ISO 3448:1992 工業用液体潤滑剤—ISO粘度分類 | ページ 2

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.

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 3448 was prepared by Technical Committee ISO/TC 28, Petroleum products and lubricants.

This second edition cancels and replaces the first edition (ISO 3448:1975), of which it constitutes a technical revision.

Annex A of this International Standard is for information only.

Introduction

This International Standard has been prepared to meet the immediate needs of those ISO Technical Committees that promulgate International Standards for equipment and need to refer to lubricants, i.e. TC 39, Machines tools; TC 123, Plain bearings; TC 131, Fluid power systems; and others, by providing a classification of liquid lubricants according to viscosity grades. The purpose of this classification system is to establish a series of definite kinematic-viscosity levels so that lubricant suppliers, lubricant users and equipment designers will have a uniform and common basis for designating or selecting industrial liquid lubricants according to the kinematic viscosity required in a particular application.

When the first edition of this International Standard was being prepared, systems for classifying the viscosity characteristics of industrial liquid lubricants were simultaneously under study by the American Society for Testing and Materials (ASTM) in collaboration with the Society of Tribologists and Lubrication Engineers (STLE) (ASTM D 2422-68), by the British Standards Institution (BSI) (BS 4231) and by the Deutsches Institut für Normung (DIN). The cooperative effort first resulted in this ISO classification in 1975.

It is desirable that any such classification system should cover the entire range of kinematic viscosities of liquid lubricants normally used; at the same time, the number of kinematic-viscosity grades within the classification should be limited. A continuous system, in which any lubricant within the viscosity range could be given a grade number, was first considered, but it was recognized that this would involve either an unduly large number of grades or an unduly wide range of permitted kinematic viscosities for each grade.

For the classification to be of direct use in engineering design calculations, in which the kinematic viscosity of the lubricant is only one of the parameters, it is desirable that the viscosity grade width be not more than 10 % on either side of the nominal value. This would reflect an order of uncertainty in calculation similar to that imposed by dimensional manufacturing tolerances. This limitation. coupled with the requirement that the number of viscosity grades should not be too large, has led to the adoption of a discontinuous system with gaps between the viscosity grades.

The reference temperature for the classification should be selected to be reasonably close to average service experience. It should also closely relate to other selected temperatures used to define properties such as viscosity index which can aid in defining a lubricant. A study of a series of possible temperatures indicates that 40 °C is particularly suitable for the purposes of industrial-lubricant classification as well as for the lubricant-definition properties mentioned above. This viscosity classification is consequently based on kinematic viscosity at 40 °C.

The viscosity designations are identical to those in the well-known ASTM/STLE and BSI classifications previously mentioned.

Although this ISO classification is bound to lead to a number of existing lubricants (possibly including some at present widely used) not being accommodated within the classification, there is nothing to prevent the continued use of such products by agreement between supplier and consumer. The kinematic viscosities of such out-of-classification oils should, however, be determined at 40 °C. It is expected, however, that lubricant producers will move towards the adjustment of their products so that each product will fall within one of the viscosity grade designations; that users will, in the interests of rationalization and the reduction of the number of oils which they use, call increasingly for lubricants covered by the classification; and that machine and equipment manufacturers and their component suppliers will take due note of the classification in the design stages and in their lubricant viscosity recommendations.

It is not expected that liquid lubricants of every quality, or those designed for very specific purposes, will be, or will need to be, available within every viscosity grade of this International Standard.

1 Scope

This International Standard establishes a system of viscosity classification for industrial liquid lubricants and related fluids. This includes mineral oils used as lubricants, hydraulic fluids, electrical oils and for other applications. The usual method for kinematic-viscosity determination is that specified in ISO 3104, but this may give anomalous results when used with non-Newtonian fluids (i.e. those whose coefficient of viscosity varies significantly with rale of shear). For such fluids, it is therefore important to state the particular method by which viscosity has been determined.

It is also recognized that there may be some pure chemicals and naturally occurring products, used as lubricants, which will nol fall within this classification.

2 Normative reference

The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was 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 edition of the standard indicated below Members of IEC and ISO maintain registers of currently valid International Standards.