SAFETY INTEGRITY LEVEL (SIL)
Business Challenge
Electrical, electronic, or programmable electronic (E/E/PE) safety-related systems are designed to implement the required safety functions and execute the necessary integrity to achieve or maintain a secure state for the equipment under control. The ANSI/ISA S84.01 standard and the IEC 61508 standard requires the operating companies to assign a target SIL for all safety instrumented system applications. One main principle is to separate random failures from systematic failures. Random failures occur at random times, which result from the possible deterioration of one or more mechanisms in the hardware. Systematic failures are determined by certain causes, which can only be eliminated by modifications in the design of the manufacturing processes, operational procedures, documentation or other relevant factors. The challenge is to utilize a method that can detect the safety integrity of a device or system.
Solution
What is Safety Integrity Level (SIL)?
The ANSI/ISA S84.01 and the IEC 61508 standards suggest that the effects of the random failures must be evaluated in a quantitative way by utilizing Safety Integrity Levels (SIL). SIL is a statistical representation of the availability of a required safety instrumented function. There are 4 SIL designations provided in ANSI/ISA S84.01 and IEC 61508; SIL 4 has the highest level of safety integrity and SIL 1 has the lowest.
The diagram below displays the target failure frequency for an operating safety function and its safety integrity level. Bureau Veritas has technical staff dedicated to helping clients comply with the ANSI/ISA S84.01 standard and IEC 61508 to demonstrate their safety management systems and to build strong justifications.
Target failure frequency
|
SIL |
Low demand mode of operation (Average
probability of failure to perform its design function on demand PFD) |
High
demand or continuous mode of operation (Probability of a dangerous failure per hour PFH) |
|
1 |
10-2 < PFD < 10-1 |
10-6 < PFH < 10-5 |
|
2 |
10-3 < PFD < 10-2 |
10-7 < PFH < 10-6 |
|
3 |
10-4 < PFD < 10-3 |
10-8 < PFH < 10-7 |
|
4 |
10-5 < PFD < 10-4 |
10-9 < PFH < 10-8 |
Why Choose Bureau Veritas?
Bureau Veritas offers services for various safety lifecycle activities including the initial concept; hazard analysis and risk assessment; development of safety requirements; specification; design and implementation; operation and maintenance; modification; and final decommissioning and/or disposal.
Our focus is to encompass all aspects of the system and corresponding subsystems that carry out the safety function. This may include hardware, software and failure mechanisms (random hardware and systematic). Our methods contain requirements for preventing failures (by avoiding the introduction of faults) and for controlling failures (ensuring safety even when faults are present). These techniques and measures are necessary to achieve the required safety integrity for our client’s products.
FAQ - Frequently Asked Questions
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We manufacture components used in safety functions for the process industry. Are SIL assessments required? Is Bureau Veritas capable of performing laboratory tests?
Yes. SIL certified products are an essential business need for many manufacturers. We conduct assessments of the product design and analyze field experience data to then certify your product (E/E/PE systems) to its SIL level. If required, laboratory tests are carried out by our partner company (LCIE).
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Do you combine HAZOP and SIL Classification workshops?
Yes, we have an experienced technical staff capable of carrying out combined HAZOP and SIL Classification sessions for our clients.
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To get a better idea on how we can provide you with this service, fill in the quotation form. We will contact you.
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