Overview
EN ISO 29461-4:2025 - Air intake filter systems for rotary machinery - Part 4: Test methods for static filter systems in coastal and offshore environments (ISO 29461-4:2025) - defines standardized laboratory test procedures to evaluate static air intake filters exposed to coastal and offshore conditions. The standard describes performance testing of individual filter elements and complete filtration systems for flow rates up to 8 000 m3/h per filter element, using ultra‑fine salt aerosol (mostly sub‑micron) and variable humidity to simulate real marine environments. It is published by CEN and is the European adoption of ISO 29461-4:2025.
Key topics and technical requirements
- Test scope and limits: Intended for static filter systems and individual elements operating up to 8 000 m3/h per element; focuses on salt and water challenges typical of coastal/offshore environments.
- Aerosol challenge: Uses ultra‑fine salt particles (sub‑micron) to assess salt removal and cumulative penetration under variable humidity.
- Performance thresholds: Filters with an initial conditioned efficiency below 50% for ePM1 (filter class T7) are likely to underperform and are not recommended as single‑stage solutions.
- Test rig and instrumentation: Requirements for a calibrated test rig, test duct layout, air conditioning, airflow measurement, pressure‑drop measurement, and sodium flame photometer (SFP) for salt concentration measurement.
- Water handling: Procedures for water spray/deluge devices, water collection, and assessment of water removal efficiency and droplet distributions.
- Qualification and calibration: Protocols to qualify the test rig (pressure testing, aerosol uniformity checks, droplet sedimentation) and schedule of qualification.
- Test procedure and measurements: Steps for installation, flushing, salt loading, water deluge challenges, relative‑humidity cycles, and measurement of pressure drop, salt removal efficiency, cumulative salt loading and penetration.
Applications and users
This standard is essential for:
- Filter manufacturers validating designs for marine and offshore applications.
- OEMs and system integrators specifying intake filtration for rotary machinery (engines, gas turbines, compressors).
- Test laboratories performing standardized salt/fog challenge testing and certification.
- Operators and asset owners (offshore platforms, coastal power plants, marine vessels) evaluating filter lifecycle performance, maintenance intervals, and single‑stage vs multi‑stage choices.
- Procurement and certification bodies writing technical specifications and acceptance criteria.
Related standards
- Part of the ISO 29461 series on air intake filter systems for rotary machinery. EN ISO 29461-4:2025 is adopted by CEN without modification and should be used alongside other parts of the ISO 29461 series and national filtration standards for comprehensive specification and compliance.
