ISO 28520:2009

Ships and marine technology - Lubricating oil systems - Guidance for grades of cleanliness and flushing

ISO 28520:2009 provides guidance for flushing of lubricating oil systems, and grading of the resultant cleanliness. The flushing process is twofold: to remove dirt from the erection and installation, and to demonstrate that the pipes and the system as a whole is sufficiently clean. Crankcase and, where applicable, gearbox etc. are cleaned separately before flushing, and requirements relating to this are also specified in ISO 28520:2009. Similar considerations apply to the system tank and other components of the system. For the purposes of ISO 28520:2009, the cleaning process is considered as “washing through” when the Reynolds is equal to or less than 3 000 and “flushing” when the Reynolds number is equal to or greater than 3 000. Where available, any original equipment manufacturer requirements for flushing take precedence over the requirements outlined in ISO 28520:2009.

Navires et technologie maritime — Circuits d'huile de graissage — Guide relatif aux degrés de propreté et de rinçage

General Information

• Status: Published
• Publication Date: 08-Feb-2009
• ICS: 47.020.99 - Other standards related to shipbuilding and marine structures
• Technical Committee: ISO/TC 8/SC 3 - Piping and machinery
• Drafting Committee: ISO/TC 8/SC 3 - Piping and machinery
• Current Stage: 9060 - Close of review
• Completion Date: 04-Mar-2030

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.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 28520
First edition
2009-02-15
Ships and marine technology —
Lubricating oil systems — Guidance for
grades of cleanliness and flushing
Navires et technologie maritime — Circuits d'huile de graissage —
Guide relatif aux degrés de propreté et de rinçage

Reference number
©
ISO 2009
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ii © ISO 2009 – All rights reserved

Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Recommended degrees of pipe cleaning. 2
4.1 Degrees of pipe cleaning during/after prefabrication. 2
4.2 Inside surface treatment . 2
5 Cleaning of system components . 2
5.1 Pumps, valves, filters, oil coolers, etc. 3
5.2 Engine crankcase . 3
5.3 Gearbox . 3
5.4 Tanks. 6
5.5 Special comments . 6
6 Flushing . 6
6.1 Flushing practice (2-stroke engine). 6
6.2 4-stroke engines (practical execution) . 12
6.3 Flushing execution . 12
6.4 Flushing practice (turbines and turbo generators) . 13
7 Approval of flushing. 13

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 28520 was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 3, Piping and machinery.
iv © ISO 2009 – All rights reserved

INTERNATIONAL STANDARD ISO 28520:2009(E)

Ships and marine technology — Lubricating oil systems —
Guidance for grades of cleanliness and flushing
1 Scope
This International Standard provides guidance for flushing of lubricating oil systems, and grading of the
resultant cleanliness. The flushing process is twofold:
⎯ to remove dirt from the erection and installation, and
⎯ to demonstrate that the pipes and the system as a whole is sufficiently clean.
Crankcase and, where applicable, gearbox etc. are cleaned separately before flushing, and requirements
relating to this are also specified in this International Standard. Similar considerations apply to the system tank
and other components of the system.
For this International Standard, the cleaning process is considered as “washing through” when the Reynolds
number, R , is u 3 000, and “flushing” when the R W 3 000.
e e
NOTE If available, any original equipment manufacturer requirements for flushing take precedence over the
requirements outlined in this International Standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 4406, Hydraulic fluid power — Fluids — Method for coding the level of contamination by solid particles
ISO 8501-1, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel
substrates and of steel substrates after overall removal of previous coatings
1)
ISO 28521 , Ships and marine technology — Hydraulic oil systems — Guidance for grades of cleanliness
and flushing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

1) To be published.
3.1
main engine
ME
prime mover used for propulsion of the vessel or to drive a ship's generator
3.2
turbocharger
TC
centrifugal blower driven by exhaust-gas turbines and used to supercharge an engine
3.3
lubricating oil
LO
petroleum product designed to reduce friction and heat between moving parts in internal combustion engines
3.4
Reynolds number
R
e
dimensionless ratio of the internal flow forces to the viscous forces within a fluid
NOTE An indicator of the flow characteristics (laminar or turbulent) of a moving fluid.
4 Recommended degrees of pipe cleaning
This clause specifies the recommended degrees of pipe cleaning during and after prefabrication for pipes or
parts, possibly followed by inside surface treatment.
To ensure the best possible conditions for flushing, individual prefabricated parts should be made and
cleaned, before erection on-board.
4.1 Degrees of pipe cleaning during/after prefabrication
Concerning prefabrication of pipes and parts, it is recommended that these are completely cleaned inside,
which means that all welds associated with the welding of pipe sections and pipe branches should be smooth
and free of slag, welding spatter, burns and porosities. Fillet welds on flanges should be smooth and finely
grounded and should also be free of roundings as these can damage part of the joint faces. Concerning
possible subsequent chemical acid-cleaning or mechanical blast-cleaning, the degree of cleaning should
correspond to Sa 2 1/2 as specified in ISO 8501-1.
Steel sand should not be used for shot blasting, due to the risk of adhesion by magnetism or rusting; copper
(Cu) slag should be used instead. Sealing surfaces are to be mechanically well protected during shot blasting.
4.2 Inside surface treatment
In order to maintain the above-mentioned degree of cleaning before erection on-board, it is recommended that
the inside of the pipes be treated with an appropriate oil product.
Painting the inside with appropriate paint is sometimes prescribed by various manufacturers, and any such
requirements should be followed.
5 Cleaning of system components
Shot blasting, grinding, painting and welding should not be executed in the near vicinity during cleaning
operations on the items listed in 5.1 to 5.4.
2 © ISO 2009 – All rights reserved

