Cone Flow Meters
FLEXIBLE FLOW METERS - Cone Flow Meters
The Cone Flow Meters are based on the principle of differential pressure for flow devices. The principal theory among these is Bernoulli's theorem for the conservation of mass and energy in a closed pipe. According to this principle, the obstruction to the flow of fluid in a cone flow meters causes an increase in flow velocity thereby, creating a pressure drop. The flow rate can be determined by measuring the upstream pressure, variation in the static pressure between the upstream and the minimum cross-sectional area, and the temperature. Thus, the flow rate of any given is calculated by applying the law of conservation of mass and energy.
The structure of Cone flow meters is comprising of a tube with a Cone hanging in the center which is responsible for varying the cross-section area of the fluid passing through the pipe. Due to a reduction in the area of cross section of the pipe as it moves forward, the velocity of the fluid increases which increases its kinetic energy due to fall in the static energy. This creates a low-pressure zone by the downstream.
The fluid entering the flow meter is at pressure P1 and it drops to pressure P2 as it reaches the confined area of the cone.
Both P1 and P2 are measured at the Cone flow meters taps using a variety of differential pressure transducers. The differential pressure produced will increase and decrease exponentially with respect to the flow velocity. As the shrinking of fluid flow area increases, the differential pressure created will increase for the same flow rates.
This Cone creates a controlled turbulence region which flattens the incoming irregular velocity profile and induces a stable differential pressure that is sensed by a downstream tap. The beta ratio of a Cone flow meter is defined such that a cone and an orifice with equal beta ratios will have equal opening areas. The beta ratio is equal to the flow area at the largest cross section of the cone divided by the inside diameter of the flow meter. It is given as:
Beta ratio = (D2 – d2)0.05/D
Where,
d is the cone diameter
D is the inside diameter of the pipe.
With this design, the beta ratio can exceed 0.75. The cone is designed to function in a wide variety of mild to harsh environments. The restriction of the Cone flow meters has a unique geometry that minimizes accuracy degradation due to wear; it offers repeatability features, wider range, and reduced maintenance benefits, making it a good choice for high velocity flows and erosive/corrosive applications.
