orifice flow meters

Orifice flow meter also called orifice plate flow meter,

or orifice plate is a kind of differential pressure flow meter.

With easy installation, integral orifice plate transmitter can measure the steam, liquid flow,

and all kinds of industrial pipe flow.

With Differential Pressure Measurement principle.

Orifice plate flows meters are differential pressure sensors for flow rate.

You may like: Nitrogen flow meter— air / gas flow meter

Sino-Instrument offers integral orifice flow meter,

working together with an orifice plate,

differential pressure transmitters, with easy installation.

Orifice flow meters can measure steam, gas, liquids, and many industrial areas.

Applications include steam flow, boiler feedwater,

and fluid flow rates in building water lines.

Designed for use wherever there is an application, for a conventional flow orifice plate.

What are the types of flow meter?

Orifice flowmeter specification:

SI-LG integrated orifice flowmeter is a high-range ratio differential pressure flow device,

composed of standard orifice plate and multi-parameter differential pressure transmitter

(or differential pressure transmitter, temperature transmitter and pressure transmitter).

It can measure the flow of gas, steam, liquid and natural gas,

and is widely used in process control and measurement in petroleum,

chemical, metallurgy, electric power, heating, water supply, and other fields.

SI-LG Orifice flow meter

The orifice throttling device is a standard throttle,

that can be produced directly in accordance with national standards without calibration:

Nominal Bore:DN20~ DN2000mm
 Nominal Pressure0.6 ~ 32MPa(≥20MPaHigh-pressure lens plate or fully welding )
Medium Temperature-20 ~ 530℃
Accuracy±0.5% ~ ±1.5%

Advantages of Orifice meter:

  • The Orifice meter is very cheap as compared to other types of flow meters.
  • Less space is required to Install and hence ideal for space-constrained applications
  • The operational response can be designed with perfection.
  • Installation direction possibilities: Vertical / Horizontal / Inclined.

Applications of Orifice meter:

  • Natural Gas
  • Water Treatment Plants
  • Oil Filtration Plants
  • Petrochemicals and Refineries

Orifice meter diagram

Orifice plate installation

1. Meter manifold piping should always be installed to enable calibration as well as to protect the differential element against overage.

2. The meter should be installed as close as possible to the orifice fitting.

3. Always slope the manifold lines gently from the orifice fitting to the meter to eliminate any high or low points in the manifold lines.

4. Use condensate chambers or air traps to remove either liquid from a gas system or gas from a liquid system if lows or highs in the manifold piping cannot be avoided.

It is important when pressurizing or depressurizing differential measuring devices to apply or release pressure to or from the high and low meter chambers uniformly,

so as not to impose excessive overage.

What is an Orifice Meter?

An orifice meter is a conduit and a restriction to create a pressure drop.

An hourglass is a form of the orifice.

A nozzle, venturi or thin sharp-edged orifice can be used as the flow restriction.

In order to use any of these devices for measurement,

it is necessary to empirically calibrate them.

That is, pass a known volume through the meter and note the reading in order to provide a standard for measuring other quantities.

Due to the ease of duplicating and the simple construction,

the thin sharp-edged orifice has been adopted as a standard and extensive calibration work has been done,

so that it is widely accepted as a standard means of measuring fluids.

Provided the standard mechanics of construction are followed no further calibration is required.

The minimum cross-sectional area of the jet is known as the “vena contract”.

How does an orifice flow meter work?

I guess most people wondered
What is the working principle of orifice meter?

As the fluid approaches the orifice the pressure increases slightly

and then drops suddenly as the orifice is passed.

It continues to drop until the “vena contract” is reached,

and then gradually increases,

until at approximately 5 to 8 diameters downstream,

a maximum pressure point is reached,

that will be lower than the pressure upstream of the orifice.

The decrease in pressure as the fluid passes thru the orifice,

is a result of the increased velocity of the gas passing thru the reduced area of the orifice.

When the velocity decreases as the fluid leaves the orifice the pressure increases,

and tends to return to its original level (To level transmitters).

