ORIFICE PLATE

The simplest pipe line restriction for flow metering is the orifice plate, which is a thin, circular metal plate with a hole in it. Its hold in the pipe line between two flanges called orifice flanges. The pressure below the orifice less then above the orifice, this difference in pressure is a measure of the rate of flow.

There are four types of orifice plate.

(1) Concentric orifice plate

(2) Eccentric orifice plate

(3) Segmental orifice plate

(4) Quadrant orifice plate

                        CONSENTRIC ORIFICE PLATE:- it is usually made of stainless steel and it’s thickness varies from 3.175 to 12.7mm (⅛” to ½”) depending on pipe line size. It has a circular hole in the middle. It is also made from other material such as nickel, monel, phosphor bronze. Use for liquid, gas and stem service.

                  ECCENTRIC ORIFICE PLATE:- The eccentric orifice plate has a circular hole located below its center. Used for viscous and slurry flow measurement.

                        SEGMENTAL ORIFICE PLATE:- The segmental orifice plate has a hole that is only partly circular located below it center. Used for viscous and slurry flow measurement.

                        QUADRANT ORIFICE PLATE:- This type of orifice plate is used for flows such as heavy crudes and slurries and viscous flows.

ADVANTAGES OF ORIFICE PLATE

Ø It’s cost low.

Ø They can be used in wide range of pipe size (3.175 to 1828.8mm).

Ø They can be used with differential pressure device.

Ø They are well known and have good characteristics.

Ø They are available in many materials.

The orifice plate is provide:-

1.       Indication of orifice plate in the line.

2.       Orifice diameter marked on it.

3.       The material of orifice plate.

4.       The tag number of orifice plate.

5.       The marked the inlet of orifice plate.

Guide lines for the installation of orifice plate

1.     Confirm the location of the orifice carrier (orifice flange) from P & I.

2.     Confirm the tag number to service using P & ID.

3.     Confirm the flow direction.

4.     Ensure HP tapping of DP transmitter is on the upstream (inlet) of orifice flange.

            Don’t assume transmitter is installed correctly.

5.     Checked the orifice plate for any signs of damage.

6.     Installed the orifice plate between two new spiral wound (metal flex) gasket.

For orifice plate in nonvertical (Horizontal) line

1.     Tab to point down for liquid service.

2.     Tab to point up for gas service.

3.     Text on tab to face upstream (inlet).

Orifice plate in vertical line

1.     Have no drain hole.

2.     Orifice plate is horizontal line must have a drain hole.

3.     Hole is at the bottom in stem and wet gas line.

4.     Hole is at the top for liquid service.