Protective layer design

Specificity The IPL is capable of detecting, preventing, or mitigating the consequences of specified hazardous event, that is, one protection layer designed to prevent or mitigate the one sequences of one potential hazardous event. 

By attempting to maintain process conditions at or near their design values, the process controls so attempt to prevent abnormal conditions from developing within the process. Although process controls can be viewed as a protective layer, this is really a by-product and not the primaiy func tion. Where the objective of a function is specifically to reduce risk, the implementation is normally not within the process controls. Instead, the implementation is within a separate system specifically provided to reduce risk. This system is generally referred to as the safety interlock system. 

A biotic barrier is a gravel and rock layer designed to prevent the intrusion of burrowing animals into the landfill area. This protection is primarily necessary around the cap but, in some cases, may also be needed at the bottom of the liner. Animals cannot generally penetrate an FMC, but they can widen an existing hole or tear the material where it has wrinkled. 

The gap between the process risk and the owner/operator s risk criteria establishes the requirements for risk reduction. The risk gap can be managed by a single safety function or by multiple functions allocated to protection layers. The team defines the risk reduction that must be provided by each safety function and allocates the safety function to a protection layer that is designed and managed to achieve the allocated risk reduction. 

Most facilities are designed around layers of protection commonly referred to as Independent Layers of Protection (ILP). A protection layer or combination of combination of protection layers qualifies as a ILP when one of the following conditions are met (1) the protection provided reduces the risk of a serious event by 100 times, (2) the protective function is provided with a high degree of availability (i.e., greater than 0.99) or (3) it has the following characteristics - specificity, independence, dependability, and auditability. 

The aforementioned requirements on surface stability are typical for all exposed areas of the metallic interconnect, as well as other metallic components in an 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... 

Protective layer, in landfill design, 25 879 Protective overcoat layers, in photography, 19 199... 

Reference [20] notes that any such system should be easy to learn and use, accurate, easy to update, flexible, well based and linked to existing design methods and tools. It should recognise innovation, include diverse environments and be acceptable to all partners in the construction process. The authors point out that the clear statement of assumptions enables them to limit the number of factors. Apart from the environment and the material, joints, contact with other materials and local movement all provide sites for degradation. Protective layers help provided that they remain intact, but degradation proceeds rapidly once they are penetrated. 

Figure 10.3 Layer design of protection systems for a batch reactor.

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. 

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