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1627.4-2005

Australian Standard

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 AS 1627.4—2005 1627.4—2005 A  S  1   6  2  7  .4  — 2   0   0   5  Australian Standard ™ Metal finishing—Preparation and pretreatment of surfaces Part 4: Abrasive blast cleaning of steel    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A This Australian Standard was prepared by Committee MT-009, Metal Finishing. It was approved on behalf of the Council of Standards Australia on 22 November 2005. This Standard was published on 23 December 2005. The following are represented on Committee MT-009: Australian Institute of Metal Finishing Australian Chamber of Commerce and Industry Australian Industry Group Department of Defence Galvanizers Associations of Australia Institute of Materials Engineering Australia The Royal Australian Chemical Institute Society of Automotive Engineers Australia    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Keeping Standards up-to-date Standards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments which may have been published since the Standard was purchased. Detailed information about Standards can be found by visiting the Standards Web Shop at www.standards.com.au and looking up the relevant Standard in the on-line catalogue. Alternatively, Alternative ly, the printed Catalogue provides provides information current at 1 January each  yea r, and the mo month nth ly mag azi ne, The Global Standard , has a full listing of revisions and amendments published each month. Australian Standards   and other products and services developed by Standards Australia are published and distributed under contract by SAI Global, which operates the Standards Web Shop. We also welcome suggestions for improvement in our Standards, and especially encourage readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at [email protected], or write to the Chief Executive, Standards Australia, GPO Box 476, Sydney, NSW 2001. TM This Standard was issued in draft form for comment as DR 05292. This Australian Standard was prepared by Committee MT-009, Metal Finishing. It was approved on behalf of the Council of Standards Australia on 22 November 2005. This Standard was published on 23 December 2005. The following are represented on Committee MT-009: Australian Institute of Metal Finishing Australian Chamber of Commerce and Industry Australian Industry Group Department of Defence Galvanizers Associations of Australia Institute of Materials Engineering Australia The Royal Australian Chemical Institute Society of Automotive Engineers Australia    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Keeping Standards up-to-date Standards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments which may have been published since the Standard was purchased. Detailed information about Standards can be found by visiting the Standards Web Shop at www.standards.com.au and looking up the relevant Standard in the on-line catalogue. Alternatively, Alternative ly, the printed Catalogue provides provides information current at 1 January each  yea r, and the mo month nth ly mag azi ne, The Global Standard , has a full listing of revisions and amendments published each month. Australian Standards   and other products and services developed by Standards Australia are published and distributed under contract by SAI Global, which operates the Standards Web Shop. We also welcome suggestions for improvement in our Standards, and especially encourage readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at [email protected], or write to the Chief Executive, Standards Australia, GPO Box 476, Sydney, NSW 2001. TM This Standard was issued in draft form for comment as DR 05292.  AS 1627.4— 1627.4—2005 Australian Standard ™ Metal finishing— finishing—Preparation and pretreatment of surfaces Part 4: Abrasive blast cleaning of steel    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Originated as AS CK9.4—1964. Previous edition AS 1627.4—2002. Fourth edition 2005. COPYRIGHT © Standards Australia  All rig hts ar e r eser ved . N o part of thi s wor k m ay be rep rod uce d o r c opi ed in any for m o r b y any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 7071 1  AS 1 627. 4—20 05 2 PREFACE This Standard was prepared by the Australian members of the Joint Standards Australia/Standards New Zealand Committee MT-009, Metal Finishing, to supersede AS 1627.4—2002,  Metal finishing—Preparation and pretreat ment of surfaces, Part 4:  Abrasive blast cleaning. After consulting with stakeholders in both countries, Standards Australia and Standards  New Zealand decided to develop this Stand ard as an Australian Standard rather than an Australian/New Zealand Standard. The objective of this revision is to include additional information on abrasives and to include Class classification, which was deleted in the last edition. This revision was the result of requests from Australian Industry who were not satisfied with the previous adoption of ISO 8504-2:2000. This Standard is Part 4 of a series of Standards covering the preparation and pretreatment of metal surfaces used in metal finishing. During the preparation of this Standard cognizance was taken of ISO 8504-2:2000,  Preparation of steel substrates before application of paints and related product—Surface  preparation methods, Part 2: Abra sive blast-cleaning . The series comprises the following Parts:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A AS 1627 1627.0 1627.1 1627.2 1627.4 1627.5 1627.6 1627.9 Metal finishing—Preparation and pretreatment of surfaces Part 0: Method selection guide Part 1: Removal of oil, grease and related contamination Part 2: Power tool cleaning Part 4: Abrasive blast cleaning of steel (this Standard) Part 5: Pickling Part 6: Chemical conversion treatment of metals Part 9: Pictorial surface preparation standards for painting steel surfaces The term ‘informative’ has been used in this Standard to define the application of the appendix to which it applies. An ‘informative’ appendix is only for information and guidance. 3  AS 1 627. 4 — 2 005 CONTENTS  Page FOREWORD.............................................................................................................................. 4 SECTION 1 SCOPE AND GENERAL 1.1 SCOPE ........................................................................................................................ 5 1.2 REFERENCED DOCUMENTS .................................................................................. 5 1.3 DEFINITIONS ............................................................................................................ 7 SECTION 2 ABRASIVES 2.1 MATERIALS AND TYPES ...................................................................................... 10 2.2 REQUIREMENTS..................................................................................................... 10 2.3 SELECTION CONSIDERATIONS........................................................................... 10 SECTION 3 ABRASIVE BLAST CLEANING METHODS 3.1 DRY ABRASIVE CLEANING ................................................................................. 15 3.2 WET ABRASIVE BLAST CLEANING.................................................................... 16 3.3 FLASH RUSTING .................................................................................................... 17    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A SECTION 4 INITIAL RUST GRADES AND CLASSES OF BLAST CLEANING 4.1 INITIAL SURFACE ASSESSMENT........................................................................ 18 4.2 CLASSES OF BLAST CLEANING.......................................................................... 18 4.3 OTHER ASSESSMENT REQUIREMENTS............................................................. 19 SECTION 5 PROCEDURE 5.1 GENERAL ................................................................................................................ 20 5.2 PREPARATION BEFORE BLAST CLEANING ...................................................... 20 5.3 SELECTION OF BLAST CLEANING PARAMETERS........................................... 20 5.4 AFTER BLAST CLEANING .................................................................................... 20 5.5 ASSESSMENT OF THE BLAST CLEANED SURFACE......................................... 