We take safety seriously and have ISO 18001:2007 certification (see our HSE case study here) as well as ISO 14001:2004 and SafeContractor approval.
We take pride in delivering quality systems. We have spent 25 years building a reputation and we know it is our most precious asset. Since 2005 we have been specifying, delivering and maintaining life safety systems under BS EN 61508. We lead the field in applying this standard to road and rail tunnels. The Fixed Fire Fighting System for the Dartford tunnels was the first SIL2 certified FFFS in the world.
Although the standard does not mandate third party approval for SIL 2 systems, our policy is to use independent safety consultants (for example Abbot Risk Consulting) to verify our compliance with the standard.
BE EN 61508 – Safety Systems
AIS and Siemens design and develop systems that are in compliance with the Safety System standard BS EN 61508 up to and including Safety Integrity Level 3 (SIL3). Siemens provide equipment that is type approved for use in SIL3 systems.
Siemens equipment is used extensively for safety systems projects, including applications such as the Mont Blanc Tunnel and the Metro in France.
We work with clients from the point at which potential hazards are identified, to assessing the SIL requirement (SIL Determination Study), through to the design, implementation and final system validation.
For Highways Agency projects where there is also a CAT3 requirement (in accordance with BD), the independent quality consultancy can also act as CAT3 checkers, as much of their role as verifiers of BS EN 61508 compliance overlaps with that of the CAT3 check.
Safety integrity levels (SIL)
In part four of the standard, safety integrity is defined as ‘the likelihood of a safety related system satisfactorily performing the required safety functions under all the stated conditions, within a stated period of time’, and a safety integrity level (SIL) as ‘a discrete level (one of four) for specifying the safety integrity requirements of safety functions’.
Whereas a SIL is derived from an assessment of risk, it is not a measure of risk; it is a measure of the intended reliability of a system or function. Four safety integrity levels are defined. The target probabilities of dangerous failures to which they relate are defined in the table.
Safety integrity level
Low demand mode of operation
(Average probability of failure to perform its design function on demand)
|4||≥ 10-5 to < 10-4|
|3||≥ 10-4 to < 10-3|
|2||≥ 10-3 to < 10-2|
|1||≥ 10-2 to < 10-1|