Overview
ISO 28522:2009 - Ships and marine technology - Hydraulic oil systems - Guidance for assembly and flushing - provides practical guidance for assembling, flushing, testing and commissioning hydraulic oil pipework and components on ships. The standard’s primary objective is twofold: remove dirt introduced during erection and installation and demonstrate that pipes and the overall system meet required cleanliness levels before entering service.
Key topics and technical requirements
- Assembly checks
- Verify blank-offs on pipes and components are undamaged; repeat cleaning if needed.
- Blow through assembled pipework with dry high‑pressure air or nitrogen; lint‑free cloths may be pulled through pipes.
- Leak tests with dry air and/or soap and water; components can be bypassed or blanked-off during testing.
- Shock testing
- Pipe systems shall be shock tested a minimum of 25 cycles at the specified test pressure with components bypassed.
- Flushing procedure
- Use a flush‑rig with the correct filter rated by beta ratio (β) - defined as (particles > x µm at filter intake) / (particles > x µm at filter discharge).
- Connect equivalent pipe dimensions and flush separately to avoid pressure loss; circuits should be connected in series.
- Bypass or blank off built‑in components during initial flushing; vibrating units may be used.
- Maintain flush oil temperature at least equal to expected service temperature but not exceeding 60 °C (disposal max 80 °C).
- Continue flushing until cleanliness criteria are met (see ISO 28521 for specific cleanliness tables and recommended flow velocities).
- Pressure testing
- Conduct pressure tests (with components bypassed/blanked-off) to verify pipe strength and system integrity.
- Commissioning
- Replace non‑system flushing oil with designated system oil (use a filter when filling).
- Start pump units, manage breathing/refilling, set pressure regulating/relief valves, and invite supplier representative to verify cleanliness. Documentation of achieved cleanliness follows ISO 28521.
Practical applications and users
ISO 28522 is intended for shipbuilders, marine system integrators, naval architects, shipboard engineers, hydraulic technicians and maintenance crews responsible for:
- Commissioning new hydraulic systems on vessels and offshore units
- Overseeing installation quality and cleanliness verification
- Planning flushing and testing activities to minimize contamination-related failures
Related standards
- ISO 28521 (referenced throughout ISO 28522) - provides the detailed grades of cleanliness, flushing acceptance criteria and recommended flow velocities (listed as to be published in the ISO 28522 document).
Keywords: ISO 28522, hydraulic oil systems, flushing, marine hydraulic systems, assembly guidance, cleanliness, beta ratio, pressure testing, commissioning.