Overview
ISO 13351:2009 - Fans - Dimensions specifies standardized flange and size designation details for general‑purpose fans. The standard covers both circular flanges and rectangular flanges, defining the pitch circle diameters, number of bolt holes and hole diameters that enable mechanical interchangeability of fan components. It applies to nominal impeller tip diameters from 100 mm to 2 000 mm and is not applicable to cross‑flow fans or fan appliances for individual household use.
Key objectives:
- Promote interchangeability and reduce technical barriers to trade
- Provide a common dimensional basis without unduly restricting fan design
Key topics and technical requirements
- Flange types: Circular and rectangular flange dimensions are given; only essential mounting dimensions are specified so manufacturers can retain design freedom (flange thickness and external diameters are not constrained).
- Circular flange series: Three flange series for different duty levels:
- Light‑duty (typical air conditions, pressures up to ~2 kPa)
- Medium‑duty (pressures up to ~10 kPa)
- Heavy‑duty (sea‑going / heavy industry, pressures up to ~40 kPa)
- Specified parameters: Pitch circle diameter, number of holes (usually divisible by 4 to allow 90° orientation), hole diameters and bolt sizes. Flange thickness, internal/external diameters and some other details left to good engineering practice.
- Nominal impeller tip diameter (D): Based on Renard R 20 preferred numbers per ISO 497; R 40 (and R 80 if needed) used for intermediate sizes.
- Rectangular flanges: Standardized bolt hole locations and sizes (Table 4) with two alternative aspect‑ratio systems (Tables 5 & 6). Options are provided for lap‑weld, butt, fabricated and rolled flange designs.
- Tables and figures: The standard includes tables for light/medium/heavy circular flanges (Tables 1–3), rectangular flange pitches and hole data (Table 4) and outlet aspect‑ratio series (Tables 5–6).
Applications and users
ISO 13351:2009 is intended for anyone involved in the design, manufacture, specification or procurement of industrial fans:
- Fan manufacturers - to design flanges that are compatible with market norms
- HVAC and mechanical engineers - for specifying fan connections and ensuring fit with ductwork or equipment
- Plant designers and shipbuilders - selecting heavy‑duty fans with compatible mounting patterns
- Purchasing/procurement teams - ensuring equipment interchangeability across suppliers
Practical benefits include easier replacement, simplified integration into duct systems, and reduced installation complexity.
Related standards
- ISO 13349 - Industrial fans: vocabulary and definitions
- ISO 497 - Preferred numbers (Renard series R20/R40/R80)
- ISO 6580:2005 - Content incorporated into this edition
Keywords: ISO 13351:2009, fans dimensions, circular flange, rectangular flange, fan size designation, flange dimensions, Renard R20, ISO 497, fan standard, interchangeability.