Electric Blasting Caps with delay

The electric blasting cap (EB cap) consists of a cylindrical aluminum or copper shell containing a series of powder charges ( Figure 28). Electric current is supplied to the cap by means of two leg wires that are internally connected by a small length of high-resistance wire known as the bridge wire. The bridge wire serves a function similar to the filament in an electric light bulb. When a current of sufficient intensity is passed through the bridge wire, the wire heats to incandescence and ignites a heat-sensitive flash compound. Once ignition occurs, it sets off a primer charge and base charge in the cap near instantaneously. Instantaneous EB caps are made to fire within a few milliseconds (ms) after current is applied. Instantaneous caps contain no delay tube or delay element.