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Oil Tanker operation : Procedure and basic guidance

Tankers are specialized vessels that include crude oil, product, chemical, LNG, and other tanker types. Tankers spend considerable time in ballast given the typical one -way nature of the underlying trades. Tankers are selfdischarging and most are equipped with a series of pumps that allow for a fast turnaround in port.

When carrying certain oil types, many tankers will be asked to heat the cargo (using the ship’s heating coils) to reduce the cargo’s viscosity. World trade relies on tankers. There are different categories of oil tankers—a crude tanker is used for transporting bulk volume of unrefined crude oil from the oil extraction facilities to the refineries. The movement and storage of crude oil in large volume requires the largest sized tankers.

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Oil Tanker Safety Guide
Those in the tanker industry are familiar with methods for describing the vessels. For example: Very Large Crude Carriers (VLCC) – which range between 150,000 – 320,000 deadweight tons. Large crude oil tankers can carry in excess of 2,000,000 barrels of oil and even a vessel of 120,000 deadweight tons may be considered a modest size tank vessel today.

Suezmax and Aframax tankers – which range between 75,000 - 150,000 deadweight tons. Their smaller size allows for greater flexibility in the ports called.

tanker deck area
tanker deck area

Product tankers – the larger ones being around 60,000 – 90,000 deadweight tons while the smaller so called “handy” sized vessels load between 20,000 and 50,000 tons. Product tankers are used to carry refined products from oil refineries to the markets/consumer facilities. Specialized parcel tankers with stainless steel tanks and segregated pumping systems allow for the carriage of a variety of sensitive liquid cargos while reducing the risk of commingling and contamination.

There are other tanker types. For example, a replenishment tanker is used for refueling ships at sea and old nonoperational oil tankers may be used as floating oil storage units.

The largest tankers are unable to berth in port and must load and discharge at offshore platforms. Vessels can load at very fast rates and can easily turnaround in port in less than a day. Tankers are also fitted with special systems, not found on dry bulk ships, such as IGS (inert gas systems) and COW (crude oil wash). Obviously, there are pronounced environmental regulations that crew and shore side staff must be concerned with.

The tanker market has historically been dominated by the oil majors (Exxon, Shell, BP, etc.) as well as large state owned oil companies such as Saudi Aramco, Pemex, and others. Like Amoco, many of these majors owned large fleets of vessels (their proprietary fleet) which was supplemented by chartering tankers owned by independent tanker owners. In recent years the trend is for the oil companies to reduce their proprietary fleets and rely more on vessels owned by independents.

So tankers and the tanker trades are special. However, a tanker is after all a ship and tanker owners are routinely tasked with the same concerns that their dry cargo counterparts must address, such as crewing, maintenance, drydocking, insuring, chartering, etc. Nevertheless, the special nature of tankers – as outlined above – present unique concerns.

External Links
  1. The International Association of Independent Tanker Owners (INTERTANKO) is a voice for independent tanker owners (non-oil companies and non-state controlled tanker owners). Independent tanker owners operate about 80% of the world's tanker fleet.

  2. Stolt Nielsen, Ltd. and its related “Stolt” companies is one of the largest tanker owners specializing in chemicals and other products. They have offices in Connecticut and worldwide.

  3. Fairfield Chemical Carriers has offices in Connecticut and controls a large fleet of chemicals carriers.

  4. Teekay is the largest operator of mid-sized tankers including suezmax, aframax, and long range two (LR2) vessels.Teekay and its related companies is probably the largest tanker owner in the world and earns revenues in the billions annually. They have offices in the USA and abroad.

  5. AET has offices world wide including an office in Houston. They operate a large fleet of crude oil tankers.

  6. International Seaways, Inc. is engaged in the ownership and operation of crude, product, and chemical tankers around the world and has offices in Manhattan. is one of the largest tanker companies worldwide providing energy transportation services for crude oil and petroleum products in International Flag markets. International Seaways owns and operates a fleet of 40 vessels, including 13 VLCCs, two Suezmaxes, five Aframaxes/LR2s, 13 Panamaxes/LR1s and 5 MR Tankers.

Major oil companies such as Shell Oil, Exxon Mobil, and bp (among others) own and operate large fleets of crude oil and product tankers.