21 APPENDICES A PURCHASING GUIDELINES.................................................................................. 22 B CLASSES OF SURFACE PREPARATION.............................................................. 23 C SAFETY CONSIDERATIONS AND REQUIREMENTS......................................... 26 D SWEEP (BRUSH) BLASTING CLEANING ............................................................ 31  AS 1 627. 4 — 2005 4 FOREWORD Abrasive blast cleaning utilizes a stream of abrasive particles directed onto a metal surface to remove millscale, rust, corrosion products, process scales and foreign particles. The abrasive may be propelled by centrifugal force, or carried in an air or water stream, or both. Abrasive propelled by centrifugal force using impeller wheels in closed recirculating systems is suited to production line work and other specialized applications. Airborne abrasive is projected through a nozzle and is suitable for open field or on-site conditions, enclosed blasting chambers and portable enclosed circulating systems. The various forms of wet blasting are carried out with non-metallic abrasives sometimes with a corrosion inhibitor added to the water. The method serves to minimize dust levels. The high velocity of water, with or without abrasive, aids in removal of contaminants such as salts and process fallout, especially so in pitted steel. There are two general classes of abrasive, i.e. metallic and non-metallic. Practitioners should be aware that a general dust hazard exists for all forms of dry abrasive blast cleaning, and that the use of silica abrasives in dry abrasive blast cleaning represents a specific health hazard to blasters and other people close by as this can cause silicosis. Abrasives containing free silica are therefore banned for dry blasting by many statutory authorities. The texture and colour of the blasted surface may vary depending upon the type of abrasive and method used.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A The surface roughness or profile achieved depends on several factors. These include metal substrate, blasting process, abrasive type, abrasive velocity at impact (affected by distance between the workface and nozzle, or wheel), and angle of the blast stream to the workface.  AS 1 627. 4 — 2 005 5 STANDARDS AUSTRALIA Australian Standard Metal finishing—Preparation and pretreatment of surfaces Part 4: Abrasive blast cleaning of steel S E C T I O N 1 S C O P E A N D G E N E R A L 1.1 SCOPE This Standard specifies abrasive blast cleaning methods for th e preparation of steel surfaces before coating with paints and related products. It also contains information on the effectiveness of the individual methods and their fields of application.  NOTE S: 1 Information on purchasing guidelines may be found in Appendix A. 2 Information on abrasive blasting of surfaces other than steel is discussed in Appendix D. This Standard is applicable to new and corroded steel surfaces and also to steel surfaces that are uncoated or have been previously coated with paints and related products.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A These methods are essentially intended for the surface preparation of hot-rolled steel but could also be used for cold-rolled steel of sufficient thickness to withstand the deformation caused by the impact of abrasive. Items considered as a part of surface preparation before coating are edge grinding, removal of grease and oil, removal of weld spatter, removal of burrs and other sharp edges, grinding of welds, filling of pits, porosity of welds and other surface imperfections and removal of water-soluble contaminants that may cause premature failure of the coating system (see AS 1627.0 for more information). Such defects cannot be satisfactorily treated by abrasive blast cleaning. WARNING: THE PROCEDURES DESCRIBED IN THIS STANDARD ARE INTENDED TO BE CARRIED OUT BY SUITABLY TRAINED AND SUPERVISED PERSONNEL. THE SUBSTANCES AND PROCEDURES USED IN THESE METHODS MAY BE INJURIOUS TO HEALTH IF ADEQUATE PRECAUTIONS ARE NOT TAKEN. ATTENTION IS DRAWN IN THE TEXT TO CERTAIN SPECIFIC HAZARDS. THIS STANDARD REFERS TO THE TECHNICAL SUITABILITY OF THE METHODS AND DOES NOT ABSOLVE THE USER FROM STATUTORY OBLIGATIONS RELATING TO HEALTH AND SAFETY.  NOTE : Fo r guidance on workin g place haza rds ref er t o Appendix C. 1.2 REFERENCED DOCUMENTS The following documents are referred to in this Standard. AS 1627 Metal finishing — Preparation and pretreatment of surfaces 1627.0 Part 0: Method selection guide 1627.1 Part 1: Removal of oil, grease and related contamination 1627.2 Part 2: Power tool cleaning 1627.9 Part 9: Pictorial surface preparation standards for painting steel surfaces 3894 Site testing of protective coatings  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 6 AS 3894.5 3894.6 3894.9 Method 5: Determination of surface profile Method 6: Determination of residual contaminants Method 9: Determination of adhesion 4361 4361.1 Guide to lead paint management Part 1: Industrial applications AS/NZS 1270 Acoustics — Hearing protectors 1336 Recommended practices for occupational eye protection 1715 Selection, use and maintenance of respiratory protective devices 1716 Respiratory protection devices 2161 2161.1 Occupational protective gloves Part 1: Selection, use and maintenance 2210 2210.1 Occupational protective footwear Part 1: Guide to selection, care and use 2312 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings 4501 4501.2 Occupational protective clothing Part 2: General requirements ISO    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A 11124 11124-2 11124-3 11124-4 11126 11126-3 11126-7 11126-9 11126-10 11127 11127-6 14877 Preparation of steel substrates before application of paints and related products — Specifications for metallic blast-cleaning abrasives Part 2: Chilled-iron grit Part 3: High-carbon cast-steel shot and grit Part 4: Low-carbon cast-steel shot Preparation of steel substrates before application of paints and related products — Specifications for non-metallic blast-cleaning abrasives Part 3: Copper refinery slag Part 7: Fused aluminium oxide Part 9: Staurolite Part 10: Almandite garnet Preparation of steel substrates before application of paints and related products — Test methods for non-m etallic blast-cleaning abrasives Part 6: Determination of water-soluble contaminants by conductivity measurements Protective clothing for abrasive blasting operations using granular abrasives SSPC SSPC-SP 5/NACE No.1, White metal blast cleaning SSPC-SP 6/NACE No.3, Commercial blast cleaning SSPC-SP 7/NACE No.4, Brush-off blast cleaning SSPC-SP 10/NACE No.2, Near-white blast cleaning SSPC-SP 14/NACE No.8, Industrial blast cleaning © Standards Australia www.standards.com.au 7  AS 1 627. 4 — 2 005 1.3 DEFINITIONS For the purposes of this Standard the following terms and definitions apply: 1.3.1 Abrasive Material which, when projected against a surface at high velocity, will wear and/or roughen the surface. 1.3.2 Abrasive blast cleaning The cleaning and roughening of a surface by impingement of the abrasive onto a surface to be prepared. 1.3.3 Almandite garnet Processed naturally occurring iron and aluminium silicate which is washed, dried and sieved, with or without mechanical crushing, and prepared for use as a blast cleaning abrasive. 1.3.4 Cast-steel shot A steel abrasive material that is predominantly spherical in shape produced by a special casting process. 1.3.5 Chilled-iron grit A metallic blast-cleaning abrasive obtained by crushing various chilled iron-shot sizes into sharp-edged angular particles.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A 1.3.6 Chilled-iron shot A cast iron abrasive that is predominantly spherical in shape produced by a special casting process. 1.3.7 Corrosion inhibitor A chemical added to the water used in wet abrasive cleaning or water blasting to reduce the susceptibility of the surface to flash corrosion. 1.3.8 Cut steel wire Sharp-edge steel particles used for abrasive blasting, having a length-to-diameter ratio of typically 1:1 cut so that faces are approximately at right angles to the centre-line. 1.3.9 Embedment The residual of the abrasive remaining attached to the surface. 1.3.10 Feathering (Feather edging) Tapering the thickness of the edge of a dry paint film. 1.3.11 Flash rust Flash rust is the development of a thin iron oxide soon after blasting in the presence of high humidity or moisture. 