Session: 14-02-02: Reliability and Risk in Energy Systems

Paper Number: 111159

111159 - Dependency of the Blast Wave Characteristics on the Rupture Mode of a Failed Pneumatic Test of a Pipe Segment 

Pneumatic test failure results in high-pressure blast waves that propagate outward and impact humans, structures, and objects, potentially causing fatality and damages. To mitigate the risk of such damage, codes recommend safe exclusion distances depending on the stored energy that would release and drive these blast waves.  However, there are different opinions about the amount of stored energy and how to quantify it in a more definitive and  science-based manner. As such, the approach taken in this work was to study the relevant blast wave characteristics generated from four different modes of pipe failure bracketing two extreme pipe failure modes. One extreme  assumes the pipe ruptures in a totally arrested fracture such that the pipe severs, and two-sided full cross-sectional area ejecting high-pressure directional  jets drive the external blast waves. The other extreme is a pipe rupture in an un-arrested longitudinal running ductile fracture along the entire length of the pipe so that the contained high-pressure test medium is released to ambient radially in a cylindrical (or semi-cylindrical) fashion. Other intermediate modes of ruptures are also considered between these two extremes, based on a fixed rupture length of 8D according to ASME PCC-2,  or an actual  ductile fracture arrest length based on fundamental fracture mechanics.  Respective correlations are provided to aid in the development of risk assessment programs, and safety management plans prior to commencing a contemplated pneumatic test in a given environment and surrounding infrastructures.  The developed correlations are based on stored energy quantified in terms of kg of TNT at the point source into a free-air ambient environment, and the relevant blast wave characteristics.  The commonly used scaled distance concept described in the literatures relates the normalized overpressure to the scaled distance normalized with the cube root of the source energy.  It was found that the blast wave characteristics in terms of overpressure, impulse, arriving time and impulse duration are not only very dependent on the failure mode of pipe rupture, but also whether the object of concern is located in the near field or the far-field from the respective point of energy release.  The two extreme modes of pipe rupture were found to generate higher overpressures and impulses, particularly at the relatively far field than that generated from the intermediate modes.  This is important findings and should be considered in the development of risk mitigation plans prior to commencing a pneumatic test in a given environment, test conditions and surround structures.

Presenting Author: Andrew Hawryluk NOVA Chemicals

Presenting Author Biography: Andrew Hawryluk is a Senior Engineer with NOVA Chemicals with 15 years of mechanical engineering experience. He has a B.Sc. in mechanical engineering from the University of Calgary.

Authors:

Kamal Botros NOVA Chemicals
Andrew Hawryluk NOVA Chemicals
Eric Clavelle NOVA Chemicals
Michael Martens TC Energy