1、 NACE International 1 Standard Practice Control of Corrosion Under Thermal Insulation and Fireproofing MaterialsA Systems Approach This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not i
2、n any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any rig
3、ht, 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 against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no w
4、ay be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility
5、 for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual vo
6、lunteers. Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address al
7、l potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environment
8、al protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revi
9、sed or withdrawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or r
10、evision. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Dr., Houston, TX 77084-490
11、6 (telephone +1 281-228-6200). Revised 2010-6-25 Reaffirmed 2004-3-31 Approved 1998-2-20 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-049-1 2010, NACE International NACE SP0198-2010 (formerly RP0198) Item No. 21084 SP0198-2010 NACE International i
12、_ Foreword This NACE standard practice provides the current technology and industry practices for mitigating corrosion under thermal insulation and fireproofing materials, a problem termed corrosion under insulation (CUI) in this standard. Because this corrosion problem has many facets and impacts s
13、everal technologies, a systems approach has been adopted. This standard is intended for use by corrosion-control personnel and others concerned with corrosion under insulation and/or fireproofing of equipment. This standard is organized into sections by function. Each section was written by speciali
14、sts in that subject. These specialists are industry representatives from firms producing, specifying, designing, and/or using thermal insulation and fireproofing products on refinery and petrochemical equipment. This standard was originally prepared in 1998 by NACE Work Group T-5A-30a, “Corrosion Pr
15、otection Under Insulation,” with the assistance of Task Group (TG) T-6H-31, “Coatings for Carbon and Austenitic Stainless Steel Under Insulation,” and ASTM(1)Committee C16.40.3, “Corrosion Under Insulation.” Work Group T-5A-30a supported NACE TG T-5A-30, “Corrosion Under Thermal Insulation,” a compo
16、nent of NACE Unit Committee T-5A, “Corrosion in Chemical Processes.” The standard was reaffirmed in 2004 by Specific Technology Group (STG) 36, “Process Industry: Materials Performance in Chemicals.” It was revised in 2010 by TG 325, “CUI: Revision of NACE Standard RP0198, The Control of Corrosion U
17、nder Thermal Insulation and Fireproofing MaterialsA Systems Approach,” with the assistance of Technology Exchange Group (TEG) 255X, “Coatings, Thermal-Spray for Corrosion Protection.” TG 325 is sponsored by STG 03, “Coatings and Linings, ProtectiveImmersion and Buried Service,” and STG 04, “Coatings
18、 and Linings, ProtectiveSurface Preparation.” This standard is issued by NACE International under the auspices of STG 36. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and mu
19、st are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. _ (1)ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken,
20、PA 19428-2959. SP0198-2010 ii NACE International _ NACE International Standard Practice Control of Corrosion Under Thermal Insulation and Fireproofing MaterialsA Systems Approach Contents 1. General . 1 2. Corrosion Mechanisms 2 3. Mechanical Design . 9 4. Protective Coatings 20 5. Insulation, Firep
21、roofing, and Accessory Materials . 27 6. Inspection and Maintenance 31 References 37 Bibliography 39 FIGURES Figure 1: Effect of Temperature on Steel Corrosion in Water . 4 Figure 2: Typical Vessel Attachments Where Water May Bypass Insulation . 11 Figure 3: Attachment to Piping Where Water May Bypa
22、ss Insulation 12 Figure 4: Vessel Insulation Support Ringthe Problem (a) and the Solution (b). 13 Figure 5: Vertical Vessel Bottom Support Ring Minimizing Water Accumulation. 13 Figure 6: Vessel-Stiffening Ring Insulation Detail . 14 Figure 7: Center Nozzle at Top Head of Vessel. 14 Figure 8: Common
23、 Nameplate Insulation Detail. 15 Figure 9: Seal-Welded Cap on Insulation for Personnel Protection. 15 Figure 10: Double-Pipe Heat Exchanger Insulation Penetrated by C-Channel Support. . 16 Figure 11: Protrusions Through Jacketing. . 16 Figure 12: Pipe Supports Without Protrusions. . 17 Figure 13: Co
24、ld Service Pipe Support Without Continuous Vapor Barrier. 18 Figure 14: Cold Service Pipe Support with Continuous Vapor Barrier. 18 Figure 15: Pipe Insulation Penetrated by Column Fireproofing. . 19 TABLES Table 1: Typical Protective Coating Systems for Austenitic and Duplex Stainless Steels Under T
25、hermal Insulation 22 Table 2: Typical Protective Coating Systems for Carbon Steels Under Thermal Insulation and Fireproofing 25 _ SP0198-2010 NACE International 1 _ Section 1: General 1.1 Corrosion under insulation (CUI) has been occurring for as long as hot or cold equipment has been insulated for
26、thermal protection, energy conservation, or process stabilization. The destructive results and nature of the corrosion mechanism were not mentioned in the literature until the 1950s. As more problems have been experienced, concern and interest have built around this subject. Many articles and sympos
27、ium papers have been published since 1983 as interest and activity in CUI have increased. The increased activity was driven largely by many occurrences of severe CUI resulting in major equipment outages, production losses, and unexpected maintenance costs in refineries, gas plants, and chemical plan
28、ts. 1.2 To correct these problems, companies have developed their own criteria and approaches to the prevention of CUI. When comparing the various approaches, it is evident that there are many similarities, some differences, some new ideas, and some old ideas that have stood the test of performance.
