Petroleum products - Determination of oxidation stability of gasoline - Induction period method (ISO 7536:1994)

The principle of the method specified is oxidizing the sample in a pressure bomb initially filled at 15 °C to 25 °C with oxygen at 690 kPa, heating at a temperature between 98 °C and 102 °C, reading the pressure at stated intervals or recorded continuously until the breakpoint is reached. The time required for the sample to reach this point is the observed induction period at the temperature of test, from which the induction period at 100 °C may be calculated. The method is applicable for aviation and motor gasolines in their finished form only.

Mineralölerzeugnisse - Bestimmung der Oxidationsbeständigkeit von Ottokraftstoff-Induktionsdauerverfahren (ISO 7536:1994)

Produits pétroliers - Détermination de la stabilité à l'oxydation de l'essence - Méthode de la période d'induction (ISO 7536:1994)

1.1 La présente Norme internationale prescrit une méthode pour la détermination de la stabilité de l'essence aviation et de l'essence pour moteur sous forme de produit fini seulement et dans des conditions d'oxydation accélérée, par la mesure en bombe d'oxydation de la période d'induction jusqu'au point critique. 1.2 La méthode1) n'est pas destinée à la détermination de la stabilité des coupes essences individuelles, en particulier celles qui présentent un pourcentage élevé de fractions insaturées à bas point d'ébullition car celles-ci créent des conditions explosives à l'intérieur de l'appareillage. Étant donné que l'on peut avoir à tester des échantillons de nature inconnue, l'appareillage incluant la bombe d'oxydation est muni de disques de rupture afin d'assurer la sécurité de l'opérateur. 1.3 La période d'induction peut être utilisée comme une indication de la tendance d'une essence à former des gommes pendant le stockage. Il est cependant reconnu que la corrélation entre les résultats de l'essai et la formation de gommes pendant le stockage peut varier de façon importante en fonction des conditions de stockage et suivant les différentes essences.

Naftni proizvodi - Ugotavljanje oksidacijske obstojnosti bencina - Metoda z indukcijskim časom (ISO 7536:1994)

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SIST EN ISO 7536:1998

Petroleum products - Determination of oxidation stability of gasoline - Induction period

method (ISO 7536:1994)

Mineralölerzeugnisse - Bestimmung der Oxidationsbeständigkeit von Ottokraftstoff-

Induktionsdauerverfahren (ISO 7536:1994)

Produits pétroliers - Détermination de la stabilité a l'oxydation de l'essence - Méthode de

la période d'induction (ISO 7536:1994)
Ta slovenski standard je istoveten z: EN ISO 7536:1996
75.160.20 7HNRþDJRULYD Liquid fuels
SIST EN ISO 7536:1998 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 7536:1998
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SIST EN ISO 7536:1998
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SIST EN ISO 7536:1998
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SIST EN ISO 7536:1998
First edition
Petroleum products - Determination of
Oxidation stability of gasoline - Induction
period method
Produits p6 troliers - Determination de Ia stabilit6 2 I ’oxyda tion de
I ’essence - Methode de Ia Periode d ’induction
Reference number
EO 7536:1994(E)
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SIST EN ISO 7536:1998
ISO 7536: 1994(E)
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. Esch 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.
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.
International Standard ISO 7536 was prepared by Technical Committee
ISO/TC 28, Petroleum products and lubrican ts.
Annexes A and B form an integral part of this International Standard.
0 ISO 1994

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced

or utilized in any form or by any means, electronie or mechanical, including photocopying and

microfilm, without Permission in writing from the publisher.
International Organkation for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
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SIST EN ISO 7536:1998
Petroleum products - Determination of Oxidation
- Induction period method
stability of gasoline

- The use of this International Standard may involve hazardous materials, operations


and equipment. This Standard does not purport to address all of the safety Problems associated

with its use. lt is the responsibility of the User of this Standard to establish appropriate safety and

health practices and determine the applicability of regulatory limitations Prior to use.

2.1 breakpoint: Point in the pressure-time cun/e
1 Scope
that is preceded by a pressure drop of exactly
14 kPa within 15 min and succeeded by a drop of not
1.1 This International Standard specifies a method
less than 14 kPa in 15 min.
for the determination of the stability of aviation and
2.2 induction period: Time elapsed between the
motor gasolines in their finished form only, under ac-
placing of the bomb in the bath and the breakpoint at
celerated Oxidation conditions, by measuring the in-
duction period to breakpoint in a pressure bomb 100 OC.
3 Principle
1.2 The methodl) is not intended for the determi-
The Sample is oxidized in a pressure bomb initially
nation of the stability of gasoline components individ-
filled at 15 “C to 25 “C with Oxygen at 690 kPa and
ually, particularly those with a high percentage of
heated at a temperature between 98 “C and 102 ‘C.
low-boiling unsaturated compounds, as they may
The pressure is read at stated intervals or recorded
Cause explosive conditions within the apparatus.
continuously until the breakpoint is reached. The time
However, because of the unknown nature of certain
required for the Sample to resch this Point is the ob-
samples, the specified bomb assembly includes a
served induction period at the temperature of test,
safety burst-disc in Order to safeguard the operatot-.
from which the induction period at 100 “C may be
1.3 The induction period may be used as an indi-
WARNING - To provide protection against the
cation of the tendency of gasoline to form gum in
possible explosive rupture of the bomb, the bomb
storage. lt should be recognized, however, that this
should be operated behind an appropriate safety
correlation may vary markedly under different storage
conditions and with different gasolines.
4 Reagents and materials
2 Definitions
4.1 Toluene, C,H,CH,, 99 % minimum purity.
For the purposes of this International Standard, the
following definitions apply. 4.2 Acetone, CH,COCH,, 99 % minimum purity.

