An insert plate is used to replace any damaged steel plate of ship's hull. The insert plate must have identical characteristics with the original steel plate ( type /grade/thickness etc). The damaged part of the steel plate has to be cropped-out and renewed by welding using the same welding consumables. The minimum consumable grades. All ship's Class Societies consider the above mentioned requirements as permanent repairs for maintaining the ship’s Classification Certificates fully valid. On the contrary, doubler steel plates which are welded on top of a damaged structure plate is considered as temporary repaired with a short limit date until the full permanent repairs are dealt with
Marine Engineering exam notes for Seafarers