Tuesday, October 6, 2015

The Virtues of a Cone Meter for Your Next Challenging Flow Application

V cone meter
"V" shaped cone meter for controlling flow.
A cone meter, also referred to as a "V Cone" (trademark of McCrometer), is an advanced differential pressure instrument, ideal for liquids, steam or gas in rugged conditions where accuracy, low maintenance and cost are important.

Cone meters operate on the same physical principle as other differential pressure flowmeters, such as orifice plates, flow nozzles or venturi tubes, using the theorem of conservation of energy in fluid flow through a pipe.

The cone interacts with the fluid flow and reshapes the fluid’s velocity profile, which in-turn creates a region of lower pressure immediately downstream. The pressure difference between the upstream side and the downstream side of the cone can be measured via two pressure sensing ports. One port is placed slightly upstream of the cone, the other is located just downstream of the cone. The pressure difference can then be calculated to determine the fluid flow rate. Because the cone is positioned in the center of the flow, the velocity profile is automatically optimized at the point point of measurement, which assures highly accurate, reliable flow measurement irrespective of the upstream flow.

The theories behind differential pressure type measurement are based on Bernoulli’s theorem for the conservation of energy in a closed pipe. The theorem states that for a constant flow, the pressure in a pipe is inversely proportional to the square of the velocity in the pipe. Simply put, the pressure decreases as velocity increases.

In real life situations, pipe flow profile is never ideal. Flowmeters are rarely installed in well developed, planned situations. Changes to piping, like elbows, valves, reductions, expansions, pumps, and tees will corrupt well-developed flow. Measuring disturbed flow is difficult for other flowmeter technologies because of the errors introduced. The cone flow meter overcomes by using its contoured shape and localized position to reshape the velocity profile upstream of the cone. As the flow approaches the cone, the flow profile flattens and becomes much better developed, even under extreme conditions. This ensures there will always be a predictable flow profile at the cone which in-turn ensures accurate measurement.

Contrary to popular opinion, cone meters measure much more than just gas. They also measure steam and a wide variety of liquids in many industries including oil/gas, chemical, electric power, food/beverage, HVAC systems, metals and mining, pulp/paper, water and wastewater treatment, and more.

The following video illustrates more on how cone meters work, how their flow control is superior to other devices, and why their design is so beneficial in today's industrial applications.