Wednesday, June 22, 2011

Conditions of assignment

In the name of ALLAH who is the most beneficient and merciful

The load line rules are based on the very reasonable assumption that the ship is built to and maintained at a high level of structural strength and will sail in a safe and seaworthy condition.

Until recently the rules laid down the standard of longitudinal and transverse strength. The classification societies usually found it necessary to increase these standards although in some design considered the rules excessive. It is now felt that the structural strength of the ship is more properly the function of the classification societies who may well be the assigning authority.

Standards of stability are given in the rules for both small and large angles of heel. Details of the information required to be carried on a ship are stated, together with typical calculations, all the information is based on an inclining experiment carried out on the completed ship in the presence of a DTp surveyor.

It is essential that all openings in the weather deck are water tight. Hatch coamings, hatch covers, ventilator coamings, air pipes and doors must be strong enough to resist the pounding from the sea and standards of strength are laid down. The rules also specify the height of coamings, air pipes and door sills above the weather deck, those at the force end being higher than the remainder.

It is important to remove the water from the deck quickly when a heavy sea is shipped. With completely open decks, the reserve buoyancy is sufficient to lift the ship and remove the water easily. When the bulwarks are fitted, however, they tend to hold back the water and this may prove dangerous. For this reason openings knows as freeing ports are cut in the bulwarks, the area of the freeing ports depend upon the length of the bulwark. If the freeing ports are wide, grids must be fitted to prevent crew being washed overboard. In addition, scuppers fitted to remove the surplus water from the deck. The scuppers on the weather deck are led overboard whilst those on intermediate decks are may led to bilges or, if automatic nonreturn valves are fitted, may be led overboard.

Type A ships, with their smaller freeboard are more likely to have water on the decks and it is a condition of assignment that open rails be fitted instead of bulwarks. If the vessel has midship accommodation, a longitudinal gangeway must be fitted to allow passage between the after end and midships with out setting foot on whether deck. In larger ships it is necessary to fit shelters along the gangway. Alternatively access may be provided by an underdeck passage, but while convenient for bulk carriers could prove dangerous in oil tankers.

WRITTEN BY S/C ZEESHAN AHMED (A/C 2988)
INSTRUCTOR: CHIEF ENGINEER YASEEN SAHAB
DATE: 25/10/2009
TIME: 10:05:00 AM