orifice flow meters

Orifice flow meter also called orifice plate flow meter, differential pressure flowmeter, or orifice plate.

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

Can be used with gases, liquids, corrosive, and high temperature fluids.

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.

Orifice flow meter 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:

  1. National standard GB2624-81<Design and installation of flow measurement throttling device>;
  2. International Standard ISO5167 < Various Throttling Devices stipulated by International Standards Organization>
  3. Ministry of Chemical Industry Standard GJ516-87-HK06.

Orifice flowmeter application range:

1. Nominal diameter: 15 mm ≤ DN ≤ 1200mm

2. Nominal pressure: PN≤10MPa

3. Working temperature: -50 °C ≤ t ≤ 550 ° C

4. Turndown ratio: 1:10, 1:155. Accuracy: 0.5, 1

Orifice meter diagram

Orifice plate installation

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.

Orifice plate types

Sino-Instrument supplies all kinds of 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 current accepted standards.


The quadrant edge bore is an orifice with the inlet edge rounded. Instead of beveling, the plate is counter bored 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 steam 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. Or engineer will offer help.

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