ISO 29461-4:2025

Overview

ISO 29461-4:2025 - Air intake filter systems for rotary machinery - Part 4: Test methods for static filter systems in coastal and offshore environments - specifies laboratory test methods to evaluate the performance of individual filter elements and whole static filtration systems exposed to coastal and offshore conditions. The standard is intended for filters rated up to 8 000 m³/h per filter element and simulates real-world challenges by loading filters with ultrafine salt aerosol (mostly sub‑micron) under variable humidity and water-deluge conditions. It notes that filters with an initial conditioned efficiency below 50% for ePM1 (filter class T7) are likely to underperform as single‑stage solutions.

Key topics and technical requirements

• Test scope and flow rating: Procedures apply to static filter elements and systems up to 8 000 m³/h per element.
• Salt aerosol challenge: Use of ultrafine dry solid salt particles (sub‑micron) to simulate coastal/offshore alkali contamination.
• Environmental conditioning: Variable relative humidity cycles and controlled water deluge (spray) challenges to reproduce offshore exposure.
• Test rig and qualification: Detailed requirements for test rig layout, test duct, air conditioning, aerosol mixing, and rig qualification (aerosol uniformity, pressure system checks).
• Measurement methods: Measurement of pressure drop, salt removal efficiency, water removal efficiency, cumulative salt loading and penetration, and instrumentation requirements (including sodium flame photometer).
• Sampling and generation: Specifications for salt aerosol generation and sampling probes, injection, and water collection devices.
• Test procedure and reporting: Preparatory checks, stop criteria, flow rate adjustment, weighing protocol (primary/secondary), test sequence (salt loading, water deluge, humidity cycles), and reporting template.

Practical applications and users

ISO 29461-4:2025 is targeted to organizations involved in selection, design, testing and procurement of air intake filters exposed to marine or offshore conditions:

• Gas turbine and rotary machinery OEMs specifying intake filtration for coastal/offshore installations.
• Filter and filtration-system manufacturers validating element and system performance against salt and moisture challenges.
• Test laboratories and certification bodies conducting standardized performance testing.
• Operators and asset owners in oil & gas, marine, and power generation assessing filter lifecycle, maintenance planning and spare‑parts specification.
• Procurement and QA teams requiring objective acceptance criteria for intake filtration in harsh environments.

Related standards

• Part of the ISO 29461 series on air intake filter systems for rotary machinery.
• Developed by ISO/TC 142 (Cleaning equipment for air and other gases) in cooperation with CEN/TC 195.

Keywords: ISO 29461-4:2025, air intake filter systems, static filter systems, coastal and offshore environments, test methods, salt aerosol, ePM1, pressure drop, filter efficiency.