(73b) Management of Safety Critical Elements As a Base for Risk Management of Major Accident Hazards

Management of Safety Critical Elements as a base for Risk Management of Major Accident Hazards

Recent accidents have indicated the importance of safety barriers on management of major accidents, reducing its likelihood or minimizing consequence. Buncefield, Texas City and Macondo, just to indicate some, have stated in their accident investigation reports the failure of safety barriers or non-existance  of adequate ones as potential causes for the major accident occurence.

This paper presents a methodology for management of Safety Critical Elements (SCE), from the identification of them, definition of relevant importance to each activity performed by the installation and establishing alternatives and contingencies for the failure or absence of the SCE.

SCE, in this paper, is defined as indicated by HSE, as being the Barriers that can avoid or mitigate Major Accident Hazards.

Considering that, the following steps are proposed for management of these elements:

Step 1. Perform Process Hazard Analysis (PHA) for identification of accidental scenarios and classification according to Risk Matrix, defined by each company. Normally Major Accidental Hazards (MAH) are those with highest consequence classification. Some safety barriers are normally identified on this PHA and will be reviewed and detailed on the next steps.

Step 2. Develop bowtie diagrams for each MAH. During this analysis, to be develop with a multidisciplinary team from the company, each barrier, preventive or mitigating, will be classified as critical or non-critical and the responsible person or function will be indicated. SCE will be the barriers classified as critical for each bowtie.

Step 3. Develop Summary of Operations Boundaries analysis to evaluate for each activity developed by the installation, if, in the case of the barrier being degraded or not available, that activity can be performed, performed with restriction or not performed. Activities will vary depending on e type of installation. Some examples are:

- for process industries: loading or unloading of trucks or railcars, operation above normal operation conditions, increase of capacity.

- for offshore production and drilling: offloading, helicopter operation, supply vessels approximation, drilling.

Step 4. Develop Contingency Plan for Each Safety Critical Element, considering restrictions of operation, alternative measures or procedures for continuous operation, indicating duration of the alternatives and approval person for each one.

Step 5. Define priority maintenance procedures for SCE, including preventive maintenance routines, inspections routines and definition of spares,  where applicable.

The implementation of above steps will assist the company on managing their major risks, with guarantee of continuous safe operation.