Tubular primers

The primary safety considerations in the formulation, manufacture, and use of explosives are that they must never explode prematurely but always explode when desired. Often this balance is achieved with an insensitive main charge being initiated by the least amount of a more sensitive explosive. This concept is expanded to that of an explosive train in which a series of decreas-ingly sensitive explosives is ultimately sufficient to initiate an insensitive main charge. The sensitivity of explosives to initiation provides a common means of classification  

Other explosives may be added to explosive trains to sensitize certain components or add a time delay. There are as many combinations as necessary to 

Mercury fulminate detonators were widely replaced due to their extreme sensitivity. Contemporary simple nonelectric detonators contain a small quantity of primary explosive (often lead azide) which, once ignited by a fuse, ignites the more powerful base charge of a secondary explosive (an additional low explosive may be used between the fuse and the primary explosive). 

Often another controlled volume of low explosive is placed between the matchhead and the primary charge. This bums for a specified period introducing a delay (from a few milliseconds to a few seconds) into the detonator. However, any low explosive delay device syn. delay electric igniter) introduces imprecision because the chemicals are affected by moisture, temperature, and time. High precision delay electric detonators implant the match-head directly into the primary explosive and control the delay with an integrated circuit within the detonator. 

Detonators for ammunition include primary explosives to detonate the main charge. They may or may not be co inected to a fuze. 

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Other primers are detonated by electricity, heat, or friction. In larger ammunition, such as for cannon, tubular primers may include a supplementary low explosive and be used to fire bag charges. 

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