ISO 21963:2020

INTERNATIONAL ISO
STANDARD 21963
First edition
2020-09
Ships and marine technology —
Marine environment protection
— Tanks and piping systems for
facilitating 5 ppm oil-water separation
Navires et technologie maritime — Protection de l'environnement
marin — Réservoirs et systèmes de systèmes de tuyauterie utilisés
pour faciliter la séparation entre le pétrole et l'eau à 5 ppm
Reference number
ISO 21963:2020(E)
©
ISO 2020

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ISO 21963:2020(E)

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© ISO 2020
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Published in Switzerland
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ISO 21963:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Technical specifications . 1
4.1 Oil-water separation equipment (OWSE) . 1
4.2 5 ppm OWS . 3
4.3 Oil content meter (OCM) . 4
4.4 Automatic discharge stopping device (ADSD) . 4
4.5 Electric and electronic systems . 4
4.6 Heating facilities . 4
5 Installation requirements. 4
5.1 5 ppm OWS . 4
5.2 Oil content meter (OCM) . 5
5.3 Automatic discharge stopping device (ADSD) . 5
6 Testing of the 5 ppm OWS . 5
Annex A (informative) Examples of schematic diagrams for the management
of oil‑water effluents on fixed offshore marine structures . 6
Annex B (normative) Testing of 5 ppm OWS. 8
Annex C (normative) Environmental testing for the switchboard of the OWSE .18
Bibliography .20
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ISO 21963:2020(E)

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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 2, Marine environment protection.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 21963:2020(E)

Introduction
Marine environment protection is required by national, regional and international regulations.
The International Convention for the Prevention of Pollution by Ships (MARPOL) was adopted in 1973 and
it has been regularly updated by amendments made by the Marine Environment Protection Committee
(MEPC) of the International Maritime Organization (IMO). MARPOL is the legal basis for the prevention
of marine pollution. MARPOL requires the installation of oil-water separation systems to treat fluids
consisting of mixtures of oil and water generated on board ships.
On fixed offshore marine structures (e.g. converter stations and transformer substations of offshore
wind turbines), oil-in-water emulsions, oily mixtures of surface water, fuel and lubrication oil, and many
other substances covered by regulations might spill or otherwise cause hazards. Hence there is a need
to separate these mixtures to an oil concentration of less than what is currently required by MARPOL.
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INTERNATIONAL STANDARD ISO 21963:2020(E)
Ships and marine technology — Marine environment
protection — Tanks and piping systems for facilitating 5
ppm oil-water separation
1 Scope
This document provides requirements and test methods for tanks, piping and separation systems
facilitating the separation of contaminated fluids of oil and water on fixed offshore marine structures
and ships, where treatment is performed by separation systems that optimize oil-water separation to a
concentration equal to or less than 5 ppm.
It is applicable to fixed offshore marine structures and to ships operating in designated sea areas
determined by the relevant authorities.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 8217, Petroleum products — Fuels (class F) — Specifications of marine fuels
ISO 9377-2, Water quality — Determination of hydrocarbon oil index — Part 2: Method using solvent
extraction and gas chromatography
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
parts per million
ppm
number of parts of oil per one million parts of water, expressed by volume
Note 1 to entry: 1 ppm equals to 1 μl of oil per 1 l of water.
3.2
ppm display
numerical scale display of the parts per million (3.1)
4 Technical specifications
4.1 Oil-water separation equipment (OWSE)
Oil-water separation equipment (OWSE) installed on fixed offshore marine structures shall be
constructed suitable for offshore use.
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ISO 21963:2020(E)

The OWSE shall comprise:
— an oil-water separator (5 ppm OWS);
— a 5 ppm oil content meter (5 ppm OCM); and
— an automatic discharge stopping device (ADSD).
If intended to be fitted in locations where flammable atmospheres can be present, OWSE are expected
to comply with the relevant safety regulations for such spaces. Any electrical or electronic equipment
which is part of the 5 ppm oil-water separation equipment shall be either intended and designated for
use in non-hazardous areas, or, if intended to be used in hazardous areas, it shall be type-approved by
the Administrations or recognized organizations on their behalf as safe for use in hazardous areas.
Figure 1 shows an example of the functional layout of an OWSE.
The OWSE shall be resistant to corrosion and to other conditions of the marine environment where it
is in use.
The OCM may include an oil content alarm.
An example of a schematic plan for the management of oil-in-water effluents in fixed marine offshore
structures is shown in Figure A.1.
An example of a schematic diagram for the management of the separation and treatment of oil-in-water
effluents on fixed marine structures is shown in Figure A.2.
Fixed offshore marine structures or ships fitted with an OWSE shall, at all times, have a copy of the
operating and maintenance manuals available.
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ISO 21963:2020(E)

Key
1 5 ppm OWS 8 ADSD
2 mixture inlet, filling and rinsing (oil-free water) 9 sampling location
3 discharge treated water, oil <5 ppm into the sea 10 back to bilge water holding tank or bilge
4 discharge separated media into waste oil tank 11 OCM
5 manual recirculation facility or valve for testing 12 flushing water inlet
(inherently safe)
13 back to bilge water holding tank or bilge
6 discharge for testing 14 flow switch controller
7 recirculation water, oil >5 ppm
Figure 1 — Example of functional layout of an OWSE
4.2 5 ppm OWS
The 5 ppm OWS shall be designed to reduce the oil content in an oil-in-water mixture to a volume
concentration equal to or less than 5 ppm.
The 5 ppm OWS shall be so designed that it functions automatically. However, fail-safe arrangements to
avoid any discharge in case of malfunction shall be provided.
The 5 ppm OWS may include any combination of a separator utilizing gravity separation, filtration, and
coalescence to produce an effluent with an oil content not exceeding 5 ppm by volume.
The 5 ppm OWS shall utilize a continuous automatic process and shall indicate when it is in operation. It
shall be capable of continuous operation for at least 24 h or normal duty without attention.
All parts of the 5 ppm OWS which are subject to wear and tear shall be easily accessible for maintenance.
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ISO 21963:2020(E)

