throttling orifice plate

It has nothing to do with valves; the function of a flow control orifice plate is to limit flow and pressure, depending on the requirements of the process environment – it is unrelated to valves

Throttle orifice plates have nothing to do with valves. Whether they are needed depends entirely on the requirements of the process and the equipment. Here are a few simple examples: For centrifugal pumps, a minimum flow rate requirement exists, which necessitates the use of throttle orifice plates; these can be installed either before or after the valve – this is a requirement inherent in centrifugal pump design. In pipelines for introducing nitrogen, throttle orifice plates are sometimes used to prevent problems arising from overly large valves that could make regulation difficult and lead to fluctuations in the process. Throttle orifice plates are also used in pressure relief pipelines to control the rate at which pressure is released; this is again a requirement dictated by the process. As for other applications, whether such orifice plates are used depends on the requirements of the process and the equipment, and it has no connection to valves

Generally behind the valve. . . Any place where it is easy to empty the system and remove it will do. . .

Valves do not require flow-limiting orifice plates; the function of such devices is to limit both flow rate and pressure, and they are commonly used in pump return lines or circulation pipelines in towers