- Standards for the Double Hull Construction of Oil Tankers - TP 11710 E (2009)
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- Oil Tanker Construction Rules
- Oil Tanker Construction Rules
Standards for the Double Hull Construction of Oil Tankers - TP 11710 E (2009)International and national regulations remain unaffected. For the purposes of these Rules, tankers are: a. Ships for the carriage of liquids in tanks which form part of the hull, and b. Ships with fixed tanks independent of the hull and used for the carriage of liquids. Requirements for tankers in this chapter shall apply to tankers carrying crude oil or petroleum products having a flashpoint not exceeding 60C closed cup testas determined by an approved flashpoint apparatus, and a Reid vapour pressure which is below the atmospheric pressure or other liquid products having a similar fire hazard. Category 2 : Commonly known as MARPOL oil tankers of size 20, dwt and above to carry Crude oil, Fuel Oil, Lubricating Oil or Heavy Diesel Oil as cargo and of 30, and above carrying other oils, which do comply with requirements for protectively located segregated ballast tanks. Category 3 :Oil tankers of dwt and above but less than dwt specified for Categories 1 and 2. Prevention of Hazards from the cargo and cargo vapour. Prevention of Pollution hazard. Prevention of fire hazard. Each of the above objectives are achieved only when a tanker is constructed as well as operated in accordance with well established rules and regulations. Also in the Safety Management System Manual required by the ISM code the safe operating procedures are to be given for various operations onboard the ships. Commission for Navigation on the Rhine is the oldest international organisation in modern history and was established with an objective of controlling the river transport through Rhine. The Oil Companies International Marine Forum OCIMF is a voluntary association of oil companies established in with an interest in the shipment and terminalling of crude oil, oil products, petrochemicals and gas with an objective of achieving safe and environmentally responsible operation of oil tankers, terminals and offshore support vessels, promoting continuous improvement in standards of design and operation. International Chamber of shipping is the principal international trade association for the international shipping industry, representing all sectors and trades of shipping and was established in IACS was founded on September 11,in Hamburg, Germany they are the technical body formulating precise rules for the construction of ships in line with IMO regulations. Although IACS is a non-governmental organization, it also plays a role within the International Maritime Organization IMOfor which IACS provides technical support and guidance and develops unified interpretations of the international statutory regulations developed by the member states of the IMO. IACS has consultative status with the IMO, and remains the only non-governmental organization with observer status which also develops and applies technical rules that are reflective of the aims embodied within IMO conventions. The regulations apply to new oil tankers of grt and above for which; 1. The building or major conversion contract is placed on or after 6th July2. The keel is laid or construction work commenced after 6th January3. Delivery is made or work completed on or after 6th July Construction Rules-Hull Design The entire cargo tank length shall be protected by ballast tanks. This distance h shall be measured at right angles to the shell plating and prevail upto a height of 1. Where h and w are different, at the turn of the bilge, w shall prevail at a height above 1. Suction wells of cargo tanks may protrude into the DB tank below provided that the well is made as small as possible and the height of the suction well from the bottom is not less than 0. Ballast, Vent pipes and Sounding pipes shall not pass through cargo tanks and vice versa; except for short lengths of pipes which has to be of complete welded construction or equivalent. Oil shall not be carried in spaces forward of the collision bulk head or similar bulk head in the location. The double bottom tank may be dispensed with if the weight of the cargo plus the vapor pressure is less than the outside water pressure, so that in the event of a hull failure the out side water pressure will prevent the out flow of oil, like in mid deck design. Here the depth of cargo tank is calculated as follows: 1. The wing tank partition shall extend up to the bottom shell. In the turn of the bilge area, the tank top shall extend parallel to the line of mid-ship flat bottom to meet the ship side. In smaller double hull tankers the two longitudinal divisions are omitted from a single centre tank and hence the free surface effect is increased. Due to the second outer hull the centre of gravity of the cargo is raised causing a reduction in GM. For ships loading and or offloading in port only, the GM corrected for free surfaces measured at 0 heel shall be not less than 0. In practice the resulting GM in modern smaller size Panamax double tankers are very near to the above value. The greatest problem occurs towards completion of loading or initial stages of discharging when the tanks are almost full and the ballast is almost empty with both ballast and cargo providing free surface effect and raising KG. At these stages the concerned officers should take extreme care not to reach the angle of loll, especially when multiple tanks are loaded or discharged. Other than the above designs may also be accepted by IMO provided that they offer equal amount of protection incase of a damage to the hull. One such revolutionary design was the Coulombi egg design created by the Swedish naval engineer Anders Bjokman.
