Risk based inspection

Benefits of Risk Based Inspection to the Oil and Gas Industry
Paper presented at the RBI Conference, Presented in Perth, Australia 27-28 April 2000

Jens P. Tronskar Det Norske Veritas Singapore

Lynne C. Kaley Det Norske Veritas, Houston, Texas USA

ABSTRACT
RISK BASED INSPECTION (RBI) is a methodology which prioritises inspection activities on the basis of risk. RBI uses the results ofquantified risk and production availability analyses to assess the potential failure consequences. It combines material technology with load and resistance models to determine the probability of failure. A quantified ranking of process equipment, piping and transmission pipelines in terms of personnel and environmental risk, loss of production and damage cost, focuses the inspection towards highrisk components and potential/active failure damage mechanisms for an optimal utilisation of inspection resources on key assets. Case studies for downstream and upstream applications are discussed.

1 INTRODUCTION
The oil and gas industry, which operates offshore installations and topside processing facilities, pipelines, petrochemical and petroleum refining plants, handles a wide range offlammable and toxic materials which are potentially hazardous. These industries have a good safety record compared to the industry as a whole [1]; however, occaisonal incidents occur emphasizing the inherent hazards involved in the business. As a result, local legislation has been imposed in various parts of the world to define requirements for management of these plants and facilities that requireoperators to demonstrate that potential hazards have been identified and plans developed for maintaining safe facilities through periodic inspection and mitigation activities. In addition, increasing business pressures require efficient use of company resources while production schedules require high operating equipment efficiency. Risk Based Inspection (RBI) methodology is a systematic approachwhich prioritises inspection activities on the basis of risk. The fundamentals of Risk Based Inspection apply universally to all types of oil and gas processing and petrochemical processes, either onshore or offshore installations, as well as to other industries. There are, however, some differences in the application of these basic fundamentals depending on the specifics of the process and the typeof installation. Leaks of flammable/hazardous material in a plant originate from a variety of causes, and material related damage is only one of these causes. Important causes for leaks can be operator errors (simply opening live process equipment), incorrect operation, improper job training, lack of procedures for maintenance, bad weather conditions, etc. Inspection cannot prevent leaks associatedwith these causes; what is required in such cases is
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Benefits of Risk Based Inspection for the Offshore and Onshore Oil & Gas Industry

DET NORSKE VERITAS

management actions of different kind. Loss Control Management (LCM), inspection management and RBI can be seen as a part of this effort and all are part of Risk Management. Inspection management is an ongoing activitywithin a plant and a number of resources and different disciplines are involved. Figure 1 illustrates the different steps within inspection management. RBI is a tool for identifying active/potential damage mechanisms, for risk ranking and finally for inspection planning and risk reduction, i.e. inspection and monitoring for the high risk items and corrective actions for the lower risk items.

2ACTIVITIES
A typical Risk Based Inspection (RBI) programme contains the following activities: • Screen operating units within a process system or plant; identify high risk equipment or piping items • Calculate the probability of failure taking into account ongoing degradation • Calculate consequence of failure; effect of release of process fluid, business loss due to failure, repair costs. •...