Safety Instrumented System


A Safety Instrumented System (SIS) is a system comprising sensors, logic solvers and actuators whose purpose is to take a process to a safe state when normal predetermined set points are exceeded, or safe operating conditions are violated.

Recent accidents in industry show the importance of SIS implementation. It’s easy to become overconfident and complacent about safety. It’s easy to believe that we engineers and our shining technology can overcome almost any problem. History has proven, however, that we cause our own problems and we always have more to learn. The accident happened in Buncefiled  UK 2005 teach us the importance of SIS. The investigation result said “The safety systems in place to shut off the supply of petrol to the tank to prevent overfilling failed to operate”.



  • SIS Gap Assessment

The SIS gap assessment is carried out to identify any critical and potential gaps between the SIS best practices and the requirements of ANSI/ISA 84.00.01-2004 (IEC 61511) with the design and the implementation, the operation as well as the maintenance of the existing SIS. The findings will be categorized based on their impacts to the safety, business as well as environment and will be used as a basis for SIS opportunity improvement. All findings and recommendations that have significant safety, business and environmental impact shall be documented, followed-up, tracked and closed out.

  • SIL Verification

The purpose of SIL Verification is to determine if each SIF that hasn’t been verified would meet the target Safety Integrity Level (SIL) specified during the SIL classification performed during design.

For each SIF the average probability of failure on demand (PFDavg) will be calculated using commercial SIL software package (such as SIL Solver, ExSILentia) and the results compared with the PFDavg range for the target SIL. A standard test interval will be defined for all calculations. Reliability data is generally obtained from the industry database such as OREDA, EXIDA SERH (Safety Equipment Reliability Handbook). Compliance with the architectural constraints specified in IEC61508.2 is also verified as well as SIL Capability.

  • SIS Training

We provide standard and custom training of Safety Instrumented System. The detail can be seen in Training section in this website.


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