The ship would normally be swung after any of the following circumstances:
(a) Following a collision or a grounding incident where major repairs are required to be made to the ship, which could affect the vessels permanent and induced magnetism.
(b) In the event of a major fire on board the ship.
(c) If engaged on a long charter trading in high latitudes, i.e. ‘Hudson Bay’.
(d) After leaving the builders yard as a new ship.
(e) If loading a high capacity metallic cargo, e.g. railway lines on deck.
(f) In the event that compass errors became excessively large for no apparent reason or the compass becomes unreliable.
(g) If electrical or magnetic equipment is added or removed to/from the proximity of the magnetic compass.
(h) In the event that a period of 2 years has elapsed and the ship is without a record of deviations, or when the compass shows a physical defect when first installed.