Safety Integrity Level (SIL) Services

Analysis and assessment of Safety Integrity and Functional Requirements of Safety Instrumented Systems (SIS) which are the last layer of defence against critical safety, environmental and economic losses.

SAFEgroup’s team of industry certified Functional Safety Engineers have the skills and experience needed to guide your company through the Safety Lifecycle, ensuring compliance to IEC61508 and adherence to industry best practice.

Compliance with IEC61508 gives you peace of mind that a rigorous process has been followed, covering all aspects of SIS design, installation, operation, maintenance and de-commissioning.


What is the Safety Lifecycle?
The Safety Lifecycle defines the activities that need to occur at each stage of the design of the SIS. This includes:

Hazard Identification is carried out using established techniques such as Hazop and Hazid. The output is then screened and carried forward to Safety Integrity Level (SIL) Assignment.

SIL Assignment: A multi-disciplinary team of Design, Instrument and Electrical Engineers, Maintenance Technicians, Operations and Management review each identified hazard and assign a target SIL for each Hazard.

An approved technique is used, as defined in IEC61508, such as the powerful Layer of Protection Analysis (LOPA), semi-quantitative or calibrated risk graph.

Safety Requirements Specification (SRS): A critical part of the lifecycle, the SRS defines all of the requirements and special considerations for each Safety Instrumented Function (SIF).The SRS is developed in conjunction with the System Designers, Operations and Management.

This document is an important validation tool for the installed SIS, allowing identification of deviations from the agreed system to be identified and reviewed.

SIL Verification involves conducting hardware probability of failure calculations to ensure that the probability of failure of each overall SIF loop achieves the minimum requirements, as defined by the target SIL.

SIS performance analysis also incorporates assessment of other SIS design parameters, including Hardware Fault Tolerance (HFT), Common Cause Failures (CCF) and Critical Function Testing (CFT) requirements.

What are the key benefits?
The benefits of a SIL assessment include:

  • Leading practice approach to process safety engineering and process hazard risk management for all safety instrumented systems
  • Compliance with IEC61508 and 61511 standards
  • Rigorous approach ensures all hazards are managed according to defined procedure
  • Peace of mind that your system has been developed in accordance with years of experience from the world’s leading safety experts

Why Choose SAFEgroup?

  • Recognition. SAFEgroup is an industry leader specialising in conformity assessment services related to Quality, Health, Safety & Environment (QHSE). SAFEgroup is well known for its ability to adapt to changing client environments and situations and for its commitment to providing leading solutions through quality service.
  • Knowledge & Expertise. Through expert local teams and technical knowledge, SAFEgroup are able to deliver packaged and targeted solutions and information, to support our clients’ unique business requirements.

FAQ - Frequently Asked Questions

  • Does SAFEgroup have experience in different SIL assignment methodologies?
    Yes, our facilitators are experienced in many different approved techniques, including Layer of Protection Analysis (LOPA), semi-quantitative or calibrated risk graph.
  • Can SAFEgroup assist with other aspects of the Functional Safety Lifecycle?
    Yes, our group of experienced Risk Engineers can help with all SIL-related questions and investigations, including Functional Safety Management Plans (FSMP), SRS development and specialist SIS design and implementation decision support.
  • Can SAFEgroup provide SIL Verification services?
    Yes, we use approved quantitative techniques such as Fault Tree Analysis (FTA) and our own research information package to model the process and determine the probability to fail on demand of each SIL rated SIF.
  • What industry sectors are SIL assessments used for?
    All sectors. Onshore, Offshore, Refining, Mining, Chemicals and Power Generation are all applicable to the SIL standards. The IEC 61508 is an umbrella standard covering all sectors. Standards such as IEC 61511 have been extracted from 61508 and specifically modified for the process industry. SAFEgroup can even assist clients with certification of equipment for use in safety-related systems with an appropriate SIL.
  • Can you advise us what types of hazard study and risk assessment are required for our project and our location?
    Yes, SAFEgroup can advise on legislative requirements, changes and good practice compliance in most parts of the world.