A bitumen tanker is a ship that carries liquid bitumen (asphalt) hot, in insulated independent cargo tanks heated by a thermal oil system. This page covers the seagoing ship, not the road bitumen tanker truck. It explains how these tankers are designed, heated, regulated and inspected, for ship’s officers, surveyors and maritime students.
What Is a Bitumen Tanker?
A bitumen tanker is a specialised oil tanker that carries bitumen or asphalt as a hot liquid. Insulated tanks sit inside a double hull, and thermal oil heating keeps the cargo pumpable from loading port to discharge.
The trade also calls these ships asphalt tankers, asphalt carriers or high-heat tankers. They form a small niche within the wider range of oil tanker types, which is dominated by crude carriers and product tankers.
Many bitumen tankers are certified for more than one cargo family. Bureau Veritas, for example, lists “Asphalt carrier”, “Oil tanker” and “Chemical tanker” as service notations commonly combined on asphalt newbuildings. Vroon’s Iver Ships describes its 2009-built Iver Bitumen as an IMO Type 2 chemical tanker and high-heat tanker.
Is a Bitumen Tanker the Same as a Bitumen Road Tanker?
No: a bitumen road tanker is an insulated, heated tank trailer that delivers bitumen from a terminal to an asphalt plant. A bitumen tanker ship moves thousands of tonnes between refineries and import terminals. The two share the same hazards, but their design and regulations are entirely different.
Why Is Bitumen Shipped Hot?
Bitumen is semi-solid at ambient temperature and cannot be pumped. Heating lowers its viscosity until it flows, so bitumen tankers load, carry and discharge the cargo hot. Bureau Veritas puts typical liquefaction temperatures at 180–250°C.
The exact carriage temperature depends on the bitumen grade and the ship’s design limit. The 37,000 dwt Asphalt Splendor, for example, is designed to carry asphalt at up to 170°C. Indian Register’s asphalt carrier guidelines do not permit carriage above 300°C unless specially considered.
Hot shipping is not the only route. Markets without heated import terminals often receive bitumen in drums or heated tank containers instead. Bulk shipment by tanker remains the standard for larger, regular trades.
How Big Are Bitumen Tankers?
Most bitumen tankers are small to medium ships, with a large part of the fleet below about 30,000 tonnes deadweight. The largest purpose-built units reach 37,000 dwt, and Bureau Veritas has reported a 49,000 dwt asphalt carrier under construction.
Size is limited by the trade itself. Bitumen import terminals are often small regional ports, and receivers buy in parcels sized to their heated shore tank capacity. The table below compares documented examples.
| Ship | Size | Cargo tanks | Design note |
|---|---|---|---|
| Rathboyne | 5,400 m³ cargo capacity | 8 independent tanks in 2 blocks of 4 | Cargo up to 250°C, Rockwool insulation, 516 tank supports |
| Damia Desgagnés (2017) | 15,100 dwt, 15,280 m³ | Asphalt, bitumen and chemicals | Dual-fuel engine burning HFO, MDO or LNG |
| Asphalt Splendor (2016) | 37,000 dwt, 35,666 m³, 179.90 m LOA | 16 independent tanks | Asphalt carried at up to 170°C |
How Is a Bitumen Tanker Designed?
A bitumen tanker combines a double hull with insulated independent tanks that expand freely on supports. Thermal oil heats the cargo, and class rules require a thermal stress analysis at maximum cargo temperature.
The layout is a conventional tanker form with machinery aft. The design problem is heat: a full tank at 200°C or more sits a short distance from a hull at sea temperature. Every major design choice on the ship follows from managing that temperature difference.
Why Do Bitumen Tankers Use Independent Tanks?
Independent tanks are self-supporting tanks that are not part of the hull structure. On a bitumen tanker they let the hot tank expand in three directions without loading the hull. Integral tanks would transfer the cargo’s heat straight into the hull girder.
Bureau Veritas lists the penalties of integral tanks at high temperature: reduced steel strength, longitudinal thermal stresses and greater buckling sensitivity. Indian Register applies reduced yield strength and elastic modulus to steel at 80°C and above. The independent tank breaks that heat path.
