Risk-based Probability-of-Failure Equipment Ranking Procedure

Risk-based inspection methodology has become the de-facto tool by which "good engineering practice" is measured. Its use reduces the potential for catastrophic equipment failure and provides the ability to efficiently allocate limited inspection budgets and personnel.

We recognized the need for an easy to use and economical tool to rank equipment for inspection purposes that incorporated a qualitative risk-based inspection philosophy, while at the same time being practical and relatively inexpensive to implement. This awareness led to our development of a qualitative procedure for ranking equipment based on the probability of internal failure. The procedure uses equipment design, process corrosivity, inspection data, and probable failure mode scenarios to assign a numerical, relative ranking to equipment. It incorporates current industry inspection code requirements into its model, including API Standard 510, "Pressure Vessel Inspection Code" and API Standard 570, Piping Inspection Code". This probability-of-failure information can be used with consequence or "hazard" information to implement a risk-based inspection program that meets the intent of OSHA 1910.119. The ranking procedure output is easily incorporated into an equipment inspection software database for easy access, and updating.

To be effective, the procedure should be used by a knowledgeable and experienced corrosion engineer, as it assumes intimate knowledge of corrosion/cracking and material degradation processes, instead of using a detailed logic diagram approach. It is more suited for the chemical processing equipment, as compared with refining processes; however, the procedure has been sucessfully used to categorize over 2000 process equipment items. We believe that it is a cost effective tool in meeting OSHA 1910.119 inspection requirements while minimizing the possibility of equipment failure and allowing the effective utilization of inspection budgets and personnel resources. Without making any implied or expressed warranties as to its use, we are making the procedure available to the internet community interested in risk-based inspection as an open source document. We welcome any feedback and improvement suggestions.

The procedure is in the form of an Acrobat PDf file. Adobe's Acrobat Reader program will be required to open the file. To download the file, click on the following link:

RBI Procedure Download