1、THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION A GUIDE TO RISK BASED ASSESSMENTS OF in situ LARGE Ex e and Ex N MACHINES PUBLICATION No 181 : 1995 Copyright 0 1995 The Engineering Equipment and Materials Users Association ISBN 0 85931 100 7 45 Beech Street LONDON EC2Y 8AD Telephone: 0207-
2、628 7878 e-mail: salestjleemua .CO. u k website: www.eemua.co.uk Fax: 0207-628 7862 THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION A Company Limited by Guarantee Registered in England N0.477838 Registered Office: 14-15 Belgrave Square LOfldQn, WlX 8PS Telephone;o171236531 W Fa: 01 71 -245
3、 6937 PUBLICATION NO 181 - ERRATA Risk Based Assessments of In situ Large Ex e and N Machines Following the release of the frrst printing, the following errors were noted. These in no way materially affect the result of any assessments which may have been made using the guidance given. - . 1) Power
4、and poles. _ There is an error on page 15 in 5.4.1.2. The kW per pole should be 250 and not 500. ( To use kW per POLE is correct. ._ 2) Addition or multiplication of factors Factors under IPF, LPF and PPF should be added but the grand total should multiply them. Total risk probability factor is: IPF
5、(T) x LPF(T) x PPF(T) (as given on page 24). On page 40 addition of factors is given incorrectly. R BgL J Richman Technical Secretary. 27.7.95 THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION The Engineering Equipment and Materials Users Association-EEMUA-was formed in 1983 by the amalgamat
6、ion of the Oil Companies Materials Association (OCMA) and the Engineering Equipment Users Association (EEUA). It is an organisation of substantial purchasers and users of engineering products, whose members include leading national and multinational companies in the petroleum, gas, chemical and ener
7、gy industries, and engineering contractors that provide services to those companies. A list of Full and Associate Members (the latter being limited to membership of three technical committees) is given below. EEMUA is concerned with the design, installation, operation and maintenance of tine enginee
8、ring plant used by members in pursuing their business activities. The Association aims to reduce members costs by providing the opportunity for them to share resources and expertise in order to keep abreast of technological developments and improve the effectiveness and efficiency of their engineeri
9、ng activities. EEMUA supports the British Standards Institution, works with other institutions, associations, government departments, regulatory authorities and the Confederation of British industry, and is also actively involved with other standards-making bodies, both national and international, s
10、uch as the American Petroleum Institute. Work, which is carried out in-house by members alone or with the help of other organisations, may lead to the production of Association publications. These are prepared primarily for members use, but are usually offered for sale and thus for more general use.
11、 Such publications may also be submitted, normally through the British Standards Institution, as bases for appropriate national, European or international standards. A list of current EEMUA publications which may be purchased from the Association is given at the end of this document. Full Members As
12、sociate Members ABB Associated Octel BP Conoco Dow Corning ExxonMobil Foster Wheeler Energy lnnogy (was National Power) Lindsey Oil Refinery PowerGen Shell Group Transco / Advantica TXU-Europe Power (was Eastern Generation) * Subsidiaries of Lattice plc (demerged ex BG) AEA Technology AstraZeneca BA
13、SF Chevron Texaco D8C Engineering/iAERCON Netherlands Flexsys ICI Norsk Hydro Northem NDT 01s Phillips Petroleum UK Pilkington Technology Royal Vopak Netherlands Syngenta UOP Affiliate Member British Compressed Gases Association ii ABOUT THIS PUBLICATION: LEGAL ASPECTS In order to ensure that nothin
14、g in this publication can in any manner offend against or be affected by the provisions of the Restrictive Trade Practices Act 1976, the recommendations which it contains will not take effect until the day following that on which its particulars are furnished to the Office of Fair Trading. As the su
