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What is the function of the ribs on the insulator?

By Li Chenyu / hcfire360 November

A They ensure insulation and prevent flash-ove


What is flash-over?
Flash-over is when there is a spark between the terminal and the metal shell, as shown in the picture.
Flash-over can be prevented by the following.
Ribs are provided on the insulator to extend the surface distance of the insulator between the terminal and the metal shell. This ensures the insulation needed for preventing flash-over.
The correct spark can be maintained by the spark gap.

During sparking:
High voltage is constantly applied between the terminal and metal shell.

This high voltage tries to leak along the surface of the insulator.

If the voltage required by the spark gap is high, flash-over can easily occur.

Flash-over resistance voltage

NOTE : Always ensure that SPARK PLUG COVERS/CAPS are clean. Old or dirty SPARK PLUG COVERS/CAPS increase chances of flash-over.