SIST EN 60825-4:2008
(Main)Safety of laser products -- Part 4: Laser guards
Safety of laser products -- Part 4: Laser guards
Specifies the requirements for laser guards, permanent and temporary (for example for service), that enclose the process zone of a laser processing machine, and specifications for proprietary laser guards. Applies to all component parts of a guard including clear (visibly transmitting) screens and viewing windows, panels, laser curtains and walls.
Sicherheit von Lasereinrichtungen -- Teil 4: Laserschutzwände
Sécurité des appareils à laser -- Partie 4: Protecteurs pour lasers
Spécifie les exigences pour les protecteurs pour lasers, permanents et temporaires (par exemple pour l'entretien), qui protègent la zone de traitement d'une machine à laser, ainsi que les spécifications pour les protecteurs d'origine pour lasers.
La présente norme s'applique à tous les composants d'un protecteur, y compris les écrans clairs (visiblement transmetteurs) et les fenêtres d'observation, les panneaux, les rideaux pour lasers et les parois. Les exigences pour les composants du trajet du faisceau, les dispositifs d'arrêt du faisceau et les autres parties d'un capot de protection d'un appareil à laser qui ne protègent pas la zone de traitement sont contenues dans la CEI 60825-1.
De plus, la présente partie de la CEI 60825 indique:
a) comment évaluer et spécifier les propriétés de protection d'un protecteur pour lasers; et
b) comment sélectionner un protecteur pour lasers.
Varnost laserskih izdelkov - 4. del: Zaščitna oprema za laserje (IEC 60825-4:2006)
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Safety of laser products - Part 4: Laser guards (IEC 60825-4:2006)Sécurité des appareils a laser - Partie 4: Protecteurs pour lasers (IEC 60825-4:2006)Sicherheit von Lasereinrichtungen - Teil 4: Laserschutzwände (IEC 60825-4:2006)Ta slovenski standard je istoveten z:EN 60825-4:2006SIST EN 60825-4:2008en,fr,de31.260Optoelektronika, laserska opremaOptoelectronics. Laser equipmentICS:SIST EN 60825-4:1999/A2:2004SIST EN 60825-4:1999/A1:2003SIST EN 60825-4:19991DGRPHãþDSLOVENSKI
STANDARDSIST EN 60825-4:200801-januar-2008
EUROPEAN STANDARD EN 60825-4 NORME EUROPÉENNE
EUROPÄISCHE NORM October 2006
CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2006 CENELEC -
All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60825-4:2006 E
ICS 31.260 Supersedes EN 60825-4:1997 + A1:2002 + A2:2003
English version
Safety of laser products
Part 4: Laser guards (IEC 60825-4:2006)
Sécurité des appareils à laser
Partie 4: Protecteurs pour lasers (CEI 60825-4:2006)
Sicherheit von Lasereinrichtungen
Teil 4: Laserschutzwände (IEC 60825-4:2006)
This European Standard was approved by CENELEC on 2006-10-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
- 2 -
Foreword The text of document 76/342/FDIS, future edition 2 of IEC 60825-4, prepared by IEC TC 76, Optical radiation safety and laser equipment, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60825-4 on 2006-10-01. This European Standard supersedes EN 60825-4:1997 + A1:2002 + A2:2003. The following dates were fixed: – latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement
(dop)
2007-07-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow)
2009-10-01 Annex ZA has been added by CENELEC. __________ Endorsement notice The text of the International Standard IEC 60825-4:2006 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following notes have to be added for the standards indicated: IEC 60204-1 NOTE
Harmonized as EN 60204-1:2006 (modified). IEC 61310-3 NOTE
Harmonized as EN 61310-3:1999 (not modified). IEC 61496-2 NOTE
Harmonized as CLC/TS 61496-2:2006 (not modified). IEC/TS 62046 NOTE
Harmonized as CLC/TS 62046:2005 (not modified). ISO 10218 NOTE
Harmonized as EN 775:1992 (modified). __________
- 3 - EN 60825-4:2006 Annex ZA
(normative)
Normative references to international publications with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE
When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
Publication Year Title EN/HD Year
IEC 60825-1
A1 A2 1993
1997 2001 Safety of laser products
Part 1: Equipment classification,
requirements and user's guide EN 60825-1 + corr. February
A1 A2 + corr. April
1994 1995 2002 2001 2004
ISO 11553-1 2005 Safety of machinery - Laser processing machines
Part 1: General safety requirements EN ISO 11553-1 2005
ISO 12100-1 2003 Safety of machinery - Basic concepts,
general principles for design
Part 1: Basic terminology, methodology EN ISO 12100-1 2003
ISO 12100-2 2003 Safety of machinery - Basic concepts,
general principles for design
Part 2: Technical principles EN ISO 12100-2 2003
NORME INTERNATIONALECEIIEC INTERNATIONAL STANDARD 60825-4Deuxième éditionSecond edition2006-08 Sécurité des appareils à laser – Partie 4: Protecteurs pour lasers
Safety of laser products – Part 4: Laser guards Pour prix, voir catalogue en vigueur For price, see current catalogue IEC 2006
Droits de reproduction réservés
Copyright - all rights reserved Aucune partie de cette publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord écrit de l'éditeur. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commission,
