The PFS WedgeTypeTM Flow Meter

A flow metering solution for harsh service, highly viscous, slurry type, or contaminated line fluid applications


In line sizes from 0.5" through any larger size, a wedge type flow meter is a differential producer design that is generally used for difficult-to-meter line fluids, such as air entrained liquid, particulate entrained, high viscosity or slurry type. Examples of possible applications include but are not limited to abrasive or fibrous slurry such as raw sewage, sludge, tar sand, pulp mash, cement, liquid asphalt and molten sulphur. Relatively low pipe Reynolds Numbers can be addressed with some accuracy and the discharge coefficient is stable through the application range.


Accuracy, reliability and head loss characteristics are not as good as those available utilizing the PFS HVT (Halmi Venturi Meter) product lines. However, if highly viscous, particulate-laden flows and low acquisition cost is of highest priority to the exclusion of the other factors, the PFS-WM WedgeType™ flow meter can be a metering option worth consideration.


When your application requirements dictate the use of PFS WedgeType™ flow meters, Primary Flow Signal can provide expert technical assistance estimating bore size, differentials and flow rates coupled with high quality and economically priced units to best fit your needs. If you have particular requirements that do not appear in our standard offerings, we will gladly design and manufacture to your specific needs.


Design and operation information:
The basic system consists of a cylindrical pressure vessel into which a constriction wedge is fabricated thereby leaving an open segment of a known height. Pressure taps that receive the sealed sensors (extended or chemical tee, depending on design) on either side of the wedge provide the differential signal to the PFS Flow Transmitter that is then related, by formula, to the rate of flow occurring through the open segment.


For critical applications where redundant flow readings are required, PFS offers a wide variety of multiple secondary instrument tapping solutions.


Since no relationship of geometric similitude exists between designs of varying line sizes, no manufacturer can reliably state a general accuracy, and 2 Sigma confidence is not applicable. All PFS WedgeType™ flow meters are wet calibrated in the intended application flow range in order to provide +/- 0.50% of coefficient accuracy for the calibrated range when required.


Materials of construction:
The PFS-WedgeType™ design can be produced using a wide variety of materials depending upon the particular demands of the application. Typical materials selection, however, may include carbon steel, 304 and 316 stainless steel, Monel, Hastelloy, or PVC for chlorine and similar chemical applications. The sealed sensor assemblies are of 316 stainless steel with armored capillary conduits containing various fill fluid depending on the intended service.


Flow calculation theory:
Line fluid is forced downward similar to a segmental orifice plate, but is guided along a sloping wedge shape rather than a sharp edge. Pressure taps are located upstream and downstream of the wedge and in most cases are equipped with sealed sensors. The differential produced by the device is a function of the ratio between the wedge segment opening, H, and the diameter of the body, D.