The following essay will deal with the Aframax Tanker Vessel Class. Tankers between a Deadweight (DWT) of 80.000 – 120.000 metric tons belong to the Aframax Tanker Vessel Class. According to the AFRA, Scale Tankers with a Deadweight (DWT) of 80.000 – 159.999 metric tonnes are considered LR2 (Long Range 2) Tankers. The flexible market scale categorised tanker vessels with a DWT between 80.000 – 120.000 metric tonnes as Aframax Vessels and Vessels between a DWT of 120.000 – 200.000 metric tonnes as Suezmax. As mentioned before, this essay will provide information to Aframax Vessels for the most part. The term AFRA originated from the Average Freight Rate Assessment (AFRA). In 1954 Shell Oil created AFRA. AFRA is a tanker rate system to standardise charter party terms. People from the Shipping Industry call Aframax vessels “Dirty tankers”. Considering that the primary use of Aframax vessels lies in the transportation of crude Oil, this term can be considered appropriate.
2. Aframax: Main Particulars
The following table shows the main particulars of Aframax Tankers. Data from 12 Aframax Vessels were added up, and an average of these 12 vessels was made to develop the table.
|Average main particulars of the Aframax Tanker Class||Estimates|
|Deadweight||109115.73 metric tonnes|
|Gross Tonnage||59100.89 metric tonnes|
|Net Tonnage||32178,11 metric tonnes|
|Length||219.76 meters (222 – 250 meters)|
|Breadth||42.79 meters (39 – 44 meters)|
|Depth||21.05 meters (19 – 22 meters)|
|Draught / Draft at summer draft||14.72 meters (13 – 16 meters)|
|Lightship||15288.39 metric tonnes|
|Typical Speed||12.23 knots (12 to 17 knots)|
|Total Cargo Capacity||108428.54 m3 (70.000 and 120.000 metric tonnes)|
|Barrels||681991.6 and 695054.77 barrels (448717,95 – 769230,77 barrels)|
|Main Engine||13517.38 KW (18127,10 hp(I) [mechanical horsepower])|
The 12 Vessels, which were taken into consideration for the calculation of the main particulars, were not priced out because prices are negotiable. When a vessel is getting sold the shipbroker tries to get the best-selling price for the shipowner, so he at the same time also gets a higher commission. On the other hand, the buyer of the vessel tries to get the best deal possible. A buyer, who is interested in buying an Aframax Tanker, will have to estimate a price for a newly built ship to be around $60,7M (505.83 – 758.75 US$/DWT) and for a used ship to be at around $58M (483.33 – 725 US$/DWT).
3. Key cargo handling equipment
Tanker vessels need different essential equipment on board and ashore to handle cargo. When a Tanker Vessel loads cargo, the tanker will be filled through the main filling lines by the shore pumps.
The Tanker vessel is held in position on the shore terminal with the mooring lines during berthing. In case of an emergency, the vessel has two metal wires hanging from the hawse on the seaside. In an emergency, tugboats can tow the vessel on the metal wires away from the terminal. The ship is connected with a ground cable to reduce electrostatic wear on the manifold and pipelines. The manifold on the tank deck connects the cargo lines of the tanker with the cargo lines onshore.
Different terminals have different pipe connection diameters; due to that, ships have various manifold diameters on board.
Loading of Tankers is mainly done through the shorelines and shore cargo pumps located on the Shore Terminal.
Before discharging, a terminal employee will measure the cargo volume and, for that, use the ullage or innage measurement. Which method he used depends on the density and viscosity of the cargo. Measuring the cargo tank volume can be done with sounding tape over the so-called sounding pipes. The terminal employee will also take a cargo sample through one of the cargo tank openings.
After the Cargo operation ends, the onboard stripping pumps can discharge the rest out of the Tanks, and the Crude oil washing system can clean the Tanks. Inerting the cargo tank with the inerting system, is another vital step. When a tank is inert, the normal atmospheric air is exchanged for inert gas (Exhaust gases are commonly used).
4. Key cargo handling challenges and risks
Key cargo handling challenges and risks are:
* Ship to Shore Communication of plans and actions. E.g., while the loading operation, the ship has to communicate when the shore terminal has to reduce the loading rate and start with the Topping-Off the tanks to prevent overflow, likewise the shore terminal has to do the same when Topping-Off, switching tanks, pipes, or closing valves. For example, if a pump is running against a closed valve, the build-up pressure can burst the pipes, which could cause a spill and a fire/explosion as a result of that.
* Sufficient Topping-Off of tanks to limit the air pocket in the tanks. When the air pocket is limited, the risk is lower for an Explosive Atmosphere (ATEX) to build up.
