ISO INTERNATIONAL STANDARD 4256 Second edition 1996-10-15 ANsl Internat Doc Sec Liquefied petroleum gases - Determination of gauge vapour pressure - LPG method GazdepétroleliguéfiésDeterminationdelapressiondevapeur relative—MéthodeGPL ISO Reference number ISO 4256 1996(E) No reproduction or networking permitted without license from IHS Not for Resale ISO 4256:1996(E) Foreword ISO (the International Organization for Standardization) is a worldwide fed- eration of national standards bodies (lsO member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are Standard requires approval by at least 75 % of the member bodies casting a vote. ISO/TC 28, Petroleum products and lubricants. This second edition cancels and replaces the first edition (ISO 4256:1978) whichhasbeentechnicallyrevised Annexes A and B form an integral part of this International Standard. ISO1996 reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfim, without permission in writing from the publisher International Organization for Standardization Case Postale 56 . CH-1211 Geneve 20 . Switzerland Printed in Switzerland Not for Resale ISO 4256:1996(E) INTERNATIONALSTANDARD ISO Liquefied petroleum gases -- Determination of gauge vapour pressure LPG method 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 Scope of IEC and ISO maintain registers of currently valid In- ternational Standards This International Standard describes a method for the ISO 3007:1986, Petroleum products -- Determination determination of gauge vapour pressures of liquefied petroleum gas products (see clause 3) at temper- ofvapourpressureReidmethod atures within the approximate range of 35 °C to 70 °℃ ISO 4257:1988, Liquefied petroleum gases - Method ofsampling. NOTES 1 Information on the vapour pressure of liquefied petro- leum gases is required for the selection of properly de- signedstoragevessels,shippingcontainersandcustomer 3Definitions utilizationequipment,toensurethesafehandlingofthese products,andto ensurethat maximum operatingdesign For the purposes of this International Standard, the pressures are not exceeded under the foreseen ambient following definitions apply. operating conditions 2 The vapour pressure of liquefied petroleum gases is an 3.1 vapour pressure: Pressure exerted by the va- indirect measure of the lowest temperature at which initial vaporizationcanbeexpectedtooccurItmayalsobecon- pourof aliquidwheninequilibriumwiththe liguid sideredto be an indirect indication of the most volatilecon- stituent present in the product In this International Standard, the term "vapour press- ure" shall be understood as gauge vapour pressure, which is absolute vapour pressure minus atmospheric 2 Normative references pressure. The following standards contain provisions which, 3.2 liquefied petroleum gas (LPG): Hydrocarbon throughreferenceinthistext,constituteprovisionsof gas that can be stored and/or handled in the liquid this International Standard. At the time of publication, phase under moderate conditions of pressure and at the editions indicated were valid. All standards are ambient temperature. It consists essentially of C3 and subjecttorevision,andpartiesto agreementsbased C4 alkanes or alkenes, or a mixture of these, contains onthisInternationalStandardareencouraged toin generally less than 5 % by liquid volume of material of vestigate the possibility of applying the most r