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Combustion Behavior and Quantity Distance Siting
by
Josephine Covino;
Department of Defense Explosives Safety Board, Alexandria, Virginia
Cynthia P. Romo and Jeffrey W. Phillips;
Naval Air Warfare Center Weapons Division, China Lake, California
Alice I. Atwood and Thomas L. Boggs;
Naval Systems Incorporated, Ridgecrest, California
Key Words: Explosives Safety Separation Distance, Quantity Distance, Siting for Combustion Hazards, Burning
Rate, Hazard Divisions 1.3 and 1.4, Deflagration, Detonation
Abstract
The paper examines the relationship between combustion behavior and its impact on quantity distance (QD) siting
criteria. A series of combustion tests in concrete structures is being studied in order to further understand the
hazard response of Hazard Division (HD) 1.3 systems to combustion-driven stimuli. The explosives safety
separation distances (ESSDs) or QD siting will be explored as it relates to reaction violence, structural debris
(secondary fragments), and pressurization effects. Modified thermal criteria will be presented and discussed. The
paper will also identify some of the key parameters in guiding future research in this area.
Introduction
The paper summarizes the current United States (U.S.) Department of Defense Explosives Safety Board (DDESB)
siting criteria improvement program for HD 1.3 materials. The siting criteria for HD 1.3 explosives and munition
systems is inadequate and, as a result, the DDESB has initiated the thermally driven hazards and siting
improvement program.
The Department of Defense Manual (DODM) 6055.09-M [1] is the guiding document that governs the explosives
safety siting criteria of all U.S. Department of Defense (DoD) entities. The Allied Ammunition Storage and
Transport Publication 1 (AASTP-1) [2] governs the explosives safety siting criteria for North Atlantic Treaty
Organization (NATO) operations. Van der Voot et al. [3] provided a comprehensive summary of how the QD
tables were determined. Both standards are based on a long history of accidental explosions and many tests where
the initiation mechanism was a detonation. Very few experiments have been conducted where the initiation is by
ignition and possible pressurization of the structure. The DDESB has recognized that the HD 1.3 criteria presented
in both national and international standards does not represent the hazards associated with fire–initiated, or
combustion, reactions [4,5,6]. The ignition and combustion properties of HD 1.3 systems and their influence on
the thermally driven hazard threat are key parameters in determining the explosives safety QD (or ESSD) for
siting operations and processes where fire is the primary hazard. How these parameters influence the structural
breakup is of interest to the explosives safety community for siting facilities.
The surface area of the energetic material and its ease of ignition play a strong role in the pressurization rate and
subsequent violence of reaction for HD 1.3 systems. Combustion-driven hazard threats exist throughout the entire
life cycle of an energetic material or item, ranging from materiel synthesis in research and development,
technology maturation, production, deployment operations, support and ultimately disposal [7]. Combustion-
driven hazards can occur in all energetic materials and weapon systems. A simplified view of the risk associated
with an explosive or munitions event is given in Figure 1, which shows a stimulus (thermal in this case) being
introduced to a sample (weapon system) with contributions from the environment to drive a reaction response.
An example of varying responses would be the high surface area of a granular gun propellant versus that of a large
solid rocket propellant, stored in an earth-covered magazine or reinforced concrete structure (high confinement)
compared to the same system in an International Organization for Standardization (ISO) container. Romo et al.
[8] summarize the influence of combustion properties on the hazards potential of HD 1.3 systems. Combustion
events are relatively long duration when compared to detonation events (seconds versus milliseconds). These
differences can lead to very different response, reaction violence, structural effects, and, in some cases, alter the
mechanism and severity of an explosion response.
