• leaks;
  • leak frequencies;
  • process equipment;
  • quantitative risk assessment


The likelihood of leaks from process equipment is a key input to any quantitative risk assessment (QRA) of process plant. This paper describes a new source of generic leak frequencies and reviews the challenges in using it for QRA.

Established leak frequencies for onshore process equipment are poor in quality because they are based on old data sources of unknown provenance, judgmentally modified. Recent data from offshore process activities provide a high-quality data set, which appears to show that the established frequencies are much too low. Much of this discrepancy arises from the QRA practice of modeling only the most hazardous leak scenarios. Recognizing the practical difficulty of changing QRA practice to match new data, the present paper therefore describes a method of analyzing the new data to obtain leak frequencies for specific modeled scenarios.

Leaks are divided into three scenarios, allowing analysts to use frequencies for only those scenarios that are compatible with their QRA outflow modeling. Standardized leak frequencies have been developed for different types of process equipment, using leak frequency functions to ensure that consistent, nonzero frequencies are available for any equipment type and hole size. The results are consistent with traditional onshore leak frequencies, while also being traceable to specific incidents among the modern high-quality offshore leak data. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005