Wafer-Cone Flow Meter Offers High Accuracy For Natural Gas Small Line Wellhead Measurement
October 3, 2016
Engineers in search of a reliable solution for wellhead gas flow measurement will find that the flexible Wafer-Cone® Flow Meter from McCrometer provides good accuracy, versatility and low maintenance in the smaller line sizes utilized for natural gas wells.
Measurement of wellhead gas flow can pose a challenge for process engineers. To ensure accuracy, the flow meter needs to be installed as closely as possible to the wellhead. This presents two challenges including high or low flow velocities, and the need for a significant length of straight-running pipe. Unlike most flow meters that require a straight pipe run of 10 or more diameters upstream from the meter and 0-5 diameters downstream, the Wafer-Cone is designed in such a way that only 1-3 upstream diameters and 0-1 downstream diameters of straight-run are necessary. The Wafer-Cone preconditions the flow profile to pass the cone in a uniform pattern, leading to extremely precise gas flow readings without long straight pipe runs.
The space-saving, field-proven Wafer-Cone Flow Meter is easy to install and requires virtually no maintenance. The Wafer-Cone’s low maintenance combined with its long life results in lower total installation and life-cycle costs than many other flow meters. Its ability to self-condition flow is a real space-saver compared to 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 initial cost savings.
The Wafer-Cone is designed for gas or liquid service in line sizes from 1 to 6 inches--ideal for natural gas wellheads, small process lines and many other plant infrastructure tasks. Other applications include burners or ovens, cooling systems, HVAC and more. McCrometer’s advanced Wafer-Cone Flow Meter relies on differential pressure sensing technology and raises the bar for economy, ease of use and performance. Its unique DP flow sensing technology is actually designed with built-in flow conditioning to achieve an accuracy of ±1.0%, with a repeatability of ±0.1%. It operates over a flow range of 10:1.
The Wafer-Cone Flow Meter’s design is inherently more accurate within a shortened pipe run than traditional DP instruments 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 that increases accuracy. The flow sensor‘s design features a centrally-located cone inside a tube, which 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, can be 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 and forms very short vortices as the flow passes the cone. These short vortices create a low amplitude, high frequency signal for excellent signal stability, resulting in a highly stable flow profile that is repeatable for continuous accurate measurement.