5.1 Pumps, valves, filters, oil coolers, etc.
System oil requirements shall be requested from suppliers of these auxiliaries.
5.2 Engine crankcase
When engines (especially large engines) are delivered without cleaned and sealed lubricating oil systems,
including the crankcase, the crankcase shall be cleaned before flushing. This can be done as follows.
a) Blank-offs are placed on each oil drain to the engine mainframe. Starting at the top of one cylinder block
at a time, the inside of the crankcase is washed down with oil to remove rough particles. During this task
the engine crankshaft is turned at regular intervals so that chains, chain wheels, and the crankshaft are
washed down and cleaned.
b) A thin, non-drying oil, is recommended (about SAE 10 to 30 cSt), the remainder of which is compatible
with the system oil, which can dissolve the rust-prevention product which the engine has been coated
with when delivered. System oil (SAE 30 − 90 cSt or SAE 40 − 175 cSt) may be employed instead,
provided the oil is heated to 55 °C to 60 °C. In practice, 200 l to 400 l per cylinder have proven to be
sufficient, with the same quantity used for camshaft drive.
When the camshaft drive is cleaned, the thrust bearing cover is removed, if possible, and the thrust bearing is
washed down. Furthermore, the thrust-bearing ahead and astern thrust-pads are taken out for wiping if
possible. Ensure that the flash point of the oil is not too low (danger of fire).
Some rust prevention oils can influence the foam characteristic of the system oil; this occurrence can be
limited in the following way. The work can be partly done from the outside of the crank and shaft casting
through various inspection covers. After an appropriate amount of time, allowing for dripping and draining, the
dirty flush oil and deposited sediments shall be removed from the oil sump. The inside of the engine is then
wiped with lint-free and non-frayed cloths, and an inspection is made before the actual flushing is
commenced.
5.3 Gearbox
If gears are delivered with no cleaned and sealed lubrication oil systems, including pump and pipes, the gears
shall be cleaned before flushing.
5.3.1 Sealed gearboxes
For sealed gearboxes, external piping, filters and pumps, see 6.3.1.
5.3.2 Non-sealed gearboxes
For non-sealed gearboxes (when assembling gearboxes, including external pump, piping, filters and coolers)
see 6.3.2.
5.3.3 Choice of cleanliness level
The most impurity-sensitive components in a gearbox are, typically, ball- and roller-bearings. Information
concerning required bearing-cleanliness may be obtained from the bearing supplier, but shall in all cases be
stated by the gearbox supplier.
To a wide extent, the demand for life cycle and bearing load conditions shall guide the choice of cleanliness
level.
Bearing manufacturers have developed a bearing-lifetime theory, which among other items includes the
influence of impurities on service lifetime based on system lubrication oil. Figures 1 and 2 show the
relationship between size and hardness of impurities, how harmful they are to bearing life, and how important
it is to focus on cleanliness.
Key
X grain hardness, expressed in Vickers hardness (HV)
Y grain size, expressed in micrometres
a
Harmless.
b
Harmful.
NOTE In the calculation of these results the following parameters are used: friction coefficient, µ, 0,1; oil film
thickness 0,4 ∝m; hardness of outer track and roller 800 HV.
Figure 1 — Attrition particle's damaging effects with relation to their size and hardness
4 © ISO 2009 – All rights reserved

Key
L bearing lifetime, expressed in million revolutions
X absolute filter fineness, expressed in micrometres
Figure 2 — Bearing lifetime (L ) as a function of filter fineness
Table 1 indicates proposals for the degree of cleanliness for the various gear types.
Gear type, in this context, is a specification that combines and includes such characteristics as speed, load
variation and lifetime frequent start-stop.
Table 1 — Level of cleanliness for the various types of gear
Type of gear Level of cleanliness Level of cleanliness Max. allowable Typical service oil
after approved after commissioning contamination during filter
flushing trial service
ISO 4406 ISO 4406 ISO 4406
β > 75
x
1 16/14/11 17/15/12 18/16/13 3-5 µm
2 17/15/12 18/16/13 19/17/14 5-10 µm
3 18/16/13 19/17/14 20/18/15 5-10 µm
4 21/19/16 22/20/17 23/21/19 20-50 µm

The classification of type of gear (number) is explained as follows.
1) Demand for long service life, high operational reliability, high gear load, rpm (> 3 000), frequent start-stop,
such as on ferries with gas turbines on short crossings, and high loaded gear with mu
...