En Iso 13849-2 Pdf
Graziana Getz
ISO 13849 is a safety standard which applies to parts of machinery control systems that are assigned to providing safety functions (called safety-related parts of a control system).[1] The standard is one of a group of sector-specific functional safety standards that were created to tailor the generic system reliability approaches, e.g., IEC 61508, MIL-HDBK-217, MIL-HDBK-338, to the needs of a particular sector. ISO 13849 is simplified for use in the machinery sector.
ISO 13849 is designed for use in machinery with high to continuous demand rates. According to IEC 61508, a HIGH demand rate is once or more per year of operation, and a CONTINUOUS demand rate is much, much more frequent than HIGH. For systems with a LOW demand rate, i.e., less than once-per-year, see IEC 61508, or the appropriate sector-specific standard such as IEC 61511.
According to an informal stakeholder survey done in 2013, more than 89% of machine builders and more than 90% of component manufacturers and service providers use ISO 13849 as the primary functional safety standard for their products.[4]
The second edition of ISO 13849-1 was published in 2006. That edition introduced MTTFd, DCavg, and CCF for the first time. The revisions incorporated the recommendations developed through the EU STSARCES project.[6] and [7]
The third edition of ISO 13849-1 was published in 2015. The revision included additional technical explanations and clarification of the analytical methods.This edition was reaffirmed in 2020, while a new revision was started.
Following ISO 13849-1, the design of the safety system is based on a risk assessment performed by the manufacturer of the machine.[8] The risk assessment identifies the safety functions required to mitigate risk and the performance level these functions need to meet to adequately mitigate the identified risks, either completely, or in combination with other safeguards, e.g., fixed or movable guards or other measures.
The Annex A decision tree, Figure A.1, is provided as an example of how the PLr can be determined. The Annex A method is not a risk assessment tool since the output from the tool is in terms of Performance Level, not risk. Figure A.1 cannot be used for risk assessment. Examples of a risk matrix and a risk decision tree are given in ISO/TR 14121-2.[9]Risk assessment is typically done in at least two cycles, the first to determine the intrinsic risk, and the second to determine the risk reduction achieve by the control measures implemented in the design.
Each safety function identified in the risk assessment is assigned a required Performance Level (PLr) based on the intrinsic risk determined through the risk assessment. The intrinsic risk is the risk posed by the machine if no risk control measures were present, or if the risk control measures fail or are defeated by the user.
The Performance Level of a safety function is determined by the architectural characteristics of the controller (classified according to designated architectural categories, Category B, 1, 2, 3, 4), the MTTFD of the components in the functional channel(s) of the system, the average diagnostic coverage (DCavg implemented in the system, and the application of measures against Common Cause Failures (CCF). Category B, 1 and 2 architectures are single channel, and therefore offer no fault tolerance.
Each designated architecture has an associated block diagram. When analyzing SRP/CS designs, a block diagram should be developed to assist the analyst in calculating the MTTFD of the functional channel(s).
Category B represents the basic category. This category is single-channel, and can include components with MTTFD = Low or Medium. Components must be suitable for use in the application, and specified appropriately for the conditions of use, i.e., voltage, current, frequency, switching frequency, ambient temperature, pollution class, shock, vibration, etc. Since Category B is single channel, DCavg = NONE. CCF is not relevant in this category.
Category 1 achieves increased reliability as compared to Category B through the use of MTTFD = High components. These components are deemed "well-tried components" and are listed in ISO 13849-2, Annexes A through D. Additionally, components that have been tested by the manufacturer and approved according to the relevant component safety standard, e.g., IEC 60947-5-5, are also considered well-tried. Since Category 1 is single channel, DCavg = NONE. CCF is not relevant in this category.
Safety-related parts of control systems (SRP/CS) require validation. ISO 13849-2 includes all of the details required for the validation using analytical techniques (including FMEA, FMECA, FMEDA, IFA SISTEMA or any of the other analytical tools available), functional testing, and documentation in a validation record.
ISO 13849-2:2012 specifies the procedures and conditions to be followed for the validation by analysis and testing of the specified safety functions, the category achieved, and the performance level achieved by the safety-related parts of a control system (SRP/CS) designed in accordance with ISO 13849-1.
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This document specifies the procedures and conditions to be followed for the validation by analysis and testing of the specified safety functions, the category achieved, and the performance level achieved by the safety-related parts of a control system (SRP/CS) designed in accordance with ISO 13849-1. Some validation requirements are general and some are specific to the type of technology used. ISO 13849-2 also specifies the conditions to be followed for the validation by testing of safety-related parts of a control system. Descriptions of the safety functions and the requirements for the categories and performance levels are given in ISO 13849-1 dealing with the general design principles. This second edition replaces the first edition which has been technically revised in order to adapt to the current ISO 13849-1:2006. Furthermore, the new Annex E gives an example for validation of fault behaviour and diagnostic means. This standard deals in particular with aspects of occupational health and safety and product safety and is primarily directed at manufacturers of machines. The committee responsible for this standard is NA 095-01-03 GA "Gemeinschaftsarbeitsausschuss NASG/NAM/DKE: Steuerungen" ("Joint working group NASG/NAM/DKE: Control systems") at DIN.
By reading ISO 13849-2, I found in table D.19 requirements suitable for optocouplers. However both ISO 13849 and IEC 61508 do not mention requirements for any other digital isolator. In my project I would like to use a gavanic isolator like ISO721 or similar, to isolate a SPI interface between a safety uC and another regular uC.
For optocouplers, the standards require that the device must be built in accordance with overvoltage category III and polution degree 2, as described in IEC 60664-1. Does it applies for galvanic isolators too? is that possible to use ISO721 or similar in safety applications?
Digital isolators are tested to the same standards that were originally written for opto-couplers. For example, digital isolators are certified to UL 1577, IEC 60747-5-x, CSA CA5A. There are efforts underway to publish standards written specifically for digital isolators, such as IEC 60747-17.
ISO721 has been certified by UL, VDE and CSA. VDE and CSA certifications were performed for pollution degree 2 and overvoltage category II. Specific details can be found in the certification reports which are available on our website.
SMC provides validated products for use in safety-related parts of control systems.
However, some product options may not be validated.
Please check compatible product numbers from the "How to Order" at the end of the respective reliability data document.
Validated SMC products are validated based on ISO 13849-2:2012 appendices A, B, and D.
Please click here to go to the download area for the SISTEMA library and technical documentation.
We provide reliability data for individual components, which are used in the calculations required to demonstrate the reliability of safety-related parts of control systems.
The customer should convert this to MTTFD.)