What is the difference between PL and SIL level ?

The Performance Level (PL) is a measure of the reliability, stability, and performance of a system. It is often used to assess the general-purpose functions of a control system, such as temperature control, pressure control, or process control. The PL level is typically not explicitly concerned with safety-related functions, and therefore does not meet specific safety requirements.Systems certified with a PL level undergo rigorous analysis and testing to assess their overall safety performance. However, they may still have some safety-related components, such as redundancy, diagnostics, and fault tolerance, to mitigate the risks associated with equipment failures or malfunctions.Safety Integrity Level (SIL)

On the other hand, the Safety Integrity Level (SIL) is a measure of the safety-related functions of a system. It is often used to assess the safety of systems that are critical to the operation of a plant or process. The SIL level is designed to ensure that critical systems meet strict safety guidelines and standards, and therefore they must adhere to a wide range of safety requirements. These requirements may include emergency stop capabilities, safety interlocks, and safety monitoring systems.The SIL level is often required in critical applications such as nuclear power plants, chemical processing plants, and oil exploration facilities, where any failure can lead to catastrophic consequences.The higher the SIL level, the stricter the requirements for system design, validation, and maintenance.In summary, the PL level focuses on general-purpose control functions, while the SIL level emphasizes safety-related functions. The PL level is typically not explicitly concerned with safety-related requirements, while the SIL level ensures that critical systems meet strict safety guidelines and standards.