EN ISO 6251:1998

SLOVENSKI STANDARD
01-november-1999
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SIST EN ISO 6251:1998
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Liquefied petroleum gases - Corrosiveness to copper - Copper strip test (ISO 6251:1996)
Flüssiggase - Korrosionswirkung auf Kupfer - Kupferstreifenprüfung (ISO 6251:1982)
Gaz de pétrole liquéfiés - Action corrosive sur le cuivre - Essai a la lame de cuivre (ISO
6251:1982)
Ta slovenski standard je istoveten z: EN ISO 6251:1998
ICS:
75.160.30 Plinska goriva Gaseous fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL
STANDARD
Second edition
1996-l l-01
Liquefied petroleum gases -
Corrosiveness to copper - Copper
strip test
Gaz de p&role liq&fi& -
Action corrosive sur le cuivre - Essai 2 la lame
de cuivre
Reference number
IS0 6251 :I 996(E)
IS0 6251:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
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 IS0 6251 was prepared by Technical Committee
ISO/TC 28, Petroleum products and lubricants.
IS0 6251: 1982
This second edition ca ncels and replaces the first edition
which has been techni tally revised.
Annex A forms an integral part of this International Standa d .
0 IS0 1996
All rights reserved. Unless otherwise specified, no part of this publication may be
reproduced or utilized in any form or by any means, electronic or mechanical, including
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-121 1G eneve 20 l Switzerland
Printed in Switzerland
ii
IS0 6251:1996(E)
INTERNATIONAL STANDARD 0 IS0
Liquefied petroleum gases - Corrosiveness to copper -
Copper strip test
WARNING - 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. It
is the responsibility of the user of this International Standard to establish appropriate safety and health
practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard describes a method for the determination of the corrosiveness to copper of liquefied
petroleum gases.
NOTE - For an equivalent copper strip test applicable to less volatile petroleum products, see IS0 2160.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
IS0 2160:1985, Petroleum products - Corrosiveness to copper - Copper strip test.
- Specification and test methods.
IS0 3696: 1987, Water for analytical laboratory use
3 Definition
For the purposes of this International Standard, the following definition applies.
3.1 liquefied petroleum gas (LPG): Hydrocarbon gas that can be stored and/or handled in the liquid phase under
moderate conditions of pressure and at ambient temperature. It consists essentially of C3 and Cd alkanes or
alkenes, or a mixture of these, contains generally less than 5 % by liquid volume of material of higher carbon
number, and having a gauge vapour pressure not exceeding approximately 1 600 kPa at 40 “C.

@ IS0
IS0 6251:1996(E)
4 Principle
A polished copper strip is immersed for 1 h at a temperature of 40 “C in 100 ml of water-saturated LPG sample
contained in a test cylinder at a suitable working pressure. At the end of this period, the copper strip is removed
and the corrosiveness to copper of the LPG sample is rated as one of four classifications given in table 1 by
comparison with a copper corrosion standard plaque.
Table 1 - Copper strip corrosion classifications
DescriptionI)
Classification Designation 1
I I
Freshly polished copper Untarnished 2)
i
strip
Light orange, almost the same as a freshly polished strip
1 Slight tarnish
Dark orange
Claret red
2 Moderate tarnish
Lavender
Multicoloured with lavender blue and/or silver overlaid on claret red
Silvery
Brassy or gold
Dark tarnish Magenta overcast on brassy strip
Multicoloured with red and green showing (peacock), but no grey
Corrosion Transparent black, dark grey or brown with peacock green barely showing
Graphite or lustreless black
Glossy or jet black
1) The copper corrosion standard is comprised of strips characteristic of these descriptions.
2) The freshly polished strip is included in the series only as an indication of the appearance of a properly polished strip before a test run;
it is not possible to duplicate this appearance after a test even with a completely noncorrosive LPG sample.
I
5 Reagents and materials
5.1 Wash solvent, analytical grade acetone free from sulfur, or 2,2,4-trimethylpentane, 99 % minimum purity.
5.2 Water, conforming to grade 3 of IS0 3696.
5.3 Copper strip, 75 mm + 5 mm long, 12,5 mm * 2,5 mm wide, and I,5 to 3,0 mm thick, conforming to the
specification for copper given in IS0 2160 and having a hole of 3 mm diameter drilled approximately 3 mm from
one end and centred across the width of the strip.
5.4 Polishing materials, including silicon carbide grit paper of various degrees of fineness, one of which is 65 pm
paper or cloth; also a supply of 105 pm silicon carbide powder and pharmaceutical grade absorbent cotton (cotton
wool).
5.5 Copper corrosion standardsl)
The care and inspection for stability of such plaques shall be carried out in accordance with IS0 2160.
6 Apparatus
6.1 Corrosion test cylinder (see figure I), capable of withstanding a hydrostatic pressure test of 7,0 MPa, and
leaktight when filled with gas at a pressure of 3,5 MPa and immersed in the water bath (6.2). It shall consist of the
following items:
1) The copper strip corrosion standard is available commercially. Details may be obtained from the Secretariat of lSO/TC 28.
@ IS0 IS0 6251:1996(E)
6.1.1 Stainless steel test cylinder, of the form and dimensions shown in figure 1 and tapped at the lower end to
take a suitable type of 6 mm needle-valve, top-end threaded for attachment with top closure.
NOTE - A needle-valve with V-cone stem tip design has been found suitable.
6.1.2 Top closure, of stainless steel, with a chloroprene rubber O-ring on the internal surface and with threaded
coupling to secure to the stainless steel test cylinder.
The closure shall be tapped to take a suitable type of 6 mm needle-valve (see note in 6.1 .I) and to carry a stainless
steel dip-tube, at the lower end of which there shall be a hook from which the copper strip is hung.
Dimensions in millimetres
6 mm needle
valve A
Top closure
Chloroprene O-ring
Threads
Dip tube
@ int. 3
Q, int. 38
Copper strip
6 mm needle
valve B
Material of test cylinder, dip tube, needle-v
...