1、SSPC: The Society for Protective Coatings (SSPC) and NACE International (NACE) issue thisreport in conformance with the best current technology regarding the specific subject. This re-port represents a consensus of those individual members who have reviewed this document. Itis intended to aid the su
2、pplier, the user and the general public. Its acceptance does not in anyrespect preclude any person or organization, whether they have adopted the report or not, frommanufacturing, marketing, purchasing, or using products, processes, or procedures not in con-formance with this report. Nothing contain
3、ed in this report is to be construed as granting anyright, by implication or otherwise, to manufacture, sell, or use in connection with any method,apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone againstliability for infringement of Letters Patent. This report
4、 represents minimum requirements andshould in no way be interpreted as a restriction on the use of better procedures or materials.Neither is this report intended to apply in all related cases. Unpredictable circumstances maynegate the usefulness of this report in specific instances. SSPC and NACE as
5、sume no respon-sibility for the interpretation or use of this report by other parties and accept responsibility foronly those official interpretations issued by SSPC or NACE in accordance with their respectivegoverning procedures and policies, which preclude the issuance of interpretations by indivi
6、dualvolunteers.Users of this report are responsible for reviewing appropriate health, safety, and regulatory docu-ments and for determining their applicability in relation to this report prior to its use. This SSPC/NACE report may not necessarily address all safety problems and hazards associated wi
7、th theuse of materials, operations, and/or equipment detailed or referred to within this document.CAUTIONARY NOTICE: SSPC/NACE reports are subject to periodic review and may be revisedor withdrawn at any time without prior notice. SSPC and NACE require that action be taken toreaffirm, revise, or wit
8、hdraw this report no later than five years from the date of initial publication.The user is cautioned to obtain the latest edition. For information on this and other joint SSPC/NACE publications, contact either organization. The SSPC Operations Department may be reachedat 40 24th Street, Pittsburgh,
9、 PA 15222-4656 (telephone +1 412-281-2331). The NACE Interna-tional Membership Services Department may be reached at P.O. Box 218340, Houston, Texas77218-8340 (telephone +1 281-228-6200).Approved May 1998 1998, SSPC and NACE InternationalNOTICE TO THE READER: The SSPC and NACE releases of this publi
10、cation containidentical wording in the same sequence. Publication format may differ.SSPC: The Society for Protective Coatings NACE International40 24th Street, 6th Floor P.O. Box 218340Pittsburgh, PA 15222-4643 Houston, TX 77218-8340+1 (412) 281-2331 +1 (281) 228-62001Joint Technical ReportWet Abras
11、ive Blast CleaningSSPC-TR 2 NACE 6G198SSPC-TR 2/NACE 6G198May 1, 19982ForewordThis joint report was prepared by the SSPC/NACE JointTask Group C on Wet Abrasive Blast Cleaning, which is com-prised of members of both the SSPC Surface Preparation Com-mittee and the NACE Unit Committee T6G on Surface Pr
12、epa-ration. It is intended to be used primarily by specifiers, own-ers, painting contractors, inspectors, and others involved insurface preparation of industrial structures.1. ScopeThis document covers procedures, equipment, and mate-rials involved in a variety of air/water/abrasive, water/abrasive,
13、and water-pressurized abrasive blast cleaning systems. Equip-ment usage and safety are also discussed.2. Description and Use2.1 Air/water/abrasive blasting is a cleaning method inwhich water is injected into the air/abrasive stream generatedby conventional air-pressurized abrasive blasting equipment
14、.2.1.1 Water helps to remove contaminants from the sub-strate, to wet the abrasive, and to substantially reduce disper-sion of fine particulates (dust). Particulates are often causedby the breakup of the abrasives, surface corrosion products,and paint if the surface has been previously painted. Dust
15、suppression is achieved by thoroughly wetting the abrasiveand other particles to encapsulate them with a thin film ofmoisture. The objective is to remove contaminants and sup-press the dusting effect caused by the impact of the abrasiveon the substrate, while retaining the blasting characteristics o
16、fdry abrasive, including creation of anchor profile.2.1.2 Air/water/abrasive blasting is an alternative to wa-ter jetting, dry blasting, and water blasting with abrasive injec-tion.2.1.3 Air/water/abrasive blasting is referred to hereafteras “wet blasting.”2.2 Water/abrasive blasting is a cleaning m
17、ethod in whichabrasive is injected into the water stream generated by con-ventional fluid pumps.2.2.1 Water is the primary agent to remove the contami-nants from the substrate. The abrasive is injected to help re-move brittle contaminants and create a profile where neces-sary . Compared to wet blast
18、ing methods, water/abrasive blast-ing has a higher water to abrasive ratio. Dust suppression isachieved by the wetting of the abrasive and other particles.The objective is to remove contaminants with water and im-pact the abrasive on the substrate to retain the blasting char-acteristic of dry abrasi
19、ve, including creation of anchor profile.2.2.2 Water/abrasive blasting is an alternative to dry blast-ing, wet blasting, or water jetting.13. Procedures and Parameters3.1 Wet blasting is generally considered suitable for useon any substrate for which the use of abrasive is appropriate.Wet blasting c
20、an often be adjusted to clean delicate substrates.3.2 Some wet blasting systems can utilize the same widevariety of available abrasives as conventional dry abrasive blastsystems. Wet abrasive is more difficult to recycle than dryabrasive. In some cases, recycling of wet abrasive may notbe possible.
