【国外标准】 Standard Guide for Evaluating Polymeric Lining Systems for Water Immersion in Coating Service Level III Safety-Related Applications on Metal Substrates

5.1 Safety-related service water system (SWS) components are designed to provide adequate cooling to equipment essential to the safe operation and shutdown of the plant. Linings in these systems are installed to maintain the integrity of the system components by preventing corrosion and erosion of the metal materials of construction. Linings on SWS surfaces upstream of components, including heat exchangers, orifice plates, strainers, and valves, the detachment of which may affect safe-plant operation or shutdown, may be considered safety-related, depending on plant-specific licensing commitments and design bases.5.2 The testing presented in this guide is used to provide reasonable assurance that the linings, when properly applied, will be suitable for the intended service by preventing corrosion and erosion for some extended period of time. Additionally, the test data derived allows development of schedules, methods, and techniques for assessing the condition of the lining materials (see Guide D7167). The ultimate objective of the testing is to avoid lining failures that could result in blockage of equipment, such as piping or heat transfer components, preventing the system or component from performing its intended safety function.5.3 It is expected that this guide will be used by:5.3.1 Lining manufacturers for comparing specific products and systems and to establish a qualification basis for recommended linings and5.3.2 End users seeking a consistent design basis for candidate coating systems.5.4 In the event of conflict, users of this guide must recognize that the licensee's plant-specific quality assurance program and licensing commitments shall prevail with respect to the selection process for and qualification of CSL III lining materials.5.5 Operating experience has shown that the most severe operating conditions with respect to heat exchanger linings occur on pass partitions. A phenomenon known as the “cold wall effect” accelerates moisture permeation through a coating applied to the warmer side of a partition that separates fluids at two different temperatures. The thickness and permeability of the lining are key variables affecting the ability of a lining to withstand cold wall blistering.5.5.1 This effect is particularly pronounced when the separated fluids are water, though the effect will occur when only air is on the other side, for example, an outdoor tank filled with warm liquid. A heat exchanger pass partition represents geometry uniquely vulnerable to the water-to-water maximized temperature differentials (ΔTs) that drive the cold wall effect.5.5.2 Pass partitions separate relatively cold incoming cooling water from the discharge water warmed by the heat exchanger's thermal duty. Improperly designed coatings will exhibit moisture permeation to the substrate accelerated by the cold-wall effect. Many instances of premature pass partition warm-side blistering have been noted in the nuclear industry. Such degradation has also been seen on lined cover plate and channel barrel segments that reflect water-to-air configurations.5.6 Large water-to-water ΔTs are known to be the most severe design condition. The test device used to replicate ΔT configurations is known as an “Atlas cell.” Atlas cell testing is governed by industry standard test methodologies (Test Method C868 and NACE TM0174). A lining proven suitable for the most severe hypothesized ΔT would also be suitable for service on other waterside surfaces.5.7 Plant cooling water varies in composition and temperature seasonally. For purposes of standardization, demineralized water is used in Atlas cell exposures rather than raw plant water. It is generally accepted in polymeric coatings technology that low-conductivity water (deionized or demineralized) is more aggressive with respect to its ability to permeate linings than raw water. Thus, stipulating use of low-conductivity water as the test medium is considered conservative.1.1 This guide establishes procedures for evaluating lining system test specimens under simulated operating conditions.1.2 Lining systems to be tested in accordance with this guide are intended for use in both new construction and for refurbishing existing systems or components.1.3 The lining systems evaluated in accordance with this guide are expected to be applied to metal substrates comprising water-wetted (that is, continuous or intermittent immersion) surfaces in systems that may include:1.3.1 Service water piping upstream of safety-related components,1.3.2 Service water pump internals (draft tube, volutes, and diffusers),1.3.3 Service water heat exchanger channels, pass partitions, tubesheets, end bells, and covers,1.3.4 Service water strainers, and1.3.5 Refueling water storage tanks and refuel cavity water storage tanks.1.4 This guide anticipates that the lining systems to be tested include liquid-grade and paste-grade polymeric materials. Sheet type lining materials, such as rubber, are excluded from the scope of this guide.1.5 Because of the specialized nature of these tests and the desire in many cases to simulate to some degree the expected service environment, the creation of a standard practice is not practical. This standard gives guidance in setting up tests and specifies test procedures and reporting requirements that can be followed even with differing materials, specimen preparation methods, and test facilities.1.6 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.