Overview
ISO 23820:2023 - Determination of the filtration efficiency of urea filter modules - specifies a laboratory test method for assessing the ability of AUS 32 / diesel exhaust fluid (DEF) filters to remove suspended matter. It applies to urea filter modules for both passenger vehicles and commercial vehicles and covers filters with nominal flow rates from 3 l/h to 30 l/h (default: 5 l/h for passenger vehicles, 25 l/h for commercial vehicles). The procedure measures initial filtration efficiency and retention (clogging) capacity using controlled test rigs, particle counters and defined contaminant injections.
Key topics and technical requirements
- Two-stage test procedure
- Stage 1: Initial filtration efficiency with an upstream contaminant concentration of 5 mg/l for 60 minutes.
- Stage 2: Retention (clogging) capacity with a higher upstream contaminant concentration (typically 800 mg/l) to determine mass required to reach a specified differential pressure (commonly 10 kPa, or per customer specification).
- Performance metrics
- Cumulative overall mean filtration efficiency (E_x) - percent removal of particles > x µm, measured upstream and downstream.
- Reference filtration rating (S) - particle size at which cumulative efficiency ≥ 99 %.
- Retention capacity - contaminant mass required to reach the target ΔP.
- Test rig and equipment
- Single-pass filter test circuit with main recirculation and bypass loops, clean-up filters (recommended 99 % at 1 µm for recirculation), automatic particle counters (ISO 21501‑3), flow meters, temperature control at 23 ± 2 °C, and 316L stainless steel piping.
- Injection circuits for 5 mg/l and 800 mg/l contaminant concentrations with mixing, level control and sampling per ISO 4021.
- Validation and reporting
- Test rig validation and repeatability requirements; expression of results and a specified test report layout.
- Normative references: ISO 11218, ISO 11923, ISO 21501‑3 (see Related Standards).
Applications and users
- Filter manufacturers - validate product performance, set filtration ratings and retention specifications.
- Automotive OEMs and Tier suppliers - qualify urea/DEF filtration modules for passenger and commercial vehicle SCR systems.
- Independent test laboratories - provide standardized, repeatable measurement of filtration efficiency and clogging behavior.
- Quality and compliance teams - ensure fluid-conditioning devices protect dosing systems, injectors and catalysts from particulate contamination.
Practical benefits include improved SCR system reliability, reduced injector/catalyst fouling risk, and consistent specification of urea filter performance.
Related standards
- ISO 11218 - Cleanliness classification for hydraulic fluids
- ISO 11923 - Determination of suspended solids by filtration
- ISO 21501-3 - Liquid-borne particle counter (light extinction single-particle methods)
Keywords: ISO 23820:2023, urea filter modules, filtration efficiency, AUS 32, DEF filter testing, retention capacity, diesel exhaust fluid filtration, test rig validation.