1.3.12 Foreign matter Any material contamination of the abrasive. 1.3.13 Fused aluminium oxide A synthetic mineral blast cleaning abrasive, which is classified as two types, A and WA. Type A: This type is mainly composed of crystalline corundum which is brown in colour and consists of a minimum of 94% aluminium oxide and a maximum of 4% titanium dioxide.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 8 Type WA: This type consists of crystalline corundum which is whitish in colour and contains at least 99% aluminium oxide. 1.3.14 Grit Particles that are predominantly angular, that have fractured faces and sharp edges and that are less than half-round in shape. 1.3.15 High-carbon cast-steel grit A metallic blast cleaning abrasive obtained by crushing high-carbon cast-steel shot into sharp-edged angular particles. 1.3.16 Ilmenite  Natural occurrin g mineral sand which is separated, dried and siev ed and prepared for use as a blast cleaning abrasive. 1.3.17 Preparation classes Classification describing the quality of preparation achieved by a method of surface cleaning. 1.3.18 Profile See ‘Surface profile’. 1.3.19 Profile comparator See ‘Surface profile comparator’.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A 1.3.20 Rust grades (Initial rust grades) Classification describing the initial amount of mill scale and rust on a steel surface before any surface preparation has taken place. 1.3.21 Spot (Selective) blasting The abrasive blast cleaning of a previously coated surface to produce areas of bare exposed metal and areas of brush-blasted surface. 1.3.22 Shot See ‘Cast steel shot’. 1.3.23 Slag A metal silicate abrasive manufactured by granulation in water, drying and sieving, with or without mechanical crushing processes, from slag originating from smelting operations. It is basically iron silicate slag.  NOTE : Sl ags manufa ctu red by air-cooling ins tead of granulation in wat er are generally of a different mineral structure and are therefore not covered by this Standard. 1.3.24 Staurolite  Natural occurrin g mineral sand which is separated, dried and siev ed and prepared for use as a blast cleaning abrasives. 1.3.25 Surface profile The micro-roughness of a surface generally expressed as the height of the major peaks related to the major valleys.  NOTE : Me thods o f determi nin g m axi mum pro file h eight are given in AS 3894. 5. 1.3.26 Surface profile comparator A specimen surface, or surface of known average profile, representing a particular abrasive blast cleaning process. © Standards Australia www.standards.com.au 9  AS 1 627. 4 — 2 005 1.3.27 Sweep (brush) blasting Light abrasive blast cleaning to roughen the surface or remove light rust, foreign particles and outer surface coating. 1.3.28 Visible rust and millscale Rust or millscale which can be seen without magnification, with normal or corrected vision. 1.3.29 Water jetting The method of cleaning a surface by the use of a jet of water under pressure. The jet of water may be accompanied by abrasives.  NOTE : This process is not spec ifi ed b y t his Sta ndard. 1.3.30 Wet abrasive blast cleaning Abrasive blast cleaning of a surface by compressed air or mechanical means using a mixture of abrasive and water, with or without air mixed into the abrasive stream. 1.3.31 Whipblast An abrasive blast of a previous blast cleaned surface to restore a class of surface preparation which has deteriorated with time.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 10 S E C T I O N 2 A B R A S I V E S 2.1 MATERIALS AND TYPES A wide variety of natural and synthetic granular materials are used for abrasive blastcleaning. A range of solid materials commonly in use for the preparation of steel surfaces before coating is given in Table 2.1. Each material provides a characteristic performance and surface finish. 2.2 REQUIREMENTS Abrasives shall be dry (except when added to pressurized liquid or slurry blast cleaning systems) and shall be free-flowing to permit consistent metering into the blast stream. The level of soluble salt contamination in the abrasive can be critical to the performance of a coating system particularly when used to contain fresh water. An upper limit of conductivity shall be 25 mS/m as assessed by ISO 11127 -6. The effect of salt contamination is more pronounced in hot, humid or fresh water environments.  NOTE : Fo r guidance on safety require men ts see Appe ndix C. 2.3 SELECTION CONSIDERATIONS 2.3.1 Abrasives and equipment    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Selection of a suitable abrasive, together with an appropriate blast-cleaning method and operating conditions, is necessary to achieve the required standard of surface preparation. The type of blast cleaning abrasive, i.e. its composition, particle size distribution, shape, hardness, density and impact behaviour (deformation or shatter characteristics), is important in determining the standards of cleanliness, the cleaning rate and the resulting surface profile of the blast cleaned surface. 2.3.2 Preliminary tests Preliminary blast cleaning tests are recommended to determine the most effective abrasive, blasting parameters, the resulting surface preparation grade, (see Appendix B) and the resulting surface profile, see AS 3894.5. If recycled abrasive is to be used for the surface preparation work, it is essential that a preliminary test be carried out with the same material, as new abrasive may give misleading results. The size and shape of the particles may change during use and this may affect the resultant surface profile of the blast-cleaned steel if the abrasive is reused. © Standards Australia www.standards.com.au 11    d   r   a    O   d    S    I   n   a    t    S    0    1      6    2    1    1    1    O    S    I    0    1      6    2    1    1    1    O    S    I   e   c   r   u   o    S    l   a   r   e   n    i    M    l   a   r   e   n    i    M    2  .    1      1  .    0    2  .    1      1  .    0    d   e    M    d   e    M     w   o    L    h   g    i    H   e   e   z   g   n    i    S   a   r    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A    1  .    2    E 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  e   n    d   r   a    H    l   a    i   r   e    t   a    M  www .st and ard s.c om.a u   s    h   o   m  AS 1 627. 4—20 05    3      6    2    1    1    1    O    S    I    9      6    2    1    1    1    O    S    I    l   a   r   e   n    i    M    t   c   r   u   e   d    t    l   o   e   r   m  p    S   y    b    t   c    l    l   u   a   a   e    t   r   r    d   e   e   s   r   n    i   n   a   o    i   p    W    M    M   y    b    5  .    0      1  .    0    0  .    3      2  .    0    6  .    0      1  .    0   w   o    L    h   g    i    H   m   u    i   n   t   e    i   m  a   c   u   i    l    l    i   a    /   s   n   o   r    I    )    7      6    2    1    1    1    O    S    I    d   e   u   n    i    t   n   o   c    (    d    d    d   e   r   e   r   e   r   u   u    t   u    t    t   c   c   c   a   a   a    f    f    f   u   u   u   n   a   n   a   n   a    M    M    M    0    2  .  .    0  .    3    1     -    3   -    5    5    1  .    0  .    0  .    0    0 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   l   e   e    t    S www.standards.com.au 13  AS 1 627. 4—20 05 2.3.3 Abrasive selection When selecting an abrasive, the following considerations shall be taken into account: (a) Metallic abrasives are denser, give a deeper profile for a given particle size and are easily recyclable but are heavy, expensive and difficult to handle. They are often used only in enclosed situations. (b) Non-metallic abrasives are more versatile for use in site work. (c) Abrasive shape: angular particles cut faster and give a sharper profile. Shot abrasives tend to give a more rounded profile and create less wear on equipment. (d) Profile, largely depends on abrasive type and particle size, see Table 2.2. (e) Surface condition: hard dense particles are more effective on mill scale, old pitted steel is more effectively cleaned by smaller abrasives. The abrasive used to remove aged coatings depends on their nature, condition and thickness.  NOTE : For lightl y abrad ing gal vani zed sur faces refer t o A ppendix D. (f) Degree of embedment; see Table 2.1. Economic factors that shall be considered are abrasive consumption, abrasive cost delivery to site, abrasive cleanup and disposal cost, blasting labour cost and cleaning production rate.