29、 This standard incorporates the experience of many companies throughout the oil, gas, and chemical industries. 1.3 The first ASTM standard relevant to CUI was ASTM C692,1adopted in 1971 and originally titled “Evaluating the Influence of Wicking Type Thermal Insulations on the Stress Corrosion Cracki
30、ng Tendency of Austenitic Stainless Steels.” 1.4 A symposium was held jointly by NACE, ASTM, and Materials Technology Institute (MTI)(2)on this subject with speakers from industries worldwide in October 1983. The papers were published in 1985 as ASTM Publication STP 880.21.5 The first NACE state-of-
31、the-art report on CUI was written in 1989 by Task Group T-6H-31 and issued as NACE Publication 6H189.3NACE Task Group T-5A-30 was organized shortly thereafter to serve as a forum for further discussion regarding CUI. In addition to reviews of the corrosion mechanisms, perspectives on such CUI topics
32、 as methods for mitigation, insulation materials, and inspection were often exchanged. While corrosion engineers were becoming knowledgeable about CUI, ASTM Committee C16 on Thermal Insulation was preparing standards for testing insulation with a propensity to cause chloride stress corrosion crackin
33、g (SCC) of austenitic stainless steel. These two groups interacted but proceeded to develop their standards and information separately. 1.6 In this standard, the term equipment includes all objects in a facility with external metal surfaces that are insulated or fireproofed and subject to corrosion.
34、 1.7 In previous editions of this standard, carbon steel and austenitic stainless steels were the primary metals addressed. Because of their increased usage in applications where CUI is a concern, duplex stainless steels have been more explicitly addressed in this revision. 1.8 Although most of the
35、attention has been focused on corrosion under thermal insulation, fireproofing materials also function, at least in part, as insulation applied to protect equipment during a potential fire. Other fire protection mechanisms initiated as endothermic reactions within the fireproofing material during a
36、fire are not covered in this standard. Corrosion mechanisms, the root cause of failure, and corrosion prevention are the same for corrosion under fireproofing as for corrosion under insulation. 1.9 Whenever CUI is a consideration, a protective coating or coating system should be applied to the equip
37、ment before it is insulated. Protective coatings or coating systems may have service lives that are shorter than the anticipated operational life of the equipment, and thus may require inspection and maintenance to effectively maintain integrity and to minimize the threat of CUI. (2)Materials Techno
38、logy Institute (MTI), 1215 Fern Ridge Parkway, Suite 206, St. Louis, MO 63141-4405. SP0198-2010 2 NACE International _ Section 2: Corrosion Mechanisms 2.1 Carbon Steel Carbon steel corrodes, not because it is insulated, but because it is contacted by aerated water. The role of insulation in the CUI
39、problem is threefold. Insulation provides: (a) An annular space or crevice for the retention of water and other corrosive media; (b) A material that may wick or absorb water; and (c) A material that may contribute contaminants that increase the corrosion rate. The corrosion rate of carbon steel may
40、vary because the rate is controlled largely by the metal temperature of the steel surface and contaminants present in the water. These factors and others are reviewed below. 2.1.1 Effects of Water, Contaminants, and Temperature 2.1.1.1 Sources of Water Under Insulation The two primary water sources
41、involved in CUI of carbon steel are: (a) Infiltration from external sources; and (b) Condensation. Water infiltrates from such external sources as the following: (a) Rainfall; (b) Drift from cooling towers; (c) Condensate falling from cold service equipment; (d) Steam discharge; (e) Process liquids
42、spillage; (f) Spray from fire sprinklers, deluge systems, and washdowns; (g) Groundwater; and (h) Condensation on cold surfaces after vapor barrier damage. External water enters an insulated system primarily through breaks in the weatherproofing. The weatherproofing breaks may be the result of inade
43、quate design, incorrect installation, mechanical abuse, or poor maintenance practices. Condensation results when the temperature of the metal surface is lower than the atmospheric dew point. Although infiltration of external water can be reduced and sometimes prevented, insulation systems cannot be
44、made vapor tight, so condensation as a water source must be recognized in the design of the insulation system. SP0198-2010 NACE International 3 2.1.1.2 Contaminants in Water Under Insulation Contaminants can increase the conductivity and/or corrosiveness of the water environment. There are two prima
45、ry classes of contaminants in water under insulation: (a) Contaminants external to the insulation materials; and (b) Contaminants leached from the insulation materials. Chlorides and sulfates are the principal contaminants found under insulation. Whether their source is external or internal, they ar
46、e particularly detrimental because their respective metal salts are highly soluble in water, and these aqueous solutions have high electrical conductivity. In some cases, hydrolysis of the metal salts can cause localized corrosion because of development of low pH in anodic areas. External contaminan
47、ts are generally salts that come from sources such as cooling tower drift, acid rain, firewater deluge, and atmospheric emissions. The external contaminants are waterborne or airborne and can enter the insulation system directly through breaks in the weatherproofing. External contaminants also enter
48、 the insulation materials indirectly by depositing on the jacket surface. Subsequent wetting then carries the concentrated salts to breaks in the weatherproofing. The salts enter the insulation system by gravity or the wicking action of absorbent insulation. The salt concentrations gradually increase as water evaporates from the carbon steel surface. Contaminants contained in the insulation materials are well documented. Chloride is generally one of the contamina
