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1、Item No. 24201 NACE International Publication 10D199 This Technical Committee Report has been prepared by NACE International Task Group T-10D-17/T-6A-63 on Pipeline Rehabilitation Coatings* Coatings for the Repair and Rehabilitation of the External Coatings of Buried Steel Pipelines July 1999, NACE
2、International This NACE International technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or using products, process
3、es, or procedures not included in this report. Nothing contained in this NACE International report is to be construed as granting any right, 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
4、 protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable circum
5、stances may negate the usefulness of this report in specific instances. NACE International assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE International report are responsible for reviewing appropriate health, safety, environmental, and reg
6、ulatory documents and for determining their applicability in relation to this report prior to its use. This NACE International report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detai
7、led or referred to within this report. Users of this NACE International report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing appli
8、cable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE International reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatic
9、ally withdrawn if more than 10 years old. Purchasers of NACE International reports may receive current information on all NACE International publications by contacting the NACE International Membership Services Department, P.O. Box 218340, Houston, Texas 77218-8340 (telephone +1 281228-6200). Forewo
10、rd The purpose of this technical committee report is to provide information regarding protective coatings employed during pipeline repair, recoating, or refurbishment projects. This report is intended to be used by pipeline operators, rehabili- tation contractors, coating applicators, and pipeline i
11、nstall- ation contractors. This NACE technical committee report was prepared by Joint Task Group T-10D-17/T-6A-63 on Pipeline Rehabilitation Coatings. This report is issued under the auspices of Group Committees T-10 on Underground Corrosion Control and T-6 on Protective Coatings and Linings. Introd
12、uction Coating selection for repair and rehabilitation of existing coatings on buried steel pipelines is determined by specific criteria relating to the project to be executed. In some cases, the factors limiting coating selection are similar to those considered during new pipeline construction acti
13、vities. However, when a pipeline is recoated, there are additional factors that are considered, such as field application criteria and achievable production rates during limited operating hours. Coating repair/rehabilitation can be performed in, over, or beside a ditch, whether the pipeline is in se
14、rvice, out of service, or segmented. Pipeline recoating usually falls into one of two categories: repair coating or rehabilitation coating. Repair coatings are utilized during bell-hole operations for common pipeline maintenance, operation, or repair work. Examples of typical *Chairman Jeff Didas, C
15、olumbia Gas Transmission Corporation, Charleston, WV. Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 18:11:27 MSTNo reproduction or networking permitted without license from IHS -,-,- NACE Intern
16、ational 2 operations are coating of thermite welds, fittings, patching of coating holidays, overcoating of steel or composite pipeline repairs/reinforcements, and recoating of replacement piping or tie-in welds. Rehabilitation coatings are utilized for planned recoating operations as part of a minor
17、 or major rehabilitation project. Repair and rehabilitation coatings can be of the same coating material. The requirements of all applicable government and environmental regulations are included in the planning stages of a recoating project. Such regulations relate to all compo- nents of a recoating
18、 project, including permitting require- ments, soil erosion controls, groundwater protection, coating removal and disposal (especially if asbestos, dioxin, lead, or any other hazardous/regulated substance is present), surface preparation, dust control, abrasive disposal, volatile organic compounds (
19、VOCs), hazardous air pollutants (HAP), and coating application. In addition, the steel substrate is evaluated prior to the coating operation to ensure that the pipeline can be safely coated. The coating selection itself is usually based on both laboratory and field-performance testing. Laboratory te
20、sting using accelerated test conditions can give a good indication of the expected life of a coating material. However, field test- ing can provide the best indication of coating performance. Coating Removal and Surface Preparation Proper surface preparation of the steel is often considered the sing
21、le most important step in the coating application process and the primary factor controlling long-term per- formance of a coating. A variety of contaminants can be present on the surface of in-service, oxidized steel. Proper surface preparation removes these contaminants, provides an adequate anchor
22、 pattern/profile, and removes surface scale and oxide. Many methods to remove the existing coating system and/or properly prepare and clean the surface of the steel are available. These methods include solvent cleaning (SSPC(1)- SP 11), power tool cleaning (SSPC-SP 3,2 and SSPC-SP 113), hand tool cl
23、eaning (SSPC-SP 24), mechanical cleaning, abrasive blasting (NACE No. 3/SSPC-SP 65 and NACE No. 2/SSPC-SP 106), water jetting (NACE No. 5/SSPC-SP 127), industrial blast cleaning, or a combination of methods. The coating material manufacturer specifies the minimum surface preparation for the selected
24、 coating material and the appropriate surface preparation for the existing coatings at the interface. A common method of surface preparation of steel is abrasive blasting using sand, slag, or other appropriate material. This method, as described in NACE No. 2/SSPC-SP 10 and NACE No. 3/SSPC-SP 6, can
25、 be used to remove most coating and some contaminants. However, abrasive blasting may generate an unacceptable level of dust. A two-step process can be used to control dust and remove soluble salts while removing the coating: First, the existing coating is removed using high-pressure or ultrahigh-pr
26、essure water jetting. The water strikes the surface of the coating at pressures of 140 to 380 MPa (20,000 to 55,000 psi), which removes the existing coating. High-pressure water jetting is a very effective way to remove water-soluble contaminants from the pipe surface. The quality of the water used