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 14    d   e   s    h   s   s   a   u   l   r   g    C   m   m    0  .    3   e    d    i    b   r   a   c    i    S    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A    2  .    2    E    L    B    A    T    S    E    Z    I    S    /    S    E    P    Y    T    E    V    I    S    A    R    B    A    S    V    E    L    I    F    O    R    P    E    C    A    F    R    U    S    T    N    A    T    L    U    S    E    R    2    1    #   e    d    i   x   o    l    A    6    1    #    6    1 #    2    1    #   e   n   o    t   s   e   m    i    L   s   u    l    P    /    T   e    t    i    l   o   r   u   a    t    S    0    6    /    0    3   m   m    0  .    1   m   m    0  .    2   m   m    0  .    3   g   a    l    S   e    t    i   n   e   m    l    I   e    t    i   n   e   m    i    L    t   e   n   r   a    G    t   o    h   s    l   e   e    t    S   e    l    i    )    0    f    5   o   m      µ    1   r    (    P © Standards Australia    0    3    3    S    0    9    3    S    8    1    G    0    4    1    0    3    1    0    2    1    0    1    1    0    0    1    0    8    2    S    0    9    0    8    0    7    5    0    G    7    0 G    0    3    2    S    0    8    G    0    5    G    0    4 G    5    2    G    0    8    2    1 G    7    1    G    4    2 G    9    3    G    0    6    /    0    3    0    4    /    0    2    0    2    /    2    1    t    i   r   g   n   o   r    i    d   e    l    l    i    h    C    t    i   r   g    l   e   e    t    S    0    8    #    0    6 #    6    3    #    0    2    #    0    8 #    0    6 #    6    3    #    0    2    #   m   m    5  .    1   m   m    0  .    2    0    6    0    5    0    4    0    3    0    2    0    1 www.standards.com.au 15 S E C T I O N 3 A B R A S I V E B L A S T M E T H O D S  AS 1 627. 4 — 2 005 C L E A N I N G 3.1 DRY ABRASIVE CLEANING 3.1.1 Compressed air abrasive blast cleaning Compressed air abrasive blast cleaning is carried out by incorporating an abrasive or abrasive mixture into an air stream, and directing the resulting high velocity air/abrasive flow through a nozzle onto the work piece. The abrasive is usually injected into the air stream from a pressurized container. The method is suitable for cleaning work of all types, including large structures having variable rust grades, and may be used either continuously or intermittently. The system can be used in enclosed plants, rooms or cabinets, or on-site, and is able to be designed so that abrasive can be recovered, cleaned and recycled. This method may give rise to dust when used in open areas and its use may be restricted by environment or legislative requirements, in which case dust suppression or collection facilities are required. Compressed air abrasive blast cleaning will not remove oil, grease and related contamination, and will not remove chemicals such as soluble salts. Additional treatment is required if removal of such contaminants is necessary.  NOTE : Fo r s wee p (brus h) blas ting see Appe ndix D. 3.1.2 Vacuum or suction head abrasive blast cleaning    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Vacuum or suction head abrasive blast cleaning is similar to compressed air abrasive blast cleaning, but with a blasting nozzle enclosed in a suction head which is sealed to the metal surface and collects spent abrasive and contaminants. Alternatively, the abrasive air stream may be held on to the surface by negative pressure at the suction head. The method is particularly suitable for localized cleaning, and where the dust and debris resulting from unconfined compressed air blast cleaning techniques are unacceptable. The production rate is slower and generally less effective than other blast cleaning methods, as the velocity of the abrasive is substantially below that of the other methods. It is not recognized as being suitable for cleaning heavily corroded steel, and is not applicable for irregular shapes, due to the necessity of close sealing to the surface, and difficulties in handling the equipment. As with compressed air abrasive blasting, it will not remove oil and grease or chemicals, such as s oluble salts. 3.1.3 Centrifugal abrasive blast cleaning Centrifugal abrasive blast cleaning is carried out in enclosed plants or mobile units in which the abrasive is fed to rotating wheels or impellers positioned to propel the abrasive evenly, and at high velocity, onto the surface to be cleaned. The method is generally confined to a fixed abrasive blast cleaning station, for continuous blast cleaning of plates, pipes and of structural members before erection. In most cases, the abrasive is circulated in a closed system; the work pieces are either fed through these plants or rotated within them. In certain cases, the equipment may be mobile and may be used for cleaning large uninterrupted surfaces such as ship’s decks, tank floors. The centrifugal abrasive blast cleaning equipment has to be carefully designed to achieve an even bl ast over the total surface area. The method is limited to repetitive work associated with high volume throughput or continuous operation. Surfaces inaccessible by this method are usually blast cleaned manually. Centrifugal abrasive blasting will not remove oil and grease, nor chemicals such as soluble salts.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 16 3.2 WET ABRASIVE BLAST CLEANING 3.2.1 General Wet blasting, using a combination of water and abrasive to clean the surface, is usually used for maintenance rather than new work. It has the following advantages over dry abrasive blasting: (a) It can reduce the level of dust. (b) It can more readily remove soluble salts and other soluble contamination from a pitted surface. The disadvantages include:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A (i) The surface remains wet, and will flash rust if steps are not taken to prevent it. (ii) A wet slurry tends to build up on the work surface and surrounds which can be difficult to remove. (iii) The operation is usually slower than dry blasting. (iv) It is difficult for operators to work in wet conditions and monitor levels of cleanliness. (v) Wet blast cleaning cannot be used where water presents a hazard. (vi) Abrasives are restricted to non-ferrous expendable materials. The water used for wet abrasive blasting should have a low salt content to avoid surface contamination. Town mains drinking water is normally used. For offshore work, and in remote regions, sea water or salty water may be used, but fresh water shall be used for the final rinse. The three main categories of wet abrasive blasting are discussed in Clauses 3.2.2 to 3.2. 4. 3.2.2 Compressed air wet abrasive blast cleaning Compressed air wet abrasive blast cleaning is the most common form, and usually uses the same or similar equipment to dry blasting, but water is usually introduced just behind the nozzle so that the water is atomized and accelerated through the nozzle orifice, along with the air and abrasive. A major advantage of compressed air wet abrasive blast cleaning is that operators can independently control air, abrasive and water so they can dry blast, wet blast, wash and dry with air, all with the same equipment. Water added after the nozzle as a curtain, sometimes called a ‘wet head’ is a simple process which can cut down dust. However, it has little effect on cleaning efficiency since water does not mix with the abrasive to the same extent. 3.2.3 Slurry blast cleaning In slurry blast cleaning, the water and abrasive are mixed together in the blast pot. Special units are required which are operated at lower pressures than dry blasting and so produce a fine uniform finish on steel surfaces requiring little or no surface profile. It is less common than wet abrasive blast cleaning. 3.2.4 Water jetting with abrasive injection High pressure water jetting without abrasive, sometimes called hydroblasting, uses high or ultra-high water pressure to clean the surface. It can remove old paint and rust, as well as soluble contaminants, but may not remove tight mill-scale nor will it create a profile. This process is outside the scope of this Standard. However, abrasive can be introduced into the high pressure water stream to produce a wet abrasive stream through a nozzle. It is slow, gives an uneven finish and can be difficult and dangerous to handle. © Standards Australia www.standards.com.au 17  AS 1 627. 