The tanks rest on chocks and keys welded to the hull. Indian Register’s guidelines call for four support functions:
- Vertical load supports carrying the tank and cargo weight
- Anti-flotation supports, which stop the tank lifting if the hold space floods
- Anti-rolling supports resisting transverse movement
- Anti-pitching supports resisting longitudinal movement
Support pads also act as thermal breaks. On the Rathboyne, rubber layers sealed into 516 steel supports cut the 250°C cargo temperature to about 80°C at the support.
Are Bitumen Tanks Type A, B or C Tanks?
No. Type A, B and C are independent tank categories defined by the IGC Code for liquefied gas carriers, and Type C tanks are pressure vessels. Bitumen tanks are atmospheric tanks carrying a hot liquid, not a pressurised gas.
That difference matters operationally. Norwegian contractor guidance on hot bitumen states plainly that bitumen tanks are not pressure vessels. Any event that builds pressure inside them, such as steam from water contamination, is a structural and safety threat.
How Are the Cargo Tanks Insulated?
Bitumen cargo tanks are clad in mineral or rock wool insulation, with a void space between the insulated tank and the inner hull. The insulation slows cargo cooling and keeps heat away from the ship’s structure.
Insulation condition is a maintenance item, not a fit-and-forget one. Cracked or missing insulation causes cold spots, extra heating fuel and local cargo cooling. Insulation soaked with bitumen is also a recognised ignition risk once it contacts air.
What Hull Structure Does MARPOL Require?
Bitumen is an oil under MARPOL Annex I, so a bitumen tanker must meet oil tanker construction rules. Annex I Regulation 21 classes bitumen as heavy grade oil, which may not be carried in single-hull tankers.
- Annex I Appendix I lists “asphalt solutions” (blending stocks, roofers flux and straight run residue) among the oils covered by the Annex.
- Regulation 21 defines heavy grade oil to include “bitumen, tar and their emulsions”.
- The ban covers single-hull tankers of 5,000 dwt and above from 5 April 2005. The IMO’s summary of oil tanker construction requirements sets out the full phase-out.
- Single-hull tankers of 600 to 5,000 dwt had to stop carrying heavy grade oil by the anniversary of their delivery date in 2008.
What Does Classification Require?
Class societies issue specific notations and design guidelines for asphalt carriers. They make a thermal analysis mandatory alongside the strength analysis, and scantlings in the cargo area are heavier to absorb thermal stress and fatigue.
The notation records the design limit. Indian Register, for example, assigns “ASPHALT CARRIER (INDEPENDENT TANKS, MAX. CARGO TEMP ≤ XXX°C)”, and the thermal analysis assumes full tanks at that maximum temperature. Your classification society also expects loading rates that avoid thermal shock to tanks and hull.
How Does the Cargo Heating System Work?
Oil-fired heaters in the engine room heat thermal oil, which pumps circulate through coils inside each cargo tank. The coils run along the tank bottom and up vertical tower coils, and the cooled oil returns to the heater.
Thermal oil is used instead of steam because it reaches these temperatures at low system pressure. Steam at cargo temperatures above 200°C would need a high-pressure plant throughout the cargo area. The heating coils on conventional oil tankers handle far lower temperatures.
A typical system has these parts:
- Thermal oil heaters, usually fired on heavy fuel oil, with ratings in the order of 1–2 million kcal/h
- Redundancy, so one heater can normally cover the full cargo heating load, with extra capacity fitted for cold-climate trades
- Circulating pumps running continuously, with standby units
- Bottom coils and vertical tower coils in each tank for even heat distribution
- Temperature sensors in each tank and on the thermal oil supply and return lines
What Is a Cargo Heating Plan?
A cargo heating plan sets the temperature to hold during the voyage and the temperature required on arrival. It follows the charterer’s heating instructions and the ship’s maximum design temperature, whichever is more restrictive.
Tank temperatures are logged at fixed intervals throughout the voyage. Those records are the ship’s main defence in a heating or remaining-on-board (ROB) claim. The procedure belongs in the company’s safety management system under the ISM Code.
What Are the Main Hazards on a Bitumen Tanker?
