Delay detonator

A delay detonator for causing output device detonation a predetermined delay period of time following ignition of the detonator, comprising:

• a metal body, a primer fitted at an inner end of the body, a recess opening from the primer into an expansion chamber, a first-fire combustion section including first-fire ignition powder separated from the expansion chamber by a retention screen, a delay column proximate the first-fire combustion section including a delay powder composition to be ignited by the ignition powder, the delay column being of a relatively high length/diameter aspect ratio, a further combustion section including first-fire ignition powder for ignition by the delay column after a delay burn time thereof, and a detonator output assembly at an opposite, outer end of the body for ignition by the further combustion section;
• the delay column having a burn time which accounts substantially entirely for said predetermined delay period, being cylindrical in form and of constant diameter, and of a length/diameter aspect ratio of approximately 3:1, containing a tungsten delay composition, and being assembled by three successive charges of delay composition of essentially equivalent weight, loaded at equivalent pressures.