4 — 2 005 3.3 FLASH RUSTING Flash rusting may occur with any of the processes using water. This thin iron oxide film may need to be removed if considered detrimental to the subsequent coating. The blast cleaned surface will normally be required to dry before application of paint, except for specially formulated surface tolerant primers for damp substrates. If a corrosion inhibitor is used to prevent flash rusting, it shall be compatible with subsequent coatings, and the concentration of the inhibitor solution shall be carefully controlled to the manufacturer ’s recommendations to prevent water-soluble contamination on the surface. The use of an inhibitor may also require that special disposal procedures be carried out to comply with environmental regulations. If flash rusting does occur, the surfaces may be dry blasted to the specified class of surface preparation. The surface of existing structures (especially those in an operating environment) have a much greater propensity to flash corrode and become chemically contaminated prior to coating. Application of coatings should be carried out as soon as practicable. Normally, steel structures are coated within the same day or shift.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 18 S E C T I O N 4 I N I T I A L R U S T G R A D E S C L A S S E S O F B L A S T C L E A N I N G A N D 4.1 INITIAL SURFACE ASSESSMENT The surface of hot rolled steel may be defined according to one of four initial rust grades defined and illustrated in AS 1627.9 depending on the relative amounts of mill scale and rust. The worst grade that is evident on the steel surface to be treated shall be recorded. GRADE A Steel surface covered completely with adherent mill scale and with little if any rust. GRADE B Steel surface, which has begun to rust and from which the mill scale has begun to flake. GRADE C Steel surface on which the mill scale has rusted away or from which it can be scraped, but with little pitting visible to the n aked eye. GRADE D Steel surface on which the mill scale has rusted away and on which considerable pitting is visible to the naked eye. 4.2 CLASSES OF BLAST CLEANING This Standard defines four classes of surface preparation achievable by abrasive blast cleaning, identical to those described and pictured in AS 1627.9. The definitions are:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Sa 1 Light blast cleaning. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter. The appearance corresponds to the prints designated Sa 1 in AS 1627.9.  NOTE : Mill sca le, rust or paint coatin g is con side red to be poorl y adhe rin g if it can be removed by lifting with a blunt putty knife . Sa 2 Thorough blast cleaning. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free from most mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering (see note to Sa 1). It corresponds to the appearance of the prints designated Sa 2 in AS 1627.9. Sa 2 ½ Very thorough blast cleaning. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free from mill scale, rust, paint coatings and foreign matter. Any remaining contamination shall show only as slight stains in the form of spots or stripes and correspond to the prints designated Sa 2½ in AS 1627.9. Sa 3 Blast cleaning to visually clean steel. When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free fro m mill scale, rust, paint coating and foreign matter. It shall then have a uniform metallic colour and correspond to the prints designated Sa 3 in AS 1627.9.  NOTE : Fu rth er inf orma tion o n t he cla sse s o f s urface preparat ion, inc ludi ng relati ons hip to cla sse s in the earlier edition of this Standard and in USA Standards, is given in Appendix B. Record the assessment as the class nearest in appearance to the prepared surface. When recording the standard of cleanliness, the original rust grade and class of preparation shall be noted.  Example: A steel surface originally corresponding to rust grade B, which has been prepared by blast cleaning to preparation grade 2½, is designated B Sa 2½. © Standards Australia www.standards.com.au 19  AS 1 627. 4 — 2 005 4.3 OTHER ASSESSMENT REQUIREMENTS For other assessment requirements see Clause 5.5.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 20 S E C T I O N 5 P R O C E D U R E 5.1 GENERAL The requirements for blast cleaning, post blast cleaning and assessment are specified in Clauses 5.2, 5.3, 5.4 and 5.5. 5.2 PREPARATION BEFORE BLAST CLEANING Surfaces to be abrasive blast cleaned should be checked for the presence of contaminants including soluble iron salts, chlorides, weld spatter release agents and oil. Any surface contaminants present before abrasive blast cleaning shall be removed to a level appropriate to the coating system to be used. Oil, grease and related contamination shall be removed using the methods described in AS 1627.1. Deposits of soluble salts may be removed by fresh water washing, with or without the addition of salt removal agents. Water jetting may be required to remove some deposits of soluble salts. It may be advantageous to remove heavy, firmly adhering rust and scale by hand-or powertool cleaning (see AS 1627.2) prior to abrasive blast cleaning. The preliminary treatment of welds, the removal of weld spatter and the removal of burrs and other sharp edges should also be addressed.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Where spot or brush blast cleaning is to be employed, the soundness of existing coatings shall be assessed by attempting to lift the film with a blunt putty knife, or by determination of adhesion in accordance with AS 3894.9. Further information regarding the maintenance of existing coatings can be found in Section 10 of AS/NZS 2312. Any areas which are not to be abrasive blast cleaned shall be masked off to prevent damage. 5.3 SELECTION OF BLAST CLEANING PARAMETERS A typical procedure for blast cleaning is as follows: (a) The initial rust grade(s) of the workpiece should be assessed (see Clause 4.1) and recorded. If the structure is coated, the type and nature of the coating should be noted as it will also affect the blasting process. (b) The required class of surface preparation, surface profile and level of contaminants (if required) shall be provided in the specification or other customer-supplied documentation. The classes of surface preparation are given in Clause 4.2, and Table 2.2 shows the profile a vailable with different abrasives and sizes. (c) The appropriate blast cleaning method can be selected from those described in Section 3. (d) The appropriate abrasive type and particle size distribution can be selected to provide the required class of surface preparation and surface profile. 5.4 AFTER BLAST CLEANING After dry abrasive blast cleaning, all loosely adhering dust, debris and blast cleaning abrasive shall be removed by brushing, blowing with clean dry compressed air or by  vacuum. When required, residual soluble imp urities shall be re moved by washing with fres h water, and allowed to dry. © Standards Australia www.standards.com.au  AS 1 627. 4 — 2 005 21 Wet abrasive blast cleaning shall have all surfaces washed down with potable water to remove loosely adhering abrasive and other residues. The water may contain a rust inhibitor, subject to approval by the coating manufacturer. Clean dry compressed air may be used to assist in drying surfaces before application of paint. Any flash rusting on a freshly blast-cleaned surface may need to be removed if considered detrimental to the subsequent coating. 5.5 ASSESSMEN T OF THE BLAST CLEANED SURFACE All cleaned surfaces shall be assessed for compliance with the preparation grade requirements of the contract specification, in accordance with AS 1627.9. The relevant clauses of AS 3894.5 shall be used to assess surface profile and AS 3894.6 employed in the assessment of residual contaminants if required. AS 3894.6 may also be used to assess the presence of mill scale, should removal be a requirement of the specification. In the event o f non-compliance, the surface preparation process shall be repeated. Where spot blasting has been specified, any areas of remaining coating shall be feathered.