The main hazards are boil-over from water contact, toxic hydrogen sulphide (H₂S) in tank vapour, severe burns and fire. Each needs its own procedure in the ship’s cargo operations plan.
- Boil-over: water flashes to steam on contact with hot bitumen and expands 1,600–2,000 times. Eurobitume warns that 10 litres of water can produce nearly 20 m³ of steam in seconds, forcing foaming cargo out of tank openings.
- Hydrogen sulphide: H₂S accumulates in the vapour space of heated bitumen and vents during loading. It is heavier than air, and its smell is not a reliable warning. Shell’s bitumen safety data sheet calls for evacuation above 10 ppm without respiratory protection.
- Burns: contact with cargo at 150–250°C causes deep burns. First aid is cooling with tepid water for at least 20 minutes, leaving the bitumen on the skin for medical staff to remove.
- Fire: bitumen’s flash point is high (above 230°C for a typical paving grade), but overheating releases flammable vapour. Pyrophoric iron sulphide deposits and bitumen-soaked insulation are additional ignition sources.
Entry into a cargo tank or an adjacent void follows the ship’s enclosed space entry procedure. Gas testing covers H₂S as well as oxygen and hydrocarbons. Tanks must be gas-free before any entry, hot work or drydocking.
Does a Bitumen Tanker Need an Inert Gas System?
Not under the standard rule. The tanker fire-safety requirements of SOLAS Chapter II-2 (Regulation 1.6.1) apply to cargoes with a flash point not exceeding 60°C. Bitumen’s flash point is far higher, so ships carrying only such cargoes fall under the alternative arrangements of Regulation 1.6.4.
Heated cargoes can still need specific carriage conditions. Dual-certified ships carrying low-flash oils or chemicals must meet the full requirements, including an inert gas system where size requires one. Confirm the exact arrangement with the flag Administration and class.
Tank venting still matters on every voyage. Cargo tanks breathe through pressure/vacuum valves as the cargo heats and cools, and the vent outlets are where H₂S exposure on deck is most likely.
How Is Bitumen Loaded and Discharged?
Bitumen loads from heated refinery tanks through insulated, heated pipelines and discharges to heated shore tanks at the receiving terminal. Before loading, every tank must be confirmed free of water, and loading rates are controlled to avoid thermal shock.
The pre-loading water check is the single most important step. Eurobitume’s rule is absolute: bitumen should never be loaded into a tank containing traces of water. Condensation, an open dome overnight or leftover tank washings are all enough to start a boil-over.
During discharge the cargo must arrive at the manifold above its pumping temperature. Exclusion zones around hoses and the manifold protect personnel from hot cargo if a connection fails. Where a port has no heated shore tanks, cargo can be discharged directly into road bitumen tankers on the quay.
What Causes High ROB After Discharge?
High ROB occurs when cargo cools during the voyage or discharge. Its viscosity rises quickly, cargo clings to tank walls and coils, and the pumps can no longer clear the tank.
Cooling is fastest in cold sea and air temperatures and around damaged insulation. The fix is preventive: hold the heating plan, monitor every tank, and investigate any tank that falls behind the others.
Where Do Bitumen Tankers Trade?
Bitumen moves from oil refineries to import terminals in North and South America, Europe, Africa, Asia and Australia. Receiving terminals need bitumen pumps, insulated pipelines and heated shore tanks, which limits the number of ports a bitumen tanker can serve.
What Do Inspectors Check on a Bitumen Tanker?
Class surveyors check the independent tanks, supports, insulation and heating system. Port State Control officers focus on fire safety, gas detection and MARPOL Annex I compliance. Vetting inspectors examine heating records, H₂S procedures and cargo operations.
Class surveys. During class and statutory surveys, surveyors inspect the hold spaces around the independent tanks. They examine chocks, keys and anti-flotation supports for cracking or wear, and check insulation for damage. Any tank entry for survey, whether at sea or in drydock, requires the tank to be cleaned and gas-free first.
Port State Control. PSC officers check the IOPP Certificate, Oil Record Book, thermal oil heater safety devices, heater-space fire detection and gas detectors. Serious fire-safety or pollution-prevention failures are grounds for detention.
