Safety design phases

The pilot study is likely to use all the same Quality Management tools that were used for the integration framework development (Chapter 5). However, the limited scope of the pilot study enforces some limitations and compromises—it will not be possible to make changes outside of the department covered by the pilot. Any existing interfaces with other departments must remain the same. This will impact the design phases of the work. For example, Material Safety Data Sheets (MSDS) may currently be prepared locally, in the overall project it might be proposed to develop these centrally. However, for the pilot study it will not be possible develop the central resource so the pilot would have to continue to rely on local resources and there will be no efficiency improvement. 

Our computer model predicted the Phase I test results with accuracy adequate for safety design even though there were experimental errors. To reduce these experimental errors. In Phase I I, we made some equipment modifications and used a larger reactor. 

Since we did not measure the conversion during the experiment, we computed the equilibrium vapor pressure at the average solution temperature. We believe that, for safety design, the equilibrium vapor pressure is an adequate estimate of the styrene vapor pressure. For example, even at a 50% conversion, the difference is only 10 at the experimental temperatures. Figures 6, 7 and 8 compared the observed pressures with the computed total pressures. The latter were based on the equilibrium vapor pressure. As expected, there were increasing variations in Tests 1, 2 and 3 respectively because of their higher initial conversions. From these figures we can verify that our pressure and temperature measurements were in phase with respect to time. 

Operating complexity. Complex operations may introduce the potential for overlooking safety-related issues in the design phase and may also present challenges for operators to accurately and quickly assess plant upsets and respond with appropriate action. 

Miscellaneous design features are additional safety design methods that are usually included in the early design phases of new projects and are often the basis for safety improvements in existing plants. 

Safety reviews A safety review (HAZOP study or equivalent study for hazardous operations) must be conducted by engineers, operators, and design specialists while the modification project is in the design phase. This allows (and encourages) safety changes to be made with minimum effort. Once the system is constructed, changes are difficult and costly to make. 

Problems similar to this are usually identified in safety reviews. This accident, for example, could have been prevented if the plant had used a safety review procedure during the design phase of this plant modification. A bleed line and possibly a nitrogen blow-out line would have prevented the accumulation of this water. 

Use safety review procedures during the design phases of projects, including new installations or modifications to existing systems. 

Most of the principles of inherent safety are useful in the preliminary design phase even most process details are still missing. This is represented in Table 4 which shows in which project phase each inherent safety feature should be considered. In fact the opportunities for installing inherent safety features decrease as the design progresses (Kletz, 1991). It can be seen from Table 4 that most features can be considered in the conceptual and flow sheet stage. 

Many different alternative process configurations can be created for a process in the conceptual design phase. In choosing the most feasible alternative safety should be one of the major evaluation criterias. Therefore information on the safety features of alternative process structures are needed on preliminary process design. 

The conceptual design phase is the most critical when designing inherently safer plants, since the alternative process concepts are created and analyzed in this phase. This emphasizes the need to introduce safety evaluation tools into the preliminary process design. Time and money is saved when fewer expensive safety modifications are needed during the later stages of design. 

The Inherent Safety Index, ISI, was developed to consider a wider range of factors affecting the inherent safety of the process (Ch. 8). The ISI allows the evaluation of inherent safety of process alternatives to be done in a computerized process synthesis environment. The represented synthesis approach allows the inherent safety comparison of process alternatives to be done flexibly and interactively in the conceptual design phase. 

Some biotechnologically derived pharmaceuticals will cross-react with species that can be evaluated toxicologically, while others cross-react only with nonhuman primates such as the chimpanzee, a protected species. In this case, a well-designed safety, or Phase 0 study at doses higher than the proposed clinical dose may provide valuable safety information. However, a lack of cross-reactivity with any nonhuman species does not necessarily make preclinical safety evaluation impossible, not does it limit toxicity testing to species in which the protein lacks relevant pharmacological activity. Some alternative possibilities are summarized in Table 12.9. 

Studies aimed at gathering feasibility and toxicity data on new treatments are usually referred to as phase I trials. Phase II trials are relatively small studies (typically with sample size less than or about 100 subjects) with the purpose of detecting preliminary evidence of efficacy and safety. Phase III trials are larger studies with enough statistical power to test in a conclusive way specific hypotheses about treatment effects. The term clinical trials is often broadly used to designate phase III trials. 

Simultaneously most petroleum and chemical companies have also brainstormed a safety review which asks "What-If" questions of the process (e.g. SOHIO ca. 1967). This is common practice in the industry and during design phases of a facility but was usually verbal and less formal in its application. Therefore not as much historical documentation is available on it, as compared to the HAZOP method. 

Conceptual Design. During the conceptual design phase, the reaction pathway synthesis is undertaken the inherent process safety is incorporated the general... 

At this phase no technical hurdles are anticipated. Future actions include conducting a safety design review (HazOps analysis), establishing an activity-based target date for a critical design review, and generating a system level functional specification document which will help define the research boundaries for this project. 

The aim is to list the most important possibilities for hazards from the process and the hazard sources of the chemical plant, to formulate the tasks for the basic safety concept, and to determine whether individual safety problems must be investigated. Furthermore, it must be shown that the chosen site is suitable from the viewpoint of safety technology. The results are recorded in a safety study (basic design phase), which can have the following components ... 

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