Applications
The Atex Laboratory Division provides:
Test reports
Product testing
Pre-compliance testing
In accordance with the Performance Standards for Gas Detection, as detailed in the following tables:
Electrical
NON-Electrical
World
IEC
ISO
Europe
CENELEC
CEN
Local (Italy)
CEI
UNI
Application
IEC-CENELC
ISO-CEN
Safety / Security
Industrial + commercial
Household
IEC 60079-29-1
IEC 60079-29-0
IEC 62990-1
EN 50194-1
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-
Refrigeration
Industrial + commercial
Household
IEC 60335-1 (“Annex RR”)
IEC 60335-2-40 (“Annex LL”)
EN 50676 & EN 14624
EN 50194-1
-
-
Hydrogen
-
IEC 60079-29-0
EN 50194-1
DL 0707-2023
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In addition to consulting on hardware (HW) and software (SW), the SIL Engineering Division specializes in providing consultancy for PFD (Probability of Failure on Demand) to quantify the concept of Functional Safety or SIL (Safety Integrity Level) according to international standards.
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Contact usSIL Fundamentals and Terminology
SIL (Safety Integrity Level) is a measure of the functional safety of a safety device, expressed in terms of the Probability of Failure on Demand (PFD). It is simpler to express the probability of failure than the probability of correct performance (e.g., 1 in 100,000 versus 99,999 in 100,000).
There are four distinct levels: SIL 1, SIL 2, SIL 3, and SIL 4.
The higher the SIL level, the greater the associated safety and the lower the probability of system malfunction.
The Risk Reduction Factor (RRF) is the inverse of the PFD. The SIL level corresponds to the number of zeros in the minimum RRF value. For example, for SIL 2, the minimum required RRF is 100.
Typical Examples of SIL Levels
- SIL1: A typical ATEX-certified gas detection system with IEC 61508 functional approval and regular maintenance.
- SIL2: Usually requires self-test functions in hardware components, shorter maintenance intervals for sensors, strict development requirements, and thoroughly documented software.
- SIL3: The main rule is that a single failure must not cause an unsafe (fail-safe) state. This level is achieved through redundancy, especially in detectors and microprocessors.
- SIL4: Requires redundancy and sometimes triple redundancy, together with redundant self-tests and comparison of duplicate code lines. Rarely required in gas detection applications.
According to IEC 61508, functional safety represents the protection that control systems provide to an overall process or plant.
It defines the behavior of a safety device (hardware and software) in the event of internal faults, aiming to achieve a “safe state”, meaning failures that are detected and reported by the device itself.
Since costs increase significantly with higher SIL levels, the choice must be carefully evaluated.
In most cases, the process industry accepts devices up to SIL 2, as systems above this level may cause production interruptions too frequently to meet the standards.
IEC 61508 and Gas Detection Standards
The IEC 61508 (Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems) standard introduced a risk-based approach for determining the SIL of safety instrumented functions.
It provides a comprehensive method to quantify the safety performance of electrical control systems, including design concepts, design process management, operations, and system maintenance throughout its entire lifecycle.
While IEC 61508 serves as the general reference, for gas detection equipment the specific standard is EN 50402:2005+A1:2008 – Electrical apparatus for the detection and measurement of combustible or toxic gases or of oxygen – Functional safety requirements for fixed gas detection systems.
Why SIL Matters
Sensors compliant with IEC 61508 and EN 50402 offer several advantages to users.
Since only a limited number of impartial, nationally accredited bodies can issue such certification, it guarantees the reliability of the supplier’s compliance declarations.
Furthermore, the reliability calculations of final devices are already validated and available to the user, reducing implementation times for SIL-classified safety functions.