ORIFICE PLATE
Orifice plates are one of the most popular devices for the measurement and control of fluid flow. It is frequently used more than any other flow meter. The orifice consists of a thin metal plate with a straight hole drilled in it. When a fluid passes through an orifice, the flow is often less than the amount calculated. The assumption is that the energy is conserved and the flow distributing through the orifice is uniform and parallel.
Orifice Plates are normally mounted between a set of Orifice Flanges and are installed in a straight run of smooth pipe to avoid disturbance of flow patterns from fittings and valves.
Orifice plates cover a wide range of applications including fluid and other operating conditions. They give an acceptable level of uncertainties at lowest cost and long life without regular maintenance.
Types of Orifice plate
- Concentric Bore
- Eccentric Bore
- Segmental Bore
- Quadrant Edge Bore
Concentric Bore and Quadrant Edge Bore - Difference
The difference between a square edge orifice plate and a quadrant edge orifice plate is in the proximity of the specified bore to the upstream face, as shown in the figure.
On a square edge plate the measuring bore is at 90 degrees to the upstream face.
On a quadrant edge plate the inlet edge is rounded to the shape of a quarter circle (hence the name quadrant edge), and the throat of the bore is a small distance from the upstream face.
Orifice Plate Installation
Orifice Plates are normally mounted between a set of "Orifice Flanges".
Orifice flanges differ from normal flanges in that they have an integral pipe tap and jack screw point.
An orifice that uses pressure taps integral to the flange is said to have "flange taps".
The radial pipe tap from the upstream and downstream flange are connected to the differential pressure transmitter used to determine pressure drop across the flange.
The jack screws are used to spread the flanges apart to allow change out of the orifice plate. Often only one of the mating flanges will have a jack screw