1、 INTERNAL ABRASIVE BLAST CLEANING OF FERRITIC PIPING Prepared by Pipe Fabrication Institute Engineering Committee All PFI Standards are advisory only. There is no agreement to adhere to any PFI Standard and their use by anyone is entirely voluntary. Copyright by PIPE FABRICATION INSTITUTE Dedicated
2、to Technical Advancements and Standardization in the Pipe Fabrication Industry Since 1913 USA 511 Avenue of Americas, # 601 New York, NY 10011 CANADA 655, 32ndAvenue, # 201 Lachine, QC H8T 3G6 WEB SITE www.pfi-institute.orgPFI Standard ES-29 (Revised February 2006) PFI Standard ES-29 |Denotes Revisi
3、on (Revised February 2006) INTERNAL ABRASIVE BLAST CLEANING OF FERRITIC PIPING 1. Scope 1.1 This standard describes the materials and equipment used for abrasive blast cleaning the inside of ferritic piping and it defines the different levels of surface cleanliness, which can be achieved. 1.2 Other
4、mechanical cleaning methods such as brushing, grinding, chipping, sanding, etc., may be used as a supplement to abrasive blasting when necessary to achieve the required cleanliness level. 1.3 Maintenance of blast cleaned surfaces is not covered by this standard (i.e., use of corrosion inhibitors). I
5、f internal coatings are to be applied, refer to coating manufacturers recommendations. 2. Definitions Contaminant any undesirable foreign material on the surface to be cleaned Grit irregularly shaped particles with sharp edges, to promote high effectiveness in removal of contaminants. Semi-Sharp Abr
6、asives irregularly shaped particles with some rounded and some sharp edges on one particle. Shot particles that are spherical or near spherical in shape. 3. Equipment for Abrasive Blasting 3.1 Dry direct pressure blast cleaning equipment and compressed air blast nozzles shall be used. Other equipmen
7、t is permitted provided that the required acceptance criteria can be met. 3.2 Blast nozzle selection. See Table I. TABLE I Nozzle Type Pipe Diameter Deflection 8“ and smaller Spin blast (1) 10“ thru 24“ Conventional or Straight 24“ and larger Note (1) Spin blast units are mounted on standoff, or cen
8、tering, devices with wheels which enable the operator to move the unit thru the pipe and maintain a relatively uniform blasting pattern. 4. Abrasives 4.1 Shot, grit, or semi-sharp abrasives may be used alone or in combination with each other. See Table II for a list of commonly used abrasives. TABLE
9、 II Metallic* Abrasives Synthetic Abrasives Siliceous Abrasives Chilled Cast Iron Silicon Carbide Garnet Cast Steel Aluminum Oxide Quartz Malleable Iron Refractory Slag Silica Crushed Steel Decomposed Rock Notes Re. Table II: (1) The hardest material is listed at the top of each group and the others
10、 follow in order of decreasing hardness. *(2) These should not be used on stainless steel. 4.2 Practically all of the grit and some of the shot become semi-sharp abrasives after they have been in use for a short time. 4.3 Shot blasting could result in fine mill scale and other impurities being drive
11、n into the surface of the material being blasted. 5. Blast Cleaning Procedure Selection 5.1 The actual blast cleaning procedure to be followed, including the selection of abrasives, depends on: 5.1.1 Size and configuration of the assembly to be cleaned (determines accessibility). 5.1.2 Local environ
12、mental conditions and proximity to other facilities. 5.1.3 Contaminants to be removed. 5.1.4 Available equipment. 5.1.5 Cost of reclaiming abrasives. PFI Standard ES-29 |Denotes Revision (Revised February 2006) 5.2 If the piping assembly to be cleaned is so complex that accessibility is difficult or
13、 impossible, it may be necessary to pre-blast components or partial assemblies prior to completing the fabrication. 5.3 If abrasives are to be reclaimed and reused, suitable solvents should be used to remove visible grease and oil from the surface prior to blast cleaning. 5.4 After cleaning operatio
14、ns have been completed, all visible blasting residues shall be removed by blowing out the assembly with dry, clean, compressed air, or by any other suitable method capable of achieving the required cleanliness level. 6. Cleanliness Levels and Acceptance Criteria for Cleaned Fabricated Piping 6.1 Gen
