What is Functional safety?
Functional safety systems and other risk reduction measures such as safety instrumented systems (SIS), alarm systems and basic process control systems (BPCS).
It is important to note that each of these systems must have a demonstrable independence from each other to be considered a separate layer of the overall safety of the plant.
Standards and Guidance
The general benchmark of good practice is BS EN 61508, Functional safety of electrical/electronic/programmable electronic safety related systems. BS EN 61508 has been used as the basis for application-specific standards such as: –
- BS EN 61511: process industry
- BS EN 62061: machinery
- BS EN 61513: nuclear power plants
BS EN 61511, Functional safety – Safety instrumented systems for the process industry sector. This is seen as the benchmark standard for the management of functional safety in process industries. It defines the safety lifecycle and describes how functional safety should be managed.
What does BS61511 Require you to do?
Employers must demonstrate management of the lifecycle processes: –
- Planning of the lifecycle processes,
- Risk assessment,
- Verification,
- Validation,
- Monitor,
- Audit,
- Assessment.
This is as applicable for the competence of people and organisations engaged in functional safety as much as it is about the specification and design of a safety related system. An important management process is Functional Safety Assessment (FSA) which is used to make a judgement as to the functional safety and safety integrity achieved by the safety instrumented system.
What are Safety Instrumented Systems (SIS)
SIS are instrumented systems that provide a significant level of risk reduction against accident hazards. They typically consist of sensors and logic solver functions (that detect a dangerous condition) and final elements, such as valves, that are manipulated to achieve a safe state. It sets out many engineering and management functions: –
- Assess risk by hazard analysis to identify requirements for risk reduction,
- Allocate risk reduction to all risk reduction measures, including SIS,
- Specify the required safety function, secondary functions, integrity level, fault tolerances and other requirements of the SIS,
- Design and implement the SIS to satisfy the safety requirements,
- Install, test, commission and validate the SIS,
- Operate, maintain and periodically proof-test the SIS,
- Manage modifications to the SIS,
- Decommission and removal of the SIS.
Holme Beck Engineering Ltd
The engineering team at Holme Beck Engineering Ltd have over 30 years of experience working with safety instrumented systems (SIS). We can carry out, organise, or audit the functions associated with the development, implementation and operation of the SIS: –
- Functional Safety Management Plan (FSMP),
- Safety Requirements Specification (SRS),
- Design and integration of the SIS to satisfy the safety requirements specification: –
- Equipment specification,
- Logic solver user requirement specification (URS): –
- Software development plan,
- Functional Design Specification,
- Factory Acceptance plan and test document.
- Loop drawings,
- Loop data sheets,
- SIS Performance calculations,
- Site acceptance plan and test document,
- Installation validation,
- Proof test procedures.
- Install, test, commission and validate the SIS:-
- Project installation validation,
- Project test packs,
- Project commissioning packs,
- Proof testing packs.
- Operate, maintain and periodically proof-test the SIS,
- Manage modifications to the SIS,
- Decommission and removal of the SIS.