DEEP TANKS

Deep tanks are tanks on board ship in which liquid cargoes are transported.

Deep tanks may be found on board Tankers, they may also be constructed on board general cargo ships.

Deep tanks on board Tanker ships are generally located abaft the collision bulkhead. These tanks are only used for storing extra fuel on ships which make long international voyages, or calling at port where bunkers are not readily, or not at a competitive price.

Deep tanks extend through the depth and breadth of the ship abaft the collision bulkhead, in addition forward and aft of the deep tank a void space is retained known as the cofferdam.

The deep tanks and the cofferdam are sub-divided with one or more longitudinal bulkhead. Fuel heating and pumping system must be fitted.

On Board General cargo ships, deep tanks are of two types:

1. Dedicated liquid carrier deep tanks.

2. Multi-purpose deep tanks

1. DEDICATED DEEP TANKS

Location of the dedicated deep tanks are planned during the constructional stage of the ship.

In case of a single deck General cargo ship, deep tanks extend from the tank top to weather deck, this volume could be a part of the cargo hold or a entire small hold.

ln case of a Tween Deck General ship, Deep tank could be a part of the lower hold.

ln cases of dedicated Deep tanks in a tween deck ship, the man hole will be of the flushed to deck, however, in case ofa single deck ship, flushed or coaming type of man hole may be found.

2. MULTI - PURPOSE DEEP TANKS

ln case of a single deck General cargo ship, deep tanks extend from the tank top to weather deck, this volume could be a part of the cargo hold or a entire small hold.

ln case of a Tween Deck General ship, Deep tank could be a part of the lower hold.

ln cases of Multi-purpose Deep tanks in a tween deck of a single deck ship, the access way will be of large hatch cover type , suitable for small general cargo operations.

GENERAL

In case of dedicated deep tanks, cargo heating coil arrangements could be open on the tank top or concealed under the tank top, however, in case of multi-purpose tanks, cargo heating system will

always be concealed under the tank top and bilge pumping arrangements must be provided.

ln both cases, extra strengthening of the Bulkheads, shipside and tank top must be provided; the tanks must be provided with sounding and air pipes.

Temperature may or may not be provided

ON BOARD GENERAL. CARGO SHIP - TWEEN / SINGLEDDECKER.

Deep Tanks" are specially designed compartments for carriage of Dry Cargoes, liquid cargoes or ballast, these tanks may be located in the Lower Hold in case of Tween Decker or extend throughout the depth of the cargo hold in case of Single Decker.

Deep Tanks may be designed for multipurpose use QR designated for liquids only. In case of multipurpose deep tanks, General Cargoes / Dry Bulk Cargoes can be loaded  and stowed through large tank openings provided on the Tween Deck / weather deck; the closing arrangements is with heavy steel covers designed with suitable securing arrangement tor water tightness. The opening can be at Tween Deck level or on the Weather Deck.

In case of deep tank designated for liquids only, the tank opening design can be of flushed manhole type or tank access way of coaming type. In both cases the covers must be Water Tight.

ON BOARD TANKERS

The deep tank is generally located abaft the Collision Bulkhead and forward of the cargo tank.

A cofferdam is located Forward and Aft of the deep tank to avoid contamination in case of a leakage/puncture in the water tight bulk-head.

The deep tank is generally used for carriage of Ship’s fuel.

PARAMETERS OF DEEP TANK ON BOARD SHIP/GENERAL CARGO & TANKERS.

Deep Tanks may be divided by a center line bulkhead to form Port & Starboard tank. Deep tank tank is space confined between center line bulkhead and Hull plating on each side of the ship; Forward and Aft watertight bulkhead, and between Tank Top and Tween Deck or weather deck as the case may be.

The shipside frames are closely spaced in way of deep tanks in no case not more than 600 mm apart.

Tae Fore & Aft watertight bulkhead plates are thicker at the bottom than normal bulkhead, enable them withstand the head pressure exerted by the liquid.

The Fore & Aft bulkheads and center line bulkhead must he adequately strengthened with vertical and horizontal stiffeners to with stand the free surface effect.

The vertical stiffeners must be attached at the Deck Head & at the tank top with brackets / knees.

The Deep Tanks must be pumping arrangements & heating coils system.

The Deep Tanks, must be provided with Sounding pipe, Temperature pipe, & Air pipe, they must be fitted with water tight closing arrangements.

ln case of multipurpose deep tanks, hold bilge system must he provided.