An Introduction To An Orifice Meter

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1. Introduction
An Orifice Meter is a type of flow meter used to measure the rate of flow of Liquid in form of steam, using the Differential Pressure Measurement principle. It is used for robust applications as it is known for its durability and is economical. It consists of an Orifice Plate which is the basic element of the instrument. A differential pressure drop is developed across the Orifice Plate which is linear and is in direct proportion to the flow-rate of the liquid. Since there is a drop in pressure it is used where a drop in pressure or head loss is permissible.
An orifice is an opening of a specific dimension removed from the head (orifice plate) which can be characterised by its shape or type of edge in the side/ base of a
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Best results occur between value of 0.4 and 0.6. beta ratio means ratio of the orifice bore to the internal pipe diameters. Fig 1.1 Concentric plates
Concentric plates are the one used majority of time because of its symmetric shape and size.
1.1.2. Eccentric
The eccentric orifice plate has a hole eccentric. It is useful for measuring containing solids, oil containing water and wet steam. Eccentric plates can use either flange or vena contracta taps, but the tap must be at 180º or 90º to the eccentric opening. Fig 1.2 Eccentric plates
Eccentric orifices have the bore offset from centre to minimize problems in services of solids-containing materials.
1.1.3. Segmental
The segmental orifice place has the hole in the form segment of a circle. This is used for colloidal and slurry flow measurement. For best accuracy, the tap location should be 180º from the centre of tangency. Fig 1.3 Segmental plates
Segmental orifices provide another version of plates useful for solids containing materials.
1.1.4. Quadrant edge
It is commonly used in Europe and are particularly useful for pipe sizes less than 2 inches. Fig 1.4 Quadrant edge plates
Quadrant edge orifices produce a relatively constant coefficient of discharge for services with low Reynolds numbers in the range from 100,000 down to 5,000.

1.2. Advantages of Orifice meter
1. The Orifice meter is economical and accurate.
2. Less space is
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