15、bject dealt with seems likely to be of wide.interest, this publication is also being made available for sale to non-members of the Association. Any person who encounters an inaccuracy or ambiguity when making use of this publication is asked to notify EEMUA without delay so that the matter may be in
16、vestigated and appropriate action taken. . It has been assumed in the preparation of this publication that the user will ensure selection of those parts of its contents appropriate to the intended application and that such selection and application are correct carried out by appropriately qualified
17、and competent persons for whose guidance the publication has been prepared. EEMUA does not, and indeed cannot, make any representation or give any warranty or guarantee in connection with material contained in its publications, and expressly disclaims any liability or responsibility for damage or lo
18、ss resulting from their use. Any recommendations contained herein are based on the most authoritative information available at the time of writing and on good engineering practice, but it is essential for the user to take account of pertinent subsequent developments and / or legislation. All rights
19、are reserved. No part of this Publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording or other. Infringement of copyright is not only illegal, but also reduces the Associations income thereby jeopardisin
20、g its ability to fund the production of future publications. . Ill iv TABLE OF CONTENTS Page 1 FOREWORD 1 2 SCOPE . 3 3 BASIS FOR THE SELECTION OF MACHINES 5 3.1 General . 5 3.2. Area classification 5 3.3 Equipment - Type of protection 5 3.4 Test and Certification 6 3.5 Repairs to Certified Equipmen
21、t 7 3.5.1 Certification and test requirements 7 4 IGNITIONS AND IGNITION MECHANISMS 8 4.1 Ignitions which have been notified . 8 4.2 ignition mechanisms . 8 4.2.1 Circulating currents in non-active parts and bonding straps . 9 4.2.2 Internal sources of ignition 9 4.2.2.1 Stator coil movement 9 4.2.2
22、.2 Coil/rotor bar movement . 9 4.2.2.3 High voltage discharges 10 4.2.2.4 Contamination . 10 4.2.2.5 Thermal ageing 11 4.2.3 Common seal and lube oil systems . 11 5 RISK CONSIDERATIONS FOR EXISTING MACHINES . 13 5.2 Procedure for undertaking a risk assessment . 13 5.3 Use of Decision Trees 13 5.3.1
23、Decision tree approach to ensure a gas free start . 14 5.3.2 A more detailed Decision tree approach 14 5.4 Undertaking a more detailed risk assessment . 15 5.4.1 Ignition Probability Factor (IPF). see Table 1 . 15 5.4.1.1 Voltage 15 5.4,1.2 Power 15 5.4.4.3 Number of Poles 15 5.4.4.4 Start frequency
24、 15 5.4.4.5 Contamination 16 5.4.4.6 Winding age . 16 5.4.4.7 Rotor construction 16 5.4.2 Consequences of ignition depending on location and product . (LPF) . . 17 5.4.2.1 Type of flammable material involved 17 5.4.2.2 Location of the machine . 18 5.4.3 Risk associated with presence of people . (PPF
25、) 20 5.4.3.1 Presence of people within 50 metres . (PPF A) . 20 5.4.3.2 People between 50 and 200 m (PPF B) 20 5.4.3.3 21 5.1 Legal aspects 13 People between 200 and 1000 m . (PPF C) 6 UTILISATION OF NUMERICAL ANALYSIS SCORES 23 6.1 General . 23 6.2 Totalisation of scores . 23 6.3 Criticality of sco
26、res . 24 6.5 Actions based on design considerations and operating procedures 25 6.4 A Case Study . 25 V 6.5.1 Circulating currents in the framework . 25 6.5.2 Common lube-seal oil systems 6.5.3 Pressurisation, pre-purging or periodic purging . 6.5.3.1 Pressurisation . 26 6.5.3.2 Pre-purging . 26 6.5
27、.3.3 Periodic purging 26 26 26 6.5.4 Use of gas detection equipment . Considerations relevant to replacing all, or parts of, a machine 6.6.1 Relevant to both Ex e and Ex N machines 6.6.2 Changing complete machine 6.6.3 Changing rotors 28 6.7 Considerations relevant to Area Classification 28 6.7.1 Zo
28、nes and Area Classification 28 6.7.2 Extent of Zones 28 6.7.3 Improving ventilation in buildings 29 6.8 Improvement in maintenance techniques . 29 27 27 27 27 6.6 7 THEFUTURE . 31 7.1 International. European and British Standards 31 7.2 European Directives 32 7.3 Ex N Machines 33 7.4 Ex e Machines .
