Derating System Factors

Derating factors are often vaguely related to the foaming tendency 

The application of dm ting factors is fraught with confusion. Cao tion is required, especially when communicating with an outside otHB-pany whose deratii practices may differ. The following need to he cemefiilly specified. 

Caustic wash 0.66 8 The author suspects that this low factor refers only to some caustic wash applications but not to others. 

The flooding mechanism to which the derating factor applies (entrainment flood, downcomer backup, downcomer choke, or all). 

Avoiding double derating. For instance, the values in Table 6.7 apply with the equations in Sec. 6.2.6, since these do not take foaminess into account. However, they wiU double-derate the flood calculation if applied jointly with a correlation or criterion that 

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GPSA engineering data book [I] also recommends to derate K factor for following system ... 

The selection process of power cables is almost the same as that of a bus system discussed in Section 28.3. For simplicity we consider only the basic data for selection which would suffice the majority of applications. For accurate calculations a similar approach will be essential as for the bus systems (Chapter 28). For site conditions and laying arrangements which may influence the basic rating of a cable, corresponding derating factors have also been provided. The information covered here will be useful to users to meet their cable requirements, although the data may vary marginally for different manufacturers. For more data on cables, not covered here, reference may be made to the cable manufacturers. 

Derating factors vary from source to source, and may depend on the correlation used as well as the system. For instance, some caustic wash applications have a track record of foaming more severely than other caustic wash applications (see note in Table 14-9). The derating factors in Table 14-9 are a useful guide, but are far from absolute. 

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