Vetting. A vetting inspection tests how the ship is run rather than how it is built. Inspectors compare the heating log with the charterer’s instructions and check H₂S monitoring and boil-over precautions.
Findings to prepare for on a bitumen tanker include:
- Thermal oil leaks at flanges, valves or pump seals, especially near hot surfaces
- Portable H₂S detectors out of calibration or not issued to the deck team
- Damaged or bitumen-soaked insulation in the hold spaces
- Gaps or inconsistencies in the cargo temperature records
- No documented water check before loading
Who Operates Bitumen Tankers?
Bitumen tankers are operated by a small group of specialist tanker companies, often with refinery or asphalt-trading links. Documented examples include Sargeant Marine, Groupe Desgagnés, Wisby Tankers, Vroon’s Iver Ships and Tarbit Shipping.
- Sargeant Marine took delivery of the 37,000 dwt Asphalt Splendor, built by Avic Dingheng in China and classed by Bureau Veritas.
- Wisby Tankers took two 37,000 dwt asphalt carriers from Hyundai Mipo Dockyard, according to Bureau Veritas.
- Groupe Desgagnés (Canada) operates Damia Desgagnés, delivered in 2017 by Beşiktaş Shipyard in Turkey as the first dual-fuel LNG asphalt tanker.
- Iver Ships (Vroon, Netherlands) entered the high-heat market in 2009 with Iver Bitumen and carries asphalt, bitumen and liquid pitch.
- Tarbit Shipping (Sweden) has long operated high-heat tankers in the European bitumen trade.
How Do Bitumen Tankers Reduce Fuel Use and Emissions?
The thermal oil heaters burn fuel on top of propulsion, so cargo heating raises a bitumen tanker’s fuel consumption. Better insulation and waste heat recovery cut the heating load.
Propulsion is the other lever. Damia Desgagnés uses a Wärtsilä 5RT-flex50DF dual-fuel engine that can burn heavy fuel oil, marine diesel oil or LNG.
Related Topics
- VLCC: Very Large Crude Carriers
- ULCC: Ultra Large Crude Carriers
- Slop Tanks on Oil Tankers
- Types of Cargo Ships
Frequently Asked Questions
What does bitumen tanker mean?
A bitumen tanker is a ship that carries hot liquid bitumen (asphalt) in insulated, heated cargo tanks. The term is also used for road tanker trucks that deliver bitumen ashore, but at sea it means a specialised oil tanker.
Is a bitumen carrier a tanker or a bulk carrier?
A bitumen carrier is a tanker. It carries bitumen as a hot liquid and is regulated as an oil tanker under MARPOL Annex I. A bulk carrier, by contrast, carries dry cargo in holds.
At what temperature is bitumen carried by ship?
Bitumen is usually carried at about 150–250°C, depending on the grade and the ship’s design limit. Bureau Veritas cites 180–250°C for liquefaction, and each ship’s class notation records its maximum cargo temperature.
How is bitumen transported?
Bulk bitumen moves by bitumen tanker from refineries to heated import terminals, then by insulated road tanker to asphalt plants. Smaller markets without heated terminals receive bitumen in drums or heated tank containers.
Why do bitumen tankers use independent tanks?
Independent tanks are not part of the hull, so the hot tank can expand without stressing the ship’s structure. Supports with thermal breaks and insulation keep the cargo’s heat away from the hull girder.
What heating system does a bitumen tanker use?
Bitumen tankers use a thermal oil system. Oil-fired heaters in the engine room heat the thermal oil. It circulates through bottom and tower coils in each tank and reaches high temperatures at low pressure.
How big is a bitumen tanker?
Most bitumen tankers are small to medium ships, many below 30,000 dwt. Large purpose-built asphalt carriers such as Asphalt Splendor reach about 37,000 dwt and 180 m in length.
What propulsion do asphalt tankers use?
Most asphalt tankers use conventional diesel engines burning fuel oil. Damia Desgagnés, delivered in 2017, was the first dual-fuel LNG asphalt tanker and can burn heavy fuel oil, marine diesel oil or LNG.
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