Feature of Coastal tanker ASPERITY
(According to The Motor Ship June 1997)

The double-hulled coastal tanker ASPERITY was built by Singmarine Dockyard and Engineering, Singapore. A major feature of the cargo tank arrangement is the elimination of the centreline bulkhead to reduce discharge time to halve the number of tanks to pump. In the result, the ship has five cargo tanks of varying size, which allow small parcels of differing product grades to be transported. Each cargo tank is equipped with the Wärtsilä Svanehoej variable speed deepwell pump with a capacity of 550 m3/h at 90m liquid column. Loher 174 kW explosion proof motors are sited on the trunk top and drive the pumps using Cardan shaft.

Oil tanker at sea
Fig: Oil tanker at sea

All cargo lines and tank fittings are made of stainless steel. Cargo valves are stainless steel high-performance butterfly valves. Cargo stripping and tank washing valves are stainless steel ball valves. The cargo control system comprises a loading computer, tankradar and temperatures probes, ballast, bunker, fresh-water and draught gauging and an independent hi-hi tank alarm system.

Two computer monitors with light pens control the five deepwell cargo pumps, the slop pump and ballast pumps. Other details monitored are cargo tank ullages and pressures, slop tank ullage and pressure, tank temperatures. The control system has mimic diagrams and monitors the control plan and two-valve segregation parameter. Dynamic colouring of pipelines indicates flow and the opening of valves. Continous information of tank levels is provided to the Kockumation loading computer for a continuous update of tank status and ship stability.

A main engine develops 2000kW at 825 rev/min. It drives a 3.3m diameter CP propeller at 160 rev/min through a gearbox. An arrangement of clutches allows the shaft alternator to be used as the emergency propulsion, providing a “get-you-home” speed of 9 knots. Length, oa: 88.76m, Length, bp: 82.20m, Breadth, moulded 16.50m, Depth, moulded: 7.65m, Draught: 5.60m, Displacement: 5490t, Lightweight: 1712t, Deadweight: 3778dwt, Service speed: 12.5 knots, Cargo capacity: 4266m3.

Oil tanker more safety guideline: The operation of modern oil tankers involve numerous complexities and careful consideration will need to be made for various shipboard activities. Our site is a quick guide to finding tanker vessel operation related information.

How to ensure safe working atmosphere onboard oil tankers

The basic procedure - Restriction of Smoking, other Burning activities and Naked Lights

The basic procedure of ship to ship transfer

For dealing with Unforeseen Emergencies, such events can be contained and their effects minimized by preparing the ship’s crew through a system of drills

Pumproom inspection procedure for oil tanker

A pump room contains the largest concentration of cargo pipelines of any space within the ship and leakage of a volatile product from any part of this system could lead to the rapid generation of a flammable or toxic atmosphere

How to ensure safe working area onboard oil tankers

Before work, the conditions of working area, such as the density of inflammable gas and fire, shall be positively managed, and the work shall be started after necessary safety of the work is confirmed

Tanker operation : Matters That Require Attention At Sea

Maintenance of Vent Line System, Cautions about Sparks from Funnel, Avoidance of Thunder Storms, Ballasting and Cargo Oil Transfer Operations

Tanker operation: Inert gas system

The oxygen content of the Inert Gas supplied to cargo tanks should be 5% or less. However, it is to be noted that too less content of oxygen in the IG would introduce other impurities into the cargo tanks

Safety preparation for oil tanker prior entering freezing area

The Master shall ensure that the appropriate measures have been taken to prevent damage to Vessel, Machinery, Pipelines and Equipment prior entry into areas with Freezing Conditions

Daily soundings of tanks and bilges

Bilge (Hold, Engine Room, Cofferdam, Void space, Chain Locker, Emergency Fire Pump Room, Bow Thruster Room, etc.),Ballast Water Tanks , Fresh Water Tanks

Oil pollution control

Equipment For Oil pollution Control, Equipment for Oil Pollution Mitigation, Guidelines For Prevention Of Oil Pollution Mitigation, Action by Duty Officer, Plugging Deck Scupper Plugs

Gas freeing procedure onboard oil tanker

It is generally recognized that Tank cleaning and Gas freeing is the most hazardous period of tanker operations. This is true whether Washing for clean ballast tanks, Gas freeing for entry, or Gas freeing for Hot work.