29、 34 7.5 Other types of machine 35 APPENDIX A . 37 Page 1 RISK ASSESSMENT DECISION TREE No . 1 37 Page 2 ALTERNATIVE 0 Part 6.Electrical Apparatus for Potentially Explosive Atmospheres. Increased Safety Type e. Note that BS EN 5001 9 is equivalent. BS 6941 : Specification for Electrical Apparatus for
30、 Explosive atmospheres with type of protection N Reference should also be made to IEC Standard 79. Parts 7 and 15 Research has shown that there is a probability that large machines designed and installed to existing Standards may, under certain circumstances, produce discharges capable of igniting e
31、xplosive gas mixtures. Thus if an explosive gas mixture is present within the casing of the machine, coincidental with ignition capable incendive activity, the consequences could be far reaching. In machines with loose covers, sparking at joints has been noted. Such sparking might ignite an external
32、 explosive atmosphere. The machines under consideration in this document are those with protection type Ex e and type Ex N. With these machines it is possible that, if an internal explosion should occur, this in turn could precipitate ignition of any external flammable gas. Flameproof Ex d and press
33、urised Ex p machines may have.internal ignition sources but their design is such that any external source of flammable gas will not become ignited. High voltage is considered to be above 1.0 kV. Whilst this document is primarily concerned with high voltage machines the scoring system may be used to
34、evaluate the risk presented by very large LV machines. All in-service machines do not impart the same degree of risk. A number of factors contribute to the actual risk. These are not all of equal value and weighting factors are required to enable a simple Risk Value to be obtained. These factors are
35、 discussed, and values are given, based on experience gained during many years of operation. These will enable the comparative risks identified with different machines to be evaluated. As an aid for those whose task is to assess the risk associated with existing HV machines installed in potentially
36、explosive atmospheres, Decision Trees have been prepared. The use of the first Decision Trees (APPENDIX A) will quickly eliminate many machines not requiring more detailed assessment and by following the additional procedures appropriate action can be determined for the vast majority of the remainin
37、g units. It is probable that the need to carry out a more rigorous Quantitative risk assessment (beyond the scope of this document) will apply only to an exceptionally small percentage of the machines in service. By pursuing the procedures outlined in this document the user will have :- - assessed t
38、he risk associated with all motors he is responsible for - highlighted those which require attention - selected the most effective solution - discharged his legal duties. 3 4 3 BASIS FOR THE SELECTION OF MACHINES 3.1 General Machines are selected in accordance with the environment in which they may
39、be working. Assessment of the type of environment in relation to the probability of an explosive gas being present is referred to as Area Classification. Machines themselves vary in the construction details adopted to make them suitable for operating safely in the various allotted Zones. 3.2. Area c
40、lassification Area Classification is carried out in accordance with procedures developed over many years in consultation with Manufacturers, Users and Government Health and Safety departments. A number of British, European and International Standards give guidance on procedures to employ. Amongst th
41、ese IEC 79-1 0 Classification of Hazardous Areas is the most relevant international work. Areas are divided into Zones based on the probability and duration of an Explosive gas or vapour being present. Zone 0. Higher risk. Defined as :- An area in which an explosive gas atmosphere is present either
42、continuously or for long periods. Zone 1. Intermediate risk. Defined as :- An area in which an explosive gas is likely to occur in normal operation. Zone 2. Area at lower risk. Defined as :- An area in which an explosive gas atmosphere is unlikely to occur in normal operation and, if it does occur,
43、is likely to do so infrequently and will exist for a short time only. Note: Further consideration of zones and classification is included in Section 6.4 3.3 Equipment - Type of protection. It is not within the scope of this document to discuss in detail the types of protection available at the prese
44、nt time. Detailed information may be obtained by reference to the relevant Standards as listed in Appendix D. The following brief details of the types suitable for large machines may be useful. Ex d. Flame proof (Explosion protected) A strong machine such that if an internal ignition of gas did occu
45、r there is no possibility of an external flammable gas being ignited. The casing has sufficient strength to withstand any internal pressure resulting from an ignition and any allowable gaps such as at flanged covers, breathers and bearings are designed to 5 prevent the passage of combustion products
46、 having sufficient energy to ignite an external flammable gas. Ex p. Pressurised apparatus. A machine which is pressurised internally by air (or inert gas) drawn from a safe area. The fact that the machine is pressurised prevents any possibility of an external flammable gas entering into the machine
47、 enclosure. In certain instances it is permissable to draw air from a Zone 2 Area provided that gas monitoring equipment is used to ensure that the air inside the motor has a gas content below the LEL (Lower Explosive Limit) of that gas. Continuous dilution of the gas inside a machine with air drawn
48、 from a safe or zone 2 area in association with gas detectors to monitor the gas content is also possible. Ex N. Reduced risk. These machines are similar in design to a standard machine but special attention is given to bearings, concentricity of rotorktator, and the impact resistance of some constr
49、uctional parts. Ex e. Increased safety machine. A machine where special attention is paid to the following:- - mechanical features similar to type Ex N - increased terminal clearances - minimisation of static pick up on plastic fans by choice of material. - temperature rise of windings (usually 1 OC cooler than a standard machine), - limitation of rotorktator temperature rise during any start by use of specified starting equipment which is tested and certified with the motor. 3.4 Test and Certification Test and certifying authorities