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 22 APPENDIX A PURCHASING GUIDELINES (Informative) A1 GENERAL Australian Standards are intended to include the technical requirements for relevant products, but do not purport to comprise all the necessary provisions of a contract. This Appendix contains advice and recommendations on the information to be supplied by the purchaser or end user at the time of enquiry or order. A2 INFORMATION TO BE SUPPLIED BY THE PURCHASER The purchaser should supply the following information at the time of enquiry or order:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A (a) Scope of work. (b) Presence of any hazardous material, such as lead. (c) Any contaminant, dust extraction and waste disposal requirements, (if applicable). (d) Blast cleaning method to be used, (if applicable). (e) Class of cleaning required. (f) Requirements for removal of existing coatings. (g) Surface profile (if required) height, shape, and method of measurement (see AS 3894.5). (h) Type and grade of abrasive to be used, (if applicable). (i) Type and concentration of inhibitor, (if applicable). (j) Acceptable limits for total dissolved salts content for abrasives, (if applicable). (k) Any preparation required before blast cleaning, such as treatments required for welds and steel defects, (if applicable). (l) Quality control and inspection requirements. (m) Special requirements for particular site and weather conditions, (if applicable). (n) Test reports, (if applicable). (o) Acceptable level of non-visible contaminants and methods of measurement, see AS 3894.6, (if applicable). © Standards Australia www.standards.com.au 23  AS 1 627. 4 — 2 005 APPENDIX B CLASSES OF SURFACE PREPARATION (Informative) B1 GENERAL This Appendix covers the four grades of surface preparation after abrasive blast cleaning defined in Section 4, describing the differences between them, where they are used and how the descriptions relate to the earlier version of this Standard and to SSPC and NACE Standards. It also describes some aspects of inspection of blast cleaned surface that should be considered.  Note that the class of visu al cleanliness is only one factor in specifying surface preparation. The class of blast does not give any indication of the profile nor of the level of invisible contaminants on the surfaces. If these are critical, they should be separately specified. B2 CLASSES OF VISUAL CLEANLINES S AFTER BLAST CLEANING B2.1 General    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A The four classes of visual cleanliness are given in Clause 4.2. The required class of blasting will usually be given by the coating manufacturer, and the specifier will normally follow this advice. A lower standard should not be specified unless specifically approved by the coating manufacturer. However, the specifier may require a higher standard of cleanliness that that required by the manufacturer in critical applications or for greater durability or both. B2.2 Light blast cleaning (Sa 1) Light blast cleaning, previously known as Class 1, is the lowest standard of surface preparation. The required cleaning is such that loose mill scale, loose rust and foreign particles are removed. It will not remove firmly adherent paint, rust or mill scale. The appearance of the surface approximates to Sa 1 in the pictorial surface preparation AS 1627.9. It is a similar cleanliness standard to SSPC-SP 7/NACE No.4, where it is referred to as ‘brush-off ’ blast cleaning. This class of surface preparation is a relatively low cost standard of cleaning. The finish produced is not suitable for high quality coatings, for coatings that are subjected to severe service conditions or where long lifetimes are required. Any paints used on such surfaces should have good wetting properties. It can be used where hand and power tool cleaning have been specified. With proper facilities, costs can be less or of the same order as those for hand or power tool cleaning, although generally the overall surface finish is usually better with blast cleaning B2.3 Thorough blast cleaning (Sa 2) This class of cleaning, previously referred to as Class 2, is such that mill scale, rust and foreign particles are substantially removed and grey metal is visible. The appearance of the surface approximates to pictorial surface preparation standard Sa 2 of AS 1627.9. It is a similar standard to SSPC-SP 14/NACE No.8, where it is referred to as ‘industrial’  blast cleaning. This recently released US standard allows up to 10 percent tightly adherent scale, rust or old coating to remain on the surface. Historically, Sa 2 has been regarded as the equivalent of SSPC-SP 6/NACE No.3, referred to as ‘commercial’  blast cleaning. This cleanliness standard requires that all rust, scale and old coating are removed, and no more than 33 per cent of every square inch is stained, so is of somewhat higher standard than Sa 2.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 24 Sa 2 surface preparation, sometimes called ‘medium’  blast cleaning, is used when it is thought that blast cleaning is necessary, but the high cost of more thorough blast cleaning standards rules out their use. This degree of surface preparation will lead to a satisfactory life for “surface tolerant”  paint systems, or for conventional coating systems in milder environments. B2.4 Very thorough blast cleaning (Sa 2½) This class of surface preparation, previously known as Class 2 ½ and commonly referred to as ‘ Near White’, is such that mill scale, rust and foreign particles are removed to the extent that only stains remain in the form of spots or stripes. The cleaned surface will show  varying shades of grey . The appearance of the surf ace approximates the pictorial surf ace preparation Standard Sa 2 ½  of AS 1627.9. It is a similar standard to SSPC-SP 10/NACE  No.2, where it is referred to as ‘near white’ blast cleaning. This class of surface preparation is suitable for most high quality protective coatings and is commonly specified for coating systems applied in atmospheric environments, where it can provide long-term durability. Removal of the small amount of visual contamination left on the surface after a Sa 2 ½  blast is difficult and expensive. Depending upon the initial condition of the steel, it has been variously estimated that this class of blast cleaning can be carried out at a cost of 10 percent to 35 percent less than that of ‘white metal’  blast cleaning. B2.5 Blast cleaning to visually clean steel (Sa 3) This is the highest standard of the surface preparation, previously known as Class 3 and commonly referred to as ‘white metal’ blast cleaning.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A The surface preparation is such that visible mill scale, rust and foreign particles are entirely removed. The cleaned surface should have a uniform metallic colour but may show varying shades of grey when viewed at different angles. It is therefore important that the surface be  viewed at right angles for comparison with the pictorial Standard (AS 1627.9). The appearance of the surface approximates the pictorial surface preparation standard Sa 3 of AS 1627.9. The appearance is similar to SSPC-SP 5/NACE No.1, where it is referred to as ‘white metal’ cleaning. Blast cleaning to white metal is necessary as a preparation for critical coatings or for coatings which will be exposed to a very corrosive atmosphere where a high standard is considered warranted. Blast cleaning to this class will result in maximum performance of coating systems due to the removal of visible foreign matter or contaminants from the surface. This degree of blast cleaning is sometimes required to ensure adhesion of some metallic coatings. Sa 3 blast cleaning requires the surface to be completely clean visually so this degree of cleaning should only be specified when service requirements demand this, instead of the more readily achievable and more economical Sa 2 ½. In atmospheric environments its use is seldom warranted due to the marginal improvements in coating performance which can be gained over ‘near white’ class. The prevention of rust formation after blast cleaning to Sa 3 class is particularly difficult in environments where a rust-free surface is most needed as preparation for coating, such as in humid, chemical or severe marine industrial environments. Sa 3 blast cleaning must be conducted at a time when no contamination or rusting can occur, and when prompt coating is possible. It is also difficult to achieve Sa 3 when t he original surface condition shows rust pitting (original condition D), as there will be invisible pockets of contamination in the corrosion pits that will re-rust rapidly. Wet abrasive blasting or water jetting are desirable for preparing original condition D if a long life is required. Table B1 relates current and former classes of surface preparation by abrasive blasting, along with SSPC and NACE approximations. © Standards Australia www.standards.com.au  AS 1 627. 