Precise Flow Measurement In Wet Gas With Self-Conditioning Flow Meter

Process and plant engineers in rugged industries who must frequently measure various hydrocarbon-based gases with wet particulates will find the Wafer-Cone^® Flow Meter from McCrometer (USA) features a unique self-conditioning design that achieves superior flow measurement accuracy in small line sizes.

The Wafer-Cone Flow Meter is ideal for industrial process and plant applications, including coal-bed methane gas extraction.   The process of extracting this gas typically includes water within the gas seam in the coal bed, which results in a wet gas with tiny water particulates that are difficult to measure accurately.

McCrometer’s innovative Wafer-Cone Flow Meter solves this problem. It relies on differential pressure technology with built-in flow conditioning and achieves flow measurement accuracy of ±1% or better, with a repeatability of ±0.1% in gas, liquid or steam applications, including coal-bed methane recovery.  

The Wafer-Cone Flow Meter operates over a turndown range of 10:1. It is designed for service in small process line sizes from 0.5 to 6 inches, which makes it ideal for a wide range of other industrial applications, such as conventional natural gas wells, chemical refining, as well as industrial waste treatment and even landfill applications where biogas is frequently present and may be utilized for electric power co-generation purposes. 

With the ability to self-condition flow, the Wafer-Cone Flow Meter is a real space-saver too. It eliminates the need for extensive up/down stream straight pipe runs required by other DP technologies, such as orifice plates and venturi tubes. It can be installed virtually anywhere in a piping system or be easily retrofit into an existing piping layout, resulting in significant installation flexibility and in new installation initial cost savings.

Unlike traditional DP instruments such as orifice plates and Venturi tubes, the Wafer-Cone Flow Meter’s design is inherently more accurate because the flow conditioning function is built-into the basic flow sensor design. The Wafer-Cone conditions fluid flow to provide a stable flow profile with high signal stability that increases accuracy. The flow sensor‘s design features a centrally-located cone inside a tube. The cone interacts with the fluid flow and reshapes the velocity profile to create a lower pressure region immediately downstream. 

The pressure difference, which is exhibited between the static line pressure and the low pressure created downstream of the cone, is measured via two pressure sensing taps. One tap is placed slightly upstream of the cone and the other is located downstream of the cone. 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 that is repeatable for continuous accurate measurement. All of this is possible with a minimal straight pipe run of 0 to 3 diameters upstream and 0 to 1 diameters downstream from the flow meter.

The field-proven Wafer-Cone is an easy to install space-saving flow meter that requires almost no maintenance. Wafer-Cone’s low maintenance combined with its long life results in lower total installation and life-cycle costs than many other flow meters.