1) Further information tan be found in the June 1978, January 1979 and June 1986 editions of the Institute of Petroleum

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SIST EN ISO 7536:1998
cf) ISO
ISO 7536:1994(E)

4.3 Gum solvent, mixture of equal volumes of move with respect to each other when the tightening

toluene (4.1) and acetone (4.2).
load is applied.
4.4 Oxygen, commercially available extra-dry, of not
5.2 Gasket, of any suitable material that will pass
less than 99 % purity.
the following test.
Place a gasket of the type under test in the bomb in
4.5 Detergent cleaning Solution, able to clean
the absence of gasoline and use a similar gasket to
used Sample Containers and covers to match the
make the seal with the lid. Fill the bomb with Oxygen
quality with regard to visual appearance and mass loss
at a pressure of 690 kPa and immerse in a bath at
on heating under test conditions obtained by im-
approximately 100 “C. If the pressure does not drop
mersing similar used Sample Containers and covers in
more than 14 kPa from the maximum in a 24 h period
fresh chromic acid cleaning Solution for 6 h followed
with the bath temperature constant at 100 “C
by rinsing with water as specified in 6.1.
+ 1,O “C, the gasket shall be considered satisfactoty.
NOTE 1 The type of detergent and condition of use need
to be established in each laboratory on the basis of cleaning
5.3 Sample Container and cover, in accordance
used Sample Containers and covers.
with figure 2.
WARNING - Chromic acid is potentially hazard-
NOTE 2 The cover is intended to prevent the material

ous in contact with organic materials and is toxic refluxing back through the bomb stem from entering the

Sample, but not to prevent free access of Oxygen to the
and highly corrosive. If used, wear full-face shield
and full-length protective clothing including
5.4 Bomb Stern, with a filier rod, constructed of the
same material as the bomb lid and having dimensions
5 Apparatus
in accordance with figure 1.

5.1 Pressure bomb, of corrosion-resistant steel, The filier rod and the inside of the stem shall have a

with inside dimensions of the Portion that encloses
high polish to facilitate cleaning and prevent corrosion.

the reacting gasoline-Oxygen mixture in accordance The stem shall be fitted, in the Position shown in fig-

with those shown in figure 1. ure 1, with a circular metal plate 89 mm in diameter

to serve as a closure for the bath when the bomb is
The interior surfaces of the bomb and lid shall be
in place.
highly polished to facilitate cleaning and to prevent
5.5 Burst-disc assembly, of stainless steel, fitted
to the bomb Stern, which will rupture if subjected to
Other structural details, such as method of closure
a pressure greater than 1 530 kPa + 10 %. Any
(polygonal or knurled), gasket material and outside di-
expelled gas shall be directed away from the Operator.
mensions, are optional provided the limitations given
in 5.1 .l and 5.1.2 are observed.
5.6 Connection for a pressure gauge and a tightly
Carry out initial testing and periodic examination of the
closing needle valve to the bomb stem as shown in
bomb to ensure its fitness for Service.
figure 1. A quick-release air coupling fitted to the nee-
dle valve shall be used to facilitate Oxygen entry to the
5.1.1 The bomb shall be constructed to withstand a
working pressure of 1 240 kPa at 100 “C, with an ul-
timate strength at least equal to that of a bomb con-
5.7 Needle valve, suitable for complete shutoff,
structed of 18 % mass fraction chromium and 8 %
fitted with a finely tapered needle and orifice.
mass fraction nickel-alloy steel. A suitable material is
an alloy steel conforming to the specification in
NOTE 3 The needle valve should be used while purging,
annex A.
pressurizing and exhausting the bomb with Oxygen.
5.1.2 The closure shall be capable of making a seal
5.8 Pressure gauge, indicating or recording type,
that will not leak when the bomb is filled with Oxygen
reading to at least 1 380 kPa.
to 690 kPa at 15 “C to 25 “C and plunged into a bath

at 100 “C. lt is preferable that the closure ring be Any half of the scale interval between 690 kPa and

constructed from an alloy different from that of the 1 380 kPa (i.e. 345 kPa) shall be at least 25 mm in

body if the mating threads of the two Parts are to length measured along the arc of the scale. The

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