4 — 2 005 25 TABLE B1 BLAST CLEANING STANDARDS Blast cleaning class Description Former  AS 16 27.4 designation SSPC NACE SPC/NACE Description Sa 1 Light Class 1 SP 7 No.4 Brush-off Sa 2 Thorough Class 2 SP 14 SP 6  No. 8  No. 3 Industrial Commercial Sa 2½ Very thorough Class 2½ SP10 No.2 Near white Sa 3 Visually clean Class 3 SP 5 No.1 White B3 FACTORS INFLUENCING BLAST APPEARANCE Assessment of the surface is by colour, so it should be noted that colour variations of the surface can be influenced by the following:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A (a) The type and size of abrasive and whether an angular or round medium was used. The photographs in AS 1627.9 are of a sand blasted surface, which tends to give a brighter and whiter finish than most other abrasives. A surface cleaned with shot abrasive appears grey when compared with the ‘white metal’  appearance of a grit blasted surface, and may be mistaken for mill scale remaining on the steel surface. The difference in appearance with different abrasives is most noticeable with Sa 3 and Sa 2½  standards of surface preparation. A deeper profile may give a darker appearance than a shallow profile because of a greater degree of shadowing. (b) Whether wet blasting or dry blasting was used. Flash rusting after wet blasting will discolour the surface. (c) Angle of viewing of the surface and angle of blast will influence shadow effect and influence appearance. (d) Condition of lighting. Good diffuse daylight or equivalent artificial illumination should be used when comparing the surface with the photographs. The photographs should be placed close to and i n the plane of the steel surface to be assessed. Determining surface cleanliness can be subjective and requires experience. It is stressed that the class of cleanliness should meet the written description. The photographs are only a guide to supplement the written description and it is essential that they not be used as an absolute indication.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 26 APPENDIX C SAFETY CONSIDERATIONS AND REQUIREMENTS (Informative) C1 HEALTH HAZARDS The nature of the hazards associated with blast cleaning include the following: (a) Physical danger of the blast stream (including high pressure air and water). (b) Respirable dust produced by the operation.  NOTE S:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A 1 It is important to ensure that adequate instructions are given and that all required precautions are exercised. 2 The following should not be used as a blasting medium: (a) Materials containing more than 1 percent free crystalline silica. (b) Recycled materials that have not been treated to minimize respirable dust. (c) Materials containing radioactive substances, refer to Regulation 1961 or the Health (Radioactive substances) Regulation 1994. (d) Copper and zinc slags that have high levels of heavy metals. Blasting with these materials may produce levels of lead in the air which may exceed limits for occupational, health and safety requirements. (c) General unsafe conditions existing in the working environment. (d) Toxic substances in the existing coatings, such as lead or asbestos, should be determined before abrasive blast cleaning. Abrasive blasting of coatings containing such materials is extremely hazardous and should not be carried out without protecting the operator or public. The environment may require specific containment, extraction and disposal procedures in order to comply with statutory requirements, see AS 4361.1. State and local government authorities have restricted dry abrasive blast cleaning in some areas while banning it in others, or requiring licensing. The appropriate state authority should be consulted before commencing abrasive blast cleaning. C2 CONTROL MEASURES C2.1 Isolation Abrasive blasting activities should be isolated from other workplace activities to reduce the possibility of workers being struck by particulate matter and exposure to dust. This may be done by using blasting chambers, blasting cabinets, temporary enclosures and exclusion zones. Abrasive blasting plant may also incorporate guards to reduce the possibility of particulate matter striking the operator.  NOTE : The ris k of sus tai ning a seriou s injury from part iculat e mat ter is inc reased whe n blasti ng in a confined space, working in an elevated position and when the operator is out of the line of sight of a pot tender or there is no dedicated pot tender who may provide assistance if required. C2.2 Self-actuating cut-off devices Abrasive blasting equipment should be fitted with a fast acting self-actuating cut-off device under the direct control of the nozzle operator. © Standards Australia www.standards.com.au  AS 1 627. 4 — 2 005 27 WARNING: USING A BLAST MACHINE WITHOUT A FAST ACTING SELFACTUATING CUT-OFF DEVICE UNDER THE DIRECT CONTROL OF THE OPERATOR IS A DANGEROUS PRACTICE THAT MAY RESULT IN SERIOUS INJURY OR DEATH. The device most commonly used is called a remote control or ‘dead man control’ which is usually attached to the nozzle. When the nozzle is dropped, the air supply shuts off and prevents the whipping hose injuring the worker and the abrasive material firing at the operator or other people nearby. C2.3 Whip checks Hose whip checks or hose coupling safety locks or both should be fitted to hoses.  NOTE S: 1 To prevent serious injury due to hose or coupling failure, a whip check should be fitted to each hose connection and from equipment to hose. The whip check should be installed in the fully extended position (no slack) for proper safety assurance. 2 A regular survey should be carried out of all compressed air power equipment to assess the integrity of the couplings, clamps and hoses and immediate action taken where necessary. C3 PROTECTIVE CLOTHING Each operator should be provided with eye protection (see AS/NZS 1336) protective gloves (canvas or leather see AS/NZS 2161.1), protective footwear (see AS/NZS 2210.1), respiratory equipment and protective clothing (overalls, long trousers, blast suits and aprons, see AS/NZS 4501.2).    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A C4 FACE AND EYE PROTECTION Workers engaged in abrasive blasting should be supplied with and should wear an air line positive pressure hood or helmet complying with AS/NZS 1716 , fitted with an inner bib and a shoulder cape, jacket or protective suit complying with ISO 14877. To keep out dust and abrasive grit, protective suits or clothing should also have leather or elastic straps at the wrist and ankles, and o verlapping flaps at all suit closures. C5 EAR PROTECTION C5.1 General  Noise is unwanted sound that may damage a person’s hearing. The amount of damage caused by noise depends on the total amount received over time. The degree of risk is affected by the intensity (loudness) and the frequency (pitch) of the noise, as well as the duration and pattern of exposure and th e individual’s susceptibility to hearing impairment. Each operator should minimize the risk of exposure to excessive noise. Excessive noise is defined as a level of noise above —  (a) L (b) L Aeq, 8h   of 85 dB(A) that is, an 8 hour equivalent continuous A-weighted sound pressure level of 85 dB(A), referenced to 20 micropascals; or c,peak of 140 dB(C) that is, a C-weighted peak sound pressure level of 140 dB(C) referenced to 20 micropascals. C5.2 Typical noise sources In the abrasive blasting industry, the main noise source is from the discharge of compressed air at the blast nozzle. For the operator, the next major source is the feed air inside the protective helmet. Small blast cabinets as used by many workplaces in the metal industry are also significant sources of noise exposure for operators. Other sources of noise include air compressors, ventilation systems and air releases during pot blow-down.