Handbook of Reliability, Availability, Maintainability and Safety in Engineering Design - Part 49 studies the combination of various methods of designing for reliability, availability, maintainability and safety, as well as the latest techniques in probability and possibility modelling, mathematical algorithmic modelling, evolutionary algorithmic modelling, symbolic logic modelling, artificial intelligence modelling, and object-oriented computer modelling, in a logically structured approach to determining the integrity of engineering design. . | Analytic Development of Availability and Maintainability in Engineering Design 463 Problem definition The first step in systems engineering analysis is to define the problem. It is extremely important to examine critically whether the statement of the problem expresses the reality of the problem. In most process engineering designs the design problem considers the criteria of system configuration process description and problem definition. For example consider the following process engineering design Systems configuration two coal slurry preparation gasifier and gas cleaner scrubber lines in parallel each with separate oxygen inputs into the gasifier. Process description 1 A coal plant feeds coal to two coal slurry preparation mills. 2 The slurry mills feed two coal gasifiers each with separate oxygen inputs from two oxygen compressors. 3 The gas from the two gasifiers are fed into two gas cleaners or scrubbers from which raw fuel gas is obtained. Problem definition determine the reduction in plant flow capacity as the number of unavailable sub-systems increases due to system deterioration and consider the most appropriate alternatives to maintaining optimum availability. System objectives It is also important to examine statements of objectives carefully for possible inconsistencies. An example of an inconsistent objective is the frequently expressed maximising effectiveness at the least cost . It is however highly unlikely that effectiveness can be maximised and costs minimised simultaneously. The objective should be stated as maximisation of effectiveness for a given cost or alternatively minimisation of cost for a given effectiveness . For the example coal slurry preparation plant the system objective may be stated as maximising plant flow capacity by optimising systems availability. System boundaries A problem always encountered in systems engineering analysis with systems optimisation is the difficulty or impracticality of analysing the entire system or .
