An orifice flange is a type of flange that is designed to measure the flow rate of a fluid through a pipe. It has a concentric or eccentric bore that contains an orifice plate, which creates a restriction in the flow path. By measuring the pressure drop across the orifice plate, the flow rate of the fluid can be calculated.

Orifice flanges are commonly used in process industries such as oil and gas, chemical, and petrochemical, where accurate flow measurement is critical for process control and optimization. They are available in a variety of materials, including carbon steel, stainless steel, and alloy steel, and can be designed for both standard and high-pressure applications.

Orifice flanges are typically used in combination with a differential pressure transmitter, which measures the pressure drop across the orifice plate and calculates the flow rate of the fluid. The transmitter is connected to a control system that adjusts the flow rate to maintain the desired process conditions.

One advantage of orifice flanges is that they provide accurate flow measurement with a relatively simple and inexpensive design. However, they can cause a significant pressure drop in the piping system, which can affect the overall efficiency of the process. The orifice plate also needs to be carefully sized and installed to ensure accurate measurement.