Oil handling procedure

Bunkering Operation, Measures during Extreme Weather, Restrictions on Use of Fire, smoking, and other General Precautions to the Crew

General safety measures against oil pollution accident

Working system and preparation , Planning for Cargo Oil Operations ,Pre-safety meeting , Effective Communication ,Promote techniques of Hazard Prediction Training, Preparation of Watch Schedule & PIC of Oil Transfer Operations, Have a complete meeting beforehand with terminal ,Cargo Oil Transfer Check Lists ,Ship / Shore Safety Checklist ,Pre Arrival Checks ,Check Operational Conditions and Training of Crew

Preparations For Oil Loading

Preparation of the Cargo Plan, Preparing of Ballast Pumps,Cargo Oil Transfer Check Lists, Hose Connection,Display of warning notices and signs, Cargo Oil Transfer Meetings with Terminal representative,Dry Survey / OBQ survey,Lining up Pipelines and Valves,Precautions for Loading Heated Cargo, Personnel arrangement

Tanker Standard Equipment Of Prevention Of Oil Spillage

Cargo Tank Level Measuring System and Level Alarm System, Emergency Hydraulic Hand Pump, “Software”/Guidelines For Prevention Of Oil Spillage ,Operation Guidelines for Cargo / Ballast valves, Prevent Erroneous Operation of Valves, Valve Handling with Avoiding Liquid Hammer, Securing Indication for Closed Valves

Loading operation onboard oil tankers

Line up of the Vent lines, Safety Confirmations and Clearance,Leakage Monitoring System ,Cargo Loading Rates , De-Ballasting of Segregated Ballast, Preparation for Topping Off ,

Guidelines For Toxic Gases Hazards

HYDROCARBON VAPORS Characteristic ,Toxic Hazards of H.C. Vapors , HYDROGEN SULFIDE (H2S), H2S Gas Concentration, Precautions for Hydrogen Sulfide (H2S), Health Concerns in connection with Benzene, Health Concerns of Inert Gas, Oxygen-deficient atmosphere

Crude oil washing procedure

Supervision Of Crude Oil Washing (COW) Operations, Discharging Strategy ,Advance Notice In Port ,Safety Measures For Crude Oil Washing Operations , Confirming Atmosphere in Tanks to be Crude Oil Washed, Pressure Test

Standard Procedures for Tank Cleaning, Purging and Gas free Operation

Gas-Freeing for Cargo Tank entry ,Safety Precautions ,Non Flammable Atmosphere , Atmosphere Control during Tank Cleaning Operations ,Purging with Inert Gas (IG),Forced Air Ventilation

Matters that require attention while loading and discharging oil and ballast water

Control Of Discharge Of Oily Mixture Originating From Cargo Oil From Tankers & Restriction of carriage of oil and water ballast

Tanker vessel : Operations during laden voyage

Water And Cargo Oil Measurement, Vapor Control, Topping Up Operation, Cargo Oil Heating, Line Pressure Test

General Precautions Confirming Working Area Onboard Oil Tanker

Confirming Working Area, Anti-Electrostatic Clothes and Shoes for Ship’s crew, Permission of Hot Work ,Use of Explosion-proof Type Electric Torch equipment, Use of Hand Tools, Prohibition of Carrying Unnecessary Tools, Attention to Shock Sparks by Lighter Metals, handling of Aluminum Products

Preparation for discharge onboard oil tankers

Preparation of the Cargo Plan, Cargo Equipment, Cargo Oil Transfer Check Lists, Display of Warning Notices and Signs, Hose Connection, Cargo Oil Transfer Meetings with Terminal representative, Ullage measurement and Cargo Quantity Calculation, Lining up Pipelines and Valves

Oil Cargo Discharging Operations

Supply of I.G to cargo tanks being discharged, Line up of the IGS, Safety Confirmations and Clearance, Deck Watch and Personnel Arrangement

Tanker operation : Personnel for Cargo Handling

Watch Schedule, Supervision Of Operations, Personnel Arrangement During Cargo Operations

Measures For Handling Cargo Oil Having A Flash Point Exceeding 60c

Ensure that sufficient reliable evidence available that the flash point of the cargo oil is above 61° C and the temperature of the cargo oil does not exceed 5° C less than the flash point.

Tanker operation : Disposal for Spilled Oil and Prevention for Secondary Disaster

Tanker Standard Equipment For Disposal Of Spilled Oil & Secondary Disaster Prevention Slop Dump (Surface) Valve Arrangement (Emergency drains)

Tanker operation : Inspection Of Cargo Work Equipment And Machinery

The Chief Engineer and Chief Officer shall jointly be responsible for the inspection and maintenance of the cargo oil transfer equipment and machinery before entering port

Tanker operation : Measures For Pump room entry

Entry Permit into Enclosed Space ,Atmosphere Control, Effective communication ,Gas Monitoring , Maintenance Work in Pump Room

Shipping industry recognizes environmental protection as one of its highest priorities and that every effort should be made to conserve and protect the environment from marine, atmospheric and other forms of pollution.
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