3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, SwitzerlandTelephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch
Web: www.iec.ch CODE PRIX PRICE CODE XB Commission Electrotechnique InternationaleInternational Electrotechnical Commission
60825-4 IEC:2006 – 3 –
CONTENTS FOREWORD.9 INTRODUCTION.13
1 Scope.15 2 Normative references.15 3 Definitions.15 4 Laser processing machines.19 4.1 Design requirements.19 4.2 Performance requirements.21 4.3 Validation.21 4.4 User information.23 5 Proprietary laser guards.23 5.1 Design requirements.23 5.2 Performance requirements.23 5.3 Specification requirements.23 5.4 Test requirements.25 5.5 Labelling requirements.25 5.6 User information.27
Annex A (informative)
General guidance on the design and selection of laser guards.29 Annex B (informative)
Assessment of foreseeable exposure limit (FEL).33 Annex C (informative)
Elaboration of defined terms.47 Annex D (normative)
Proprietary laser guard testing.51 Annex E (informative)
Guidelines on the arrangement and installation
of laser guards.55 Annex F (informative)
Guideline for assessing the suitability of laser guards.75
Bibliography.133
Figure B.1 – Calculation of diffuse reflections.35 Figure B.2 – Calculation of specular reflections.35 Figure B.3 – Some examples of a foreseeable fault condition.37 Figure B.4 – Four examples of errant laser beams that might have to be contained by a temporary guard under service conditions.39 Figure B.5 – Illustration of laser guard exposure during repetitive machine operation.41 Figure B.6 – Two examples of assessed duration of exposure.43 Figure B.7 – Assessed duration of exposure for a machine with no safety monitoring.45 Figure C.1 – Illustration of guarding around a laser processing machine.47 Figure C.2 – Illustration of active laser guard parameters.49 Figure D.1 – Simplified diagram of the test arrangement.53
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Figure F.1 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO2 laser.111 Figure F.2 – Damage resistance of 1 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW CO2 laser.111 Figure F.3 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO2 laser.113 Figure F.4 – Damage resistance of 2 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW CO2 laser.113 Figure F.5 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO2 laser.115 Figure F.6 – Damage resistance of 3 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW CO2 laser.115 Figure F.7 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s exposure to a defocused beam during experiments using a CW CO2 laser.117 Figure F.8 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s exposure to a defocused beam during experiments using a CW CO2 laser.117 Figure F.9 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s exposure to a defocused beam during experiments using a CW CO2 laser.119 Figure F.10 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO2 laser.119 Figure F.11 – Damage resistance of 6 mm thick polycarbonate sheet derived from 10 s exposure to a defocused beam during experiments using a CW CO2 laser.121 Figure F.12 – Damage resistance of 6 mm thick polycarbonate sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO2 laser.121 Figure F.13 – Damage resistance of 1 mm thick zinc coated steel sheet derived from 10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.123 Figure F.14 – Damage resistance of 1 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.123 Figure F.15 – Damage resistance of 2 mm thick zinc coated steel sheet derived from 10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.125 Figure F.16 – Damage resistance of 2 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.125 Figure F.17 – Damage resistance of 3 mm thick zinc coated steel sheet derived from 10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.127
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Figure F.18 – Damage resistance of 3 mm thick zinc coated steel sheet derived from 100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.127 Figure F.19 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.129 Figure F.20 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.129 Figure F.21 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.131 Figure F.22 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser.131
Table D.1 – Laser guard classification.53 Table F.1 – Application of ALARP.81
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INTERNATIONAL ELECTROTECHNICAL COMMISSION ___________
SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). 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. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 60825-4 has been prepared by IEC technical committee 76: Optical radiation safety and laser equipment. This second edition of IEC 60825-4 cancels and replaces the first edition published in 1997, its amendment 1 (2002) and its amendment 2 (2003). The document 76/342/FDIS, circulated to the National Committees as amendment 3, led to the publication of the new edition.
