When designing a safety circuit, it is straightforward to calculate the Performance Level (PL) using sistema or a similar tool for assessing hardware components. However, when dealing with different levels of software involvement, such as in a PLC with a safety program, the approach is unique. In this scenario, the CIP-phase status (running, held, etc.) is transmitted to the safety program and integrated with additional logic to initiate motor stoppage. Instead of a traditional hardware input and output circuit, this setup relies on a Code input and hardware output circuit for operation. Deciphering the handling of various software degrees is essential for optimizing safety measures in industrial settings.
The PLC and programming software compiler are pre-certified with built-in diagnostics and error checking to ensure the PLC operates according to the program's specifications with a certain level of reliability. In the realm of AB, the safety CPU has a reliability value suitable for SIL2, but when paired with a safety partner, crosschecking and additional diagnostics can achieve SIL3. This is essential for sistema evaluation, regardless of the PLC's internal programming. In Siemensland, profisafe includes robust error checking that deems networking errors insignificant for safety reliability calculations, similar to CIP safety. However, network architecture can impact reaction time, so it should be considered in calculations. Validation and system testing are still necessary to confirm the program operates as intended, separate from the system's overall reliability.
In theory, the PLC and programming software compiler have undergone pre-certification, with built-in diagnostics and error checking to ensure the PLC performs according to the program's specifications, meeting a certain reliability level. In the realm of Allen-Bradley systems, the safety CPU itself holds one reliability rating (suitable for SIL2), while a higher reliability level (SIL3) is achieved when working in partnership with a safety CPU (crosschecking/reliability/diagnostics). This setup is crucial for sistema evaluation, regardless of the specific programming within the PLC. In Siemens systems, profisafe incorporates sufficient error-checking mechanisms that networking errors are considered negligible for safety reliability calculations, although network architecture can impact reaction times. It is important to consider this in your calculations. Despite this, validation and system testing are still necessary to ensure that the program functions as intended, which differs from system reliability. When making changes to software within the safety portion, re-validation is required. However, signals sent from the rest of the program to the safety portion may result in varied outcomes without altering the safety program itself. It is essential to validate the normal program as usual, but discrepancies in the behavior of the safety code without changes to the program may arise. In our discussions, it is understood that the code remains stable post-validation and that hardware errors, with components having failure rates, are addressed in the PL calculations.
The safety program must have the ability to shut down independently of the standard program, even if there is conflicting data. Additionally, the safety program can be triggered to shut down by the standard program. While the behavior of the safety code remains the same, it may react to both safe and non-failsafe data. For instance, it is possible to program the safety code to respond to a standard stop in the same way as an emergency stop (Estop). If the standard stop unexpectedly triggers a safety shutdown, it may impact productivity but does not compromise safety. Conversely, if the standard stop fails to activate when anticipated, it may disrupt the process but does not pose a safety risk, as emergency stops can still be used if necessary. In this scenario, as long as the standard stop does not interfere with the emergency stop, the system remains secure. By incorporating a SIL1 or PLa stop function, you have enhanced the safety features of your potential SIL3/PLE emergency stops.
Absolutely, the main concept is centered around forcibly closing operations without considering the information contained within the standard program. Thank you for clarifying.
You bring up a really important point about the complexities introduced by software in safety circuits! It definitely requires a shift in mindset when you're integrating various levels of software logic with hardware components. The need to ensure that the PLC's safety program accurately processes and reacts to the CIP-phase status adds layers of intricacy that aren’t present in purely hardware solutions. I think a thorough risk assessment and testing protocol, especially in the software logic, becomes critical here to maintain safety integrity. It's fascinating how software can enhance functionality, but it also demands diligence to ensure that all potential failures are accounted for.
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Answer: - Answer: Software-based PL calculations can be optimized by integrating the CIP-phase status with additional logic in the safety program to ensure proper motor stoppage. Understanding the unique approach required for software involvement, such as in a PLC with a safety program, is crucial for effective safety measures.
Answer: - Answer: Considering different levels of software involvement is crucial as it requires a unique approach compared to traditional hardware-based safety circuits. Understanding how the software interacts with hardware components and the integration of additional logic is essential for optimizing safety measures.
Answer: - Answer: Relying on Code input and hardware output circuits for safety calculations may require a different method of assessing the Performance Level (PL) compared to traditional hardware-based circuits. Integrating the software and hardware components effectively is essential in ensuring the safety measures are optimized.
Answer: - Answer: Tools like sistema or similar software can be used to assess hardware components in safety circuits. However, when dealing with various software degrees, understanding the unique approach required for software involvement and integrating it with hardware components is key to optimizing safety measures.
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