A guide to ballast tanks on ships bp gas prices ny


Similar in construction to the topside ballast tanks, these water ballast tanks are located on the bottom wing sides of each cargo hold of the ships, and they are kept in continuation to the double bottom tanks which run through the centre of the vessel. The hopper tanks provide the following advantages:

In some ships, such as container and bulk ship, the double bottom space is divided transversely into three sections (instead of two). This is done to provide a cofferdam in the centre known as the`duct keel’ which are used to carry ballast and bunker tank valves, and pipings for ships ballast tank and bunkering system.

The valve used to control the flow of water in the ballast tank can either be manually controlled butterfly valve or hydraulically operated remote valve. For fore and Aft peak tanks, only remote control (hydraulic) valves are used due to their location. Types of Ballast Tanks As Per Usage On Oil Tankers

As per MARPOL Annex 1, Regulation 18 – Every crude oil tanker of 20,000 tonnes deadweight and above and every product carrier of 30,000 tonnes deadweight and above delivered after 1 June 1982, as defined in regulation 1.28.4, shall be provided with segregated ballast tanks.

Multiple ballast pumps are provided in the engine room which takes the suction from the main seawater line (from sea chest) and during the deballasting operation, they discharge the water from ballast overboard line and valve. The CCR is provided with the ballast tank level monitoring system, and the pump cutoff is controlled once the water level reaches the sensor level to activate the trip.

The volume monitoring of the ballast tank is done to achieve the ballast/ deballast rate of the pumping system. This is done by the loadicator software installed on the ship, and the ship’s officer will manipulate the results displayed by the loadicator to operate the fill/ discharge valve of the ballast tank.

The change in the volume of the ballast tank is used to calculate the ballast pump rate, which in turn, determines the time needed to finish the ballasting or deballasting operation. This helps the chief officer to complete the stability operation in time to maintain the ship’s Estimated Time of Departure (ETD). Ballast Tank Protection

Coating in the tank surface is the most common protection system used on the ship. The advantage of the coating is that it protects the entire tank at a time and if the right quality of coating is applied, the ballast tank can work without any problem for a long period. It is the layer of the coating which protects the seawater to come in contact with the steel of the tank.

If the atmosphere of the ballast tank can be controlled to reduce the oxygen content, the corrosion rate decreases drastically. This system is known as oxygen stripping which is done by introducing inert gas to maintain the oxygen level in the tank below 4%.

The extent of corrosion inside tank surface should be noted, and localised corrosion should be marked appropriately. If the corrosion wastes of the tank surface exceed 75% of the allowable margin, repair such as renewal of hull structural to be carried out.

Coating plays an important role in ship ballast water tank surface protection hence proper inspection of coating to be performed. Visible failure of the coating to be noted along with rusting of tank surface especially on the weld lines and edges of the tanks.

The history of the ships (previous inspection records) plays a critical role in the current inspection method followed and even records of sister vessel can be used to decide for repair, if needed, followed by a survey and pressure testing of the ballast tank post repairs.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.