ISO 22241-4:2023

Overview

ISO 22241-4:2023 - "Diesel engines - NOx reduction agent AUS 32 - Part 4: Refilling interface" specifies the refilling interface needed to dispense AUS 32 (aqueous urea solution) into on-board tanks for vehicles equipped with selective catalytic reduction (SCR) systems. The standard sets minimum functional and geometric requirements for open refilling systems (and compatibility conditions for sealed systems in Annex A) to ensure reliable, safe and compatible interaction between on-board and stationary off-board refilling equipment. It applies to commercial vehicles and buses (ISO 3833) with a gross vehicle mass > 3.5 t, and to the nozzles of stationary refilling systems.

Key technical topics and requirements

• Scope & compatibility: Ensures on-board filler necks, inlet adapters and off-board nozzles are compatible for AUS 32 refilling.
• Flow rate: Specified maximum flow range 20–40 L/min for typical refilling (excludes canister and production-line filling).
• Automatic shut-off: Nozzles must include an automatic shut-off to protect against overfill (e.g., compliant with EN 13012).
• Spillage limits: Spillage thresholds depend on filler neck angle:
  • < 30 ml per refilling at 50°–90° from horizontal
  • < 50 ml per refilling at 30°–50°
• Filler neck geometry: Minimum dimensions (e.g., inlet diameter ≥ 39.5 mm, support ≥ 37 mm, stop height ≤ 48 mm) and recommended filler neck angle to minimize spillage.
• Inlet adapter & magnet ring: Inlet adapters must prevent misfueling and accept a magnet ring. Standard magnet option: NdFeB ring - outer Ø 34 mm, inner Ø 24 mm, height 10 mm; remanence 1.2–1.3 T; coercivity 800–900 kA/m; north pole outwards. Alternative magnet solutions can be validated by the test method (magnet resistance force Fres ≥ 0.5 N).
• Misfilling prevention: Misfilling of AUS 32 into diesel fuel tank limited (≤ 80 ml per filling trial) and design prevents fuel entering AUS 32 tank.
• Materials & cleanliness: Materials in contact with AUS 32 must be compatible (see ISO 22241-3) and surfaces must be free of contaminants.
• Temperature & freezing: Operational temperature ranges specified (e.g., −30 °C to +80 °C for on-board components) and designs must account for AUS 32 freezing behavior (freeze point ≈ −11.5 °C, ~7% volume expansion).

Applications - who uses this standard

• Vehicle manufacturers and OEMs designing on-board AUS 32 filler systems and tanks
• Component and inlet-adapter suppliers, nozzle and service-station equipment manufacturers
• Fleet operators, maintenance providers and service-station engineers implementing stationary off-board refilling
• Regulatory bodies and procurement teams specifying SCR refilling safety and interoperability requirements

Practical benefits

• Prevents misfueling and contamination of diesel fuel and AUS 32
• Standardizes refilling interfaces to ensure interoperability between vehicles and filling equipment
• Improves safety, reduces spillage and supports reliable SCR NOx reduction operation

Related standards

• ISO 22241-1 - AUS 32 quality requirements
• ISO 22241-3 - Handling, transportation and storage of AUS 32
• ISO 2575 - Symbols for vehicle controls/indicators
• EN 13012 is referenced for nozzle automatic shut-off examples

Keywords: ISO 22241-4, AUS 32, refilling interface, filler neck, inlet adapter, filler nozzle, SCR, NOx reduction, misfilling prevention, commercial vehicles.