Safety system design calculation procedure

The ultimate goal in process system safety and risk analysis is to control the risks. This final task is carried out by comparing the risks calculated with risk criteria specified by an authority. The criteria can be subjectively determined, based on the past experience or the existing background risks. However, many companies (1,2) have established numerical targets for risks. Given calculated risks beyond the specified limit, decisions will be made to improve the design or operation and maintenance procedures to reduce the risks. 

The design procedure requires trial and error calculations. Pipes are available in fixed sizes and so the procedure adopted here is to select a pipe size and determine the saltation velocity from Equation (8.1). The system pressure loss is then calculated at a superficial gas velocity equal to 1.5 times the saltation velocity [this gives a reasonable safety margin bearing in mind the accuracy of the correlation in Equation (8.1)]. The calculated system pressure loss is then compared with the allowable pressure loss. The pipe size selected may then be altered and the above procedure repeated until the calculated pressure loss matches that allowed. 

The measures designed to increase safety, and thus minimize risks within a material flow, are often influenced by the reliability of its individual components (transport machinery). Quantitative assessment of safety is carried out in the form of risk estimation or calculation the acceptable risk level is defined by the value of its acceptability for individual machines and machinery types. Using risk for the purpose of safety assessment of the material flow requires interdisciplinary procedures. It is crucial to correctly define a relationship between the probability of failure or a negative event occurrence and the consequence that the failure or negative event may cause. It is also essential to take into consideration various causes of negative events within the Man-Machine-Environment system as well as their consequences (location, time, person involved, duration of consequences, etc.). Appropriate statistical methods should be used for the purpose of risk (especially the probability of negative event occurrence) estimation or assessment. 

Once the problem is formulated from a mathematical point of view, the further step deals with the evaluation of the structural response to perform the prediction of the safety of structural systems. In this framework, the maximum absolute peak of stationary or nonstationary stochastic responses may be useful in design information of several engineering situations (see, e.g., Lin 1976 Lutes and Sarkani 2004 MuscoUno and Pahneri 2005 Li and Chen 2009). Approximate procedures to calculate the statistics of the maximum absolute peak of the response have been proposed. These procedures lead to the probabilistic assessment of structural failure as a function of barrier... 

---