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The text of this standard is based on the first edition, its amendment 1, amendment 2 and the following documents: FDIS Report on voting 76/342/FDIS 76/351/RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication will be
• reconfirmed, • withdrawn, • replaced by a revised edition, or • amended.
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INTRODUCTION At low levels of irradiance or radiant exposure, the selection of material and thickness for shielding against laser radiation is determined primarily by a need to provide sufficient optical attenuation. However, at higher levels, an additional consideration is the ability of the laser radiation to remove guard material – typically by melting, oxidation or ablation; processes that could lead to laser radiation penetrating a normally opaque material. IEC 60825-1 deals with basic issues concerning laser guards, including human access, interlocking and labelling, and gives general guidance on the design of protective housings and enclosures for high-power lasers. This part of IEC 60825 deals with protection against laser radiation only. Hazards from secondary radiation that may arise during material processing are not addressed. Laser guards may also comply with standards for laser protective eyewear, but such compliance is not necessarily sufficient to satisfy the requirements of this standard. Where the term “irradiance” is used, the expression “irradiance or radiant exposure, as appropriate” is implied.
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SAFETY OF LASER PRODUCTS –
Part 4: Laser guards
1 Scope This part of IEC 60825 specifies the requirements for laser guards, permanent and temporary (for example for service), that enclose the process zone of a laser processing machine, and specifications for proprietary laser guards. This standard applies to all component parts of a guard including clear (visibly transmitting) screens and viewing windows, panels, laser curtains and walls. Requirements for beam path components, beam stops and those other parts of a protective housing of a laser product which do not enclose the process zone are contained in IEC 60825-1. In addition this part of IEC 60825 indicates: a) how to assess and specify the protective properties of a laser guard; and b) how to select a laser guard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60825-1:1993, Safety of laser products – Part 1: Equipment classification, requirements and user’s guide 1) Amendment 1 (1997) Amendment 2 (2001) ISO 12100-1:2003, Safety of machinery – Basic concepts, general principles for design – Part 1: Basic terminology, methodology ISO 12100-2:2003, Safety of machinery – Basic concepts, general principles for design – Part 2: Technical principles and specifications ISO 11553-1:2005, Safety of machinery – Laser processing machines – Safety requirements 3 Definitions For the purpose of this part of IEC 60825, the following definitions apply in addition to the definitions given in IEC 60825-1.
–––––––––––– 1)
A consolidated edition (1.2) exists, including IEC 60825-1:2001 and its Amendments 1 (1997) and 2 (2001).
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3.1 active guard protection time for a given laser exposure of the front surface of an active laser guard, the minimum time, measured from the issue of an active guard termination signal, for which the active laser guard can safely prevent laser radiation accessible at its rear surface from exceeding the class 1 AEL
3.2 active guard termination signal the signal issued by an active guard in response to an excess exposure of its front surface to laser radiation and which is intended to lead to automatic termination of the laser radiation NOTE The action of a safety interlock becoming open circuit is considered a "signal" in this context.
3.3 active laser guard a laser guard which is part of a safety-related control system. The control system generates an active guard termination signal in response to the effect of laser radiation on the front surface of the laser guard 3.4 foreseeable exposure limit
FEL the maximum laser exposure on the front surface of the laser guard, within the maintenance inspection interval, assessed under normal and reasonably foreseeable fault conditions 3.5 front surface the face of the laser guard intended for exposure to laser radiation 3.6 laser guard a physical barrier which limits the extent of a danger zone by preventing laser radiation accessible at its rear surface from exceeding the class 1 AEL 3.7 laser processing machine a machine which uses a laser to process materials and is within the scope of ISO 11553-1 3.8 laser termination time the maximum time taken, from generation of an active guard termination signal, for the laser radiation to be terminated NOTE Laser termination time does not refer to the response of an active laser guard but to the response of the laser processing machine, in particular the laser safety shutter.
