Hazard studies cycle

In June 1966, MIL-S-38130 was revised. Revision A to the specification once again expanded the scope of the SSP by adding a system modernization and retrofit phase to the defined life-cycle phases. This revision further refined the objectives of an SSP by introducing the concept of maximum safety consistent with operational requirements. On the engineering side, MIL-S-38130A also added another safety analysis the Gross Hazard Study (now known as the Preliminary Hazard Analysis). This comprehensive qualitative hazard analysis was an attempt to focus attention on hazards and safety requirements early in... 

The ISA standard is a much less ambitious standard than lEC 61508 and it confines itself to the core instrument engineering activities relevant to process industries. It does not attempt to deal with the hazard study and risk definition phases of the safety life cycle. 

The first 3 levels of process hazard studies align closely with the first three phases of the lEC safety life cycle model. 

Hazard study report to be maintained throughout the life cycle... 

Alignment of process hazard studies with lEC safety life cycle... 

This figure shows how the lEC and ISA safety life cycle models for safety instrumented systems correspond to the established process safety life cycle models for hazard studies. The point of departure for the SIS life cycle is ideally at the end of hazard study 3 when the safety requirement s specification has been finalized. 

It seems pretty clear that the first phases of the SLC are similar in principle to the older process safety design life cycle. The main difference is the emphasis in the SLC on risk assessment in the preliminary and detailed hazard studies. This is because risk assessment leads to risk reduction, which in turn defines the SIL requirements of the safety related system. 

As the hazard study, progresses there will be particular items of interest to instrument engineers or those responsible for the safety life cycle project. Here are some of them. 

The new safety life cycle is also required to identify specific hazards and risks in the context of the EUC, the EUC control system and all other external factors. Everything that the SLC needs for stages 2, 3 and 4 is obtainable via the hazard 2 study. Therefore, it may be helpful at this point to draw up an activity model to show how we can link up the SLC phases and the hazard studies to save everyone on a project team from a lot of duplicated effort. 

What if the hazard analysis is fully done by the hazard study engineers Then the results can simply be captured into the SLC phase 3 report to complete that phase of safety life cycle. 

Suggestion If a hazard study life cycle is used the instrumentation team involved in using ISA or lEC standards may need to assist or encourage the plant engineers to generate the hazard and risk analysis as an extension to the basic HAZOP study. 

Suggestion Instrument and control engineers can use a checklist during the hazard studies to ensure that all the data they are going to need for the safety life cycle records has been obtained and agreed to with their colleagues. 

Outcomes of the study should be recorded on the Hazard Study 2 Summary Table . The summary table will be developed during hazard study 2 and subsequent studies to provide a concise overview of the hazard control measures. This information should form the basis for phases 3 and 4 of the safety life cycle records for the project. 

The hazard 1 study may have decided that functional safety items such as hazards arising fi om operation of the process or its equipment should be managed in accordance with the principles laid down in lEC 61508. In such cases the hazard study team will be directed to provide inputs to the Safety Life-Cycle (SLC) Phase 2 and Phase 3 studies and to provide continuing support for the SLC studies. 

Finally we take a look at some methods of determining SILs that may be used in the course of arriving at the SILs for each individual safety function. Various methods for determining SIL requirements have been developed in the past and most of these have now been captured into the lEC and ISA standards in the guideline sections. It s a subject that causes considerable difficulties in organizations, perhaps because it is not an exact science and there can be a lot of expense at stake. These methods depend on the quality of information flowing from the hazard studies and thus provide continuity in the safety life cycle. 

The advantages of using a database package to record SIL decisions include the ability to maintain a life cycle record of the hazard study results and operating data that may have been used in the initial decision. The software can keep a record of all changes affecting the safety functions and is easily revisited for periodic safety audits. 

In this practical the results required from the hazard study team are shown in bold type in the following table which shows their relevance to the safety life cycle. 

In preparation for the specification of overall safety requirements lEC safety life cycle phase 4. The hazard study 2 is often used to propose the safety ftmctions diat will be incorporated into phase 4 after analysis.)... 

One important consideration in any catalyst oxidation process for a complex mixture in the exhaust stream is the possible formation of hazardous incomplete oxidation products. Whereas the concentration in the effluent may be reduced to acceptable levels by mild basic aqueous scmbbing or additional vent gas treatment, studying the kinetics of the mixture and optimizing the destmction cycle can drastically reduce the potential for such emissions. 

Adjuvant tamoxifen therapy generally is initiated shortly after surgery or as soon as pathology results are known and the decision to administer tamoxifen as adjuvant therapy is made. The administration of tamoxifen should be limited to administration after completion of chemotherapy based on results from a study that randomized patients to receive chemotherapy for six cycles with concurrent tamoxifen, followed by continued tamoxifen for a total of 5 years, or chemotherapy with sequential tamoxifen for 5 years.39 After a median follow-up of 8.5 years, the administration of sequential tamoxifen resulted in an estimated DFS advantage of 18% [hazard ratio (HR) = 1.18] compared with the concurrent use of tamoxifen with chemotherapy.39 It is believed the growth-inhibitory effect of... 

Most survey respondents indicated that they perform reactive hazard evaluation studies during specific life-cycle phases of a process or product. These phases include process development, commercial process design, periodic re-evaluation, and before proposed modifications. The protocol for hazard evaluation of reactive systems varies from company-to-company. At a minimum, all surveyed companies employ qualitative hazard evaluations.58... 

Due to environmental concerns regarding the use of certain classes of preservatives, there has recently been a renewed interest in wood modification. Wood modification represents a process that is used to improve the material properties of wood, but produces a material that be disposed of at the end of a product life cycle without presenting an environmental hazard any greater than that associated with the disposal of unmodified wood. Although wood modification has been the subject of a great deal of study at an academic level for over 50 years, it is only comparatively recently that there has been significant commercial development. 

A fundamental objective of a computer system applied to automate a pharmaceutical GMP operation is to ensure the quality attributes of the drug product are upheld throughout the manufacturing process. It is therefore important that quality-critical parameters are determined and approved early in the validation life cycle. The exercise should be undertaken to a written procedure with base information from the master product/production record file examined and quality-critical parameter values and limits documented and approved for the process and its operation. In addition, the process and instrument diagrams (P IDs) should be reviewed to confirm the measurement and control components that have a direct impact on the quality-critical parameters and data. This exercise should be carried out by an assessment team made up of user representatives with detailed knowledge of both the computer system application and process, and with responsibility for product quality, system operational use, maintenance, and project implementation. This exercise may be conducted as part of an initial hazard and operability study (HAZOP) and needs to confirm the quality-related critical parameters for use in (or referenced by) the computer control system URS. 

Studies have indicated that repeated exposure of dinitrotoluene has resulted in testicular atrophy and disturbances in the spermatogenesis cycle in experimental mice, rats, and dogs. Female mice also revealed nonfunctioning ovaries 89,90 Conflicting reports regarding the potential reproductive toxicity of dinitrotoluene among workers demand more confirmatory data 91,92 NIOSH has classified technical dinitrotoluene as a human reproductive health hazard in industrial workplaces. Isomers of dinitrotoluene have caused complete liver cancers in animals, but technical-grade dinitrotoluene failed to induce any kind of hepatic cancer in humans.37,93... 

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