27、for water jetting/blasting is at least that of potable water. Deionized water or water with a conductivity no greater than 100 S/cm (250 S/in.) is normally used.7 Second, abrasive blasting of the steel can then be performed as necessary to obtain the anchor pattern for the new coating material. Note
28、s: 1.If the original anchor pattern is intact and compatible with the new coating material, abrasive blasting is not utilized. 2.Oil and grease are not water-soluble and thus reduce the performance of the newly applied coating if present as contaminants. SSPC-SP 1 solvent cleaning removes oil- based
29、 contaminants. Automated systems are available to increase the daily production rate of external pipeline coating rehabilitation. Automated equipment for coating removal, surface prep- aration, and coating application can maximize available operating time on large-scale recoating projects. Other fac
30、tors such as weather (e.g., lightning), equipment, and terrain can also affect daily production. External coating rehabilitation projects conducted under adverse environ- mental conditions can compromise coating performance and decrease anticipated daily production rates. Key environmental parameter
31、s such as relative humidity, dew point, and pipe surface temperature are measured, recorded, and documented. (1) The Society for Protective Coatings (SSPC), 40 24th Street, 6th Floor, Pittsburgh, PA 15222-4656. Copyright NACE International Provided by IHS under license with NACELicensee=IHS Employee
32、s/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 18:11:27 MSTNo reproduction or networking permitted without license from IHS -,-,- NACE International 3 Pipeline Recoating: Material Properties and Other Considerations Physical and Chemical Properties Typical performance criteria for pi
33、peline recoating materials are generally the same as those for a new pipeline. NACE Standard RP01698 contains listings of desirable physical and chemical coating material properties. These are as follows: a.effective electrical insulation b.is an effective moisture barrier c.can be applied to the pi
34、pe by a method that does not adversely affect the properties of the pipe d.can be applied to piping with a minimum of coating defects e.good adhesion to pipe surface f.ability to resist development of holidays with time g.ability to resist damage during handling, storage, and installation h.ability
35、to maintain substantially constant electrical resistivity with time I.resistance to disbonding j.resistance to chemical degradation k.ease of repair l.retention of physical characteristics m.nontoxicity to the environment n.resistance to changes and deterioration during above- ground storage and lon
36、g-distance transportation Additional Considerations In addition to the coating properties listed in NACE Standard RP0169, other factors typically considered include the following: a.physical accessibility of the pipeline b.ambient temperature during application c.geographical and physical location o
37、f the pipeline d.type and condition of existing pipeline coating e.pipeline reinstallation methods f.cost of the coating material and the overall recoating project g.steel surface preparation requirements h.recoat interval and/or time to backfill i.daily production rate at which coating can be appli
38、ed j.environmental considerations plexity of application equipment and availability of trained/skilled workers I.chemical compatibility of the old and new coatings in transition areas m.attainable surface temperature of the pipeline (sweating pipe, etc.) n.pipeline movement o.pipeline diameter p.res
39、istance to soil stress q.nontoxic and nonhazardous to the user whenever possible r.resistance to ultraviolet (UV) light and weathering at soil- to-air interface locations Discussion The types of coatings that have been utilized for pipeline recoating work are similar to those employed during new con
40、struction. Coating systems used on pipeline recoating projects include hot- and cold-applied tapes, coal tar enamel, coal tar epoxy, coal tar urethane, vinyl ester, polyurethane, polyureas, epoxies, mastics, and hot- or cold-applied wax and wax tapes. These coatings account for the vast majority of
41、recent pipeline recoating work. Only fusion-bonded epoxy coatings have not gained widespread use in the recoating of pipelines. This is because during the application of this type of coating, the pipe is heated to the specified application temperature and held at that temperature until the coating h
42、as reached a predetermined degree of cure. This is difficult to maintain during field operations. Although some products perform extremely well under- ground, many underground pipe installations have exper- ienced deterioration at soil-to-air interface locations. These problems are primarily due to
43、the poor resistance of the coating to ultraviolet light and/or weathering. Addressing these problems can, for some underground coating systems, include the need for an additional product to be used specifically at interface locations. Many challenges exist in the use of rehabilitation coatings. Thes
44、e include the development of effective quality assurance and quality control programs, providing ditch padding to protect the new coating once the pipe is placed in the ditch or backfilled in place, providing protective measures for the environment and/or personnel, and ensuring compatibility of exi
45、sting coatings to repair and rehabilitation coatings at the transition stage. Product Descriptions The following paragraphs summarize a few of the salient features and properties of the protective coatings used for pipeline repair or rehabilitation. Detailed information is contained in Appendix A an
46、d is available from coating manufacturers and pipeline coating applicators. Coal Tar Enamel: These are hot-applied coating systems that have been widely used since the turn of the century in both new construction and recoating/rehabilitation projects. Coal tar enamel has been applied on the right-of
47、-way as well as in the coating plant. Coal Tar Epoxy: Coal tar epoxies have been widely used for many years as immersion coatings and on underground structures. Historically, they have performed very well in the field and in most standard performance tests. However, Copyright NACE International Prov
48、ided by IHS under license with NACELicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/05/2007 18:11:27 MSTNo reproduction or networking permitted without license from IHS -,-,- NACE International 4 most coal tar epoxies are applied in multiple coats, which extends the time t
49、hat the ditch must remain open. Coal Tar Polyurethane: This coating has been used suc- cessfully on large-scale recoating projects. The addition of coal tar improves the moisture-absorption resistance of the coating. Application properties are almost identical to those of polyurethane. Epoxy: Epoxy coatings come in many formulations, some of which have been developed for pipeline work. Epoxy systems work well for fittings, valves, and tees. Mastics: These mat