An orifice plate is normally mounted -----

An orifice plate is typically mounted between two flanges because this configuration allows for the proper integration of the orifice into a pipeline system where it can accurately measure the flow rate of fluid passing through. The flanges secure the plate in place and create a tight seal that minimizes leaks and ensures that all fluid flows through the orifice. This is crucial for maintaining the precision of flow measurements, as any bypass or leakage can significantly affect the accuracy of the readings.

Mounting the orifice plate in this manner also facilitates ease of maintenance and replacement since it can be removed simply by unbolting the flanges. This setup is essential in various applications, such as in processing plants and water distribution systems, where flow measurement is required for monitoring and control purposes.

Other options might suggest different mounting or usage scenarios but do not reflect the standard application and installation practices for an orifice plate in flow measurement systems within a pipeline.