(78n) Pressure Vessels Burst Directional Blast Effects

A pressure vessel burst (PVB) is a class of explosion that presents both blast and fragmentation hazards at virtually all chemical processing facilities. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. All of the published blast curves were developed for spherical vessel bursts. Unfortunately, pressure vessels predominantly in use in industry are cylindrical vessels, not spherical. Blast effects around a bursting cylindrical vessel are not uniform as they are for a spherical vessel. A blast occurring to the side of a cylindrical vessel is stronger than to the ends, creating non-circular pressure contours. The directional effects diminish with distance as the shock wave becomes spherical. A correlation was developed in the 1970s to account for directional effects using high explosive test data, the best available resource at the time. Like all test programs, pressure transducers extended to limited distances from the explosive charge, yet the data are often incorrectly extrapolated to greater distances. This paper presents the numerical results of recent research on directional effects specific to bursting cylindrical pressure vessels and provides new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions. The results can be used to predict the blast hazards from cylindrical PVBs over the range of standoff distances for which directional effects exist.