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SIL Verification Overview
Definitions of terms used in the SIL Verfication module of SIL Comp® and in the SIL Verification guides.
Device
The physical item, for example a pump, temperature indicator or Logic Solver.
Requires the following data:
- Subsystem – Determines if the device is a Sensor, Logic Solver or Final Element
- Category – Is the device a temperature indicator, pump, valve etc.
- Manufacturer
- Description
- Dangerous Failure Mode – Outlines what will cause a dangerous failure e.g. valve failing closed or temperature sensor failing high
- λDD – The dangerous detected failure rate
- λDU – The dangerous undetected failure rate
- λS – The safe failure rate
- Safe Failure Fraction (SFF) – The sum of safe and dangerous detected failures divided by the total failure rate
- Source – The source from which the data comes from e.g. Exida certificate
- Source Short – A short form of the Source
- Type – Used for architectural SIL calculations, devices can be either Type A or B
- Max Architectural SIL – The maximum architectural SIL that can be claimed for the device in a simplex (i.e. 1oo1) configuration
Element
The device with additional data that is required in the PFD/PFH calculations.
Requires the following data:
- Tag – Unique identifier (e.g. TIC-1001).
- Mean Repair Time– How long it takes to repair the device when a fault is found
- Proof Test Coverage – The percentage of dangerous failures that are revealed during a proof test
- Proof Test Interval – How often the proof test is conducted
- Periodic Automatic Testing Coverage – The percentage of dangerous failures that are revealed during periodic automatic testing (also referred to as Partial Stroke Testing)
- Periodic Automatic Testing Interval – How often the periodic automatic testing is conducted
Channel
Consists of one or more elements that combine to make up sections of the SIF being analysed.
Requires the following data:
- Dangerous Failure Mode – Selected from the Dangerous Failure Modes of the devices that make up the element being selected
- Voting Type – The voting configuration in use i.e. 1oo1, 1oo2, 2oo3 etc.
- β Factor – Only required for voting configurations with redundancies i.e. 1oo2, 2oo3 etc.
Branch
The complete Sensor, Logic Solver or Final Element subsystem that consists of defined channels.