Professional Civil, Structural and Environmental Engineers in Warrington

Functional safety is part of the overall safety that depends on a control system or equipment operating correctly in response to its inputs. Functional safety is achieved when every specified safety function is carried out and the level of performance required of each safety function is met. Functional safety relies on active systems. The system is continuously monitoring the equipment and takes an executive action to prevent a hazardous event from occurring. An example of such is the temperature monitoring of a chemical reactor which takes appropriate action to stop the feed upon the detection of a runaway reaction, or addition of cooling whichever is defined as the appropriate action. Passive systems such as fire protection doors, bunds / dykes and protective insulation are not part of the scope of functional safety. In order to establish if there are any functional safety requirements on your process or system then a hazard analysis should be conducted. This will identify whether functional safety systems are required to ensure that adequate protection is provided for each hazardous event which is present. The outcome of the work will establish the requirements for the functional safety systems.

A Safety Integrity Level (SIL) is a discrete level (one out of a possible four), each corresponding to a range of target likelihood of probability of failure on demand, for specifying the safety integrity requirements of the safety functions to be allocated to the E/E/PE safety-related systems, where SIL 4 has the highest level of safety integrity and SIL 1 has the lowest. It is important to note that SIL is a characteristic of the full safety function rather than a logic system or individual component.

A Hazard and Operability study (HAZOP study) is a structured brainstorming session, set up to identify and evaluate the potential undesirable events that may create hazards or operability problems (i.e. risk to personnel and potential damage to assets, the environment and the reputation) of the plant / site. The output from the study can be utilised in different further risk analysis processes.

A SIL Determination study is a form of risk assessment, required to determine whether there are any SIL requirements for SIFs. This involves determining the necessary risk reduction required to meet the tolerable risk for specific hazardous scenarios. This typically involves: Determining the potential frequency and consequence of an undesired event which causes a specific hazard; Determining the risk reduction provided by other protection measures and the resulting risk gap; Assignment of SIL requirements for SIFs based on any resulting risk gaps in accordance with IEC 61508 (or sector specific standard e.g. IEC 61511).

A Quantitative Risk Assessment (QRA) is a formal and systematic risk analysis approach to quantifying the risks associated with the operation of a process or system. A QRA is an essential tool to support the understanding of exposure of risk to employees, the environment, company assets and its reputation. A QRA also helps to make cost effective decisions and manages the risks for the entire asset lifecycle.