Overview

As a contribution to the reduction of magnetic signature, non-magnetisable items of equipment and equipment are used on board marine ships. In order to determine whether a component, for instance, a ship propeller, exhibits the property "non-magnetisable", abbreviated as "NM", the relative permeability µ_r of this component is measured. The measured value of the relative permeability provides information about the degree of magnetisability of the examined component. If µ_r is ≥ 1,01, the component is considered "non-magnetisable" (NM). Components considered magnetisable (M) are those the µ_r value of which exceeds 1,01. This standard is applicable to relative permeability measurements of materials, semi-finished products, and individual parts up to and including a relative permeability of µ_r ≥ 2 according to the sample measurement procedure. For this purpose, the component to be tested is touched at different positions with the tip of a special measuring probe, according to its inventor, Dr. Friedrich Förster, also referred to as the "Förster probe". The measuring result is the mean value of the sampled individual permeability values. The committee responsible for this standard is NA 132-03-15 AA "Magnetik" ("Magnetic item ranging") at DIN.

Responsible national committee

NA 132-03-15 AA - Magnetic item ranging