Q) Sketch and Label Mid-Ship Section of a Double Hull Oil Tanker.
- The above figure is the midship section of a double hull tanker. The right half of the drawing shows an ordinary frame, where the outer and inner hull plates are longitudinally framed. The centre tank is used for storage of cargo oil, and the wing tanks or segregated ballast tanks (SBTs) are used for carrying sea water ballast. The SBTs are epoxy coated so as to prevent corrosion. Do observe that the longitudinal stiffeners on the wing tank longitudinal bulkhead are placed towards the wing tank, and not the centre cargo oil tank. Why? In order to prevent oil accumulation on them. The double bottom spaces are also used for water ballast, and the stiffeners on the inner bottom plating are always towards the double bottom space.
- A deep transverse web frame (left half of the above figure) is given at every three to four frame spaces in order to provide transverse strength to the ship. The longitudinal stiffeners are welded to these web frames. Stringers are provided on these transverse webs to provide further strengthening.
- Today, irrespective of the classification society certifying the design of a tanker, the structural design of double hull tankers is done according to The Harmonised Common Structural Rules (CSR) for Tankers, by IACS.
