Orifice flow meters are 100+ years old.
Yet they’re still installed in modern plants alongside the latest “smart” instruments.
There’s a reason for that.
In this short carousel, I’ve broken down the essentials:
Orifice Flow Meters
Principle – Differential pressure across a restriction (orifice plate) is related to flow rate (Bernoulli’s principle).
Typical elements – Orifice plate + primary tap + DP transmitter + impulse lines.
Important Design Parameters
Beta ratio (β) – Ratio of orifice diameter to pipe diameter (typically 0.3–0.75).
Reynolds number – Must be sufficiently high for accurate measurement.
Straight pipe requirement – Typically 10D upstream and 5D downstream depending on installation.
Key advantages:
Simple construction, well-understood theory
Widely standardized (ISO 5167 / ASME MFC standards)
Suitable for gases, liquids, and steam
Low initial cost compared to many flow technologies
Main disadvantages:
Permanent pressure loss (energy cost)
Accuracy depends heavily on installation and plate condition
Requires long straight pipe lengths
Not ideal for very low flow or dirty/slugging services
Common applications:
Oil & gas, refineries, and petrochemicals
Steam and condensate lines
Utility services (air, nitrogen, water) in process plants
Power plants for steam flow measurement
Typical Accuracy
Around ±1% to ±2% of flow rate when properly installed and calibrated.
Where do you still prefer orifice flow meters over other DP or inline technologies in your plant or projects?
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