BS 4231:1982 pdf free download.British Standard Classification for Viscosity grades of industrial liquid lubricants.
O INTRODUCTION
BS 4231 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, Machine tools; TC 123. Plain bearings; TC 131 • Fluid power systems and components; and others, by providing a classification of liquid lubricants according to viscosity grades. The purpose of this 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.
Systems for classifying the viscosity characteristics of industrial liquid lubricants have been simultaneously under study by the American Society for Testing and Materials (ASTM) in collaboration with the American Society of Lubrication Engineers (ASLE) (ASTM 0 2422•68), by the British Standards Institution (BSI) (BS4231), and by the Deutscher Normenausschuss (DNA). The co•operative effort has resulted in this ISO classification.
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 a similar order of uncertainty in calculation 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 well suited for purposes of industrial lubricant classification as well as those other properties. This viscosity classification is consequently based on kinematic viscosity at 40 °C.
The viscosity designations are identical with those in the well-known ASTM/ASLE and BSI classifications previously mentioned. These classifications were based on a temperature of 100 °F (37,8 °C). It has been decided to phase out the use of the Fahrenheit temperatures at an appropriate rate. It is recommended that this should be achieved by allowing a limited period of up to 3 years during which systems using 40 °C and 37,8 °C would be equally acceptable. It is intended that after this interim period, the classification based on 40 °C will be the only recognized classification. It should be noted that for most lubricants the difference between the kinematic viscosities at 37.8°C and 40°C will be approximately 10 % (see the annex). This difference is recognized as being of no practical significance in industrial lubrication.
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 outof-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 reduc3ion 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 flood to be, available within every viscosity grade of this International Standard.
NOTE — The Society of Automotive Engineers (U.S.A.) established many years ago standards for identifying and/or classifying the viscosity characteristics of lubricants used in automotive engines or gears. Their systems, which are widely known and used in most countries of the world, are bawd on the measurement of kinematic vIscosity at temØeratures that are considered to represent the normal operating range; the nomenclature used is for example SAE lOW, 20W and 30 for engine oils (SAE J 300a) and SAE 75W, 90 and 140 for gear oils (SAE J 306a). It should be noted that this ISO classification for industrial liquid lubricants ii not Intended to replace either of the SAE systems; on the other hand the latter systems while they have desirable features for automotive lubricants, are not suitable for extension to Industrial lubricants In general.
1 SCOPE AND FIELD OF APPLICATION
BS 4231 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 rate 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 not fall within this classification.
2 REFERENCE
ISO 3104, Petroleum products — Transparent and opaque liquids — Determination of kinematic viscosity and calculation of dynamic viscosity.1)
3 CLASSIFICATION
3.1 The classification defines 18 viscosity grades in the range 2 cSt2) to 1 500 cSt2) at 40,0 °C; this covers, as far as petroleum-based liquids are concerned, approximately the range from kerosine to cylinder oils.
3.2 Each viscosity grade is designated by the nearest whole number to its mid-point kinematic viscosity in centistokes at 40,0 °C, and a kinematic viscosity range of ± 10 % of this value is permitted. The 18 viscosity grades with the limits appropriate to each are given in the table.
3.3 The classification is based on the principle that the mid-point kinematic viscosity of each grade should be approximately 50 % greater than that of the preceding one. The division of each decade Into six equal logarithmic steps provides such a system and permits a uniform progression from decade to decade, but in order to provide simple numbers the logarithmic series has been rounded off. The maximum deviation of the mId-point viscosities from the logarithmic series is 2,2 %.
3.4 The classification Implies no quality evaluation, and provides Information only on the kinematic viscosity at the defining temperature of 40,0°C. The kinematic viscosities at other temperatures depend on the viscosity/temperature characteristics of the lubricants, which are usually reported as viscosity/temperature curves or stated in terms of viscosity index (VI).
3.5 The kinematic viscosities of the same lubricants defined by BS 4231, but identified at other temperatures customarily used in some countries, are shown in the annex. Three values of viscosity index have been used. These are given here only for the purpose of general guidance in understanding or adoption of this International Standard.
4 TRANSITION PERIOD
For a period of not more than 3 years following approval of BS 4231, the classification of lubricants at 37,8 °C (100 °F) will be regarded as acceptable. Following this interim period, 40 °C will be the only recognized classification system temperature.
5 DESIGNATION
The following wording shall be used to designate a particular viscosity grade
ISO viscosity grade… (ISO 3448)
which may be abbreviated to
ISOVG…