How to Specify an Orifice Plate ~ Learning Instrumentation And Control Engineering Learning Instrumentation And Control Engineering

How to Specify an Orifice Plate

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Orifice plates are commonly used in flow measurement applications. After prolonged use, there may be need to order a new orifice plate to replace the one in service. In most industrial applications for large flow measurement, the orifice plate is often contained in a dual orifice chamber fitting and is usually replaced online in these types of fittings. In flange types, the orifice plate is sandwiched between flanges. The main reason for replacing an orifice plate is often due to deterioration and corrosion in service. Therefore to order a new orifice plate, the following specification checklist tabulated below should be handy so that mistakes are not made in the ordering process:

Specifications Description

Type or Tag Number

Different manufacturers have their own unique type or tag numbers. You should be familiar with that of the orifice plate manufacturer. Commonly this number is stamped on one side of the orifice plate.
Line Size This is the size of the line where the orifice plate is to be used

ANSI Flange Pressure Rating
Specify the pressure rating of the system where the orifice plate is to be used e.g. is it class 150, 300, 600 etc

Material of Construction
Specify the material of construction of the orifice plate. orifice plates are manufactured in different materials. You should know the exact material of construction of the orifice plate you are replacing as this borders on service conditions – erosion, corrosion etc. Common materials of manufacturer include Carbon Steel or Stainless Steel. There are also variations of other alloys.

Quantiy
Specify the quantity of orifice plates required for your application

Orifice Bore Type
Specify whether it is, square edge, concentric, quadrant edge, eccentric edge, or segmental.

Orifice Plate Outer Diameter (OD)
Specify the outer diameter (OD) of the orifice plate in inches

Orifice Plate Thickness
Specify the orifice plate thickness in inches or mm

Other items that could be ordered in conjunction with the Orifice plates include plate holders and various forms of seal rings and seals.

Typical Thickness of Orifice Plates for Different Line Sizes:


Line Size, DN (mm) Orifice Plate Thickness (mm)
< 150 3.18
> 200 < 400 6.125
> 400 9.53