Repair Strategies for Civil Structures Utilizing New Risk Based Inspection Methodology

Introduction

Assessing risk is an integral part of working at a refinery. Process safety changes, equipment upgrades, and work tasks are risk assessed every day. Infrastructure supporting the miles of piping, process vessels, and the platforms and ladders used in daily unit operations are often taken for granted. Refinery structures do not have an infinite design life and may pose certain risks as they degrade over time. In a large refinery like BP’s Whiting Refinery with over 12,000 structures, these risks must be assessed to prioritize repair and mitigation efforts. The Civil Structures Management Program (CSMP) at the BP Whiting Refinery was developed in 2004. Since the program’s inception, millions of dollars have been spent in the yearly execution of refinery structural repairs. Like other on-going repair projects, funding and program scope are scrutinized as yearly budgets are developed. A review of the repairs made during the last 10 years of the program revealed no clearly definable reduction in the level of risk exposure. It was also recognized that there was not a good understanding of whether the level of risk was increasing or decreasing. Though tens of millions of dollars had been spent on repairs, there was no way of showing real reduction in structural risk in the refinery.

Prior to the development of the enhanced Civil Structures Inspection Program (CSIP), over 2500 inspections had been completed on the refinery’s 12,000 structures. These lengthy and detailed inspection reports, assembled by a local contractor, were the basis of setting the CSMP yearly repair scope. Each report was a catalog of inspection findings for a particular structure. It consisted of a free text write up, photos of all specification deviations and structural defects, and an AutoCAD drawing of the structure. The duration of the structural inspection in the field combined with the creation of the reports could take a full day for a small structure. For large unit structures, inspecting and assembling the report could take months.

In each of the historical inspection reports, the findings were binned into Priorities 1-6. By 2012 over 3700 items had been identified as Priority 1 repairs by the inspection contractor. There was no rigor or consistency around what constituted a Priority 1 repair, but it was rather based on inspector judgment. Additionally, each of these priorities was based on the condition of the structure, regardless of the consequence of failure. There was also inconsistency in the identification of deficiencies and prioritization of repairs. Engineers tasked with the time-intensive process of reviewing the civil structural inspection reports saw a need for more consistency in identification of high priority repairs. Only a subset of the 3700 Priority 1 items actually posed substantive risk for inclusion in the CSMP repair strategy. The quantity of Priority 1 repairs on a particular structure was not a good indication of the actual structural risk. The combination of these factors had the potential to misguide the program in the identification of the highest structural risks.