Differential Pressure Devices using a constriction in the pipeline have been the most common technique used for measuring fluid flow until the development of more advanced methods like use of non-contact Ultrasonic or Coriolis Technologies. Even with the development of these modern methods, differential pressure is still widely used technique. A constriction causes an increase in fluid velocity in the area of the constriction, which in turn will result, in a corresponding pressure drop across the constriction. This differential pressure (d.p) is a function of the flow velocity and density of the fluid.
A flowmeter in this category would normally comprise a primary element to develop a differential pressure and a secondary element to measure it. The secondary element is effectively a pressure transducer. There are various types of primary elements. The main types includes: Orifice plate, Venturi, Dall, Rotameter, Gate meter, V-Cone, Nozzle, Target Meter and Giflo Element. In this article we look at Orifice Plate.
Orifice Plate
A orifice plate in its simplest form is a thin steel plate with a circular orifice of known dimensions located centrally in the plate. This is termed a concentric orifice plate.The plate would normally be clamped between adjacent flange fittings in a pipeline, a vent hole and drain hole being provided to prevent solids building up and gas pockets developing in the system.
The differential Pressure is measured by suitably located pressure tapping on the pipeline on either side of the orifice plate. These may be located in various positions depending on the applications
A flowmeter in this category would normally comprise a primary element to develop a differential pressure and a secondary element to measure it. The secondary element is effectively a pressure transducer. There are various types of primary elements. The main types includes: Orifice plate, Venturi, Dall, Rotameter, Gate meter, V-Cone, Nozzle, Target Meter and Giflo Element. In this article we look at Orifice Plate.
Orifice Plate
A orifice plate in its simplest form is a thin steel plate with a circular orifice of known dimensions located centrally in the plate. This is termed a concentric orifice plate.The plate would normally be clamped between adjacent flange fittings in a pipeline, a vent hole and drain hole being provided to prevent solids building up and gas pockets developing in the system.
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Advantages of using Orifice Plates
- Inherent Simple in
- No moving parts
- Long-term reliability
- Inexpensive
Disadvantages of using Orifice Plates
- Poor turndown ratio
- Square root relationship
- Critical Installation requirements
- High irrecoverable pressure loss
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