Risk-based inspection (RBI) is an approach to asset integrity management (AIM) where the probability of failure and the likelihood of failure are evaluated to provide risk rankings for components and systems.

The highest risk components and systems then receive more frequent, and more detailed evaluation of their fitness for continued service. This common sense approach focuses the inspection process where it properly belongs, on those components which are most likely to fail with significant consequences.
Prior to implementation of an RBI programme at an Asian refinery and its associated gathering system, the facility experienced a series of multi-million-dollar production losses. Factors leading to these substantial losses were:
• Unclear focus for the existing AIM programme;
• Mechanical and physical risks as a result of hazardous material transportation and climatic extremes;
• Unplanned and costly integrity-related outages;
• Inconsistent inspection data and limited mechanical and process data; and
• Ineffective AIM management systems.
Development and implementation of the RBI programme resulted in elimination of all significant product releases, greater than 90 per cent reduction in unplanned down-time, and a greater than 65 per cent reduction in the expenditures for turnaround contingencies compared to previous years.

RBI Process Overview
The implementation programme sought to implement a programme which represented an industry best practice RBI programme which was compliant with applicable government guidelines and good engineering practices. This required development of a specific inspection scheme which reflected API, British, and national protocols, guidelines, and procedures
The basic components and work flow of the RBI implementation are shown in Figure 1.  Existing data and programmes are incorporated into the basic asset integrity management system. Historical and known failure mechanisms are evaluated for each system and component and a probability of failure is established. The consequences of failure are determined by a combination of factors. Chief among these is the nature of the chemicals which would be released if containment failure occurred. High consequence is typically assigned to release of flammable or toxic gases or hydrocarbons. Furthermore, government regulations and penalties for releases may impact consequence.
A rigorous, quantitative risk prioritisation matrix was developed for this facility. Once these risk profiles were completed, written schemes of examination, the inspection programme, and the data acquisition programme were developed and implemented.  Because the release and outage problems were well documented at the facility, this historical data facilitated identification of the individual process units subject to the most common upsets. The inspection programme implementation focused on the units in order of risk.

Key Tasks
Twelve dedicated plant integrity specialists, including engineers, inspectors, and technicians, were embedded in the refinery’s inspection organisation. Key tasks included:
• Identification of local environmental factors which could impact loss of containment (temperature, humidity, etc).
• Identification of possible failure mechanisms.
• Assignment of risk ranking for each component based on the product of the probability of failure and the consequence of failure.
• Evaluation of multiple failure mechanisms due to local conditions, such as seismic stress or brittle failure.
• Establishment of repeatable, credible, and well documented inspection methodologies to predict corrosion rates and evaluate fitness for service (FFS).
• Review of and entry of validated historic inspection data into the corrosion monitoring database to establish the condition of the plant at the start of RBI implementation.
• Determination of critical and essential items for monitoring based on significance, safety, economic outcomes and corporate reputation.
• Inspection and maintenance planning including assessment of FFS outcomes, remaining life, turnaround data and extent, and next inspection dates.
• Establishment of the risk acceptance level, and adjustment of inspection frequency and intensity to achieve the risk acceptance level for all units (Figure 2)
• Coordination with national legislators for a shift in time-based inspection constraints to risk-based parameters.
• Installation of commercial AIM RBI software and data entry into the system. Installation of a commercial pipeline asset integrity management system and data entry into the system.
• Verification that the implemented RBI system meets integrity, safety and economic milestones and expectations.

Deficiencies
During the RBI implementation, several key deficiencies were identified. Some deficiencies were present before the components were put into service, such as fabrication defects, segregation, wrong materials of composition, welding flaws, poor fabrication techniques, and incomplete and inaccurate records. These deficiencies were prioritised with respect to risk, and remediation programmes we developed for each.
Deficiencies resulting from the components being on-stream were also discovered. Typical of these were generalised corrosion, corrosion under insulation, stress cracking, other metallurgical changes, pressure excursions, and delayed maintenance. As with the other deficiencies, these were prioritised for remediation. 

RBI Programme Impact
Over a two-year period from 2004 through 2006, the refinery experienced seven unplanned gas releases.  The combination of lost product, production losses, and regulatory fines ranged from about $100,000 to $100 million. The total impact was over $200 million. The two year RBI project described above was initiated at the facility in 2006. During the first year the programme was developed, and implementation was started on the highest priority units. During the second year, the facility’s remaining units were addressed.  
As the high risk items were addressed, issues within the plant began to decrease. In the second year, the unplanned releases stopped entirely and unplanned outages from all sources were reduced by 92 per cent.
One area where the impact of the RBI programme was most apparent was on the contingency budget for turnarounds. In 2006, the budget and expenditures were $80 million. For  2007, the actual spending was reduced to only $26 million, representing a savings of $54 million.

Conclusions
Implementation of an RBI programme at a facility requires a significant investment in time and personnel. It requires complex evaluations and analysis in order to produce effective risk evaluation. The result of implementing a risk-based inspection programme is that the inspection resources are focused on the logical targets, those components most likely to fail and with the greatest consequence of failure. This reduces unplanned releases, thus increasing safety and reducing reactive maintenance.

About the Authors
Paul F Schubert is global sales and marketing manager for SGS’ Asset Integrity Management business. Schubert has 26 year years of experience in the petrochemical and natural gas industry. Prior to SGS, he held various technical and marketing management positions with Syntroleum Corporation, Monitor Labs, Catalytica, Phillips Petroleum, and Engelhard Corporation. Schubert is the inventor or co-inventor on 16 US patents. These patents include synthetic fuels process development, polyolefin processes and catalysts, sulphur absorbents, dehydrogenation catalysts, dimerisation catalysts, and bromine recycling processes and catalysts. He holds a PhD in inorganic chemistry from the University of Illinois at Champaign-Urbana, and a BS in chemistry from the University of Arkansas, Fayetteville. He conducted graduate studies in Business Administration at San Jose State University.
Glen Gannon is an operations director for SGS’ Global Asset Integrity Services. Gannon has 28 years of integrity-based experience in the oil, gas and maritime industries. Prior to joining SGS, Gannon worked with major contractors including BSP, Esso BHP, BP -GUPCO, Stena JV’s, ExxonMobil, Oceaneering, Subsea International, and Australian Blue Water Shipping Contractors. Particular areas of expertise include long-term multi-faceted inspection engineering, project “Front End” multi-discipline inspection, NDT/ RBI and corrosion mitigation. Gannon is a graduate of the Australian Maritime College, and is currently pursuing an MBA in project management.