Segmental orifice plate

Segmented orifice plates, 77 657-658 Segmented polyurethanes, as biomaterials, 23 722... 

Eccentric orifice plates shift the edge of the orifice to the inside of the pipe wall. This design also prevents upstream damming and is used in the same way as the segmental orifice plate. 

For liquids with entrained gas or vapor, a "vent hole" should be provided, and for gases with entrained liquid, a "drain hole." Meters for liquid with entrained gas or gas with entrained liquid services should be installed vertically. Normally, the flow direction would be upward for liquids and downward for gases. The use of vent and drain holes is discouraged, if in order to keep them from plugging, the holes would need to be large and would adversely affect accuracy. On severe entrainment applications, eccentric or segmental orifice plates should be used. 

Fig. 6. Orifice plates (a) concentric, (b) eccentric, (c) segmental, (d) universal, and (e) quadrant-edge.

Orifice plates. Either the concentric orifice, eccentric orifice, or segmented orifice-type. Choice depends on the quality of the fluid handled. Venturi tubes. These consist of a well-rounded convergent section at the entrance, a throat of constant diameter, and a divergent section. Their accuracy is high however, installation, unless planned for in advance, is very difficult in the field. 

The holes in orifice plates may be concentric, eccentric or segmental as shown in Figure 8.3. Orifice plates are prone to damage by erosion. 

Three kinds of orifice plates are used concentric, eccentric, and segmental (as shown in Figure... 

Segmental and eccentric orifice plates are functionally identical to the concentric orifice. The circular section of the segmental orifice is concentric with the pipe. The segmental portion of the orifice eliminates damming of foreign materials on the upstream side of the orifice when mounted in a horizontal pipe. Depending on the type of fluid, the segmental section is placed on either the top or bottom of the horizontal pipe to increase the accuracy of the measurement. 

Orifices can be used in a wide range of applications because these plates are available in a variety of materials and in many designs, such as concentric, segmental, or eccentric. Another advantage is that the orifice plate can be badly worn out or damaged, and yet will still provide a reasonably repeat-able output, albeit significantly inaccurate. Yet another very convenient feature of the orifice-type installation is the possibility to service or replace the readout or transmitter without the need to remove the orifice or to interrupt the process flow. 

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