Three bore geometries
The bore position and shape are chosen for what's actually moving through the pipe — clean fluid, entrained solids, or condensate — not picked from habit.
| Type | Bore | Typical service |
|---|---|---|
| Concentric | Centred on the pipe axis | Clean liquids, gases, steam — the reference geometry behind ISO 5167-2 and ASME MFC-3M |
| Eccentric | Offset toward the pipe wall | Fluids carrying solids or condensate, where a centred bore would trap material against the plate face |
| Segmental | A circular-segment opening, not a round bore | Dirty fluids and slurries — an open channel along the bottom of the pipe for heavy carry-over |
Edge profile
The upstream edge geometry is a separate decision from the bore position, and it changes which discharge-coefficient correlation actually applies.
- Sharp (square) edge — a 90° edge with no radius, held sharp and burr-free. This is the standard edge for concentric plates under ISO 5167-2 / ASME MFC-3M, valid down to a defined minimum Reynolds number.
- Quadrant (quarter-circle) edge — the upstream edge is rounded to a specified radius rather than left sharp. Used below the Reynolds number range a sharp edge is qualified for — typically higher-viscosity or lower-velocity flows — under its own separate correlation (ISO/TR 15377 covers this geometry).
Edge condition isn't cosmetic: a sharp edge that's gone round from wear or a poor finish shifts the discharge coefficient away from the value the flow calculation assumes.
Sizing one
The bore diameter — and therefore the beta ratio β = d/D — comes from the pipe size, fluid properties, flow range and target differential pressure, not a lookup table. Our orifice calculator runs the same Reader-Harris/Gallagher discharge-coefficient structure used in ISO 5167-2 against your process conditions and returns a preliminary bore, β, Reynolds number and engineering status checks.