Requirements for Protective Layers

The aforementioned requirements on surface stability are typical for all exposed areas of the metallic interconnect, as well as other metallic components in a SOFC stack (e.g., some designs use metallic frames to support the ceramic cell). In addition, the protection layer for the interconnect, or in particular the active areas that interface with electrodes and are in the path of electric current, must be electrically conductive. This conductivity requirement differentiates the interconnect protection layer from many traditional surface modifications as well as nonactive areas of interconnects and other components in SOFC stacks, where only surface stability is emphasized. While the electrical conductivity is usually dominated by their electronic conductivity, conductive oxides for protection layer applications often demonstrate a nonnegligible oxygen ion conductivity as well, which leads to scale growth beneath the protection layer. With this in mind, a high electrical conductivity is always desirable for the protection layers, along with low chromium cation and oxygen anion diffusivity. 

Health and safety regulations and concerns As discussed in Section 18.1.2, dusty or liquid additive forms may create another layer of plant cost burden required for protecting worker health and safety. This begs the questions Must an additive be handled in-house in a problematic form, or can a nondusting or safer form of it be used Or should the material s main compounding be done by another facility set up to handle the additive safely ... 

Conductive coatings are used to conduct a current used for the operation of a device, and in most cases the current density required for device operation is several orders of magnitude higher than that required for protection against antistatic discharges. Therefore, in these appKcations it is usually necessary to obtain layers with a maximum conductivity possible. In this regard, it is necessary to keep in mind that as the specific conductivity is increased, contact resistances can start to play a major role. 

The limiting value of 0.25 % for the arch elongation has developed from the consideration that a visual inspection finds only minor indentations, but this criterion has to be able to be quantified by a simple measurement. With 16/32 mm gravel this criterion fits coincidentally with the requirement of plastic technology that even local elongations may not exceed the critical limiting strain. Since it is simple to test and already established, it was maintained as a design criterion within the BAM certification for protective layers. However, 0.25 % still remains a mystery, even for some experts. 

Requirements of Protective Layers for Geomembranes in Composite Liner Systems, Certification Guidelines... 

Bentonite (geosynthetic clay liner) (pre-hydrated or dry bentonite requiring in situ hydration) - Hydrocarbon resistance - Lower maintenance - Self-sealing properties if punctured. - Pre-hydrated can be laid at performance specification required - Requires a protection layer. - Potential hidden problems at penetrations. - Potential for drying out on slopes - In situ hydration of dry systems to achieve performance specification required - Can be uncertain - Good as geotextile mat protected by layer of soil/ stone Medium... 

The birefringence of substrate materials for optical data storage devices requires special attention, especially in the case of EOD(MOR) disks. Birefringence has no importance for glass substrates (glass does not exhibit any significant birefringence) and is only a subordinate factor for polymeric protective layers of aluminum substrates because of their reflective read/write technique. 

Layer of protection analysis (LOPA) is a simplified form of event tree analysis. Instead of analyzing all accident scenarios, LOPA selects a few specific scenarios as representative, or boundary, cases. LOPA uses order-of-magnitLide estimates, rather than specific data, for the frequency of initiating events and for the probability the various layers of protection will fail on demand. In many cases, the simplified results of a LOPA provide sufficient input for deciding whether additional protection is necessary to reduce the likelihood of a given accident type. LOPAs typically require only a small fraction of the effort required for detailed event tree or fault tree analysis. 

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