All the pressure loss is not recovered because of friction,

and turbulence losses in the stream.

The pressure drop across the orifice increases when the rate of flow increases.

When there is no flow there is no differential.

The differential pressure is proportional to the square of the velocity,

it thus follows that if all other factors remain constant,

then the differential is proportional to the square of the rate of flow.

Equations used in this orifice plate Calculator

Qv = 218.527*Cd*Ev*Y1*(d2 )*[Tb/Pb]*[(Pf1*Zb*hw)/(Gr*Zf1*Tf)]0.5 (3-6)


Cd = Orifice plate coefficient of discharge

d = Orifice plate bore diameter calculated at flowing temperature (Tf) – in.

Gr = Real gas relative density (specify gravity)

hw = Orifice differential pressure in inches of water at 60 degF

Ev = Velocity of approach factor

Pb = Base pressure – psia

Pf1 = Flowing pressure (upstream tap – psia

Qv = Standard volume flow rate – SCF/hr.

Tb = Base temperature – degR

Tf = Flowing temperature – degR

Y2 = Expansion factor (downstream tap)

Zb = Compressibility at base conditions (Pb,Tb)

Zf1 = Compressibility (upstream flowing conditions – Pf1, Tf)

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Orifice plate types

Sino-Instrument supplies all kinds of the orifice plate, for differential applications.



For the common square edge concentric bore orifice,

the bore and bevel is the standard method of limiting the plate edge thickness.

Unless otherwise specified, plates will be beveled to the currently accepted standards.


The quadrant edge bore is an orifice with the inlet edge rounded. Instead of beveling, the plate is counterbored to the desired edge thickness.

The radius of the quarter circle bore is a function of the orifice-to-pipe ratio (d/D). Thickness at the throat is equal to the radius.

This bore is specifically designed for viscous fluids such as heavy crudes, syrups, and slurries with Reynolds Numbers below 100,000.


ECCENTRIC BORE orifice plate

Eccentrically bored orifice plates are plates,

with the orifice off-center, or eccentric, as opposed to concentric.

The bore of the eccentric orifice normally is inscribed in a circle,

which is 98% of the pipe diameter,

so that solids or slurries may pass through.

Eccentric orifice plates are used in many industries,

including heavy and light chemicals, steel, paper, nuclear and petrochemicals.


Segmentally bored orifice plates are provided for measurement,

where solids are entrained in a gas or liquid flow stream.

The circular portion of the bore is inscribed within a circle,

which is normally 98% of the pipe diameter.

The segmental opening may be placed either at the top or bottom of the pipe.

Industries using these bores include sewage treatment, steel, chemical,

water conditioning, paper, and petrochemical.

RTJ Type Orifice Plates

RTJ Type Orifice Plates orifice plate

The RTJ type orifice plate incorporates an integral gasket,

either oval or octagonal ring, for mounting between ring type joint flanges.

It is based on proven technology,

has no moving parts and is suitable for high temperature and pressure applications.

RTJ type orifice plates can be supplied complete with ANSI B16.36 orifice flanges.

Orifice plates are recommended for clean liquids,

gases, and low-velocity stream flows.

Plate thicknesses depend on line size and differential pressure and should be sufficient,

to prevent the plate from bending under operating conditions.

Orifice plates can be made in accordance with customer drawings as required.

If you still have questions about orifice plate flow meters,

Just contact us. Our engineers will offer help.

Sino-Instrument offers many kinds of orifice flow meters.

Orifice plate flow meters
Orifice plate flowmeters

Sino-Instrument offers 12 orifice flow meter products.

About 90% of these are flow meters.

A wide variety of orifice flow meter options are available to you, such as brass, carbon steel.

You can also choose from free samples.

Sino-Instrument is an orifice flow meter supplier.

Orifice flow meter products are most popular in Domestic Market, Southeast Asia, and Mid East.

You can ensure product safety by selecting from certified suppliers, including 375 with ISO9001, ISO14001, and Other certification.

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