Orifice Meter Introduction | Orifice Meter Working Principle |Orifice Meter Application | Orifice Meter Types | Orifice Meter Formula

Introduction: -

Orifice Meter

An orifice meter is a device used to measure the flow rate of a fluid through a pipe by creating a pressure differential across a constriction within the pipe, usually in the form of a thin plate with a hole in the center. As the fluid flows through the orifice, the pressure drops, and the flow rate can be calculated using Bernoulli's equation and the orifice's known characteristics. Orifice meters are commonly used in industrial applications, such as oil and gas pipelines, to monitor and control the flow of liquids and gases.

Orifice Meter Working Principle: -

Orifice Meter

An orifice meter is a device used to measure the flow rate of a fluid in a pipeline. It relies on a principle known as the Bernoulli's principle, which states that the pressure of a fluid decreases as the velocity of the fluid increases. 

The orifice meter consists of a plate with a circular hole in the middle, called an orifice plate. The orifice plate is placed perpendicular to the flow of the fluid in the pipeline, causing the fluid to flow through the orifice and creating a pressure drop across the plate.

There are two pressure taps, one upstream and one downstream of the orifice plate, connected to a differential pressure gauge, which measures the pressure difference between the two taps. The gauge converts the differential pressure to a flow rate using a calibrated scale or formula.

The orifice meter principle is based on the understanding that the pressure drop across the orifice plate is proportional to the square of the flow rate, which can be calculated using the following equation:

Q = A * Co * sqrt(2g * h)

where Q is the flow rate, A is the area of the orifice plate, Co is the discharge coefficient (an empirical factor that depends on the shape of the orifice and the velocity of the fluid), g is the acceleration due to gravity, and h is the differential pressure. 

Overall, the orifice meter is a simple and inexpensive way to measure the flow rate of fluids in pipelines and is widely used in industries such as oil and gas, water treatment, and chemical processing.

Orifice Meter Application: -

An orifice meter is a flow meter used to measure the flow rate of a fluid in a pipe. It works by creating a constriction in the pipe, which causes the fluid to flow through a small opening called an orifice plate. The pressure difference between the upstream and downstream sides of the orifice plate is measured, and this pressure difference is used to calculate the flow rate of the fluid.

Orifice meters are commonly used in the oil and gas industry to measure the flow rate of natural gas, oil, and other fluids. They are also used in the chemical, petrochemical, and water treatment industries.

Some of the uses of orifice meters include:

1. Measuring the flow rate of natural gas in pipelines

2. Monitoring the flow rate of oil in pipelines

3. Measuring the flow rate of water in treatment plants

4. Controlling the flow rate of steam in power plants

5. Monitoring the flow rate of chemicals in manufacturing processes.

Orifice Meter Types: -

There are several types of orifice meters:

1. Concentric orifice meter: This is the most common type of orifice meter, where the orifice plate has a sharp-edged circular hole that is concentric with the pipe.

2. Segmental orifice meter: In this type of orifice meter, the orifice plate has a segmental cut-out, with the two edges making contact with the pipe. This type of orifice meter is useful for measuring high flow rates and abrasive fluids.

3. Eccentric orifice meter: This meter has an off-center orifice plate, which allows for the measurement of fluid flow in a pipe that may contain solids or debris.

4. Quadrant edge orifice meter: This meter has an orifice plate with a raised, quadrant-shaped edge that reduces turbulence in the fluid flow, allowing for more precise measurements.

5. Differential pressure flow meter: This type of orifice meter uses a differential pressure gauge to measure the pressure drop across the orifice plate, which can be used to calculate the flow rate of the fluid.

Differential pressure flow meter

Orifice Meter Formula: -

1. Discharge coefficient (Cd) formula:

Cd = (D/d)^2 * ((0.5961 + 0.0261 * Re^(0.8)) / (1 + 0.42 * (D/d)^1.5 * (1.35/Re)^0.5))

Where, D = diameter of orifice plate

d = diameter of upstream pipe

Re = Reynolds number

2. Velocity of fluid (v) formula:

v = (Q / Cd) / (A * sqrt(2 * g))

Where, Q = volumetric flow rate

Cd = discharge coefficient

A = area of orifice

g = acceleration due to gravity

3. Pressure drop (ΔP) formula:

ΔP = β * ρ * v^2 / 2

Where, β = orifice plate factor

ρ = density of fluid

v = velocity of fluid

4. Orifice plate factor (β) formula:

β = 0.595 + 0.026 * (Re^(0.2)) * (d/D)^2

Where, D = diameter of orifice plate

d = diameter of upstream pipe

Re = Reynolds number

Orifice Meter Uses

1. Measuring the flow rate of natural gas in pipelines

2. Monitoring the flow rate of oil in pipelines

3. Measuring the flow rate of water in treatment plants

4. Controlling the flow rate of steam in power plants

5. Monitoring the flow rate of chemicals in manufacturing processes.

Orifice Meter Advantages and Disadvantages

Advantages of Orifice meter:

1.The Orifice is small plates and easy to install/remove.
2.Offer very little pressure drop from which 60% to 65% is recovered.
3.The orifice meter can be easily maintained.
4.Measures a wide range of flows.

5.They have a simple construction.

6.They have easily fitted between the flanges.

7.They are the most suitable for most gases and liquids.

8.They are cheap, The price does not increase dramatically with size.

Disadvantages of orifice meter:

1.Requires homogeneous fluid.
2.Requires single phase liquid
3.It requires the flow of axial velocity vectors.
4.It causes a pressure drop in the fluid.
5.Its accuracy is affected by the density, pressure and viscosity of the fluid.
6.The range of measurement of viscosity limits of fluids.
7.It requires straight conduits to ensure accuracy is maintained.
8.The pipe must be totally special for the measurement of the flow of liquids.
9.They have low range capacity.

Que. Orifice Meter Working Principle

Ans - It works on the Differential Pressure Measurement principle. The liquid or gas whose flow rate is to be determined is passed through the orifice plate. This creates a pressure drop across the orifice plate which varies with the flow rate, resulting in a differential pressure between the outlet and inlet segments.

Que. What are the industrial uses of orifice meter?

Ans - 1. It is used to measure the flow rate of fluids in their single state.

2.It can also be used to measure the flow rate of fluids in a mixed state such as, wet steam, or natural gas with water.