3.9 maintenance inspection interval the time between successive safety maintenance inspections of a laser guard 3.10 passive laser guard a laser guard which relies for its operation on its physical properties only
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3.11 process zone the zone where the laser beam interacts with the material to be processed 3.12 proprietary laser guard a passive or active laser guard, offered by its manufacturer as a guard with a specified protective exposure limit 3.13 protective exposure limit
PEL the maximum laser exposure of the front surface of a laser guard which is specified to prevent laser radiation accessible at its rear surface from exceeding the class 1 AEL NOTE 1 In practice, there may be more than one maximum exposure. NOTE 2 Different PELs may be assigned to different regions of a laser guard if these regions are clearly identifiable (for example a viewing window forming an integral part of a laser guard).
3.14 rear surface any surface of a laser guard that is remote from the associated laser radiation and usually accessible to the user 3.15 reasonably foreseeable an event (or condition) when it is credible and its likelihood of occurrence (or existence) cannot be disregarded 3.16 safety maintenance inspection documented inspection performed in accordance with manufacturer’s instructions 3.17 temporary laser guard a substitute or supplementary active or passive laser guard intended to limit the extent of the danger zone during some service operations of the laser processing machine 4 Laser processing machines This clause specifies the requirements for laser guards that enclose the process zone and are supplied by the laser processing machine manufacturer. 4.1 Design requirements A laser guard shall satisfy ISO 12100-2 with respect to the general requirements for guards and also the more specific requirements with regard to its location and method of fixture. In addition, the following specific laser requirements shall be met. 4.1.1 General requirements
A laser guard, in its intended location, shall not give rise to any associated hazard at or beyond its rear surface when exposed to laser radiation up to the foreseeable exposure limit.
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NOTE 1 Examples of associated hazards include: high temperature, the release of toxic materials, fire, explosion, electricity. NOTE 2 See Annex B for assessment of foreseeable exposure limit. 4.1.2 Consumable parts of laser guards Provision shall be made for the replacement of parts of a laser guard prone to damage by laser radiation.
NOTE An example of such a part would be a sacrificial or interchangeable screen. 4.2 Performance requirements 4.2.1 General When the front surface of a laser guard is subjected to exposure to laser radiation at the foreseeable exposure limit, the laser guard shall prevent laser radiation accessible at its rear surface from exceeding the class 1 AEL at any time over the period of the maintenance inspection interval. For automated laser processing machines, the minimum value of the maintenance inspection interval shall be 8 h. This requirement shall be satisfied over the intended lifetime of the laser guard under expected conditions of operation. NOTE 1 This requirement implies both low transmission of laser radiation and resistance to laser-induced damage. NOTE 2 Some materials may lose their protective properties due to ageing, exposure to ultraviolet radiation, certain gases, temperature, humidity and other environmental conditions. Additionally, some materials will transmit laser radiation under high-intensity laser exposure, even though there may be no visible damage (i.e. reversible bleaching). 4.2.2 Active laser guards a) The active guard protection time shall exceed the laser termination time up to the foreseeable exposure limits. b) The generation of an active guard termination signal shall give rise to a visible or audible warning. A manual reset is required before laser emission can recommence.
NOTE See Annex C.2 for an elaboration of terms. 4.3 Validation If the laser processing machine manufacturer chooses to make a laser guard, the manufacturer shall confirm that the guard complies with the design requirements of 4.1 and can satisfy the performance requirements set out in 4.2. NOTE See Annex A for guidance on the design and selection of laser guards. 4.3.1 Validation of performance
4.3.1.1 The complete laser guard, or an appropriate sample of the material of construction of the laser guard, shall be tested at each FEL identified. NOTE 1 A table of predetermined PELs for common combinations of lasers and guarding materials, together with suitable testing procedures shall be issued as an informative annex in a future amendment to this standard. This could provide a simple alternative to direct testing for the majority of cases.
NOTE 2 See Annex B for the assessment of FEL.
