ISO 13351:2024

Overview

ISO 13351:2024 - Fans - Dimensions defines standardized dimensions and size designations for general‑purpose fan flanges. The standard covers both circular and rectangular flanges, specifying key parameters (pitch diameter, number of bolt holes and hole diameters) to promote interchangeability without unduly constraining fan design. It excludes cross‑flow fans and small fan appliances for individual household use. Nominal impeller tip diameters follow the Renard R20 series (ISO 3 / ISO 17) and preferred numbers from ISO 497.

Key topics and technical requirements

• Flange series: Three circular‑flange series are provided:
  • Light‑duty (air non‑toxic, non‑corrosive, up to 2 kPa; typical casing thinness),
  • Medium‑duty (design pressures up to 10 kPa),
  • Heavy‑duty (up to 40 kPa; for heavy industry and sea‑going vessels).
• Specified dimensions: The standard prescribes pitch (bolt circle) diameter, number of holes and hole diameters; flange thickness and inner/outer flange diameters are left to manufacturer engineering practice.
• Nominal sizes: Circular and rectangular flange dimensions are given for nominal diameters from 100 mm to 2 000 mm, with heavy‑duty sizes extending to 3 550 mm.
• Bolt patterns: Hole counts are divisible by four to allow fan orientation at 90° and equal distribution around centerlines; pitch and hole offsets are standardized for interchangeability.
• Rectangular flanges: Standardized bolt locations and hole sizes are defined so each outlet side can adopt standard hole patterns while allowing freedom in aspect ratio and flange design (lap‑welded, butt, rolled or fabricated).
• Sizing guidance: For intermediate sizes, the R40 (or R80 for finer increments) preferred‑number series is referenced; practical factors (casing thickness, weld fillet radii, washer size) determine minimum pitch circle diameter.
• Referenced terminology and alignment: Terms and symbols aligned with ISO 13349‑1 and ISO 13349‑2; normative cross‑references include ISO 3 and ISO 497.

Applications - who uses ISO 13351:2024

• Fan manufacturers and OEMs standardizing product lines and spare parts
• HVAC and ventilation engineers specifying flanged fan connections in buildings and industrial systems
• Shipbuilders and marine engineers selecting heavy‑duty fan flanges
• Procurement teams and spec writers ensuring compatibility across suppliers
• Test labs and conformity assessors checking flange dimensions against standard tables

Practical benefits include improved interchangeability, reduced technical barriers to trade, and clearer procurement/specification language for circular and rectangular fan outlets.

Related standards

• ISO 13349‑1, ISO 13349‑2 - vocabulary and categories for fans
• ISO 3 / ISO 17 - Renard series (R20) preferred numbers
• ISO 497 - preferred numbers guidance
• (Historical) ISO 6580 - earlier light‑duty flange values referenced for continuity

Keywords: ISO 13351:2024, fan dimensions, circular flanges, rectangular flanges, flange pitch diameter, bolt hole pattern, fan size designation, light‑duty fan, medium‑duty fan, heavy‑duty fan.