Process design, safety factors

Many designers have already used or calculated a safety factor on material, perhaps without recognizing it such as deciding what approach is used in determining the tensile secant modulus. The process appears to be simple and straightforward, but unfortunately things are never quite that simple. 

Fluxes scale directly and volumes scSe proportionately with the feed volume. A safety factor will be built into the scale-up design so that process times will not be the same. 

The changing societal, governmental, and industrial perspectives of risk will require that more detailed attention be placed on process safety factors in design and operation of chemical processing plants. 

In this thesis an inherent safety index for evaluating inherent safety in preliminary process design was presented. The inherent safety of a process is affected by both chemical and process engineering aspects. These have been dealt separately, since the index was divided into the Chemical Inherent Safety Index and the Process Inherent Safety Index. These two indices consist of several subindices which further depict specific safety aspects. The Chemical Inherent Safety Index describes the inherent safety of chemicals in the process. The affecting factors are the heat of the main reaction and the maximum heat of possible side reactions, flammability, explosiveness, toxicity, corrosiveness and the interaction of substances present in the process. The Process Inherent Safety Index expresses safety of the process itself. The subindices describe maximum inventory, maximum process temperature and pressure, safety of equipment and the safety of process structure. 

HA Duxbury, "Comments on Safety Factors to be Applied When Sizing a Simple Relief System", Notes of Short Course on "Pressure Relief The Design of Pressure Relief Systems", Session 9, Loughborough University, 1996 (This was also published with same title as Appendix 13 in F P Lees, "Loss Prevention in the Process Industries", 2nd Edn., Butterworth-Heinemann, 1996, ISBN 0 7506 1547 8. However, note misprinted power in Equation A13.2 the last term should be Zmax1/2.)... 

The conventional procedure for introducing resilience in a HEN (or general process plant) is to use empirical overdesign. That is, a nominal or conservative basis is selected for designing and optimizing the HEN. Empirical safety factors based on past experience are applied to the equipment sizes and extra units are also often introduced. However, although this empirical procedure will in general add resilience and... 

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