Overview
ISO 28520:2009 - Ships and marine technology - Lubricating oil systems - Guidance for grades of cleanliness and flushing - gives practical guidance for flushing lubricating oil systems on ships and grading the resultant cleanliness. The standard addresses both objectives of flushing: removing installation and fabrication dirt, and demonstrating that pipes, tanks and components are sufficiently clean. It distinguishes “washing through” (Reynolds number ≤ 3 000) from “flushing” (Reynolds number ≥ 3 000) and notes that any OEM flushing requirements take precedence.
Key Topics and Requirements
- Scope of cleaning: Covers pipe prefabrication cleanliness, inside surface treatment, tanks, pumps, valves, filters, oil coolers, crankcases and gearboxes.
- Degrees of pipe cleaning: Prefabricated pipes should be free of slag, spatter and porosities; recommended surface preparation corresponds to Sa 2½ per ISO 8501-1 where chemical/mechanical cleaning is used.
- Crankcase and gearbox cleaning: Crankcases and non-sealed gearboxes must be cleaned before flushing. Guidance includes use of thin non-drying oil (≈ SAE 10–30 cSt) for initial washing; system oil may be used heated to 55–60 °C when compatible.
- Flushing practice: Describes staged flushing (external shipyard piping then engine/builder piping), use of orifice pieces for internal spray, full-flow and off‑line flushing units, LO separators in recirculation mode, and auxiliary measures such as pipe vibrators. Maintaining flushing temperature (≈ 50–60 °C) is emphasized.
- Cleanliness grading and verification: Uses particle-coding concepts (referenced ISO 4406) and links cleanliness levels to component sensitivity (e.g., bearing life, filter fineness). Gearbox cleanliness selection should be guided by load, rpm, service life and bearing supplier requirements.
- Special precautions: Avoid steel sand for shot blasting (use copper slag), protect sealing surfaces, and ensure filters/separators are operable during filling.
Applications
- Commissioning and sea trials for newbuild ships and major refits
- Installation and acceptance testing of main engines, gearboxes, and lubricating oil piping systems
- Contamination control programs to extend bearing life and reduce failure risk
- Shipyards, marine OEMs and classification surveys during handover inspections
Who should use this standard
- Shipbuilders and shipyards
- Marine engineers and commissioning teams
- Engine, gearbox and auxiliary equipment manufacturers (OEMs)
- Ship operators, maintenance planners and classification societies
Related Standards
- ISO 4406 - Fluid power - Method for coding contamination by solid particles
- ISO 8501-1 - Surface preparation (Sa 2½ reference)
- ISO 28521 - Hydraulic oil systems - Guidance for grades of cleanliness and flushing
Keywords: ISO 28520, ISO 28520:2009, lubricating oil systems, flushing, cleanliness grades, ship, marine technology, Reynolds number, ISO 4406.