant environmental conditions and in a variety of clean and dirty fluids. It operates on the same proven operation principle as other differential pressure type flow meters, using the theory of conservation of energy in fluid flow through a pipe.
The unique design of the V-Cone’s differential-pressure flow meter, however, actually conditions fluid flow to provide a stable flow profile that increases measurement accuracy. The flow meter‘s design features a centrally-located cone inside a tube. The cone interacts with the fluid flow and reshapes the fluid’s velocity profile to create a region of lower pressure immediately downstream from itself.
The pressure difference, which is exhibited between the static line pressure and the low pressure created downstream of the cone, can be measured via two pressure sensing taps. One tap is placed slightly upstream of the cone and the other is located in the downstream face of the cone itself. The pressure difference can then be incorporated into a derivation of the Bernoulli equation to determine the fluid flow rate.
The cone’s central position in the line optimizes the velocity of the liquid flow at the point of measurement. It forms very short vortices as the flow passes the cone. These short vortices create a low amplitude, high frequency signal for excellent signal stability. The result is a highly stable flow profile for measurement accuracy to ±0.5% with ±0.1% repeatability over a wide flow range of 10:1. All of this is accomplished with a minimal straight pipe run of only 0 to 3 diameters upstream and 0 to 1 diameters downstream from the cone.
In addition to excellent accuracy and repeatability over a broad range, the V-Cone differential pressure flow meter is suitable for a broad range of applications in line sizes from 0.5 to 120 inches or larger. From large plant water pipelines such as those at Eastman Chemical to small process lines for ingredients or chemical injection, the V-Cone is a highly flexible flow measurement solution.
The contour shape of the cone also directs the flow without impacting it against an abrupt surface. As a result, the beta edge of the cone is not subject to wear by dirty fluids. Because it remains unchanged, V-Cones rarely, if ever, require recalibration. Their no-moving parts design requires almost no maintenance and ensures a long life. These same characteristics make the V-Cone suitable for high pressure, high temperature and corrosive environment applications as well.
Whether in retrofit applications such as at Eastman Chemical in Tennessee, or in plant expansions or new plants, the V-Cone Flow Meter is an ideal solution wherever performance, accuracy and low cost-of-ownership are important instrumentation criteria. Differential pressure flow meters, such as the V-Cone, give process engineers a simple, proven relatively low cost solution to obtaining accurate flow measurement. As the demand for water and the cost of water increases, the need for accurate liquid flow measurement is more important than ever for plant engineers everywhere.
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