BS-IEC-61624-1997.pdf

BRITISH STANDARD BS IEC 61624:1997 Guidance on the development of lists of maximum allowable temperatures for polymeric compounds used in electrotechnical equipment ICS 19.020; 29.035.20 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 This British Standard, having been prepared under the direction of the Electrotechnical Sector Board, was published under the authority of the Standards Board and comes into effect on 15 May 1998 © BSI 04-1999 ISBN 0 580 29782 9 National foreword This British Standard reproduces verbatim IEC 61624:1997 and implements it as the UK national standard. The UK participation in its preparation was entrusted by Technical Committee GEL/15, Insulating materials, to Subcommittee GEL/15/5, Methods of test, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the IEC title page, pages ii to iv, pages 1 to 10 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 © BSI 04-1999i Contents Page National forewordInside front cover Forewordiii Text of IEC 616241 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 ii © BSI 04-1999 Contents Page Forewordiii 1Scope1 2Normative references1 3Definitions1 4General discussion2 5Lists5 6Consideration of lists for “Maximum allowable temperatures for polymeric compounds under abnormal operating conditions”6 Annex A (informative) Indication of the available range of thermoplastic compounds based on the polymerization of propylene as the only or main monomer8 Annex B (informative) Designation system for thermoplastics8 Figure 1 Dynamic shear (torsion) modulus versus temperature for representative thermosets and thermoplastics, showing deflection temperature under load at 264 p.s.i (Modern plastics encyclopaedia) 13 Table 1 Recommended layout for lists5 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 © BSI 04-1999iii Foreword 1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested National Committees. 3) The documents produced have the form of recommendations for international use and are published in the form of standards, technical reports or guides and they are accepted by the National Committees in that sense. 4) In order to promote international unification, IEC National Committees undertake to apply IEC International Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with one of its standards. 6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights. The main task of IEC technical committees is to prepare International Standards. In exceptional circumstances, a technical committee may propose the publication of a technical report of one of the following types: type 1, when the required support cannot be obtained for the publication of an International Standard, despite repeated efforts; type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard; type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art”. Technical reports of types 1 and 2 are subject to review within three years of publication to decide whether they can be transformed into International Standards. Technical reports of type 3 do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful. IEC 61624, which is a technical report of type 2, has been prepared by subcommittee 15E: Methods of test, of IEC technical committee 15: Insulating materials. The text of this technical report is based on the following documents: Full information on the voting for the approval of this technical report can be found in the report on voting indicated in the above table. Committee draftReport on voting 15E/4/CDV15E/20A/RVC Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 iv © BSI 04-1999 This document is issued in the type 2 technical report series of publications (according to G.4.2.2 of Part 1 of the IEC/ISO Directives) as a “prospective standard for provisional application” in the field of polymeric compounds because there is an urgent requirement for guidance on how standards in this field should be used to meet an identified need. This document is not to be regarded as an “International Standard”. It is proposed for provisional application so that information and experience of its use in practice may be gathered. Comments on the content of this document should be sent to the IEC Central Office. A review of this type 2 technical report will be carried out not later than three years after its publication, with the options of either extension for a further three years or conversion to an International Standard or withdrawal. Annex A and Annex B are for information only. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 © BSI 04-19991 1 Scope This technical report gives guidance to technical committees wishing to develop lists of maximum allowable temperatures for polymeric compounds under normal and abnormal operating conditions. It discusses and makes recommendations concerning: a) the factors which influence the choice of an appropriate method of describing polymeric compounds, bearing in mind the complex recipes of many compounds and the resulting wide ranging properties (see 5.1); b) the factors which influence the selection of data for inclusion in lists of maximum allowable temperatures for polymeric compounds under normal operating conditions (see 5.2 and 5.3); c) lists for the maximum allowable temperatures for polymeric compounds under abnormal operating conditions (see clause 6). In this report the term “temperature” is used, although it is realized that it is customary to use “temperature rise” for practical reasons. One may be converted into the other, given an appropriate reference point, e.g. 25 °C. