ISO 21755-2:2020

INTERNATIONAL ISO
STANDARD 21755-2
First edition
2020-02
Motorcycles — Measurement method
for evaporative emissions —
Part 2:
Permeation test procedure
Motocycles — Méthode de mesure pour les émissions par
évaporation —
Partie 2: Méthode d'essai de perméation
Reference number
ISO 21755-2:2020(E)
©
ISO 2020

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ISO 21755-2:2020(E)

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ISO 21755-2:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fuel tank and fuel line assembly permeation test procedure . 1
4.1 Description of the fuel tank permeation test . 1
4.2 Test fuel . 2
4.3 Preconditioning fuel soak for the fuel tank permeation test . 2
4.4 Fuel tank permeation test procedure . 3
4.5 Fuel tank permeation test result calculation . 3
4.6 Fuel tank durability testing . 4
4.7 Fuel line assembly test requirements . 4
5 Presentation of results . 5
6 Fuel tank permeability test procedure (optional) . 5
Annex A (informative) Fuel tank permeability test procedure . 6
Annex B (normative) Presentation of the results . 8
Bibliography .10
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ISO 21755-2:2020(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
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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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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 38,
Motorcycles and mopeds.
A list of all parts in the ISO 21755 series can be found on the ISO website.
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 21755-2:2020(E)

Introduction
This document specifies the measurement method for evaporative emissions from motorcycles
by using a permeation test procedure. However, the amount of permeation from a non-metallic fuel
tank is generally larger than that from a metallic fuel tank. Therefore, this document also specifies a
permeability test procedure in an informative annex solely for non-metallic fuel tanks as optional. This
permeability test procedure is expected to be used also by fuel tank manufacturers.
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INTERNATIONAL STANDARD ISO 21755-2:2020(E)
Motorcycles — Measurement method for evaporative
emissions —
Part 2:
Permeation test procedure
1 Scope
This document specifies a basic measurement method by using a permeation test procedure for
evaporative emissions from motorcycles. It is applicable to motorcycles equipped with a fuel tank to
store liquid high volatile fuel and with a spark ignition engine (four-stroke engine, two-stroke engine or
rotary piston engine).
2 Normative references
There are no normative references in this document.
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
permeability
losses through the walls of the non-metallic fuel tank
3.2
permeation
losses through the walls of the fuel tank and fuel line assembly
4 Fuel tank and fuel line assembly permeation test procedure
4.1 Description of the fuel tank permeation test
4.1.1 Measure permeation emissions by weighing a sealed fuel tank before and after a temperature-
controlled soak according to the following flow charts (see Figure 1).
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ISO 21755-2:2020(E)

4.1.2 Fuel tank description shall be described in accordance with B.1.
Key
a
DF is the deterioration factor.
b
The length of "soak" during durability testing may be included in the fuel soak period provided that fuel remains
in the tank. Soak periods can be shortened to 10 weeks if performed a 316,2 K ± 5,0 K.
Figure 1 — Flow chart of fuel tank permeation full and short tests
4.2 Test fuel
The test fuel shall be selected in accordance with agreement among the parties involved or the
manufacturer's requirements and the specifications of test fuel shall be reported. An example of the
record form is given in B.2.
4.3 Preconditioning fuel soak for the fuel tank permeation test
To precondition the fuel tank in the fuel tank permeation test, the following five steps shall be followed:
4.3.1 The tank shall be filled with reference fuel specified in 4.2 and sealed. The filled tank shall be
soaked at an ambient temperature of 301,2 K ± 5,0 K for 20 weeks or at 316,2 K ± 5,0 K for 10 weeks.
4.3.2 The fuel tank’s internal surface area shall be determined in square metres accurate to at least
three significant figures. The manufacturer may use less accurate estimates of the surface area if it is
ensured that the surface area will not be overestimated.
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ISO 21755-2:2020(E)

4.3.3 The fuel tank shall be filled with the reference fuel to its nominal capacity.
4.3.4 The tank and fuel shall equilibrate to 301,2 K ± 5,0 K or 316,2 K ± 5,0 K in the case of the
alternative short test.
4.3.5 The fuel tank shall be sealed using fuel caps and other fittings (excluding petcocks) that can be
used to seal openings in a production fuel tank. In cases where openings are not normally sealed on the
fuel tank (such as hose-connection fittings and vents in fuel caps), these openings may be sealed using
non-permeable fittings such as metal or fluoropolymer plugs.
4.4 Fuel tank permeation test procedure
To run the test, the following steps shall be taken for a tank preconditioned as specified in 4.3.
4.4.1 Weigh the sealed fuel tank and record the weight in milligrams. This measurement sh
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