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4.3.1.2 For testing purposes, the FEL exposure shall be achieved either: a) by calculating or measuring the exposure and reproducing the conditions; or b) without quantifying the FEL, by creating the machine conditions under which the FEL is produced. The condition of the laser guard or sample shall be such as to replicate those physical conditions of the front surface permitted within the scope of the routine inspection instructions and within the service life of the guard, which minimize the laser radiation protective properties of the laser guard (for example wear and tear and surface contamination) (see 4.4.2). 4.4 User information 4.4.1 The manufacturer shall document and provide to the user the maintenance inspection interval for the laser guard, and details of inspection and test procedures, cleaning, replacement or repair of damaged parts, together with any restrictions of use. 4.4.2 The manufacturer shall document and provide to the user instructions that after any actuation of the safety control system of an active guard, the cause shall be investigated, checks shall be made for damage, and the necessary remedial action to be taken before resetting the control system.
5 Proprietary laser guards This clause specifies the requirements to be satisfied by suppliers of proprietary laser guards. 5.1 Design requirements A proprietary laser guard shall not create any associated hazard at or beyond its rear surface when exposed to laser radiation up to the specified PEL when used as specified in the user information (see 5.6). 5.2 Performance requirements The accessible laser radiation at the rear surface of the laser guard shall not exceed the class 1 AEL when its front surface is subjected to laser radiation at the specified PEL. For an active laser guard, this requirement shall apply to laser radiation accessible over the period of the active guard protection time, measured from the moment an active guard termination signal is issued. This requirement shall be satisfied over the intended lifetime of the guard under expected service conditions. 5.3 Specification requirements The full specification of a PEL shall include the following information: a) the magnitude and variation with time of irradiance or radiant exposure at the front surface of the laser guard (in units of Wm–2 or Jm–2 respectively), specifying any upper limit to the area of exposure; b) the overall duration of exposure under these conditions; c) the wavelength for which this PEL applies; d) the angle of incidence and (if relevant) the polarization of the incident laser radiation;
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e) any minimum dimensions to the irradiated area (for example as might apply to an active laser guard with discrete sensor elements so that a small diameter laser beam could pass through the guard undetected); f) for an active laser guard, the active guard protection time. NOTE 1 See Clause B.1 for an elaboration of terms. NOTE 2 In all cases, a range or set of values can be stated rather than a single value. NOTE 3 A graphical form of presentation is acceptable (for example irradiance vs. duration with all other parameters constant).
5.4 Test requirements 5.4.1 General Testing shall be performed using the complete laser guard or an appropriate sample of the material used to construct the guard. In either case, the condition of the guard or sample shall be such as to replicate or exceed the worst permissible physical condition of the front surface, including reduced surface reflection and damage permitted within the scope of the routine maintenance instructions (see 5.6). The front surface irradiation shall be either as specified by the PEL or, in the case of sample testing, as specified in 5.4.2 below.
When the front surface is subjected to the PEL exposure conditions, the accessible laser radiation measured at the rear surface of the laser guard shall not exceed the class 1 AEL (tests as prescribed in Clause 8 of 60825-1). This requirement applies over the exposure duration specified in the PEL or, in the case of an active guard, over the specified active guard protection time measured from the moment an active guard termination signal is issued. NOTE In cases where materials opaque at the laser wavelength(s) are used (for example metals), the transmitted radiation will only rise to the class 1 AEL when complete (or almost complete) physical removal of material along a path through to the rear surface has been achieved. In such cases, the rise from zero transmission to a value greatly in excess of the class 1 AEL will therefore be rapid, and sensitive radiation detectors will not be required. 5.4.2 Sample testing Sample guard testing shall be performed by irradiating the front surface of the guard material using the procedure and methodology as specified in Annex D. 5.5 Labelling requirements 5.5.1 All labelling shall be placed on the rear surface of the guard. 5.5.2 The rear surface of the guard shall be clearly identified if the orientation of the guard is important.
5.5.3 If only part of the front surface of the guard is a laser guard, this area shall be clearly identified by a bold coloured outline and words to indicate the outer boundary of the laser guard. 5.5.4 The labelling shall state the full PEL specification. 5.5.5 The manufacturer’s name, the date and place of manufacture according to ISO 11553-1, and a statement of compliance with this standard shall be provided.
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5.6 User information In addition to the specifications listed in 5.3, the following information shall be supplied to the user by the manufacturer of a proprietary laser guard: a) a description of the permitted uses of the laser guard; b) a description of the form of mounting and connection of the laser guard; c) information on the installation of the laser guard – for active laser guards this shall include interface and supply requirements for the guard; d) maintenance requirements, including for example details of inspection and test procedures, cleaning, replacement or repair of damaged parts; e) instructions, that after any actuation of the safety control system of an active guard, the cause shall be investigated, checks shall be made for damage, and the necessary remedial action to be taken before resetting the control system; f) the labels in 5.5 and their locations. If only part of the front surface of the guard is a laser guard, this area shall be identified; g) a statement of compliance with this standard.
