MODERN SAFETY REQUIREMENTS FOR INDUSTRIAL EQUIPMENT MANAGEMENT SYSTEMS (Part 2. Safety indicators of control systems)

Purpose: Analysis and determination of the main modern international safety requirements that must be met in the design, development and operation of industrial equipment management systems, as well as confirmation of the need for further improvement of the domestic regulatory framework in this area. Methodology/approach: Performed analysis of the requirements of modern international standards (IEC 62061 and IEC 61508) on the safety of electrical, electronic and programmable electronic control systems for industrial equipment and the existing sequence of protection against hazards; the algorithm of step-by-step realization of control systems and the basic features of the organization of their structures at the level of functional blocks and subsystems for maintenance of necessary level of completeness of functional safety are defined; the peculiarities of the process of design and development of each of the subsystems and the algorithm of its execution are analyzed; defined algorithms for estimating the probability of dangerous accidental hardware failures for the recommended basic architecture of subsystems (type A, B, C and D) and for the control system itself; provided recommendations on the composition of the specification of safety requirements in the design of control systems; reviewed software requirements. Conclusions: The analysis of the features of functioning and application of modern international safety standards, which must be observed in the design, development and operation of industrial equipment management systems convincingly confirms the relevance and need for further improvement of domestic regulations in this area. Research results: Modern requirements for the organization of the control system structure at the level of functional units and subsystems to ensure the required level of completeness of functional safety of electrical, electronic and programmable electronic control systems for industrial equipment are determined, as well as features of application the of algorithms for estimating the probability of dangerous accidental failures of control systems and their subsystems. Practical implications: The development and implementation of relevant national standards based on IEC 62061 and IEC 61508 should accelerate the further development of technical progress in Ukraine in the field of industrial safety. Originality/value: Defining the main features of the functioning of modern international safety standards, which must be observed in the design, development and operation of industrial equipment control systems; Appropriate recommendations for their practical application are provided; Substantiated and confirmed the relevance and importance of the development of relevant harmonized national standards based on the standards IEC 62061 and IEC 61508.

Consistency Checking of the IEC 61508 PFH Formulas and New Formulas Proposal Based on the Markovian Approach

Safety Instrumented Systems (SISs) are of prime importance in protecting people, assets and environment from hazardous events. Therefore, it is important to be able to assess accurately their performance indicators. For this end, IEC 61508 standard has provided two reliability metrics: the average failure probability of a SIS lowly demanded (PFDavg) and the average failure frequency of a SIS highly or continuously demanded (PFH). The aim of this paper is to investigate the IEC 61508 PFH formulas and to propose new ones based on the Markovian approach. Indeed, the new edition of IEC 61508 provides PFH formulas reflecting the possibility of automatic shutdown of the monitored process upon detection of a dangerous failure in the SIS. However, the IEC 61508 attempt remains incomplete and provide non-conservative results, which is dangerous from a safety point of view.

Mathematical Approaches in Functional Safety Assessment for E/E/PE Safety-Related Software

Safety integrity level (SIL)-based functional safety assessment is widely required in designing safety functions and checking their validity of electrical/electronic/programmable electronic (E/E/PE) safety-related systems after being issued IEC 61508 in 2010. For the hardware of E/E/PE safety-related systems, quantitative functional safety assessment based on target failure measures is needed for deciding or allocating the level of SIL. On the other hand, IEC 61508 does not provide any quantitative safety assessment method for allocating SIL for the software of E/E/PE safety-related systems because the software failure is treated as a systematic failure in IEC 61508. We discuss the needfulness of quantitative safety assessment for software of E/E/PE safety-related systems and propose mathematical fundamentals for conducting quantitative SIL-based safety assessment for the software of E/E/PE safety-related systems by applying the notion of software reliability modeling and assessment technologies. We show numerical examples for explaining how to use our approaches.

Application of Software Reliability Model for Safety Assessment of E/E/PE Safety-Related Software

Quantitative and analytical safety assessment methods of E/E/PE safety-related software systems based on the SIL defined by IEC 61508 have been proposed. IEC 61508 does not provide us with quantitative and analytical methods for safety assessment of the software. Our methods give us quantitative information on safety measures for deciding the safety integrity level and testing time duration for achieving certain safety integrity level of E/E/PE software, respectively. Our stochastic modeling approaches are based on software reliability modeling and software reliability assessment techniques. Numerical examples for our methods have been shown for explaining how to use our software safety assessment approaches conforming IEC 61508.

MODERN SAFETY REQUIREMENTS FOR INDUSTRIAL EQUIPMENT MANAGEMENT SYSTEMS (Part І. Safety indicators of control systems)

Purpose: Analysis and determination of the main modern international safety requirements that must be met in the design, development and operation of industrial equipment management systems, as well as confirmation of the need for further improvement of the domestic regulatory framework in this area.Performed analysis of the requirements of modern international standards (IEC 62061, IEC 61508) on the safety of electrical, electronic and programmable electronic control systems for industrial equipment and the existing sequence of protection against hazards; the main features of the architecture of such control systems are identified and algorithms for determining the main indicators of their functional safety (PL; SIL PL; PFHd) and an algorithm for ensuring the required level of security depending on the parameters of existing risks are provided. The analysis of the features of functioning and application of modern international safety standards, which must be observed in the design, development and operation of industrial equipment management systems convincingly confirms the relevance and need for further improvement of domestic regulations in this area. The main parameters (indicators) of safety of functioning of electric, electronic and programmable electronic control systems of industrial equipment are determined. Relevant recommendations are provided on the main aspects of their application and implementation according to IEC 62061 and IEC 61508.The development and implementation of relevant national standards based on IEC 62061 and IEC 61508 should accelerate the further development of technical progress in the field of industrial safety. Confirmed relevance and importance of the need to develop relevant national standards based on IEC 62061 and IEC 61508.

Errors, faults and failures

Aim. To harmonize the definitions of errors, faults, failures in the Russian and English languages. The Object of the paper is one of the most important subject matters of the dependability theory and functional safety. The Subject of the paper is the concepts and definitions of failures, errors, faults.Results of the research: analysis of the definitions of the concepts describing the dependability and functional safety of items in the Russian and international standards, such as GOST 27.002-2015, GOST R/IEC 61508-2012, IEC 60050, DIN 40041, as well as in publications by a number of authors. The analysis shows that failure is always associated with the loss of function, i.e., the ability to perform as required by all standards. It should be noted that wrong user expectation does qualify as failure. A failure should be distinguished from unintended functions. A fault is defined as a system’s inability to perform the required operation to the full extent that, under certain conditions, may escalate into a failure. An error as a discrepancy between a calculated, observed or measured value or condition and a true, specified or theoretically correct value or condition is a deviation that is present and, under certain conditions, would probably turn into a failure. A typical example is non-critical software errors. The so-called systematic failures are actually errors that can turn into critical errors (failures). Let us note that the definitions in the IEC 60050 international electrotechnical vocabulary can be used, as they show general agreement, which is not surprising for an international standard.

Audit, Validation, Verification and Assessment for Safety and Security Standards

Internal auditing is important for ensuring compliance to multiple safety and security standards. The problem is that although safety and security have similarities when it comes to auditing, they also have differences that makes auditing both areas under the same process difficult. This paper has shown how to overcome those differences and leverage the similarities to create one auditing process for both safety and security. The paper has harmonized the different terminology between safety and security and showed how the new auditing process can allow compliance to IEC 61508, ISO 27001 and IEC 62443.