Flow monitoring solution for abrasive slurries with low Reynolds Numbers
While most flow metering instruments face challenges in high viscosity or abrasive processes, the design of wedge meters offer a number of operational advantages. The slanted upstream face of the restrictor helps to protect against erosion caused by any undissolved solids in the fluid being measured. The large opening beneath the restrictor enables any secondary phase material to easily pass through rather than building up on the restriction. The formation of eddies and back currents in the flow helps to effectively scour the internals, keeping them clean. Thanks to the unique shape of the wedge restriction, wedge meters can offer linear and accurate flow rates down to a Reynolds Number of 500.
The basic operating principle behind a wedge meter is straightforward. A V-shaped restrictor in the flowmeter body reduces the available flow area, constricting the flow. This constriction increases the fluid velocity, causing a corresponding increase in the kinetic energy of the fluid being measured.
As per the conservation of energy principle, the increase in kinetic energy will see a corresponding decrease in potential energy, or the static pressure. When this happens, the fluid upstream of the restrictor will have a greater potential energy, and a higher static pressure, than the fluid downstream.
Placing pressure taps either side of the wedge meter enables us to measure the difference in pressure which can be used to directly calculate the flow rate.
The inherent benefits of wedge meters enable them to outperform other types of DP flowmeters and make them a versatile solution for a wide range of applications, as shown above: They are particularly ideal for applications such as:
- Liquids with low electrical conductivity
- Viscous and non-Newtonian liquids
- Processes with high operating pressures and/or high operating temperatures
- Bi-directional flow measurement
- CO2 or water injection to revitalize existing oil and/or natural gas fields
- Measuring media prone to agglomeration and gum formation
The ideal configuration of a wedge meter installation is shown below:
By mounting the installation horizontally, liquids, solids and entrained air are able to pass freely through the wedge restriction, in contrast to conventional orifice plate technology, where process material can build up on the measurement face, resulting in a 'damming' effect.
This article is an excerpt from a petro-online.com Publication - "Making the case for wedge flow measurement" by Steve Gorvett
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