Plant Technical Safety Concepts

The variety of plants and processes in the chemical industry makes it almost impossible to describe all existing safety concepts with the necessary detail. But this intellectual approach in itself would be a mistake, because especially with respect to process related safety concepts nearly each represents a unique solution. The reason lies in the variety of parameters which must be determined. To name just a few number of employees, qualification of the staff and internal as well as external properties of the site. Especially these parameters mentioned are hardly ever identical for two different plants or processes. 

On the other hand there are parts of the complete safety concept characterized by a unified approach, which has been developed due to systematic research and industrial experience. In consequence, some have become standardized in technical regulations or have at least become state of the art of process safety engineering. 

At this point three aspects of plant technical safety concepts shall be explained here, which have been selected because of their Sequent application in the chemical process industry  

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Please note that the technical safety concept is associated with the product development. Next to the 3 parts of product development of systems, EE-hardware and software, and the chapters about production development and plant engineering (part 7) are described. Those are activities that are considered besides the development V-cycles. Furthermore, some activities are mentioned that are not directly addressed by the norm but often necessary for the product development. 

Starting point for the safe design and operation of a process plant is a safety concept. This is understood to comprise aU the organizational and technical measures in a plant and its operation aimed at... 

Safety concepts and technical features of the safety design — the technologies previously developed and validated for the Russian AST-500 nuclear co-generation plant IAEA review of the AST-500 safety design has been conducted... 

In 1990, preliminary development work had been carried out for the Conceptual Design of BMN-170, which included an assessment of promising technical and economic performance and a report "Safety concept for the reactor plant BMN-1700". 

In the past, the safety concept of Nuclear Power Plants (NPPs) as well as licensing decisions by the competent authorities and their experts in Germany were mainly based on deterministic principles such as prevention or control of abnormal plant operational conditions and incidents by technical means to ensure high reliability. In the meantime, Probabilistic Safety Analyses (PSA) are mainly applied in the frame of periodic safety reviews and shall supplement deterministic safety demonstrations to verify the balance of the plant design related to safety. 

In the 1960s and 1970s chemical plants were expanding in many areas. Many of the technical concepts of process safety were not highly developed nor fully publicized. As a result, management did not provide a sustained focus on the potential process safety problems. 

The prototype pebble bed reactor THTR-300 [50] has demonstrated the expected large-scale applicability of HTGR technology [10] and the relatively low level of radioactivity in the HTGR plant. The measured generator power of 303 MW(e) translates into an efficiency of 39.7 %. The early shutdown after 423 efpd was not related to the reactor concept neither to any safety concerns, but primarily associated with technical and economic problems. 

The limitations and boundary conditions of this concept, which were mentioned in the introduction, mainly refer to the question of extrapolation of the results obtained. The application of this concept remains comparatively simple as long as the process to be safety technically assessed belongs to the group of homogeneous liquid phase reactions. In heterogeneous processes, the thermal conversion obtained reflects the flow conditions of the measuring apparatus. Here, special care has to be taken in the experimental design in order to obtain results which, under full observation of all rules of the similarity theory, may be used for plant scale assessment. 

Next the individual process steps are developed (design, calculations, tests, quality assurance measures). All of these activities enter the piping and instrumentation (P I) diagram, which later forms the basis for preparing the plant model, planning construction work, technical data sheets, and the safety and measurement and control concept. 

Contrary to the public conception of the nuclear industry as secretive, nuclear engineers organise public conferences covering virtually all of the technical design, safety and operating aspects of nuclear plant. Most of these conferences are international ones with delegates and papers from all over the world. 

In modem technology, which is characterized amongst others by the use of nuclear power, the operation of complex process plants and air and space travel, failure can hardly be tolerated because its consequences may be large. They can be economic, such as unplanned shut-downs or destraction of plants, or endanger humans and environment. Accidents do happen despite the numerous safety measures described in the preceding chapters. The reason is that technical measures and human interventions for avoiding accidents can never be perfect. They fail with a certain probability. This is the rationale for the barrier concept presented in Sect. 4.2. 

On completion of the assessment, the technical experts should prepare assessment reports that clearly identify all significant issues which, in their opinion, need to be resolved. The assessment reports should also give an initial indication of the acceptability of the objectives/concepts of corrective actions and/or safety improvements proposed by the plant operating organization. 

Concept Analysis of the Technical Plant after Planning. Preliminary hazard analysis and system structure analysis are intended to facilitate safety evaluation of the planned installation from the basic concept. Comprehensiveness of observation depends on the danger level of the installation. After concluding this work, basic changes in the technical procedure frequently become necessary and must be incorporated into the planning. 

The facility protection service controls the outer safety zone and, if necessary, goes into action in order to avert damage to the installation. During the planning of a technical plant, specialists must develop the facility protection concept and become thoroughly familiar with every aspect. Of greatest importance is a dear and concise definition and delimitation of individual safety zones. Only then can the specihc technical measures for the protection of the facility be initiated and the organization established. 

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