Electrical Continuity Alone Is Not Enough

Blasters check continuity during explosives safety training supported by ERM.

Blasters check for continuity during explosives safety training supported by ERM.

Recently, ERM assisted a client with a safety issue regarding the use of electric detonators.  The client’s safety policy called for ensuring that electric detonator circuits showed “continuity” before attempting to fire the shot.

Although that is a good practice, we advised the client that a better practice would be to require measurement of the circuit resistance and comparison of that number to the expected resistance.   The expected resistance is determined by measuring the resistance of the individual components of the circuit and calculating the expected resistance once they are assembled into a circuit.

The problem with simply checking for continuity is that it provides assurance that there is a pathway for the electrical current to flow, but it does nothing to assure that the path goes through the bridgewire of every electric detonator.   Many misfires have occurred because the blaster was fooled by continuity into thinking the shot would perform as planned.

Make sure you are not fooled the same way.

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