The space in between the two hull layers is often used as storage tanks for fuel or ballast water. Double hulls are more extensive safety measure than double bottoms, which have two hull layers only in the bottom of the ship and not the sides.. In case of grounding or other underwater damage, most of the time the damage is limited to flooding the bottom compartment, and the main occupied areas of the ship remain intact. In case of collision with another ship, most of the time the damage is limited to flooding the side compartment, and the main occupied compartments also remain intact.
In 1979 PNSC had 41 ships in its fleet with a cumulative weight of 310 thousands dead weight tonnage and now in 2008 they have only 14 ships weighing 346 thousand dead weight tonnage.
Latest vessels acquired by PNSC are an oil tanker, which was built 1986, and the PNSC bought it in 2006. Officials told that PNSC is facing problems due to the long and complex procedure of approvals. Due to this the private companies take advantage on PNSC, sources added.
Pakistan has only three vessels despite many seaports, causing loss of business in the shipping sector, On the other hand, he added, India has 500 vessels.