Routine industrial operations include the use of high pressure and high and low temperature piping, tanks and vessels to store gases and liquids necessary for manufacturing operations or product processing. PEC Associate Engineer Tosh Edrisi and Sr. Principals Kirk Marchand and Chuck Oswald provide support to industrial clients in the manufacturing, aerospace and energy industries to identify and mitigate hazards associated with ruptures, venting and spills from these systems.
The accidental rupture of piping, vessels or valves containing gas or liquids can generate several hazardous conditions. Inflammable (inert) gases and liquids, when stored at high pressure, can release energy in the form of overpressure and blast or can generate debris as the storage vessel, piping or valves rupture. Pressure release can be in the form of a simple volumetric expansion for gases, or can be the result of BLEVEs (boiling liquid expansion vapor explosions). Flammable mixtures or gases that, when combined with air or accelerants and exposed to an ignition source, can burn or ignite and explode. Lower density mixes can ignite and become vapor cloud explosions. These vapor cloud explosions can produce significant overpressure at long durations depending on the volume of the release, the amount of “mixed” material between the flammability limits, and the amount of obstruction in the vicinity of the ignition source and flame front. Higher density gases and liquids can ignite and become pool fires, releasing significant heat and becoming the secondary ignition source for building and equipment fires.
Our engineers have supported clients in industrial operations and hazards ranging from the routine to the complex. Routine investigations might consider the hazards associated with “bottle docks” at plants and facilities where inert gases such as oxygen, argon and nitrogen (for medical uses or for industrial “drying” and “cooling”) and flammable gases such as acetylene, propane and hydrogen (for welding and combustion) are stored in modest quantities. Accidental rupture of these bottles through impact or fire can be the source of overpressure, debris and vapor explosions. More complex investigations involving these hazards have been performed for clients in the testing business. We have designed test cells to contain vessel and piping proof test setups, where systems are routinely tested to MEOP (maximum expected operation pressure) or greater (typically 20-50% over MEOP). Test cell structure, observation ports (windows) and closures/doors are designed for overpressure and debris for these clients. We have also assessed hazards and provided mitigation schemes, structures and devices for aerospace clients developing and testing systems and sub-systems for launch vehicles and spacecraft.
As critical as structural and architectural vulnerability assessment and design are for our clients, human injury mitigation plays a larger role in our assessments. We routinely include calculations of probability of ear injury, lung damage and overall body injury due to “whole body translation” as a part of our assessments and validation of mitigation schemes and designs. We generally perform and document our analyses and designs using the procedures and methods of CPR 14E, “Methods for the Calculation of Physical Effects”, (commonly called the “Yellow Book”) published by the TNO in Belgium. The procedures and approaches in that document (for non-reactive rupture, reactive combustion (vapor clouds), BLEVEs, pool fires, debris velocity and injury calculation) are well accepted and contain sufficient detail in their scope such that results are not overly conservative. For more complex scenarios or where less conservatism is desired or warranted, computational fluids dynamics software and testing can be used to confirm our assessment and design approaches.