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Annex A
(informative)
General guidance on the design and selection of laser guards
A.1 Design of laser guards A.1.1 Passive laser guards Examples of a passive laser guard include the following. a) A metal panel relying on thermal conduction, if necessary enhanced by forced air or water cooling, to maintain the surface temperature below its melting point under normal and reasonably foreseeable fault conditions. b) A transparent sheet, opaque at the laser wavelength, which is unaffected by low value of laser exposure under normal operation of the laser processing machine.
A.1.2 Active laser guards Examples of an active laser guard include the following. a) A guard, with discrete embedded thermal sensors, which detects overheating.
NOTE The spacing between sensors should be considered in relation to the minimum dimensions of an errant laser beam.
b) A laser guard comprising two panels between which is contained a pressurized liquid or gaseous medium in combination with a pressure-sensing device capable of detecting the pressure drop following perforation of the front surface.
A.1.3 Hazard indication (passive guards) Visible indication of exposure of the laser guard to hazardous amounts of laser radiation should be provided where feasible (for example by adding a layer of an appropriate paint on both sides of the laser guard). A.1.4 Power supply (active guards) If power is required for the proper functioning of an active guard, its supply should be arranged so that laser operation is not possible in the absence of such power. A.2 Selection of laser guards A simple selection process is as follows: a) identify the preferred position for the laser guard and estimate the FEL at this position. Annex B gives guidance on the estimation of FEL values;
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b) if necessary, minimize the FEL under fault conditions, preferably by including automatic monitoring in the machine which will detect the fault conditions and limit the exposure time. Examples of alternatives include the following: – ensure that the laser guard is sufficiently far away from beam focus produced by focusing optics; – install vulnerable parts of laser guard (such as viewing windows) away from regions that could be exposed to high irradiance; – move the laser guard farther away from the laser process zone; – require in the essential servicing documentation for temporary laser guards, additions such as: • one or more persons to be present to supervise the condition of the front surface of the laser guard, to reduce the assessed exposure duration of a passive guard; • a hold-to-operate controller to be used by the person(s) supervising the condition of the front surface of the laser guard, to reduce the assessed exposure duration of a passive guard; • additional local temporary guarding, apertures and beam dumps to be employed, to absorb any powerful errant laser beams; • the danger zone to be bounded by errant beam warning devices and the guard placed beyond this zone to reduce the assessed exposure duration; – incorporate in the design of the machine, when using temporary laser guards, beam control features to facilitate improved laser beam control during servicing operations, such as:
• holders for precise location of additional beam forming components (for example turning mirrors) required during servicing; • mounts which allow only limited scope for beam steering. Three options then follow. The order below does not indicate a preference. A.2.1 Option 1: passive laser guard This is the simplest option. NOTE Design and quality control are particularly important considerations where the absorption at the laser wavelength is dominated by a minority additive, such as a dye in a plastic. In such cases, where the manufacturer of the material does not specify the concentration of the absorber or the material optical attenuation at the laser wavelength, samples from the same batch of the material should first be tested as described in 4.3.1.
A.2.2 Option 2: active laser guard If the FEL cannot be reduced to a value where common guarding materials provide adequate protection in the form of a passive laser guard, an active laser guard can always be used. A.2.3 Option 3: proprietary laser guard A proprietary laser guard can be used if the assessed FEL values are less than the PEL values quoted by the laser guard manufacturer.
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Annex B
(informative)
Assessment of foreseeable exposure limit (FEL)
B.1 General FEL values may be assessed either by measurement or by calculation (see below).
The standard ISO 14121 provides a general methodology for risk assessment. The assessment should include consideration of cumulative exposure in normal operation (for example during each part processing cycle of the machine) over the maintenance inspection interval. From this assessment, the most demanding combinations of irradiation, area of exposure and exposure duration should be identified. It is quite likely that several FELs will be identified; for example one condition may maximize the duration of exposure at a relatively low irradiance, while another may maximize the irradiance over a shorter duration of exposure. The full specification of an FEL comprises the following information. a) The maximum irradiance at the front surface of the laser guard.
