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When Inches Count: Flow Metering in Constrained Spaces

Source: McCrometer, Inc.

From offshore oil platforms that come with a hefty cost for every square foot to college campuses that rely on steam plants jammed into cramped basements, flow metering is critical to many operations where space comes at a premium.

The big problem is that most flow metering technologies conflict with space limitations because of their substantial straight pipe run requirements for accurate readings. Concentric orifice plate flow meters, for example, need as much as 40x diameters upstream and 20x diameters downstream. That means a 6” pipe will require 240” of straight pipe run, with no elbows or other obstructions in the line.

The good news is there is an alternative.

Coriolis and V-Cone meters measure liquids and gases using two different technologies.

McCrometer’s V-Cone® flow meter, an advanced differential pressure technology, requires 0x to 3x diameters of straight run upstream and 0x to 1x diameter of straight run downstream. The V-Cone acts as its own flow conditioner, so it can handle turbulent flow without the need for longer straight runs. A 6” pipe with a V-Cone flow meter, for example, would only require a maximum 18” of straight run pipe.

V-Cone is a fit for a wide variety of applications. In addition to water and wastewater, it can be used in natural gas, steam, chemical, oil and gas, and industrial settings.

By Comparison

When considering V-Cone meters versus other flow meters, an accurate cost comparison should account for the additional expense — and ability — to meet longer straight-run pipe demands. In addition to the 40/20 requirements (maximum diameters needed upstream/downstream) for concentric orifice plate flow meters, other meters include conditioning orifice plate (14/2); venturi meters (22/8); and wedge meters, which are primarily used for highly viscous fluid (10/5).

Weight savings from the elimination of excess straight-run piping is an additional benefit in some situations, such as offshore platforms.

In addition to fitting in more compact spaces, McCrometer’s V-Cone can accommodate a larger turndown ratio than most competing technologies — 10:1 or better — when enough differential pressure is available. This is ideal for users experiencing wide variations, such as colleges and universities, which want to accurately track and internally bill for steam usage in each of their buildings.

School administrators tend to encounter issues when trying to measure steam usage during the low-demand summer months. Common vortex meters work well at higher flows, but when it comes to low flows, they can stop working completely. Differential pressure flow meters coupled with the proper electronics, by comparison, can push the low flow cutoff value downward. However, most differential pressure meters don’t have the ability to get around the straight-run requirements like the V-Cone does.

Behind The Technology

McCrometer’s V-Cone flow meter is customizable and can accommodate both high-pressure and large flows. This is a big deal for the water and wastewater industry, where customers may need a meter for lines as wide as 120”. In certain applications, the V-Cone can withstand pressures up to 15,000 psi.

Other specifications include up to 0.5 percent accuracy (some applications require outside calibration to reach this level) with a wet gas accuracy of up to 2.0 percent; 25-year life span with no maintenance; little to no pressure loss; and the ability to measure wet gas when the gas volume fraction is 90 percent or higher, at a significantly lower cost than a multiphase meter.

V-Cone flow meters aren’t an off-the-shelf product. McCrometer’s engineering experience is critical to walking customers through whatever project they are working on to create the proper solution.

The technology has been in use for more than 30 years, but a relatively recent development addresses the impact of vibrations on signals in larger meters. McCrometer redesigned meters 18” and larger with six pipe supports (three upstream and three downstream) to provide more stability. This also allows for multiple tapping points for redundancy measurements, a requirement in some systems.

To accommodate smaller sizes — 1” to 6” lines — McCrometer offers the V-Cone technology in its Wafer-Cone® flow meter. This product is installed between two flanges, similar to an orifice plate flow meter, and is ideal for tight-space installations and retrofits.

The Wafer-Cone flow meter is not as customizable because it’s a screw-in solution, as opposed to a standard V-Cone meter that’s welded in place. However, the Wafer-Cone can easily be swapped out for other meters to account for varying flows and turndown needs.

Because of their minimal straight run pipe specifications, McCrometer’s V-Cone flow meters provide a strong alternative for operators faced with space and weight constraints to take highly-accurate measurements.

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