21、In some cases, the water may be recycled.3.3 The water flow rate and the ratio of water to abrasiveare usually adjustable so that a wide range of applications,from washing of surface contaminants to white metal blast,can be accomplished.3.4 After wet blasting, all traces of abrasive and otherloose p
22、articles are brushed, blown off with clean dry air, vacu-umed, washed, or otherwise removed from the surface. Clean-liness of the surface cannot be overemphasized.3.5 The injection of water to the air/abrasive stream helpsto remove contaminants such as dirt and water-soluble salts,including ferrous,
23、 chloride, or sulfate salts.23.6 Inhibitors can be used to control flash rusting duringwet or water/abrasive blasting. Many coating manufacturersprefer that inhibitors not be used in wet or water/abrasive blast-ing. (See Section 6.)3.7 Production rates vary due to variations in surfacesbeing blasted
24、, the type of abrasive used, and the level of fineparticulate dust suppression desired. Systems introducedsince 1985 claim production rates equal to or higher than con-ventional dry blasting, but independent studies have not beenpublished as of this publication date.3.8 Wet blasting is a process tha
25、t can produce surfacecleanliness and anchor profiles (surface roughness) similar tothose obtained with dry blasting. The level of surface prepara-tion specified is the same as that specified if dry blasting wasthe process being used. However, because the visual appear-ance of wet blasted surfaces is
26、 not necessarily the same asthe visual appearance of dry blasted surfaces, care and judg-ment should be exercised by inspectors. It is common to en-counter difficulty when visual inspection standards or aids pre-pared for dry blasting are used as inspection or judgment cri-teria for wet blasted surf
27、aces. This visual difficulty can be less-ened by preparation of a test patch which is agreed upon bythe concerned parties during a pre-job conference.4. Wet Blasting Equipment4.1 The equipment used for wet blasting generally con-sists of conventional dry abrasive blasting equipment supple-mented wit
28、h modules to inject water into the abrasive stream.Ideally, the water encapsulates the abrasive particles with athin film of moisture to suppress and contain the dust gener-ated by the impact of the abrasive with the substrate. Abra-sive injection into water blast equipment will also be discussed.Sy
29、stems are available that allow the operator to selectadjustable rates of air, water, or abrasive as necessary toachieve optimum results. Some systems allow independentadjustment of each of these parameters while the system is inoperation. Some systems also allow independent adjustmentfor each nozzle
30、 for multi-nozzle setups.4.2 TYPES OF WET BLASTING SYSTEMS4.2.1 General Requirements of Wet Blast Units: Mostsystems under the general classification of wet blast units con-tain a conventional dry abrasive blast pot with OSHA/NIOSHrequired deadman and other safety features, plus the normalcomplement
31、s of abrasive metering valve(s), compressed airinlet valve(s), blast hose, dry abrasive blast nozzle, etc. Withthese systems, the compressed air volumes and pressuresare the same as for conventional dry abrasive blasting. Eachof these systems can clean to SSPC-SP 5/NACE No. 1 (WhiteMetal) and create
32、 a suitable anchor pattern for paint adhesion.4.2.2 Radial Water Injectors: Some of these are com-monly referred to as “water rings,” and are available in threebasic configurations. In the first configuration, water is injectedat an angle toward the center of the blast stream as the air/abrasive str
33、eam enters the blast nozzle. The water is normallyinjected at or just above the pressure of the compressed air.(See Figure 1.) The second configuration is a “donut” that fitsSSPC-TR 2/NACE 6G198May 1, 19983FIGURE 1over the outside of the dry blast nozzle. Water is injected fromaround the outside of
34、the blast stream radially inward at anangle toward the center of the blast stream as the air/abrasivestream exits the nozzle. The third configuration utilizes a wetblast venturi nozzle which allows water and atmospheric air tobe inducted at midpoint in the nozzle behind the bore restriction.4.2.3 Co
35、axial Water Injectors: In these systems the wa-ter is injected directly into the throat of the blast nozzle. Thedirection of water injection is parallel to the flow of the air/abrasive stream. The air/abrasive stream and the water streamhave the same axis or center line. (See Figure 2.)4.2.4 Slurry
