Risk Based Work Selection (RBWS) is one of the Best Practices used by refiners in managing safety and reliability of operations for a facility. RBWS enables refiners to optimize the scope, cost and duration of major turnarounds (TA). Optimization of the work scope is accomplished by screening individual TA Work List items, using a risk-based methodology. The methodology provides a rigorous basis to justify inclusion or rejection of work list items, if they do not mitigate risks or satisfy benefit/cost criteria which are established for the facility’s assessment.
The application of risk based decision making, in the RBWS process, eliminates discretionary TA tasks and retains tasks which mitigate unacceptable risks or will provide benefits from a financial standpoint. The outcome from an RBWS assessment yields a tighter work scope leading to significant reduction in TA duration and costs .The work process covers all major equipment types (Fixed Equipment, Piping, Rotating Equipment, Instruments, Electrical, Heaters, Flare Systems, etc.) scheduled for a major Unit turnaround.
The RBWS methodology, when used with Fixed Equipment, utilizes Risk Based Inspection (RBI) data, where needed, to validate or reject TA tasks that are included in the TA Work List (WL). RBI assessments focus on equipment integrity and loss of containment, while the RBWS methodology supplements these assessments with consideration of failures and consequences in vessel internals which may cause an unplanned outage, and impact on equipment reliability performance.
The effectiveness of RBWS is critically dependent upon the following factors:
- TA Work Requests which are well defined with scope details, justification and cost data.
- A cross-functional team (CFT), which is fully engaged in the RBWS decision making
- Subject Matter Experts who are available to provide input, as needed.
- An Experienced Facilitator who guides the CFT in executing the RBWS process
- A tool which documents the CFT’s risk based decisions on inclusion/rejection of WL items.
- A deliverable database for the RBWS results which can be migrated to the TA Planners.
Becht Engineering has a proprietary and structured RBWS work process, which is semi-quantitative, knowledge based and meets all the requirements mentioned above. The process includes the application of a proprietary software tool (STRAITS) for decision making, and documentation of results. A key feature of Becht’s STRAITS technology is the analysis of benefits versus costs ratios, for including or rejecting an item on the Work List, based on the criteria established by the Owner. A non-linear plot of cumulative benefits versus B/C ratios enables optimization of the risk reduction and work scope definition.
Becht has RBWS Facilitators and Experts, who are familiar with the RBWS process. The Facilitators have led numerous refinery teams to execute hundreds of RBWS assessments at refineries over the past 5 – 10 years, both within the USA and internationally. A summary of the history from some of these RBWS assessments at refineries in North America, are shown below. These results indicate that, in almost every TA/RBWS assessment, significant work scope reductions have been achieved. This outcome has enabled refiners to use the TA window to focus on tasks for risk reduction in critical equipment and target maintenance expenses to meet the facility’s run lengths — all without causing unplanned outages.
The chart below, relates cumulative benefits to the costs of doing TA work. The plot enables TA Managers and CFTs decide the final work scope based on a cut-off point, beyond which the mitigation benefits for a Work List item are considered “marginal”. The cumulative curve assessment also gives a snapshot on the final outcome for risk reduction from TA work, and whether the work scope will meet the TA expenditures for the facility.
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