ISO 9785:2002

INTERNATIONAL ISO
STANDARD 9785
Second edition
2002-07-15
Ships and marine technology — Ventilation
of cargo spaces where vehicles with
internal combustion engines are driven —
Calculation of theoretical total airflow
required
Navires et technologie maritime — Ventilation des espaces cargaison des
navires dans lesquels des véhicules à moteur à combustion interne sont
utilisés — Calcul du débit d'air total théorique exigé

Reference number
ISO 9785:2002(E)
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ISO 2002

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ISO 9785:2002(E)
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ISO 9785:2002(E)
Contents Page
1 Scope . 1
2 Terms and definitions . 1
3 Airflow calculation . 1
4 Pollution from vehicles . 3
5 Factors of dilution . 3
Annexes
A Pollutants from vehicles in cargo spaces in ships. 4
B General information and guidance as to good practice . 8
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ISO 9785:2002(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 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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 9785 was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 3, Piping and machinery.
This second edition cancels and replaces the first edition (ISO 9785:1990), which was revised for continued
consistency with International Marine Organization provisions for calculating required ventilation in cargo spaces
where vehicles with internal combustion engines may be driven.
Annex A forms a normative part of this International Standard. Annex B is for information only.
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ISO 9785:2002(E)
Introduction
The purpose of this International Standard is to ensure that exposure to substances hazardous to health should be
kept as low as is reasonably practicable in work areas in cargo spaces in ships. This can, as a rule, be achieved by
limiting exhaust gas emissions as far as possible (by controlling the traffic) and by providing a high flow of air in the
cargo spaces. For further information and guidance regarding good practice, please refer to recent guidelines
developed by the International Maritime Organization which are contained in the IMO Maritime Safety Committee
Circular 729 (MSC Circ. 729), Guidelines and Operational Recommendations for Ventilation Systems in RO-RO
Cargo Spaces.
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INTERNATIONAL STANDARD ISO 9785:2002(E)
Ships and marine technology — Ventilation of cargo spaces where
vehicles with internal combustion engines are driven — Calculation
of theoretical total airflow required
1 Scope
This International Standard specifies methods of calculating the theoretical quantity of outdoor air required in cargo
spaces of ships where vehicles with internal combustion engines are driven, in order to dilute the polluted air to within
the permitted occupational exposure limits.
Annex A specifies average values of the amounts of pollutants in exhaust gases from vehicles with internal
combustion engines driven in cargo spaces in ships.
Annex B gives general information and guidance as to good practice for the ventilation of cargo spaces in ships
where vehicles with internal combustion engines may be driven.
Users of this International Standard should note that, while observing the requirements of the standard, they should
at the same time ensure compliance with such statutory requirements, rules, and regulations as may be applicable to
the individual ship concerned. Users should also refer to guidelines developed by the International Maritime
Organization (IMO) contained in the Maritime Safety Committee Circular 729 (MSC Circ. 729), Guidelines and
Recommendations for Ventilation systems in RO-RO Cargo Spaces.
2 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
2.1
cargo space
space used for cargo where vehicles may be driven
2.2
occupational exposure limit
highest airborne concentrations averaged over a specified period of time (time-weighted average or TWA) of
substances hazardous to health for employees at work
NOTE An occupational exposure limit refers either to a long-term exposure limit or to a short-term exposure limit as determined
by the appropriate authority.
2.3
working area
area occupied by employees at work
3 Airflow calculation
3.1 Volume of space
The volume of total cargo spaces shall be the gross volume with no deduction for the cargoes or for frames, webs,
pillars, ducts, etc. In the case of lining or insulation of cargo spaces, the volume shall be calculated from the inside of
the lining or insulation.
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ISO 9785:2002(E)
3.2 Supply airflow
3.2.1 General
The outdoor-supply airflow to the cargo spaces shall be calculated using whichever of the following criteria gives the
highest value:
— minimum number of air changes according to applicable statutory requirements;
— required outdoor-supply airflow to maintain the occupational-exposure limit-value.
3.2.2 Supply airflow to maintain the occupational-exposure-limit value
3.2.2.1 Introduction
The sum of the required outdoor-supply airflows per vehicle in operation to maintain the occupational-exposure-limit
value is calculated in accordance with 3.2.2.2 or 3.2.2.3 for normally polluted outdoor air or highly polluted outdoor
air, respectively.
3.2.2.2 Normally polluted outdoor air
The required outdoor-supply airflow, q , per vehicle in operation for normally polluted outdoor air, in cubic metres per
p
3
second (m /s), is given by the equation
q
m
q =
p
ac
where
q is the pollution per vehicle in operation, in milligrams per second (see clause 4);
m
a is the factor of dilution (see clause 5);
c is the occupational-exposure-limit value, in milligrams per cubic metre.
(See typical examples of application in B.2.)
NOTE The pollution contents of normally polluted outdoor air can be taken to be less than 1/40 of the occupational-exposure-
limit value.
3.2.2.3 Highly polluted outdoor air
The required outdoor-supply airflow, q , per vehicle in operation for highly polluted outdoor air, in cubic metres per
p
second, is given by the equation:
q
m
q =
p
�
a(c−c )
where
q , ac and are as defined in 3.2.2.2;
m
�
c is the content of the pollutant in question in outdoor air, in milligrams per cubic metre.
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ISO 9785:2002(E)
4 Pollution from vehicles
The purchaser shall specify the type of engine in the vehicles, the engine size, operation cycles (activity on board)
and the anticipated number of vehicles normally in operation simultaneously in each working area.
Where specific data on the amount of pollutants (substances hazardous to health) generated by these vehicles are
not available, the data according to A.1 shall be used. If the operation cycles are not the same as in A.1, quantities
calculated according to A.2 shall apply.
5 Factors of dilution
The factor of dilution indicates the degree of estimated or possible dilution of the air pollution in the cargo spaces.
The purchaser shall specify the factor of dilution taking into account any legal requirements. In the absence of such
a specification, the following factors shall apply:
— 0,8 in general cargo spaces;
— 0,4 in cargo spaces in car carriers;
— 0,8 in cargo spaces in ferries with a ventilation system in which the air is supplied at one end and exhausted at
the opposite end of the space.
NOTE Guidelines for factors of dilution are given in B.4.
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ISO 9785:2002(E)
Annex A
(normative)
Pollutants from vehicles in cargo spaces in ships
A.1 Assessment of pollutants in exhaust gases generated by vehicles on board ships
A.1.1 Average values of pollutants
Average values of the amount of pollutants in question in exhaust gases generated by vehicles with internal
combustion engines running in ship's cargo holds are given in A.1.2 to A.1.6.
A.1.2 Larger trucks
These are used for loading and unloading of Ro/Ro cargo ships.
Normal operating cycle: lift (45 s), transport, and some idling
Average amount of NO generated: ≈ 36 mg/s
2
Type of motor: — turbo-charged compression-ignition (diesel) engine
— power ≈ 150 kW
A.1.3 Smaller trucks
These are used for local cargo handling on board ships.
Normal operating cycle: lift, transport, and idling
Average amount of NO generated: ≈ 3 mg/s
2
Average amount of CO generated: ≈ 50 mg/s
Type of motor: — suction-fed compression-ignition engine
— power ≈ 74 kW
A.1.4 Larger ferries and coaches
These may be driven on board ferries and Ro/Ro ships.
Normal operating cycle: charging the compressed air systems for the brakes, acceleration and
running at low speed
Average amount of NO generated: ≈ 45 mg/s at
...