NOTE Irradiance is expressed as the total power or energy divided by the area of the front surface of the guard, or specified limited area, as appropriate. b) Any upper limit to the area of exposure of the front surface at this level of irradiance. NOTE No limit to the area would be appropriate for protection against scattered laser radiation while an upper limit to the exposed area would be appropriate for direct exposure to laser beams. c) The temporal characteristics of the exposure, i.e. whether continuous wave or pulsed laser radiation, and if the latter, then the pulse duration and pulse repetition frequency.
d) The full duration of exposure. NOTE See Clause B.4 for an elaboration of this term.
e) The wavelength of the radiation. f) The angle of incidence and (if relevant) the polarization of the radiation.
NOTE 1 Stipulation of angle of incidence is particularly important for laser guards exploiting interference layers to reflect impinging laser radiation.
NOTE 2 CAUTION: At Brewster's angle of incidence "p" polarized radiation is strongly coupled into the surface of the guard.
g) Any minimum dimensions to the irradiated area (for example as might apply to an active laser guard with discrete sensor elements so that a small diameter laser beam could pass through the laser guard undetected). h) For an active laser guard, the active guard protection time.
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B.2 Reflection of laser radiation
θ R PoIrradiance EAϕ Laser guard IEC
1570/06
B.2.1 Diffuse reflections Assuming a Lambertian reflector with 100 % reflectivity EPRA =
cos
coso2πθϕ⋅⋅
Figure B.1 – Calculation of diffuse reflections R A A’θ PoLaser guard IEC
1571/06
B.2.2 Specular reflections It is difficult to generalize for the case of specular reflections. For a circularly symmetric laser beam with a Gaussian distribution, power Po and diameter d63 at the focusing lens, focal length f, the maximum irradiance (at the centre of the Gaussian distribution) in a normal plane distance R from the focus is: EPdfRAA'=4o6322ρπ where ρ is the reflectivity of the workpiece surface. CAUTION: Certain curved surfaces may increase the reflection hazard. Figure B.2 – Calculation of specular reflections
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B.3 Examples of assessment conditions FELs should be assessed for the worst reasonably foreseeable combination(s) of available laser parameters, workpiece materials, geometry and processes likely to be encountered during normal operation (IEC/TR 60825-14 provides guidance for users).
Laser guardIEC
1572/06
Figure B.3a – Software failure
Laser guard IEC
1573/06
Figure B.3b – Workpiece bends or is inadequately clamped
Laser guard IEC
1574/06
Figure B.3c – Workpiece missing Figure B.3 – Some examples of a foreseeable fault condition
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Mirror missingErrant laser beam IEC
1575/06
Figure B.4a – Laser is operated with turning mirror missing
Mirror Errant laser beamIEC
1576/06
Figure B.4b – Beam displaced off mirror during alignment procedure
Beam expander out of adjustment Errant laser beams IEC
1577/06
Figure B.4c – Beam expands beyond range of optics
Reflective object enters beam pathIEC
1578/06
Figure B.4d – Reflective objects intercept laser beam
Figure B.4 – Four examples of errant laser beams that might have to be contained by a temporary guard under service conditions
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B.4 Exposure duration B.4.1 Normal operation The exposure of a guard to laser radiation during fault-free operation may comprise exposures to low levels of reflected, scattered and transmitted radiation which are repeated on each machine cycle. In this case, the assessed FEL for fault-free operation would encompass the variation in irradiance of the guard during the cycle, repeated for the maximum number of machine cycles within a safety maintenance inspection interval.
Automated processing of several pieces Scattered radiation during processing of a single piece Time Laser irradiance
of the guard (Wm-2) ≥ 8 h protection A possible value of irradiance specified in the FEL
The characteristics of the radiation (i.e. pulsed or continuous wave) also form part of the FEL IEC
1579/06
Figure B.5 – Illustration of laser guard exposure during repetitive machine operation
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B.4.2 Fault Conditions A safety control system involving some form of machine monitoring can reduce the time for which the guard must safely contain the radiation hazard under fault conditions. Two examples are given below.
Time On-line process monitoring detects fault A during processing Laser safety shutter closes Onset of fault A Assessed duration of exposure Laser irradiance
of the guard (Wm-2) IEC
1580/06
Figure B.6a – Shut-down with on-line machine safety monitoring
Machine shut down before next piece is processed Fault B occurs Post-treatment inspection during the followingmachine cycle rev
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