How is the SIL level of an instrument determined?
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1. As the title suggests, for example, in the case of a voltage transformer with a SIL rating of SIL2, how is this rating determined? Is it calculated by using the internal electronic components of the transformer itself to estimate the probability of failure (the description might not be exact; it’s roughly that idea), and is it determined through a series of calculations? 2. The SIL2 rating for a valve refers to whether the entire valve – including the solenoid valve, the valve body, and the actuator – must meet the SIL2 standard, or whether only some of its components need to meet it
At the start of a project, after conducting HAZOP, LOPA analyses, and SIL assessments, if it is determined that an SIS is needed to reduce risks, then a SIL verification of the SIF must be carried out. SIL assessment is carried out by calculating and analyzing the PFD/PFH of various components of the SIF, and by taking into account factors such as structural constraints and system capabilities in order to determine the SIL level of the SIF and verify whether it meets the required target SIL level
The SIL2 rating for a valve means that the entire valve, including the solenoid valve, the valve body, and the actuator, must all meet the SIL2 standard.
HAZOP, LOPA, and SIL are widely used in high-risk industries, especially the chemical industry. However, such excellent technologies are held in monopoly by just a few companies, and the cost of training courses is extremely high.
The SIL level of a control loop is determined using methods such as Hazard and Operability Analysis, generally by considering the failure probability and the severity of the consequences. The entire control circuit must definitely use components such as instruments and control valves of the appropriate grade.
I’m referring to the SIL rating of the instrument itself, not the loop
The SIL rating of the instrument itself is determined by a third-party certification body through standard experimental tests.
There’s no need to separate the components; it’s not a matter of calculation either. Instead, they are integrated together for testing. When our product underwent SIL3 certification, tests were conducted on the entire unit: it was switched on and off continuously 12,000 times without any maintenance, after which airtightness tests and functional integrity tests were carried out.