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In both cases, these vessels were unsuitable for the carriage of low flash products. The lines which lead from the deck to the tanks are called drop lines. The COW main line usually branches off from the main discharge line in the pump-room. It further branches out to the various tanks on deck. There is also a small diameter line Marpol line which is used to discharge the last part of the cargo from the ship. In the cargo tanks, the pipes terminate in a bellmouth. A tank may have two bellmouths — one main and one smaller stripper bellmouth. Alternatively, one bellmouth may serve the purpose of main as well as stripping discharge. The piping system has evolved over the years to cater to varying cargo requirements. In a product tanker which is designed to carry many grades, we see that there are many more pipes so that many grades can be catered to. In a crude oil tanker, the piping is straightforward and simple. It consists of lines running longitudinally in the centre tanks and branching out to bellmouths in the centre and wing tanks. The system is uncomplicated and found on some crude carriers. It is also called the circular system. This type of piping system provides for the handling of several different types of oil. The system is very versatile. The pipeline system illustrated above in Diagram 1 is better suited to the centre line bulkhead type of ship. Each tank or oil compartment has two suctions — one Direct suction and one Indirect suction. The direct suctions for the port tanks are all on the port cargo line, and feed the port cargo pump. The indirect suctions for the port cargo tanks feed the starboard cargo line and the starboard cargo pump. Master valves are provided on each line between the tanks, so as to isolate each tank from the other when necessary. This particular vessel is not fitted with a stripping line and pump. To drain the oil from the main tanks it was necessary to list first one way, and then the other, so as to keep the strum covered and to help the flow of oil towards the suction. This ship is also fitted with a stripping system. Inspection of the pipeline system shows that the pipeline travels around the ship in the wing tanks, crossing over from one side to the other. Each wing tank has a suction on the line which passes through it. The centre tanks have two suctions, one on either side leading to the port and starboard lines respectively. It will be noted that the master valves provide separation between the tanks as in the earlier system. When the level of the oil in any particular tank has fallen to a foot or less, the main pumps are switched to another full tank, and the stripping pump is brought into operation. In this system, the oil flows freely into the aft most tanks when the interconnecting gate valves are opened. Main suction bellmouths in a full free flow tanker will only be provided in the aft tanks. However, each tank is generally provided with a small stripping line. This system has the distinct advantage of having lesser and less complicated piping system in the tanks and is suitable for large tankers which usually do not carry many grades of oil. Obviously, the flexibility of operations is comparatively less as compared to other piping systems. Some ships are also designed as part free flow i. Valves: The valves used in tankers for cargo can be either butterfly valves, gate valves or sometimes rarely even globe valves. At pump discharges, a non-return flap valve is usually fitted. A detailed description of the merits and demerits of each type of valve will be outside the scope of this course.
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Before embarking on a technical analysis of alternative tank vessel designs, standard design and operational practices related to pollution prevention should be understood. This chapter will discuss the evolution of these practices, as well as the legal and regulatory framework governing the tank vessel industry. The discussion applies primarily to tankers, although some sections, as noted, apply to barges. Crude oil and petroleum products have been carried in ships for more than years. The practice of carrying the oil directly inside the single hull of a ship has been common since this type of ship was first built in The hull provided far better security for the cargo than barrels, or casks, which could split and spill oil, creating fire and explosion hazards. Tanker designs established in the late s remained virtually unchanged until shortly after World War II. Tankers commonly were of 10, to 15, DWT, with a single skin, the engine to the stern, and multiple compartmentation with either two or three tanks across. Cargoes were usually refined products, most often light or "white" oils, which were not considered polluting as they rapidly evaporated if spilled. The non-polluting cargo meant that tanks could be rinsed out with water which then was dumped at seaand the same tanks could be used for ballast sea water. Separate ballast tanks, other than the peak tanks at the ends of the shipwere virtually unheard-of until after World War II. After the war, the world economy expanded with a resulting huge increase in demand for energy in the form of oil. At the same time, a new shipping pattern evolved: Crude oil often was transported from distant sources, such as the Persian Gulf, to major marketing areas, notably North America, Northern Europe, and Japan, where the crude was refined and redistributed as product. These long voyages set the stage for a dramatic increase in ship size, which started about See Figure The numbers of tankers in the world fleet also multiplied many times over. Meanwhile, significant technical developments were afoot, including the following:. Welding replaced riveting, a major benefit to the tanker industry in assuring tightness of tanks. The practice initially led to some cracking, and ships breaking in half, but these problems were solved with better materials, welding, and design. The empirical, or rule-of-thumb, design approach was augmented and partially supplanted by theoretical techniques. This trend was facilitated by the introduction of computers in the s and s, and, in fact, was necessitated by the growth in ship size from vessels of around feet to over 1, feet, with an increase in deadweight of over twenty-fold in less than 20 years. While the basic types of static and dynamic forces acting on ship structure had been known in general for years, it was not until the s that naval architects were able to quantify the loads precisely and to carry out the stress analysis needed to design ships on a theoretically sophisticated basis. By the s, reliable theoretical quantification of loads and structural response was common for tankers; however, practical service experience remains vital to verify structural integrity and detail design.
Oil Tanker Construction Rules
The global crude oil and refined product tanker fleet uses a classification system to standardize contract terms, establish shipping costs, and determine the ability of ships to travel into ports or through certain straits and channels. AFRA uses a scale that classifies tanker vessels according to deadweight tons, a measure of a ship's capacity to carry cargo. East Coast. Their smaller size allows them to access most ports across the globe. A GP tanker can carry between 70, barrels andbarrels of motor gasoline 3. Long Range LR class ships are the most common in the global tanker fleet, as they are used to carry both refined products and crude oil. These ships can access most large ports that ship crude oil and petroleum products. An LR1 tanker can carry betweenbarrels andbarrels of gasoline This ship size is popular with oil companies for logistical purposes, and, therefore, many ships have been built within these specifications. Over the history of AFRA, vessels grew in size and newer classifications were added. VLCCs are responsible for most crude oil shipments around the globe, including in the North Sea, home of the crude oil price benchmark Brent. A VLCC can carry between 1. There are a small number of ULCC vessels currently in use, as their size requires special facilities limiting the number of places where these vessels can load and offload. These massive vessels can carry around 2 million barrels to 3. The only U. Add us to your site. Today in Energy. Mason Hamilton, U. Energy Information Administration. Source: U. Email Share Print. Send your feedback to todayinenergy eia.