Safety verification

Develop tanks for specific sizes and perform safety verification and validation tests based on NGV2-2000, modified for high pressure hydrogen... 

Organic products have a unique advantage in that they intrinsically incorporate some of these standards and safety verifications. But the majority of these products, perhaps because of their differentiated nature, have not until recently lent themselves to smooth integration into industrial processes or large-scale mass distribution channels. 

Even with approximate data, the methods began to show how designers could achieve higher levels of safety while optimizing costs. The safety verification calculations required by the new functional safety standards have shown designers how to design much more balanced designs. The calculations have shown many how to do a better job. But, failure rate and failure mode data for random failures on the chosen equipment is required. 

One of the most popular failure rate databases is the OREDA database (Ref. 4). OREDA stands for "Offshore Reliability Data." This book presents detailed statistical analysis on many types of process equipment. Many engineers use it as a source of failure rate data to perform safety verification calculations. It is an excellent reference for all who do data analysis. 

Fortunately, several instrumentation manufacturers are providing detailed analysis of their products to determine a more accurate set of numbers useful for safety verification purposes. A Failure Modes Effects and Diagnostic Analysis (FMEDA) will provide specific failure rates for each failure mode of an instrumentation product. The percentage of failures that are safe versus dangerous is clear and relatively precise for each specific product. The diagnostic ability of the instrument is precisely measured. Overall, the numbers from such an analysis are indeed product specific and provide a much higher level of accuracy when compared to industry database numbers and experience based estimates. 

Generally, less specific data turns out to be more conservative and that is appropriate for safety verification purposes following the rule that "the less one knows, the more conservative one must be." Remember that industry databases may include systematic failures, multiple technology classes, wear out failures and possible multiple reports per failure. These issues naturally cause the numbers from such sources to be high. 

When doing probabilistic modeling for safety verification purposes for a PLC, the modeler must identify what portion of the PLC is being used for the each safety instrumented function. Consider the functional subsystems of a typical single channel (lool) multi-module PLC (Figure 10-4). 

There are significant differences in performance that can only be shown by subtle changes in the model (Ref. 8). Simplistic models that do not account for all variables would not be accurate and thus provide the wrong calculation for sophisticated technology. This is ttie reason why some manufacturers, like Triconex, provide TUV approved Markov modeling perforrriance calculation sheets for any specific I/O configuration and some TUV approved safety verification tools, like the exida SlLver tool, use these models supplied by the manufacturer. 

Note. See Chapter 6 for product safety technical requirements. Chapter 4 for safety verification, and Chapter 7 for the definition of safety. 

Safety Verification. Outline the safety verification and tracking procedures to be followed. 

A qualitative safety review methodology, primarily utilized in project management, to identify hazards in activities or systems, their probability of occurrence, and determine if protection measures are adequate. It is similar to a lob Safety Analysis. It is sometimes called a Danger Analysis, Safety Verification, or Preliminary Danger Analysis. 

The purpose of the independent safety verification is to establish that the safety assessment satisfies the applicable safety requirements. While the verification may be conveniently subdivided in phases to be performed at various significant stages of the design, a final independent verification of the safety assessment should always be performed after the design is complete. 

Activities relating to the management of functional safety, verification and functional safety assessment are not shown on the Overall E/E/PE System Safety and Software Safety Lifecycles. This has been done in order to reduce the com-... 

This clause specifies the necessary information to be documented for safety-related systems for all phases of E/E/PE systems. This clause also details out the necessary information to be documented in order that the management of functional safety, verification, and the functional safety assessment activities can be effectively performed. All these documents shall be accurate and concise, easy to understand, suitable for the purpose, accessible and maintainable. 

From risk analysis to identify components needed for making the hazardous zones safe. Safety verification for CE marking. 

Safety verification also means that the operating organization has the responsibility to ensure that events important to safety are reviewed in depth and that, when necessary, equipment is modified, procedures are revised and training is given to prevent recurrence. Access to information and relevant experience from similar installations worldwide is essential in such reviews. 

System Safety Life Cycle Safety Activities System Safety Analyses Safety Trend Analysis Safety Verification Tasks Design Verification Inputs to Specifications Acquisition Tests Operational Tests Safety Tests Inspections Risk Management... 

Documenting Safety Corrective Actions and Safety Verification Tracking... 

The Safety Verification Tasks assure that the hazard control is validated to be appropriate and verified to be in place. Verification of the implementation of system safety processes into company operations is very important, not only for regulatory audit and inspection survival but also to be sure that money is spent wisely. Verification is done through review and approval of the design process, input to specifications that call for verification schemes, and various tests (i.e., acquisition, operational, safety) to physically test hazard control adequacy. Of course, physical inspections (destructive and nondestructive) are part of the verification process. This is extremely important in product safety, but also very important in any plant safety. Explaining the testing of safety-critical systems and testing systems to assure they operate safely is very important. 

Safety Verification of Multiple Autonomous Systems by Formal Approach... 

Keywords Technical Safety Concept, Technical Safety Requirements, Safety Verification, Safety arguing, Automotive, ISO 26262, AUTOSAR. 

A Software Safety Verification Method Based on System-Theoretic Process Analysis. This paper proposes a method for verifying software safety requirements derived at the system level in order to provide evidence of safety risk reduction. 

A Software Safety Verification Method Based on System-Theoretic Process Analysis... 

Abstract. Modern safety-critical systems are increasingly reliant on software. Software safety is an important aspect in developing safety-critical systems, and it must be considered in the context of the system level into which the software wiU be embedded. STPA (System-Theoretic Process Analysis) is a modern safety analysis approach which aims to identify the potential hazardous causes in complex safety-critical systems at the system level. To assure that these hazardous causes of an unsafe software s behaviour cannot happen, safety verification involves demonstrating whether the software fulfills those safety requirements and will not result in a hazardous state. We propose a method for verifying of software safety requirements which are derived at the system level to provide evidence that the hazardous causes cannot occur (or reduce the associated risk to a low acceptable level). We applied the method to a cruise control prototype to show the feasibility of the proposed method. 

Keywrords STPA approach, software safety analysis, temporal logic, safety verification, formal verification methods. 

For that, we propose a method which provides a link between the safety analysis at the system level and safety verification at the code level. This method enables the safety analyst to extract the software safety requirements at the system level and verify them at the code level. 

We give background information on the three main topics which we use in the proposed method STPA, safety verification, and formal specification and verification ... 

The first step of safety verification is to verify that the software requirements are consistent with or satisfy safety constraints. Safety verification exists to provide evidence that associated risk has been reduced or eliminated [1]. Safety verification is not the same as functional verification. Functional verification assures that the software fully satisfies its specifications, while safety verification uses the results of the safety analysis process to assure that the software meets the safety requirements [20]. The safety verification can be done in two ways [1] (1) static analysis which looks over the code and design documents of the system (e.g. fault tree, formal verification) and (2) dynamic analysis requires the execution of the software to check all of the systems safety features. Static analysis is the same as a structured code review. Systems can be proven to match requirements, but it will not catch any safety states that the requirements miss [Ij. The dynamic analysis has the ability to catch unanticipated safety problems, but it cannot prove that a system is safe (e.g. software testing). 

The safety analysis of safety-critical software provides the safety requirements which need to be tested. Safety verification shall be performed to verify a correct incorporation of software safety requirements [24]. Verification must show that hazards have been ehminated or controlled to an acceptable level of risk. Figure 1 shows the proposed method of software safety verification based on STPA at the system level. The method includes three main step>s (1) safety analysis of software at the system level (2) formalization of safety requirements and constraints and (3) verification and testing at the code level. 

---