Orifice Flow Meter

Orifice Flow Meter

What is an orifice meter?

An Orifice Flow Meter is a flow meter, generally used to measure the rate of flow of Liquid or Gas. It uses the principle of Differential Pressure Measurement.

This meter comprises an Orifice Plate and a Differential Pressure Transmitter. In the case of density, compensation is essential for the temperature, and pressure measuring devices are added to it. When the Orifice Plate is placed in a line, it acts as an obstacle to the fluid flow, as a result generating a differential pressure across the Orifice Plate. The pressure drop across the Orifice plate is in direct proportion to the square of the flow rate of the measured liquid or gas. It is also proportional to the square of the flowing density of the fluid.

The orifice is designed as per BS1042 / ISO 5167. Orifice being a mechanical element its dimensions are fixed. The advantage is that under the given conditions of operations its calibration is fixed and stable. It does not need periodical calibration frequently. This is the main advantage of using an orifice metering system. The electronics associated with it can be calibrated at the site with portable calibrators.


What is Orifice Meter used for?

This meter is typically used where there is a need for robustness, durability, and repeat accuracy while measuring the rate of flow of liquid or gas. Measurement of Steam, Thermic Fluid flow is the best examples for using an orifice-based system.


Construction of an Orifice Flow Meter

In an orifice meter, there are essentially three sections. First is the Inlet Section which is a linear section of the same diameter as that of the inlet pipe, to measure the inlet pressure of the fluid or gas. The second is the Orifice Plate which is inserted between the Inlet and outlet Sections. The differential pressure Transmitter is usually fitted with an Orifice flange assembly.  The third is the outlet section which is similar to the Inlet section. The straight lengths required in the first and third sections should be used as per the manufacturer’s specifications.


  • Suitable for all type of Gas like Biogas, LPG, CNG, PNG, Air, Oxygen, Nitrogen etc.
  • Suitable for Saturated and Superheated Steam, Condensate water, HOT water,
  • Data logging facility
  • MOSBUT RTU with RS485 communication port
  • 4-20mA Output


  • Automotive industry
  • Water Treatment Plants
  • Oil & Gas industry
  • Petrochemicals and Refineries
  • Textiles
  • Sugar Industries
  • Process Industries


  • They may get jammed due to unclear liquids and impurities in the gas.
  • Since there is a pressure drop, it is used where a drop in pressure or head loss is permissible.
  • Orifice plate life span is short due to corrosion. Also, it reflects in errors over a period of time.
  • To overcome these limitations Manas recommends Thermal Mass flow meter in such cases.


  • Mass Flow Measurement
  • Works in low Velocity
  • Online density compensation
  • Supplied with DPT, RTD, PT, Orifice plate with spool and Gas flow totalizer
  • No moving Parts
  • During installation, no wiring connection is required, so installation is very easy

Product Details

Brand manas microsystems
Mounting Wall/Panel
Max depth 185mm
Accuracy ±0.25% of Full Scale
Data logging Approx readings: 3000 for normal logging &Approx 5500 readings for extended logging
Power supply 85 to 265V AC,50Hz, single phase
Pressure range 1 to 50 kg/cm2 (g) or Bar (g) max.-programmable
Flow type Compensated/Uncompensated programmable
Enclosure Al Diecast/ABS Plastic
Comm. Port RS485 std., RS232 (Optional)
Density Compensation Online monitoring and compensation of density
Dimensions WM Type 310 (L) x 160 (W) x 105 (D)
Dimension PM Type Bezel-144mm (H) x 72mm (W) cutout-138mm (H) x 68mm (W)
For Steam Applications Click here
For Gas Applications Click here

Comparison between Vortex Flow Meter and Orifice Flow Meter

Sr. No. Parameter Orifice Vortex
1. Well established standards Available Not Available
2. Suitability for high pressure & temperature application Most suitable Seal fails in majority of cases after a certain duration.
3.  Installation Easy to install Critical & expensive because of the requirement of special machined pipe lengths.
4. Existing pipeline modifications for installation No modifications are required. Design is based on velocity & not on line size. As a result, line size at the site & selected flowmeter size may differ.
5. Recalibration of transmitter Easy & can be done in house Has to be done on a flow-rig and hence is expensive
6. Changes in Pressure, Temperature Taken care of during density compensation Needs to be taken care of.
7. Effects on resolution due to increase inline size No effect. Resolution decreases with an increase in line size.
8. Suitability for low-velocity measurement Suitable Stops the measurement.
9. Durability No moving parts and hence no wear and tear and virtually maintenance-free. Diaphragm-based sensor and hence is prone to wear and tear.

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