Investigation of Engineered Plant Systems

A process plant functions properly, if the containment (pipework, apparatuses, vessels etc.) of the materials is intact and all parameters, which characterize its state such as temperatures, mass flows, pressures, concentrations etc. are within their design tolerance ranges. A prerequisite is, of course, the correct design of the plant, whose fundamentals were treated in the preceding chapters. It must be pointed out that the tolerance ranges mentioned above can vary with different operational states such as start-up, coast-down and full or partial load. 

If deviations outside the tolerance range occur in one or several process parameters their consequences depend on the type of system, the extent of the deviations, the type and number of parameters affected and the functioning, respectively failure, of the monitoring and safety systems provided for such a case. Consequences can be restricted operation, standstill or an accident, which results in an explosion, a lire or the release of toxic or radioactive substances depending on the nature of the plant affected. Several of the consequences mentioned may occur simultaneously. 

Obviously, the relationship between deviations of the process parameters from their nominal values and the accompanying consequences can only be dealt with in concrete cases. Their treatment generally requires the interplay of several areas of knowledge, as shown in Fig. 9.1. 

One has to observe that safety-related issues provide impulses for the underlying areas of knowledge. Interrelationships exist. It should be noted that the requirements on the systems and the decision of whether a certain state is to be assigned to functioning or failure depends on the required system function (totality of systems, which have to work in order to fulfil the required task). This decision may differ depending on whether full or partial load operation, shut-down or startup are to be investigated. 

Objective Identification and valuation of weak points, proposals for improvement, demonstration of their effectiveness and implementation in order to achieve a balanced safety design 

---