Complex safety

Brunot, W.K., 1970, Reliability of a Complex Safety injection System from Digital Simulation, ANS Trans 12 p 169, June. 

More complex processes require more complex safety technology. Many industrialists even believe that the development and application of safety technology is actually a constraint on the growth of the chemical industry. 

An inherently safe plant1112 relies on chemistry and physics to prevent accidents rather than on control systems, interlocks, redundancy, and special operating procedures to prevent accidents. Inherently safer plants are tolerant of errors and are often the most cost effective. A process that does not require complex safety interlocks and elaborate procedures is simpler, easier to operate, and more reliable. Smaller equipment, operated at less severe temperatures and pressures, has lower capital and operating costs. 

Keywords System Safety Complexity Safety Analysis Software Engineering Formal Methods OF-FMEA Safety Claim Structure Safety Case Safety Assessment... 

Assigning prooftest frequencies for complex, safety-instrumentation loops requires sound engineering judgment for simple systems. For more complex, interlock systems, the frequency is a function of the tolerable hazard rates. For example, DuPont Sabine River Works (Orange, Texas) reported it had 35,000 instruments in service. Every safety interlock is... 

Biogenerics per se, that is, protein drug products approved via 505(j)(l), would need to demonstrate their bioequivalence to the innovator protein. Flowever, due to their complexity and heterogeneity, the classical biopharmaceutical principles upon which the current ratings of therapeutic equivalence are based do not apply in their current language to complex macromolecules. For example, due to the nature and complexity of an immunogenic response, one concern would be if traditional bioequivalence appropriately addresses the complex safety issues associated with biologies. 

Another issue that needs careful consideration is that currently a number of complex safety issues cover possible drug-induced problems very close to the indication of the drug, e.g. glitazones for the treatment of diabetes and cardiovascular ADRs or antidepressants and suicide risk in children and adolescents. These cases require comprehensive methods to unravel any causality of drug and event. 

Stewart MJ, Plautz GE, Del Buono L, Yang ZY, Xu L, Gao X, Huang L, Nabel EG, Nabel GJ. Gene transfer in vivo with DNA-liposome complexes safety and acute toxicity in mice. Hum Gene Ther 1992, 3, 267-275. 

There are several important questions in drug safety evaluation How to detect unexpected adverse drug reactions while handling the multiplicity issue properly How to s)mthesize data from different trials, or even different sources How to deal with rare events How to evaluate multidimensional, complex safety information as a whole Can we monitor a potential safety issue in a continuous manner during a trial so that patients can be better protected These questions lead to some unique statistical challenges in quantitative safety analysis including low power due to rare events, multiplicity. 

Considerable effort has been concentrated on the development of a plant design which has an acceptable criticality safety case, but which is not constrained in terms of its flexibility to process a wide variety of feed material and manufacture a wide range of fuel assemblies. The principal objective of the design was to make the plant inherently safe where practicable for normal operations and potential fault conditions. Only where this objective is not practicable are additional safety protection systems provided. This enhances the robustness of the safety of the plant and reduces the requirement for potentially complex safety protection systems. 

Simplified equations and fault tree analysis will be used to determine the PFDavg of the SIF shown in Figure 13-3. One advantage in using the fault tree approach for the PFDavg calculation for this SIF is that most engineering personnel are familiar with the development and analysis of fault trees. This enables them to better understand the operation of complex safety instrumented functions by reviewing its associated fault tree. 

The term human error refers to human actions or inactions outside the tolerances established by a system, potentially leading to undesired effects, even if no immediate consequences occur. Human error is an important consideration in complex safety critical systems, because it makes one of the most significant contributions to overall system safety (refer, inter alia, Edwards, 1988). In the design of such systems, it is therefore increasingly important that we understand how errors are made and what can be done to prevent (or reduce the probability) of their occurrence. 

Some facts, in particular, became even more evident than before firstly, the potential importance of multiple failures in complex safety systems and, secondly, the possible serious consequence of human errors. 

The reUabUity and safety analysis needs for complex safety critical systems development are not in contradiction with the current techniques used in SE. The effort consists in detailing new kinds of requirements and integrating the new type of analysis techniques and tools to the common SDE. Nevertheless, it imposes on the project management to define when the diverse phases of reliability and safety studies must be conducted. Indeed, it is impossible to quantify and to assess the dysfunctional behaviour of a system, only with a traditional functional model employed in classic SE. The study of the system must go through multiple phases, from the risks and failure mode identification... 

The meaning of the application of fuzzy models in risk analysis is to provide mathematical formulations that could characterize the uncertain parameters involved in complex safety evaluation me ods. Fuzzy logic is a decisional system based on linguistic rules once the membership functions have been defined for all the fuzzy variable sets, each set has to be connect by... 

Design of complex safety-related systems in accordance with lEC 61508... 

If this does not apply, the question which should be posed is about the complexity of the system. A nonstandard (and therefore complex) safety system is basically not in line with the general requirement that safety systems should be kept simple. There may be good reasons for the complexity, either because of added safety or major cost savings. If the complexity cannot be defended, one should try to change the system into something less complex. 

Strategies for handling common cause failures in complex safety instrumented systems - An example to illustrate different methods... 

ABSTRACT In older to design complex safety relevant systems, safety principles are of great use to save time and keep the safety architecture simple. An outline of safety principles has been given by one of the authors in an earlier paper on ESREL 2008. In this paper, the authors will show how the principles have been applied to the Phileas guidance system. 

Safety analysis (hazard analysis) The entire complex of safety (hazard) analysis methods and techniques ranging from relatively informal job and task safety analyses to large complex safety analysis studies and reports (SSDC). 

Subject or discipline comes from the actual needs of practice and production. Chinese mines go more and more deep, which induces more and more complex safety problems. Demand for safety geology has been more and more strongly. As a new discipline, its connotation, goal, content and system should be improved gradually. 

Safety Risk Assessment by Monte Carlo Simulation of Complex Safety Critical (Operations... 

Developers or operators of complex safety critical platforms. 

Kelly, T.P., 2003, Managing Complex Safety Cases in Current Issues in Safety Critical Systems Proceedings of the 11 Safety Critical Systems Symposium, Springer-Verlag. 

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