Flow Measurement

What is orifice meter and what is the use of orifice meter

What is orifice meter and what is the use of orifice meter

An orifice meter is a device that can measure the flow rate in a pipe by using an orifice plate. It can measure volumetric flow rates, this measuring device operates on the same principle as venturi meter which is Bernoulli’s principle and the principle states that the pressure and velocity of the fluid are related, like if the velocity increases then the pressure will decrease and vice versa. The measurement is done with the help of an orifice plate it can reduce or restrict the flow. The orifice plate will be inserted between the two pipe flanges and proper pressure connection is done too. Orifice plates are used for a wide range of applications of fluid and operating conditions. It is economical and doesn’t need regular maintenance.

How orifice meter is constructed and how does it work

The fluid flow in the pipeline can be measured by using orifice meter, the orifice plate is a thin plate and it has a hole in its center and it will be inserted between two pipe flanges. In order to process the flow, it will be installed perpendicularly. This device is very easy to construct, install, and replace in case of damage. The liquid that flows through the pipe would reach the orifice meter and when it flows through the orifice plate the pressure is reduced and velocity will increase when it enters the vena contracta when the flow continues and reaches beyond the vena contracta then the velocity and pressure would change again. By using differential pressure measuring instruments this drop in pressure is measured. The volumetric and mass flow rate can be checked by measuring the difference in fluid pressure between the pipe section and at the vena-contracta

What are the parts of orifice meter

Orifice plate – These are metal plates that have an equal diameter of the pipeline with a drilled hole in it that reduces the flow rate so that the pressure can be reduced

Inlet – this is where the fluid enters from the pipeline and the change velocity and pressure happens here

Overflow pipe – It would prevent the overflow of the glass cylinder

Flow dissipator – this is the place that we can see orifice plate, flow dissipation is done by the taps and thus pressure changes

Outlet – It is the place where the fluid exits the device

Pitot tube – it measures the pressure drop

Manometer – scale within the pilot tube

What are the types of orifice meters

Concentric square edged

This type of orifice meter is mostly used for the measurement of the flow of the clean liquids, gases, and low-velocity vapor flows. It has a sharp square-edged hole bored in a flat thin plate. This type is used for restricting flow and to reduce the pressure. If this type of meter is installed properly then high accuracy can be achieved.

Segmental orifice meter

This type is mostly used in the place where there substantial entrained water or air and also in place where suspension in the fluids. This would avoid the build-up in front of the orifice plate. This type is used for slurries and extremely dirty gases

Eccentric Orifice meter

In eccentric orifice, it doesn’t have the flow opening in the center of the plate. This type is mostly used to measure fluids that carry a small amount of non-abrasive solids. This type is mostly used in many chemical industries.

Quadrant edge orifice

This type of orifice is mostly used for fluids that have high viscosity. The inlet is a quarter of a circle and the plate thickness will be at least radius of the inlet.

What are the advantages of orifice meter

  • Low cost and simple construction
  • Easily installed
  • Regular maintenance is not needed
  • Easy replacement
  • There are no moving parts
  • It is capable to measure gases or liquids with high accuracy
  • It is available in any sizes
  • It would only occupy a small space
  • They have low range capacity

What are the disadvantages of orifice meter

  • The power consumption of this meter is high because of the high frictional loss
  • It cannot be used for dirty fluids, slurries, and wet steam
  • The process line is affected in the impulse line, the potential of freezing and plugging
  • Its accuracy will be affected by changes in the temperature, viscosity, and density
  • The measuring range is limited by fluid viscosity
  • Pressure loss and clogging
  • Downstream pressure recovery is very poor
  • The chances of plate corroding are high and it can cause inaccuracy

What are the applications of orifice meter

  • Fluid flow rates in a pipe can be measured
  • It is used in natural gas plants and water treatment plants
  • Petrochemicals and refineries
  • It is used in the oil filtration plant


post-graduate in Electronics & communication.

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