Within the United Kingdom process industry sector BS IEC 61511 and it’s parent standard IEC 61508 are recognised by the Health and Safety Executive (HSE) as relevant good practice for functional safety of safety instrumented systems (SIS). It is HSE’s view that if the requirements of IEC 61511 are met, and thereby it can be demonstrated that the risks under the control of safety instrumented systems have been reduced to a level that is as low as reasonably practicable ‘ALARP’, enough will have been done to comply with UK law so far as safety instrumented systems are concerned.
The Safety Integrity level (SIL) is a measure of the integrity / robustness and the ability of the SIS to withstand systematic failures and is based on the severity and frequency of previously identified hazardous events (HAZOP) specific to the plant that we will design the SIS to protect.
Through the Applied Integration functional safety management (FSM) system we apply the techniques and measures in BS IEC 61511 / 61508 to provide assurance to our clients that the SIS is fit for purpose and will achieve the target SIL.
The FSM includes verification which is the examination of the SIS sub system components and functions for purpose and adequacy and will determine what measures of protection and intervention they perform to minimise the risks of an incident and will establish what, if any remedial works are required to the SIS.
The AI BS IEC 61511 / 61508 FSM system covers the design phase of the safety lifecycle, the overall functional safety of the process which is not simply concerned with the aspects of design, but requires that all the relevant safety lifecycle stages including the initial concept, design, implementation, operation and maintenance through to SIS decommissioning are addressed.