Definition
The Velocity of Detonation, abbreviated V.O.D, is the speed at which the detonation wave front travels through a detonating explosive. It is a steady state property of a self sustained detonation, distinct from the burning rate of a deflagration.
For any given explosive, the V.O.D depends on the formulation, the density, the particle size, the charge diameter and the degree of confinement. Environmental factors such as ingress of water, static and dynamic pressure also influence the value reached in the field.
Units and orders of magnitude
V.O.D is expressed in meters per second (m/s), kilometers per second (km/s) or feet per second (ft/s). Industrial bulk explosives typically detonate between approximately 3,000 and 6,500 m/s. Military high explosives such as TNT, RDX or HMX based compositions can exceed 8,000 m/s. Detonating cords sit between roughly 6,000 and 7,500 m/s depending on the core load.
Why measure V.O.D
V.O.D controls how energy is released by the explosive as a combination of shock energy and heave energy. This balance directly affects rock fragmentation, muck pile profile, throw and the cost of extraction in mining and quarrying. In manufacturing, V.O.D is a quality control indicator that ties back to formulation, sensitization and aging.
Published V.O.D values describe ideal conditions. In real blast holes, the actual V.O.D can deviate significantly because of diameter, confinement, water content, temperature or substandard initiation. The only way to verify performance is to measure V.O.D in operating conditions.
How V.O.D is measured
A V.O.D recorder times the passage of the detonation wave between two or more sensing points placed along the explosive column at known distances. Dividing the distance by the time of flight returns the average V.O.D over each interval.
Two families of sensors are commonly used. Continuous resistive probes deliver a resistance versus time curve from which V.O.D is derived. Point by point fiber optic probes detect the light flash emitted by the detonation as it reaches each fiber tip. Fiber optic methods are insensitive to electromagnetic interference and well suited to harsh field conditions.
For a deeper comparison of methods, see V.O.D measurement methods.
Kontinitro instruments
Kontinitro V.O.D recorders use fiber optic point by point measurement. The Explomet 2 Series is the laboratory reference instrument, with six fiber inputs, five counters and a ±0.01 microsecond timing precision. The Explomet 3 is engineered for field deployment in quarries, mines and operational test sites, and works with the EasyProbe System and the DCS Duplex Cable System.
For very large measurement campaigns, the High Capacity Systems extend the Explomet 2 platform to 20, 24 or 30 channels.
FAQ
What is Velocity of Detonation in simple terms?+
Velocity of Detonation, or V.O.D, is the speed at which the detonation wave front travels through a column of explosive once initiation occurs. It is the single most cited performance indicator of a high explosive.
What are typical V.O.D values?+
Industrial explosives such as ANFO, emulsions and watergels typically detonate between about 3,000 and 6,500 meters per second. Military high explosives such as TNT, RDX and HMX based formulations can exceed 8,000 meters per second. Actual values always depend on density, diameter, confinement and initiation.
Why does V.O.D need to be measured?+
Published V.O.D values describe an explosive in ideal conditions. In the field, the real V.O.D depends on charge diameter, confinement, water ingress, temperature, density and initiation. Measuring the actual V.O.D in your conditions is the only way to verify performance, validate quality and optimize blast design.
What instrument measures V.O.D?+
Dedicated V.O.D recorders are used. They time the passage of the detonation wave between two or more sensing points along the explosive column, then compute the speed. Kontinitro Explomet instruments record the light pulse emitted by the detonation through plastic optical fibers and return V.O.D with ±0.01 microsecond timing precision.