Plant assessment techniques

This chapter provides general information for performing qualitative or quantitative risk assessments on buildings in process plants. For detailed guidance on risk assessment techniques, the user is referred to other CCPS books on this subject, including Reference 3, Guidelines for Hazard Evaluation Procedures, Second Edition, and Reference 4, Guidelines for Chemical Process Quantitative Risk Analysis. 

After determining what functions must be accomplished for each goal, it is necessary to determine how well each function must be accomplished to meet the top-level criteria and requirements. For this purpose, reliability evaluations and probabilistic risk assessment techniques (Ref. 3) have been used to supplement standard engineering techniques and to provide an integrated allocation of the top-level criteria and requirements to specific plant systems. PRA techniques have also been used to identify the relative importance of events and plant structures, systems, and components in responding to such events, as described in Section 3.2. 

The Safety Case produced for the Windscale Vitrification Plant in 1994 included a detailed and comprehensive assessment of fault conditions in the plant using HAZOP and Probabilistic Risk Assessment techniques. The Safety Case identified a number of major hazards. These major hazards, along with the protective measures, Operating Rules, and Safety Mechanisms designed to prevent these hazards or to mitigate them are briefly described below. 

Confirmation of current integrity status and definition of the probability and consequence of failure are essential plant management requirements. The following sections of this chapter deal with the approaches that can be made, both during the production period and at shutdown by utilising plant assessment technology to provide this information. Previous reviews (Brear, 1997 Brear and Townsend, 1997) have detailed the individual assessment techniques and the overall phased approach to component life assessment. 

Using risk assessment techniques such as those described in Chap. 12 provides a sound basis for prioritizing and managing the inspection program for plant equipment. With this approach, the risk associated with the continued operation of each piece of plant equipment is ranked by assessing the likelihood of its failure versus the severity of failure consequences. 

The concept of corrosion monitoring has developed from two distinct areas, plant inspection techniques, and laboratory corrosion testing techniques, with the original aim of assessing or predicting corrosion. 

Most chemical and petrochemical companies in the UK have made use of safety and reliability assessment techniques for plant evaluation and planning. Similar methods are regularly employed in relation to offshore production and exploration installations. 

Ncube N, Afolayan A, Okoh A (2008) Assessment techniques of antimicrobial properties of natural compounds of plant origin current methods and future trends. Afr J Biotechnol 7 1797-1806... 

Protein Content. The protein content of milk can be determined using a variety of methods including gasometric, Kjeldahl, titration, colorimetric, and optical procedures (see Proteins). Because most of the techniques are too cumbersome for routine use in a dairy plant, payment for milk has seldom been made on the basis of its protein content. Dye-binding tests have been appHed to milk for determination of its protein content these are relatively simple to perform and can be carried out in dairy plant laboratories. More emphasis will be given to assessing the nutritional value of milk, and the dependence on fat content as a basis for payment will most likely change. 

A technique called probabiUstic safety assessment (PSA) has been developed to analy2e complex systems and to aid in assuring safe nuclear power plant operation. PSA, which had its origin in a project sponsored by the U.S. Atomic Energy Commission, is a formali2ed identification of potential events and consequences lea ding to an estimate of risk of accident. Discovery of weaknesses in the plant allows for corrective action. 

Control of Plant and Process Modifications Many accidents have occurred because plant or process modifications had unforeseen and unsafe side effects (Sanders, Management of Change in Chemical Plants Learning from Ca.se Histories, Butterworth-Heinemann, 1993). No such modifications shoiild therefore be made until they have been authorized by a professionally quahfied person who has made a systematic attempt to identify and assess the consequences of the proposal, by hazard and operability study or a similar technique. When the modification is complete, the person who authorized it... 

Hazard and Risk Assessment Tools The hazard and risk assessment tools used vary with the stage of the project from the early design stage to plant operations. Many techniques are available, both quahtative and quantitative, some of which are hsted in the following section. Reviews done early in projects often result in easier, more effective changes. 

Hazard analysis (HAZAN) is a quantitative way of assessing the likelihood of failure. Other names associated with this technique are risk analysis, quantitative risk assessment (QRA), and probability risk assessment (PRA). Keltz [44] expressed the view that HAZAN is a selective technique while HAZOP can be readily applied to new design and major modification. Some limitations of HAZOP are its inability to detect every weakness in design such as in plant layout, or miss hazards due to leaks on lines that pass through or close to a unit but cany material that is not used on that unit. In any case, hazards should... 

A, Saamanen, l.M. Andersson, R. Niemela, and G. Rosen, Assessment of horizontal displace ment flow with tracer gas pulse technique in reinforced plastic plants, Building and Eninron-ment, 1995,. 30, 135-141. 

The Chemical Process Industry (CPI) uses various quantitative and qualitative techniques to assess the reliability and risk of process equipment, process systems, and chemical manufacturing operations. These techniques identify the interactions of equipment, systems, and persons that have potentially undesirable consequences. In the case of reliability analyses, the undesirable consequences (e.g., plant shutdown, excessive downtime, or production of off-specification product) are those incidents which reduce system profitability through loss of production and increased maintenance costs. In the case of risk analyses, the primary concerns are human injuries, environmental impacts, and system damage caused by occurrence of fires, explosions, toxic material releases, and related hazards. Quantification of risk in terms of the severity of the consequences and the likelihood of occurrence provides the manager of the system with an important decisionmaking tool. By using the results of a quantitative risk analysis, we are better able to answer such questions as, Which of several candidate systems poses the least risk Are risk reduction modifications necessary and What modifications would be most effective in reducing risk ... 

Various techniques for collection of root exudates are associated with the risk of root injury by rupture of root hairs and epidermal cells or rapid change of the environmental conditions (e.g., temperature, pH, oxygen availability) during transfer of root systems into trap solutions, application of absorbtion materials onto the root surface, and preparation of root systems for exudate collection. The possible impact of those stress treatments may be assessed by measuring parameters of plant growth in plants either. subjected or not subjected to the collection procedure (6) and by comparing exudation patterns after exposure of roots to the handling procedures with different intensity. 

Recurrent is the lack of adequate techniques to assess carbon flows through the plants and microbes into soil organic matter (151). Most important is the development of techniques and protocols to separate rhizosphere from nonrhizosphere soil as well as possibly to facilitate analyses of soil carbon dynamics. The use of carbon isotopes, and, where possible, application of double labeling with C and C, seems inevitable in order to separate the contribution of different substrates to the formation of the soil organic matter pool and to get to an understanding of the ecological advantage of exudates and rhizodeposits. 

Early interactions between the cell walls of the plant and the fungus and changes in their composition are essential morphogenetic events in the constitution of a functioning mycorrhiza. Cellular and molecular approaches have provided new insights into the complex and ever-changing scenario of these interactions. Cytochemical and in situ immunological techniques have demonstrated that both structure and function are less complex when assessed at the cell level (10,11,71,72). 

---