Inherently likelihood reduction

Principle 9 Increase energy efficiency. Since energy consumption always has some concomitant and negative side effect for the local and/or global environment, the reduction of energy is always a desired component of a green approach to any process. Beyond that, running reactions at milder or ambient temperatures and low or lower pressure is inherently safer since the likelihood and severity of accidents and fires will be reduced. The use of catalysts (which is also favored in Principle 5) often allows reactions to be run at milder conditions. 

SILs are order of magnitude bands of PFDavg, which also reflects the amount of risk reduction of a preventive safety instrumented function. Non-SlS Mainly two parameters, namely, consequence and likelihood, which affect risk, are considered. The consequence is the potential severity of the hazard. The likelihood is the frequency of occurrence. Risk graphs/risk matrices are used for these purposes. The inherent risk can be reduced by non-SlS risk reduction. To assess the risk, one is required to know and evaluate the effectiveness of all non-SIS risk reduction measures to ensure that the risk is reduced to as low as possible before application of any SIS. In other words, it is required to assess whether an SIS is necessary to further reduce the risk. Non-SIS risk reduction methods could be consequence reductions such as a dike, whereas blast walls or blast-resistant control buildings could reduce likelihood. 

Abstract. A high redundancy actuator (HRA) is composed of a high number of actuation elements, increasing both the travel and the force above the capability of an individual element. This provides inherent fault tolerance if one of the elements fails, the capabihties of the actuator may be reduced, but it does not become dysfunctional. This paper analyses the likelihood of reductions in capabihties. The actuator is considered as a multi-state system, and the approach for fc-out-of-n G systems can be extended to cover the case of the HRA. The result is a probability distribution that quantifies the capability of the HRA. By comparing the distribution for different configurations, it is possible to identify the optimal configuration of an HRA for a given situation. 

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