4.3 Oil content meter (OCM)
The OCM shall be able to measure the oil content in the water mixture with a resolution of 1 ppm and
shall provide a ppm display. The ppm reading shall not be affected by emulsions and/or the type of oil.
The OCM shall give an alarm signal if the oil content exceeds 5 ppm in the effluent. The response time
of the OCM, that is the duration between a deviation in the sample being supplied to the OCM and the
display showing the current oil content (ppm), shall not exceed 5 s.
If the OCM is flushed with water for more than 5 s, the system shall create an alarm.
The accuracy of the OCM shall be checked at least every 5 years according to the manufacturer's
instructions. Alternatively, the unit may be replaced by a calibrated OCM. The calibration certificate for
the OCM, certifying the date of the last calibration check, shall be retained on the fixed offshore marine
installation for inspection purposes. The accuracy checks can only be done by the manufacturer or duly
authorized entity.
The bilge alarm shall record date, time and alarm status, and operating status of the OWS. The recording
device shall also store data for at least eighteen months and shall be able to display or print a protocol
for official inspections as required. In the event the bilge alarm is replaced, means shall be provided to
ensure the data recorded remains available on board for 18 months.
To avoid willful manipulation of the bilge alarms, every access of the bilge alarm requires the breaking
of a seal.
The alarm is always activated even when clean water is used for cleaning or zeroing purposes.
[2]
The Administration shall require the type approval of the 5 ppm OCM .
4.4 Automatic discharge stopping device (ADSD)
The ADSD shall stop automatically any discharge overboard of the oily mixture if the content of the
effluent exceeds 5 ppm measured by the OCM, or when failure of the OCM occurs.
The ADSD shall consist of a valve arrangement, installed in the effluent outlet line of the 5 ppm OWS,
which diverts the effluent mixture from being discharged overboard back to the source or other tank if
the free oil content of the effluent exceeds the pre-set value.
4.5 Electric and electronic systems
The switchboard of the OWSE shall be type-approved by the Administration or recognized organization
on their behalf in accordance with Annex C of this document.
4.6 Heating facilities
If the OWSE is fitted with heating facilities to retain the oil in it to a maximum of 40 °C by any process,
the certificate of type approval shall be endorsed with the following statement:
"The 5 ppm OWSE is fitted with heating facility"
5 Installation requirements
5.1 5 ppm OWS
For inspection purposes, a sampling point shall be provided at a position in a vertical section of the
water effluent piping as close as is practicable to the 5 ppm OWS outlet. Recirculation facilities shall be
provided, after and adjacent to the overboard outlet of the stopping device, to enable the OWSE system
to be tested with the overboard discharge closed (see Figure 1).
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ISO 21963:2020(E)

The recirculating facility shall be so configured as to prevent, under all operating conditions, any by-
pass of the OWS.
The capacity of the supply pump shall not exceed 90 % of the rated capacity of the 5 ppm OWS.
The OWS shall be fitted with a permanently attached nameplate giving any operational or installation
limits considered necessary by the manufacturer.
5.2 Oil content meter (OCM)
The arrangement for the monitoring of the OWS discharge line to the OCM shall give a representative
sample of the effluent with an adequate pressure and flow.
5.3 Automatic discharge stopping device (ADSD)
The layout of the installation shall be arranged so that the overall response time, including the response
time of the OCM between an effluent discharge from the OWS exceeding 5 ppm and the operation of the
ADSD preventing overboard discharge, shall be as short as possible and in any case not more than 20 s.
6 Testing of the 5 ppm OWS
The OWS shall be tested in accordance with Annex B.
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ISO 21963:2020(E)

Annex A
(informative)

Examples of schematic diagrams for the management
of oil‑water effluents on fixed offshore marine structures
Key
1 transformer/converter room 9 holding tank for separated oil
2 collection pan 10 collector tank for extinguishing agent
3 oil cooler 11 rain water
4 engine room 12 bilge water
5 helicopter deck 13 surface water
6 collection pan 14 extinguishing agent
7 holding tank 15 clean water with residual oil ≤5 ppm
8 OWSE
Figure A.1 — Example of a schematic plan for the management of oil‑in‑water effluents
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ISO 21963:2020(E)

Key
1 5 ppm OWS 9 rinsing water/no drinking water
2 OCM 10 tank drains
3 bilge in engine room 11 recirculation
4 holding tank (bilge water tank) 12 pipeline for sludge into a sludge tank
5 outlet to function test of ADSD 13 bottom inclination ≥10 degrees
6 treated water, oil content ≤5 ppm 14 emergency bilge pipeline
7 sampling 15 non-return valve
8 separated oil 16 filling and rinsing/no drinking water
Figure A.2 — Example of schematic diagram of oil‑in‑water effluents systems
in the machinery space of fixed offshore marine structures and ships
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ISO 21963:2020(E)

Annex B
(normative)

Testing of 5 ppm OWS
B.1 General
This annex specifies the test procedures of 5 ppm OWS.
The 5 ppm OWS shall be tested using the test rig described in B.2 and the test fluids described in B.3 in
accordance with the test procedures specified in B.4. The effluent out from the 5 ppm OWS under these
tests shall be examined, in particular the oil content, in accordance with the procedures specified in
B.5, and reported in the way presented in B.6.
Where a range of 5 ppm OWS of the same design, but of different capacities, requires certification in
accordance with these specifications, the tests may be accept
...