Ray A. Mentzer

Normalization of process safety lagging metrics

This article explores new process safety metrics for measuring process safety performance in the chemical processing industry. While Process Safety Management enables an operation to optimize their process safety programs and organizational risks, there is an emerging need to evaluate process safety implementation across an organization through measurement of key indicators. Lagging metrics utilize process safety incidents as the numerator and divide it by an appropriate process‐related denominator or “normalization factor.” Currently, work hours is used extensively as a normalization factor to evaluate safety performance in the process industries. However, this lagging metric does not directly reflect process safety information and may not accurately reflect the safety performance of the process. Modified denominators are explored in this study and compared with the existing time‐based denominator to validate the effectiveness and applicability of the new metrics. Each proposed normalization factor was validated using available industry data. A statistical unitization method has been used to convert incident rates of different ranges for the convenience of comparison. Results show that some proposed process‐related metrics have potential as alternatives, used along with the time‐based metric, to evaluate process safety performance within organizations.

Experimental and numerical study of liquefied natural gas (LNG) pool spreading and vaporization on water

The investigation of pool spreading and vaporization phenomenon is an essential part of consequence analysis to determine the severity of LNG spills on water. In this study, release of LNG on water during marine operations is studied through experimental and numerical methods The study involves emulation of an LNG leak from transfer arms during side by side loading operations. The experimental part involves flow of LNG in a narrow trench filled with water and subsequent measurement of pool spreading and vaporization parameters. The numerical part involves CFD simulation using a three dimensional hybrid homogenous Eulerian multiphase solver to model the pool spreading and vaporization phenomenon. In this method, LNG is modeled as dispersed phase droplets which can interact with continuous phases - water and air through interphase models. The numerical study also employs a novel user-defined routine for capturing the LNG vaporization process. The CFD solver was capable of capturing the salient features of LNG pool spreading and vaporization phenomena. It was observed from experiment and CFD simulation that wind influenced both pool spreading and vaporization phenomenon through entrainment and convection.