The orifice is usually mounted between a pair of flanges. Care should be exercised when installing the orifice plate to be sure that the gaskets are trimmed and installed such that they do not protrude across the face of the orifice plate beyond the inside pipe wall (Figure 2.15o). A variety of special devices are commercially available for mounting orifice plates, including units that allow the orifice plate to be inserted and removed from a flowline without interrupting the flow (Figure 2.15p). Such manually operated or motorized orifice fittings can also be used to change the