The potency of a magnetic field is measured in terms of Gauss. And therefore, by definition, degausse means to reduce/eliminate the strength of the magnetic field. Degaussing coils are used to reduce the effect of Earth magnetic field on the ship’s magnetic field.
A magnetic mine is activated when the earth’s magnetic field is distorted by the magnetism of a passing steel ship. This property of the change in magnetic field was extensively used during the world war II. The process of Degaussing the ship/submarine was originated at the time of second World-war as a preventive action for not being sensed by the magnetism sensing mines laid out by the enemy ships. Degaussing may also be termed as ‘Magnetism concealing method.
There are 03 in number groups of electro magnetic coils ( one each for the three axis i.e. Three sets of electro-magnetic coils (for longitudinal/vertical/athwart axis) fitted onboard. These coils are known as Degaussing coils also. The Degaussing coils arrangement is such that whenever a DC current is passed through them, they generate a magnetic field which is same but in opposite direction to the ship’s permanent magnetism. This generated magnetic field counteracts the ship’s permanent magnetic field and nullifies it. After carrying out the degaussing, the ship almost become magnetically undetectable. And so, the odds of being sensed by magnetism sensing mines are very low.
The degaussing is achieved by use of direct current coils (degaussing coils) that produce a magnetic field which is directed in the opposite direction of the original magnetic field of the ship. A ship has three axes:
Vertical Component V (Vertical)
Lateral Component A (Arthwartship)
Longitudinal Component L (Longitudinal)
The degaussing coils are arranged parallel with the ship’s three axes and are compensated independently of each other. The various magnetic fields acting on a ship are :
- Permanent Fields
- Induced Fields
- Eddy-Current Fields
- Stray Magnetic Fields
The Degaussing system compensates only for the Permanent and Induced fields. The other two are not compensated, as their effect is minimal. The coil system is so arranged that they cater for the Permanent/Induced field separately.