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this technical report. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this technical report are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 60216, Guide for the determination of thermal endurance properties of electrical insulating materials (being revised). IEC 60335-1:1991, Safety of household and similar electrical appliances Part 1: General requirements. IEC 60695-2-1/0:1994, Fire hazard testing Part 2: Test methods Section 1/sheet 0: Glow-wire test methods General. IEC 60695-2-1/1:1994, Fire hazard testing Part 2: Test methods Section 1/sheet 1: Glow-wire end-product test and guidance. IEC 60695-2-1/2:1994, Fire hazard testing Part 2: Test methods Section 1/sheet 2: Glow-wire flammability test on materials. IEC 60707:1981, Methods of test for the determination of the flammability of solid electrical insulating materials when exposed to an igniting source. ISO 75-2:1993, Plastics Determination of temperature of deflection under load Part 2: Plastics and ebonite. ISO 178:1993, Plastics Determination of flexural properties. ISO 527-1:1993, Plastics Determination of tensile properties Part 1: General principles. ISO 3673-1:1980, Plastics Epoxide resins Part 1: Designation. ISO 7391-1:1987, Plastics Polycarbonate moulding and extrusion materials Part 1: Designation. 3 Definitions For the purpose of this technical report, the following definitions apply. 3.1 maximum allowable temperature for polymeric compounds under normal operating conditions the maximum allowable temperature for a specific polymeric compound for safe use in a general electrotechnical application when used under normal operating conditions 3.2 normal conditions expected most severe thermal conditions that may exist over the long term under which the equipment operates according to its intended use 3.3 abnormal conditions short-term thermal conditions, with a severity significantly exceeding that found under normal conditions, arising from faults and/or expected short-term abuse NOTEAbnormal conditions may exist for periods ranging from a few seconds to 10 h during unattended operation (see clause 6). 3.4 long term a period of time of the same magnitude as the expected operational life of the equipment, for example for household appliances, in the range 50 h to 8 000 h 3.5 short term a period of time that is much less than the expected operational life of the equipment Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:50:35 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61624:1997 2 © BSI 04-1999 3.6 general electrotechnical applications use of an electrotechnical product in an environment, where the predominant type of long-term degradation of the product is the result of thermally activated chemical reactions 4 General discussion 4.1 Background The plastics industry worldwide manufactures upwards of one million different polymeric compounds, many of which find use in electrotechnical equipment as moulded, cast or machined parts. The range and magnitude of temperature/time exposure over which these parts may be used are dependent upon the property levels that have to be retained for safe storage, handling and use. The properties of these types of materials change with time and temperature with the rate of change also being dependent on temperature. The different properties may change at different rates. Frequently the mode of use and the local environmental conditions also lead to additional stresses which have an effect on the useful life of the materials/parts. A number of IEC committees have used normative lists of maximum allowable temperatures for parts made of insulating materials under normal operation for many years with apparent success and safety. However, these lists consisted of data for either products manufactured to other IEC standards which gave limiting conditions of use, or parts based on recognized and proven insulation systems, for example motor windings, or insulating materials of the thermosetting type. Thermoplastic insulating materials were specifically excluded from these lists. Parts made from thermoplastic materials were required to be tested separately with requirements being based on actual temperatures that had been measured during normal and abnormal operation. The question has now to be asked whether these lists can be safely extended to include thermoplastic materials as well as a wider selection of thermosetting types. In order to attempt an answer to this question and give guidance, a first requirement is to recognize the major differences between thermosetting and thermoplastic polymers. Thermoplastics can be softened by the action of heat in a reversible manner (Figure 1) and can be more deleteriously affected by common everyday materials than thermosetting types. These, when once formed as cross-linked entities, cannot be melted and are resistant to exposure to many classes of chemicals and everyday environments. A natural con