Safety function charts

ANSl/lSA-84.00.01-2004 (lEC 61511 Mod) has a requirement for nainimum levels of "hardware fault tolerance" as a function of SIL level. This means that redundancy for purposes of achieving the safety function must be done depending on the SIL level target of the SIF. For field instruments and non-programmable logic solvers, the chart is shown in Figure 7-6. 

When following this chart without an exception, the designer must use two transmitters for S1L2 and trip if either transmitter indicates a trip. When designing a S1L3 SIF without an exception, the designer must use three transmitters or three valves, each capable of performing the safety function. 

Managing the Safety Function / 219 Figure 10-1. Typical organizational chart... 

Safety functions will be described using semiformal methods such as Cause and Effect Charts, Eogic Diagrams, or Sequence Charts. 

It is visualized by a flow chart diagram showing the procedures suggested for the management of the safety functions at each stage of the life cycle. 

Figure 14-4. Safety analysis function evaluation (SAFE) chart for process flow in Figure 14.5.

The PFDavg for entire safety instrumented function can be calculated a number of different ways. One approach is to calculate an arithmetic average of the PFD as a function of operating time interval. When this is done on a spreadsheet, the answer is approximately 0.0019. Per the low demand mode PFDavg chart, this qualifies for S1L2. 

Figure 1.1 is a simplified organizational chart that embodies the concepts discussed in this section. Some duties and layers of responsibility might be combined in a small firm or academic institution,while in very large organizations additional functions or layers might be needed. Note that the safety committees are appointed by a senior executive and have direct access to him. 

Hopp and Roof-Sturgis [55] study the problem of quoting shortest possible lead times subject to the service constraint Tmax- In their proposed due date policy (HRS), which is based on control chart methods, they break the lead time quote of job j into two components the mean flow time, which is a function of the number of jobs in the system at the arrival time of job j, plus a safety lead time, which is a function of the standard deviation of flow time. They use the following quadratic functions (applicable to a flow shop) to estimate the mean and the standard deviation of the flow time... 

Major elements of an occupational safety and health program address recognition, evaluation, and control of hazards. The activities may include risk assessment and charting of probability and severity of potential incidents. The activities may deal with routine functions as well as non-routine functions. Changes in operations and conditions or equipment may also trigger these activities. Inspections, reviews, and other analysis methods will help identify the hazards, the likelihood of occurrence and the potential severity. For example, there should be inspections of repair and maintenance work to ensure that guards and other protections are in place or an area is clear of flammable and combustible materials and sources of heat and fire. Previous chapters offered several methods for hazard recognition and control. 

Create a Safety Analysis Function Evaluation (SAFE) Chart. This is a chart showing all process components and their required safety devices. 

Appendix E Examples of Safety Analysis Row Diagram and Safety Analysis Function Evduation (SAE Chart Appendix E Toxic Gas Section Appendix G Definitions... 

The Software Preliminary Hazard Analysis Used to identify software program routines that are considered to be safety critical, this analysis is conducted prior to software program coding. To perform the analysis, the analyst should make reference to any available system specifications, interface documentation, functional flow diagrams, software flow charts, storage and file allocation specifications, and any other program descriptive information. 

Safety Organization Description and Organization Chart Safety Organization Functions, Responsibilities, and Authorities Safety Engineering Staff... 

Cause and Effects (C E) Charts (or equivalent) for all SIFs (safety instrumented functions) under consideration ... 

Figure 4.2 A software development life cycle for a simple PLC system at the application level. The above life-cycle model addresses the architectural design in the functional specification and the module design by virtue of cause and effect charts. Integration is a part of the functional test and validation is achieved by means of acceptance test and other activities listed in the quality and safety plan.

As for the work place safety and health management, very poor results were obtained, being that, only 12% of the plans presented a functional organization chart of the company, 30% the areas of responsibility, 16% referring to the information system and 24% indicated the working hours ... 

Organization. Describe how the site safety and health function fits into your overall management organization. (An organizational chart is preferred but is not required.)... 

Describe the system safety organization or function within the organization of the total program using charts to show the organizational and functional relationships, roles and responsibilities, and lines of communication. 

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