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NiCuZn · Black Owl — Engineering calculation sheet

Orifice plate flow.

Estimate liquid flow through a sharp-edged orifice plate from the measured differential pressure, with β ratio and permanent pressure loss.

Orifice and pipe
mm

102.26 mm is 4″ Schedule 40.

mm
–

About 0.6 for sharp-edged plates with flange or corner tappings.

Measurement and fluid
kPa

25 kPa = 250 mbar.

kg/m³

Results

Volumetric flow49.22 m³/h
Mass flow49,218 kg/h
β ratio (d / D)0.6
Velocity in the pipe1.66 m/s
Permanent pressure loss (approx.)15.53 kPa

Preliminary estimate for early engineering. Check against your design basis, standards and vendor data.

Method

How it is calculated

For an incompressible liquid (expansibility ε = 1), the ISO 5167 orifice equation gives the mass flow:

qm = Cd / √(1 − β⁴) · (π d² / 4) · √(2 ΔP ρ)

where β = d / D. The discharge coefficient depends on β, the Reynolds number and the tapping arrangement; ISO 5167-2 gives it through the Reader-Harris/Gallagher equation, and about 0.6 is a reasonable first value. The permanent (unrecovered) pressure loss is estimated as (1 − β1.9) ΔP.

Use this for preliminary checks and bore estimates. Flow meter sizing for operation or custody transfer should follow ISO 5167 in full, including straight-length requirements and uncertainty.

Read: how to read a P&ID →All engineering tools →Size equipment from your own balance in Black Owl ↗

Calculated with the free engineering tools at nicuzn.com/tools. Preliminary estimate for early engineering; check against your design basis, applicable standards and vendor data before use.