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Author(s): L. Demilier, C. Durand, C. Rannou, E. Hogan, M. Krupa,
A. M. Grolleau, J. Blanc & A. Guibert
Abstract:
The Corrosion Related Magnetic Field (CRM) is a part of the static magnetic
signature of ships that cannot be precisely quantified for steel hull ships because
of the ferromagnetic signature that is added to the CRM in magnetic
measurements.
For this reason, the CRM is generally evaluated by computation.
Most of CRM models are based on analytical formulas of the magnetic field
due to electric dipoles which decrease more slowly with distance than the
magnetic signature due to ferromagnetism (spatial decay law in 1/r2 instead of
1/r3).
This is the reason for the following assumption usually met in the technical
literature: CRM is dominates the ferromagnetic signature at long distance.
But
theses models don’t take into account a significant part of the CRM source: the
currents that flow through the metallic structures of the ship.
As a result,
conclusion on the distance for which the CRM is dominating the ferromagnetic
or the distance for which the CRM remains important can be corrupted.
CRM measurements have been carried out on a ship mock-up to validate a
new Finite Element software for CRM that takes into account all the CRM
sources: currents in the sea and currents flowing through the metallic structures
of the ship.
This paper describes the measurements of low levels of CRM on the
mock-up, and the first results of its validation with measurements.
Keywords:
cathodic protection; electromagnetic silencing; CRM; UEP; MINE.
...
Pages: 10
Size: 1,354 kb
Paper DOI: 10.2495/ECOR070231
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