36、Blasters: The term “slurry blasting” is com-monly used for the systems described in Sections 4.2.4 and4.2.5. In these devices, the water is injected into the air/abra-sive stream at some point substantially upstream from the blastnozzle. This allows the air/abrasive/water mixture to tumblefor some d
37、istance in the blast hose to mix with and wet theabrasive. Typically, the water is injected at the blast pot abra-sive metering valve or at a blast hose connection. Sometimesthe water is injected at the connection point of the whip hoseto the main blast hose. (See Figure 3, Configuration 1.)In Figur
38、e 3, Configuration 2, the abrasive is loaded into apressure vessel and simultaneously mixed with water. Thevessel, loaded with the abrasive/water combination, is thenpressurized using an integrated pump and the mixture is in-jected into the air stream. The unencumbered air flow reducesoverall water
39、consumption rates and provides good dust sup-4SSPC-TR 2/NACE 6G198May 1, 1998FIGURE 2FIGURE 3, Configuration 1FIGURE 3, Configuration 25SSPC-TR 2/NACE 6G198May 1, 1998pression. Wet abrasive can be reused in the Configuration 2system as long as the abrasive has not been crushed duringthe cleaning pro
40、cess and the material being removed in theblasting process is non-hazardous.4.2.5 Water Blast with Abrasive Injection: These de-vices differ from the units described in Sections 4.2.2 through4.2.4 in that the propelling force is the water stream, not com-pressed air. This method is commonly referred
41、 to as “abrasivewet jet” or “AWJ” or “slurry blasting.” The typical devices con-sist of a fluid pump with a venturi nozzle of some type in whichthe water flow draws the abrasive into the water stream or theabrasive media is injected into the water stream under pres-sure. Because the fluid stream is
42、well defined, these devicesusually cut a narrow blast pattern. (See Figure 4.)4.3 WATER DELIVERY SYSTEM4.3.1 Purity of Water: The purity of the water used forwet abrasive blasting (or any wet cleaning method) can affectthe quality of the cleaned substrate. To achieve a clean sub-strate, demineralize
43、d, potable, or other water that will not im-pose additional contaminants on the surface being cleaned isacceptable. There is no current definitive number for accept-able levels of water purity. The quality contamination of thesubstrate may be tested and confirmed. Recycled water maycontain a buildup
44、 of contaminants.4.3.2 Water Flow Rates Requirements: The system hassufficient water inlets with filters at the suction side of the pumpto provide an adequate supply of water to the pump. The pumpis capable of providing the water pressure at the required flowrates of the type of wet blast injector b
45、eing used. Typical wa-ter flow rates and water pressures are:a. Radial Water Injectors:0.5 to 31 L/min (0.2 to 8 gpm) at 0.2 to 21 MPa (25to 3,000 psi)b. Coaxial Water Injectors:2 to 4 L/min (0.5 to 1 gpm) at 0.7 to 21 MPa (100 to3,000 psi)c. Slurry Blasters:2 to 4 L/min (0.5 to 3 gpm) (Figure 3, Co
46、nfiguration 1)at 0.7 MPa (150 psi); Figure 3, Configuration 2, 0.02to 1.6 L/min (0.0005 to 0.4 gpm) at 0.2 MPa (25 psi)d. Water Blast with Abrasive Injection:10 to 38 L/min (2.5 to 10 gpm) at 34 to 280 MPa(5,000 to 40,000 psi)4.3.3 Inhibitors: Where inhibitors are used, typical in-hibitor/water rati
47、os range from 1:1 to 1:1000. The inhibitorinjector can be positively interlocked to the water pump to pro-vide a uniform metered supply and constant concentration ofinhibitor in the blasting water or mixed in a reservoir watersupply. Other techniques, such as addition of inhibitor to a res-ervoir, c
48、an be equally efficient. The inhibitor or wet blast equip-ment supplier or manufacturer sometimes sets forth specialrecommendations. (See Section 6.)5. Selection of Abrasives5.1 GENERAL: Virtually any type of abrasive commonlyFIGURE 46SSPC-TR 2/NACE 6G198May 1, 19987.2 EQUIPMENT START-UP, SEQUENCE,
49、OPERATION,AND MAINTENANCE:7.2.1 All equipment (including gauges and controls) ischecked to verify that it is clean and is operating properly be-fore work is started. The system is tested to the maximumworking pressure to ensure integrity of the connections.7.2.2 The air, water, and abrasive blast hoses are checkedto ensure that they are not frayed, kinked, or worn. This isessential for operator safety, because a blow out could be veryhazardous.7.2.3 The water supply is filtered or otherwise treated toremove contaminants that could damage pumps and valvesor leave corrosive deposits on the sur
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