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This post was last edited by zlky2005 on 2014-11-25 16:50 The selection and design of security systems are very important and should never be taken lightly. Companies in the process industry must meet the requirements of new safety standards such as IEC61508 and IEC61511, and implement safety measures for asset protection without interfering with the use of assets or at the expense of production goals. What are the basic guidelines for selecting safety and critical control equipment? What important principles must be understood to ensure successful selection and implementation of a security system? Triconex is proud to present 10 truths about safety instrumented systems. Every month, Triconex releases a white paper discussing a major truth, and the discussion of the first truth began in May. After each white paper is released, we will automatically send you an email to notify you to download it. Improve your ability to implement safety instrumented systems to meet IEC and ANSI/ISA standards, increase uptime and ensure optimal asset utilization. Here are the big facts that Triconex will discuss in the coming months: 1． SIL is a measure of safety but has no impact on the equipment's operating time. The SIL indicator is a measure of risk reduction capabilities and expected failure rates. It merely measures the "fail-safe" nature of a device and should not be the first and only criterion considered when selecting a safety system. 2. The quality of the SIS (Safety Instrumented System) has a direct impact on the performance of the plant. Each company implements quality differently. Regardless of how well its products comply with safety standards and certifications, quality assurance procedures often differ from the supplier's implementation standards. The supplier must ensure that the SIS works to the required specifications. 3． There are many companies looking to sell you a security system, but few that can solve your specific problems. For any manufacturer offering some form of process control technology or automation, companies in the process industries pursuing compliance with regulatory requirements present huge potential. Many such manufacturers scramble to claim that their products provide some level of compliance when used in safe uses. Unfortunately, while most of these "new" products offer fail-safe solutions, only a handful of them balance the requirements for safety and process uptime. 4． IEC61511 requires SIS users to demonstrate functional safety capabilities. Just as the process industry requires SIS logic solvers to hold certificates to the corresponding SIL, there is a growing trend to require that the engineers who specify, integrate, program, install and maintain these systems also be certified to competency in AS-Rheinland. 5. Your SIS should provide lifelong protection for your plant. Production assets are built for long-lasting use. Even when an investment has a planned life of 20 years, additional investments often extend its life beyond its original design specifications. Safety systems, on the other hand, can do little to extend their life and enhance the capabilities of a production asset throughout its life cycle. 6. You don’t have to choose between SIS separation and BPCS integration ； You can have both. There is no doubt that BPCS integration is a growing need in the process industry. It should enable plant operators to monitor process conditions and prevent hazardous situations, as well as monitor the health of the control system itself. The pressure to reduce costs and single-source control system hardware should not be a reason to consolidate safety system functionality with basic process regulating controllers. 7. Dual SIS technology is not less costly than TMR ； The former almost always costs more. Many companies advertise that their dual SIS technology is a low-cost alternative to TMR (triple module redundancy), while the performance of the two is equivalent. Unfortunately, this is a misinterpretation of the capabilities of the dual SIS architecture. Dual PLCs (Programmable Logic Controllers) in a 1oo2 (one of the two) configurations are the initial choice for "fail-safe protection", but they cannot overcome the inherent problem of false tripping. 8. SIS vendors advertise that they are TùV certified, but rarely tell you how to implement it and what the operational limitations are. Most security system vendors focus on how the system works when it is healthy, but do not talk about what happens when an internal fault is diagnosed. ； In the worst case scenario, the entire system shuts down. Each SIS supplier must provide clear information on factors that may affect system performance, such as system execution, specific programming or configuration requirements, selection of modules or structures, and operational limitations. 9. Make your choice and do not entrust the execution and installation of your SIS to unfamiliar parties. The choice of SIS implementer is as important as the choice of the product itself. No matter how well a system is designed or built, if the team implementing it does not follow good procedures, is inexperienced, or lacks the necessary and sufficient technical qualifications for the tasks they are asked to complete, failure is likely to result. 10. Maintaining a SIS is not just about extracting data, the system also requires the associated content needed to make informed decisions. SIS suppliers should provide diagnostic tools with clear guidance or recommendations to maintain the system and maximize the uptime of plant equipment.