Flow Orifice Meter

It is common to estimate the flow rates of clean liquids, gases, and streams using differential pressure flow instruments of the Flow Orifice Meter variety. For monitoring fluid flows in bigger pipes, it is easily accessible for all pipe diameters and quite affordable if the pressure drop it needs is free, around 6″ inches in diameter. For the transfer of possession of both liquids and gases, the orifice plate has also been given the thumbs-up by numerous standards adopted. Although many regulatory agencies are attempting to create a single, internationally accepted flow measurement solution, the flow measurement models used today—which use the Bernoulli Equation—remain distinct. The user can typically choose the ideal flow rate from various options in orifice sizing software. This article gives you all the valuable details you might want to know about the design, operation, and many other aspects of a Flow Orifice Metre.

Basic Orifice Meter Principle

The fluid or gas whose flow velocity needs to be measured passes through the orifice plate. Due to the pressure loss throughout the orifice plate that is caused by this and changes depending on the flow rate, there is a difference in pressure between the inlet and output segments.

Orifice Plates/Meters Are Used For What Purpose?

flow orifice meter

An orifice plate often referred to as a restriction plate, is an instrument used to measure flow rate, lower pressure, or limit flow. A pressure gauge meter widely used to measure natural gas is the orifice plate (also known as an orifice meter). However, based on the device’s calculations, it can also compute mass flow when measuring volume flow rate. It uses the Bernoulli equation, the same as a Venture-style meter, to imply a connection between the fluid’s velocity and pressure. As velocity rises, the pressure falls, according to this connection. The flow orifice meter can calculate the flow by comparing the pressure differences on the sides upstream and downstream of a partially obstructed pipe.

Different Forms Of Orifice Fitting

Following are the three primary categories of plugs:

· Solitary  Chamber.

As the name implies, it comprises one chamber made specifically for accurately measuring fluids or gaseous’ fluid velocity.

· Two Chambers

It comes with O-ring seals and is put alongside the downstream and upstream parts, solving the issue of maintaining the product covering. A valve seal is furthermore offered for double chamber orifice installation.

· Block twice and flow 

Two valves for various chambers are included, which improves operational safety. It also ensures the equipment’s durability and protects against harmful liquids.

Construction Of Flow Orifice Meter

· Inlet Section

The sequential piece that extends from the instrument, known as the inlet section, serves as the primary connector for the fluid moving within.

· Aspirator Plate

The orifice plate is positioned between the inlet and exit, and it is utilized to create a pressure difference that will allow the flow velocity and mass flow monitoring.

· Conditional Flow

Flow Conditioning is typically used to improve straight flow at the input part of the measurement tube after being fitted there.

· Exit Section

The exit section is the cylindrical portion that resembles the intake part and contains the pressure at which the gas or liquid expelled is measured.

· Multiple Manometers

A divergence manometer measures the pressure distinction between different locations in the same or between two different pipes. A U-tube filled with a weighty liquid is attached at both ends to the sites. The pressure difference that needs to be measured makes up a divergence manometer.

How To Estimate The Orifice’s Pressure?

The tapped hole must be shielded from the flow rate of the stream to read just the pressure distribution in a pipe. A pressure regulator is often installed in a hole bored through walls, orthogonal to the wall. Only a pressure gradient exists within the inner wall of a pipe where velocity is zero. Dynamic tapping points are used with an orifice plate flow rate and are situated on either side of the orifice. Conventionally, the downstream static tapping is half a pipe size from the orifice. The flow lines are narrow, mainly at the “venture tube” point. And the upstream static tapping is one pipe diameter downstream from the orifice.

The speed can be determined by manually plugging the differential pressure. This pressure is equivalent to flowing between two sites into an expression. It is possible to determine the amount of product flowing by calculating the flow rate and cross-sectional regions of the pipe and orifice.

Flow Meters: How Do They Operate?

A flow meter aims to gauge the quantity of liquid, gas, or steam moving by, over, or through it. However, there are various flow meter sensors. Essential exploration, control activities, or manufacturing could use the data obtained. Mass or volumetric measurements are performed using flow meters. In a volume flow meter, flow (Q) is proportional to the cross-sectional area (A) and velocity (v) of the flowing fluid: Q = A * v. The flow rate measured by a flow meter is represented in terms of mass flow as = Q. Sectors frequently take mass flow rate into account, mainly when selling or purchasing gases, burning, or performing chemical processes.

What Components Make Up An Orifice Meter?

  • Orifice plates are steel plates with openings that have the same dimension as the pipelines. These plates decrease the flow rate to lower the pressure.
  • The material flows through the inlet, changing pressure and velocity as it travels through the pipeline.
  • Overflow pipe: It would stop the glass container from spilling over.
  • Orifice plates are visible in the flow reinforced with steel, which acts as a pressure change-causing device.
  • When fluid leaves a gadget, it leaves through the exit.
  • Piton tube: it gauges pressure drop
  • Scale on the pilot tube of a manometer.

Flow Orifice Meter Applications

flow orifice meter

The primary usage of a flow orifice meter is to monitor flow rates at various locations. These include water treatment facilities, gas pipelines, petrochemical industries, and oils filtering facilities.

Pros & Cons


  • The benefits of an orifice meter are its tiny plates and ease of installation and removal.
  • Offer a very minimal pressure decrease, which results in a recovery of 60% to 65%.
  • It’s simple to maintain the orifice meter.
  • The broad variety of flows is measured.
  • They feature a straightforward design.
  • They were able to slide right in between the blades.
  • The majority of gases and liquids are the best.
  • They are affordable, and the cost does not rise significantly with volume.


  • Significant persistent volume decrease, roughly comparable.
  • Erosive and corrosive processes could alter their characteristics.
  • Pipes in cement slurry could result from it. A highly viscous fluid is not suitable.
  • Line voltage and homogeneity are requirements for the fluid.
  • Features of square roots.
  • In the range of 0.6 to 0.75, the orifice’s coefficients of discharge results in a 60–70% decrease in volume.


Flow Orifice Meter is a flow meter that uses the dynamic pressure measuring system to estimate the flow rate of fluids, primarily liquids or gases. An upper chamber is inserted in the flow orifice meter to block the fluid. As a result of the surface shrinkage brought on by the orifice that the adapter has established between the pipe and the wall, in this instance, the streamline compresses. Concerning the fluid velocity of the fluid or the gas, a differential pressure is created across the orifice plate.

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How precise are orifice meters?

When manufactured and installed following the relevant requirements, the accuracy of an inlet and outlet differential pressure flow meter can range from 0.60 percent of the rate to 1.0% of the rate.

Where is the orifice meter employed?

It is conventional to detect the mass flow of clean liquids, gases, and streams using differential pressure flow meters of the orifice plate variety.

How can an orifice lower pressure?

The standard orifice plate features an entrance with a concentric, sharp edge. The fluid velocity rises due to the decreased area, resulting in a commensurate drop in pressure. When the pressure decrease across the orifice plate is recorded, the flow rate may be determined.

How do orifice meters and venturi meters differ from one another?

The main distinction between an orifice meter and a venturi meter may be found in the fact that the orifice meter’s orifice plate can easily alter to accommodate various flow rates. In contrast, the volumetric flow is rigid about flow rate changes.

Why does pressure drop?

Relative density, fluidity, flow viscosity, pipe diameter, design, and interior smoothness are all factors that directly affect pressure loss. Consequently, pressure loss is not simply caused by the valve; flow rate also contributes to the phenomenon.