Applying Isd to the LPG Terminal Involved in the San Juanico Disaster Through the Use of QRA

Inherently Safer Design (ISD) or Inherently Safer Technology (IST) is a concept that, in direct relation to the process industries, dates from 1974, when, after the Flixborough explosion Trevor Kletz questioned the need for such large quantities of hazardous materials to be stored in process plants, as well as the need for processing at such elevated pressures and temperatures. The Center for Chemical Process Safety (CCPS) has produced a definition for Inherently Safer Technology:

“Inherently Safer Technology (IST), also known as Inherently Safer Design (ISD), permanently eliminates or reduces hazards to avoid or reduce the consequences of incidents. IST is a philosophy, applied to the design and operation life cycle, including manufacture, transport, storage, use, and disposal. IST is an iterative process that considers such options, including eliminating a hazard, reducing a hazard, substituting a less hazardous material, using less hazardous process conditions, and designing a process to reduce the potential for, or consequences of, human error, equipment failure, or intentional harm. Overall safe design and operation options cover a spectrum from inherent through passive, active and procedural risk management strategies. There is no clear boundary between IST and other strategies.”

CCPS divides ISD strategies into four categories: substitute, minimize, moderate and simplify. In this work, these four strategies will be applied to the design of a LPG terminal, based on the one involved in the San Juanico Disaster (Mexico, 1984). Through the application of the principles of ISD, different designs for the installation will be obtained, using different types of technology, number of equipment and layouts, and through the use of QRA, the risk associated to each one of them will be estimated; also, the risk associated to the original design (that suffered the accident) will be estimated. Finally, all the designs will be compared, and the one that represents the lower risk will be said to be inherently safer than the others. This work will allow demonstrating how long the industry has come in terms of safety and design since the days of the San Juanico disaster, and how ISD is a powerful tool to be used at the moment of designing a project.