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 28 An indication of the level of noise experienced in abrasive blasting processes may be obtained from the following noise readings taken at operator ear level: (a) Air discharge from blast nozzle: 112 to 119 dB(A). (b) Feed air inside helmet: 94 to 102 dB(A). (c) Blast cabinets: 90 to 101 dB(A ). (d) Air compressors: 85 to 88 dB(A). C5.3 Above the proscribed level and control measures Maximum noise levels up to 137 dB(A) and peak levels up to 145 dB(A) have been measured during blasting activities at the operator position when the abrasive runs out. Operators of small abrasive blasting cabinets are particularly at risk. They may not perceive the noise to be damaging because of the relatively short periods of use. However, average noise levels at operators’ ears have been measured between 90 and 101 dB(A). This means that at 101 dB(A), for instance, an exposure of unprotected ears of only 12 minutes is allowed in any 8 hour shift so as not to exceed the exposure limit of 85 dB(A). In addition, other work activities must not contribute to further noise exposure. Unprotected operators and others close to the blasting process may also be exposed to excessive noise, (see AS/NZS 1270). C6 RESPIRATORY PROTECTION    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Air monitoring by trained personnel should be conducted in all abrasive blasting applications as part of the initial risk assessment process. This will enable the appropriate respirator to be selected and will ensure that workers and other people are not exposed to harmful dust concentrations. The selection, use and maintenance of respiratory devices should be undertaken in accordance with AS/NZS 1715. Respirators will only provide a satisfactory level of protection when they are selected, fitted, used and maintained according to the manufacturer ’s written instructions and other regulatory and advisory guidelines. Personal protective equipment should be individually fitted and if it is to be shared, it should be disinfected and refitted before use. An air purifying respirator complying with A S/NZS 1716 should be worn by the pot attendant or any other person within the work area while abrasive blasting is in progress, during maintenance or repair work, where dust from the process is visible or during the clean-up of dust. C7 SAFE WORKING GUIDELINES  NOTE : State regu lati ons wil l g enerally set sta ndards to be a chieved. C7.1 Scaffolding and harnesses If working from heights cannot be avoided, physical barriers should be put in place to stop the person from falling, these include: (a) Edge protection systems e.g. guardrailing with mid rails, containment sheeting, hoarding. (b) Fall protection covers over holes and openings. (c) Working platforms e.g. elevating work platforms such as scissor lifts, boom type elevated. © Standards Australia www.standards.com.au  AS 1 627. 4 — 2 005 29 (d) Platforms or mast climbers.  NOTE : Sc issor lif ts and cher ry pick ers should be fit ted with operator’s cont rols and hand and toe rails. The choice of staging should take account of the operator needs for freedom of movement to complete the task safely. Extra precautions should be taken when blasting from a scaffold because an air-fed helmet does not allow a full field of vision, so planks should be wide and tightly secured for maximum footing. Where work is to be undertaken in an elevated position, the level of light should not be less than 200 lux for the working area and 50 lux for stairs or other areas giving access to the work area. Ensure the operator are able to see the following: (i) The physical limits of the work platform. (ii) Any other people in the area. (iii) All control devices.  NOTE : G ener al rules, whi ch sho uld be applied whe n blas tin g at heights a re:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A (a) No one should work below blast operators, (a nozzle or hose dropped may kill or cause severe injury). (b) Stop frequently to sweep or clean abrasive media from all horizontal surfaces on the staging, (footing may be treacherous on loose abrasive). (c) Use ropes or other strong attachment methods to secure the blast hose to the staging, (this relieves the operator from the weight of the hose and prevents a dropped hose from falling). C7.2 Personal fall protective equipment Personnel fall protection systems are systems which secure a person to a building or structure. They should only be used where it is not possible to use physical barrier systems such as working platforms, edge or fall protection covers. However, personnel fall protection may be used in addition to physical barrier systems. Personal fall protection equipment includes: (a) Travel restriction devices which prevent a person falling e.g. industrial access systems and fall-prevention systems. (b) Fall arrest systems which arrest a person once he or she has fallen, e.g. fall-arrest harness or ladder belts with lanyard assemblies.  NOTE S: 1 Persons should be properly trained and supervised in the use of this equipment. 2 When using a fall-arrest system ensure there are no obstructions in the potential fall path. C7.3 Static discharge Static electricity may build up in dry blasting operations. Nozzles should be grounded to protect the operator against electric shocks as well as to prevent explosion of flammable material. C7.4 Unauthorized personnel The blasting area should be roped off and signposted, to exclude entry of unauthorized persons.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 30 C8 WORK ENVIRONMENT C8.1 General State regulations for air quality may be in operation. Where this is the case, AS/NZS 1716 is recommended as a guide. C8.2 Ventilation Adequate ventilation and purging of flammable gases and vapours should be undertaken. C8.3 Lighting Regulations for light intensity have been set in some States, e.g. 200 lux over all parts of a chamber, measured in a horizontal plane at 1 m above the floor.    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A © Standards Australia www.standards.com.au 31  AS 1 627. 4 — 2 005 APPENDIX D SWEEP (BRUSH) BLASTING CLEANING (Informative) D1 GENERAL Sweep (brush) blast cleaning is used to clean and lightly abrade weathered but sound paint surfaces or other soft surfaces such as stainless steel, copper or fibreglass. The purpose of this treatment is to prepare —  (a) existing paints prior to the application of maintenance coatings, where the substrate remains a sound coating; and (b) galvanized coatings prior to the application of an organic paint system. D2 PROCEDURE To produce a suitable surface for painted or galvanized systems for coating, the following procedure should be implemented when sweep blast cleaning:    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A (a) A fine non-metallic abrasive should be used of a size which will pass through a test sieve of nominal size 80 mesh, e.g. garnet abrasive. (b) The blast pressure should be less than 275 kPa (40 p.s.i.). (c) The nozzle should be positioned at least 350 mm from the surface of the work piece. D3 SURFACE PREPARATION It is important that surface preparation is performed carefully to ensure the surface is not damaged. Subsequent coating should be applied before recontamination or reoxidation occurs.  ww w.s tan dard s.c om. au ©  Standards Australia  AS 1 627. 4 — 2005 32  NOT ES    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Standards Australia Standards Australia is an independent company, limited by guarantee, which prepares and publishes most of the voluntary technical and commercial standards used in Australia. These standards are developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth government, Standards Australia is recognized as Australia’s peak national standards body. For further information on Standards Australia visit us at  www.standards.org.au    )    d   e    t   n    i   r   p   n   e    h   w    d   e   e    t   n   a   r   a   u   g    t   o   n   y   c   n   e   r   r   u   c    t   n   e   m   u   c   o    D    (    6    1    0    2    t   c    O    6    2   n   o   y    t    i   s   r   e   v    i   n    U   y   e   n    d   y    S   n   r   e    t   s   e    W   y    b    d   e   s   s   e   c   c    A Australian Standards  Aust ralian Standa rds are pre pared by committ ees of experts fro m in dust ry, governmen ts, consume rs and other relevant sectors. 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