* Correct interting of Cargo Tanks and Segregated Ballast Tanks
* Insufficient Purging of Tanks before Inspections and Cleaning operations can cause an ATEX. The ATEX can cause fire, explosions, and an unbreathable atmosphere for the ship crew in the Tank. When the atmosphere is unbreathable, the ship crew working in the Tank could die.
5. Key trading areas, cargo flows, and demand of these cargoes
Shell introduced Aframax Tanker due to the size restrictions that were posed when large oil tankers entered high-traffic sea territory; because of that, the Aframax Tanker class has strict design limits.
Aframax tankers can access most ports in the world due to their well-intentioned vessel size. These Vessel Classes can operate in areas where very large and ultra-large crude carriers cannot operate due to infrastructure, which is not large enough ports or offshore oil terminals to facilitate them. Aframax tankers are ideally utilised for voyages of short to medium distances.
Common trade routes of Aframax tankers are in, but not limited to, the Black Sea, North Sea, Mediterranean Sea, South and East China Seas, and the Caribbean Sea. The main cargo flows are for North African exports to Southern Europe through the Mediterranean, along with Exports from former Soviet Union Republics to Northern Europe through the Black Sea and the North Sea, further South American oil exports to the US Gulf region through the Caribbean Sea and South-East Asian exports to the Far East.
Countries, which are often Non-Member of the OPEC (The Organization of the Petroleum Exporting Countries), are not developed enough and lack sufficient infrastructure to handle Suezmax, VLCC, and ULCC. Due to the mentioned above, they may require market participants to use smaller vessels such as Aframax. These countries comparatively produce on a smaller scale than the major Middle-Eastern countries. On the other hand, middle Eastern have a higher level of oil exports and therefore use larger vessels to transport Oil. Due to the usage of such large vessels, the traffic in specific regions is high. As a result, sea routes often get blocked, and smaller Aframax tankers end up being a preferable alternative vessel size.
6. Technologies that impact the design and the cargo handling of this ship type/size
The IMO impact the ship design with the MARPOL regulations. To be precise, MARPOL Annex I – Prevention of Pollution by Oil requires Segregated Ballast Tanks, Crude Oil Washing System, and Inerting System.
The Segregated Ballast Tanks have an impact on the structural strength due to the fact that the Segregated Ballast Tanks produce a bigger surface than a single bottom tanker. As a result of the more significant surface area, there is more surface to maintain, and it can be considered challenging to ensure that the whole Segregated Ballast Tanks have good coating all the time. Another issue is that Segregated Ballast Tanks are not enough or not at all inerted with Inert Gas, and oxygen is still in the Tanks. These two facts play hand in hand. Considering that the metal surface lacks enough coating and oxygen and water are present, Tanksurfaces are the perfect place for rust to build up. When enough metal is rusted away, and torsions forces weaken the metal bond, cracks can occur. Oil can then get through the cracks from the cargo tank into the Segregated Ballast Tanks. Since the Segregated Ballast Tanks are not sufficiently inerted, Tanks provide a good origin for a fire/explosion. For a fire/explosion to format, it is necessary to have an Explosive Atmosphere (ATEX). An ATEX is present since the Tank contains a flammable liquid vapour and oxygen. If in the Tank is an ATEX, a Fire/Explosion only needs an ignition source or the autoignition temperature to develop. Usually, the ignition source can be metal grinding on metal due to torsion.
The IMO also gives registrations on Crude Oil Washing regarding how much water is allowed to be used to wash the tanks and how much Oil can remain in the tanks after the washing operation.
Three things can be said about the layout of the deck:
* the cargo pipes are located in the middle of the deck because there are the least torsion forces.
* The cargo tanks are “breathing” cargo vapour out, the vapour then lays on the deck surface, and due to that, the deck surface is a common origination site for a fire or explosion. Through that, the firefighting system is located on the deck surface.
* Another important deck part is the helideck. When an emergency happens, the crew must abandon the ship as fast as possible. Sometimes even specialised firefighters have to enter the vessel to extinguish a fire and, later on, or in case of an unexpected circumstance, exit the vessel as fast as possible.
Three of the most important regulatory are MARPOL, the ISM-Code, and SIRE-OCIMF.
Whereby MARPOL and the ISM-Code are established and regulated by governments, the SIRE-CCIMF (Ship Inspection Report Programme) was introduced by OCIMF. The program was initially launched in 1993 to address concerns about sub-standard shipping. The SIRE Programme is a unique tanker risk assessment tool of value to charterers, ship operators, terminal operators, and governments concerned with ship safety. Vetting was required because big oil spills had great public attention and produced bad publicity and oil majors suffered from a bad public image. Since the IMO had no instruments to check technical and quality standards for the specific need of the tanker industry, the Oil Majors formed the OCIMF and introduced Vetting into the tanker industry. What a Vetting process takes into account can be reviewed on the websites such as OCIMF, Q88 Questionnaires, and INTER TANKO.
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