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A Retrospective Study on the Safety of Waterjet (WJ) and Abrasive
Waterjet (AWJ) Processing of High Explosive Ordnance
Paul L. Miller; Gradient Technology; Elk River, MN, USA
Keywords: Hazards Analysis, Waterjet, Abrasive Waterjet; Explosive Initiation; Demilitarization; Ignition
Hazards
Abstract
Waterjets (WJs) have been used for the demilitarization of high-explosive ordnance for over ninety years and
abrasive waterjets (AWJs) have been used for cutting high-explosive munitions for about thirty years. This study
reviewed the process safety of the technologies from the early low-pressure systems to the physical limits of the
systems at 1,000 MPa (147 ksi
1
). Several major safety studies focusing on processing over 700,000 projectiles were
distilled into this summary.
A summary of various hazards analyses on WJ and AWJ processes provided a probabilistic risk assessment to
determine what could go wrong, how likely the failure was, and what would be the likely consequences of the
failure. The summary analysis looks at initiation mechanisms, such as shock, impact, electrostatic discharge (ESD),
piezoelectric discharge (PED), friction, shear, thermal particle, and autothermal decomposition.
1 Introduction
Waterjets (WJs) are a non-traditional technology that have evolved from a low pressure civil and mining
engineering tool to a high pressure machining tool over the last 150+ years.
2
Although still a novelty to many, they
have been used for the demilitarization of high-explosive munitions since at least the 1920s. Later WJ variants using
added abrasives, known as abrasive waterjets (AWJs), gave the technology the capability of cutting steels and other
hard materials. AWJs have been used for the demilitarization of high-explosive ordnance for almost thirty years.
This retrospective overview of WJ and AWJ safety analyses was performed to compile the available information for
explosive safety professionals.
2 Background
The invention of the first WJs is generally credited to Lt. George McClellan, U.S. Army Corps of Engineers
(USACE), as shown in Schermerhorn (1881), who argued that McClellan first used WJs on February, 1852, at
Decrow's Point, Matagorda Bay, Texas, for civil engineering projects. As with most inventions the origin is
somewhat clouded in history. Alternative arguments on the initial inventor, according to May (1970), variously give
credit for the waterjet to Anthony Chabot, Edward Matteson, and/or Eli Miller on March 7, 1853, for hydraulic
mining of gold at the French Corral mine in Nevada County, California, near the town of Dutch Flat (Hittell, 1898).
The introduction of hydraulic mining to the California gold fields had an immediate and enduring impact.
The volume of water used on the gold field hydraulic mining monitors can be inferred from Bowie (1878) who
mentions “nine-inch nozzles under 450-foot pressure” (0.23 m nozzle at 1.35 MPa [195 psi]) that operated 24 hours
a day. Lindgren (1911) stated that the monitors typically delivered about 19,000 liter/min (5,000 gpm).
1
ksi is 1000 psig.
2
WJs work by expelling pressurized water through an orifice to form a high-speed jet stream. Unfortunately, the
term “waterjets” is so broadly defined that there are at least nine different technologies all identified as “waterjets”
that are only minimally related to each other. For example, the marine propulsion technology, such as is used to
power jet-skis and the Navy “Patrol Boat, Riverine (PBR) Mk II,” is probably the most common “waterjet”
reference in DTIC.