15、eral Comments The cleanliness and appearance of the prepared surface will depend upon the operating procedure, the equipment and the abrasive used, and the starting condition of the surface to be cleaned. Color is not a criteria of cleanliness. For example, blast cleaned surfaces using sand may appe
16、ar very white, while a blast cleaned surface using a dark abrasive such as crushed slag may have a dark appearance. The inspector must take all of the above factors into account when a “white“ or “near-white“ condition has been specified. For example, the photographs (illustrated on page 5) identifi
17、ed as: A, B and C, represent starting conditions of: A a rough, heavy mill scaled, slightly weathered surface. B a rough, heavy mill scaled, heavily weathered surface. C a smooth, light mill scaled, medium weathered surface. The photos A3, B3 and C3 are typically representative of Level 3 surfaces t
18、hat would be obtained from the illustrated starting conditions. 6.2 Surface Finish Levels 6.2.1 Level No. 1 White Metal Surface Finish. This end condition constitutes the best possible surface that can be produced by blasting. The surface when viewed without magnification, on completion of blasting
19、will be free of visible mill scale, rust, oxides, paints, or other foreign matter. The surface will appear as a uniform grayish, metallic white immediately after blasting, but may discolor after cleaning due to atmospheric conditions. When the inside of a piping assembly is being cleaned, this level
20、 of cleanliness cannot be expected to exist uniformly throughout the entire pipe inside surface unless the surface can be visually observed by the blasting operator while blasting (refer to SSPC-SP5). 6.2.2 Level 2 Near-White Metal Surface Finish. Blast cleaning to this cleanliness level is recommen
21、ded where a high degree of cleaning is required. It will remove practically all rust, mill scale, and other detrimental foreign material. The surface will not necessarily be completely uniform in color nor uniformly cleaned. Most of the surface area shall be free of all visible residues and the rema
22、inder limited to light discolorations (refer to SSPC-SP10) 6.2.3 Level 3 Commercial Surface Finish. This includes the removal of all rust scale, paint, loose mill scale, and most of the tight mill scale. It does not necessarily include the removal of all tightly adherent mill scale, fine traces of r
23、ust, stains, or discoloration. The commercial blast finish may have a streaky appearance (refer to SSPC-SP6). See photos A3, B3 and C3 (on page 5). 6.2.4 Level 4 Brush-Off Surface Finish. Brush-off blast finish permits tight mill scale, paint, and minor amounts of rust and other foreign material to
24、remain on the surface. The surfaces should be free of loose mill scale and loose rust (refer to SSPC-SP7). 7. Inspection of Cleaned Surfaces 7.1 Inspection shall consist of direct visual examination of the surface, under normal lighting, without optical aids. 7.2 The inspection should be performed a
25、s soon as possible after the blast cleaning is completed. 7.3 Due to atmospheric conditions, freshly blast cleaned surfaces are subject to the formation of a powdery surface film of rust known as a “rust bloom“. Such a condition is considered acceptable. PFI Standard ES-29 |Denotes Revision (Revised
26、 February 2006) 8. Safety Precautions and Disposal of Used Abrasives 8.1 Normal safe shop operations and good housekeeping practices should be followed to reduce airborne dust. Proper hand and eye protection precautions should be followed when handling and using abrasive materials: 8.1.1 Control mea
27、sures should be utilized that are effective in maintaining airborne dust concentrations. Where this is not feasible, N.I.O.S.H. approved air supply equipment should be worn by employees, especially when blast cleaning is being performed in an enclosed area and/or when the surface being cleaned could
28、 produce a potentially hazardous material. 8.1.2 Abrasives should be supplied with “Material Safety Data Sheets“ or facsimile. 8.2 Federal, State, and Local Regulations for disposal of spent abrasives should be followed. MAGNIFICATION IX FOR EACH PFI Standard ES-29 |Denotes Revision (Revised February 2006)
