Specifications and Requirements for LPG and LNG Ships to Sail in International Waters

A large number of merchant ships are designed and constructed for carrying different types of liquefied gases from one port to another. Since cargo in gaseous form will take much more volume than when in liquid condition, the gases are condensed and liquefied for carrying them in ships.

Types of Liquefied Gas Carriers

There are basically two types of gas carrier ships:

1)      LPG Carrier: Liquefied petroleum gas Ships carries LPG gas along with some other gases like ammonia, propylene, ethylene as their construction and equipments are suited to carry such gases also.

LPG Carrier

Ethylene cannot be carried in LPG tanker as its boiling point is very low (-104 ̊C).

2)      LNG carrier: LNG gas or Liquefied Natural gas from which, major impurities like sulphur and carbon dioxide have been removed, is carried in LNG carrier ships.

LNG carrier

LNG is transported in the form of liquefied methane after cooling it to its boiling point, – 163 ̊C.

Regulatory Requirements for LNG and LPG

As per International Maritime Organisation, a liquefied gas ship can only run in international waters if it is constructed and operated as per International Gas Carrier (IGC) 1986 code and complies with SOLAS 74 chapter VII part C –“construction and equipment of ships carrying liquefied gases in bulk.

The brief requirements described in IGC code are:

  • Damage limitations to cargo and ship survival in case of collision or grounding.
  • Safety arrangement requirements for such ship.
  • Cargo containment and cargo handling procedure.
  • Material of construction for containment and carriage facility.
  • Requirements for cargo loading and discharging.
  • Pollution control requirements.
  • Usage of cargo as ship’s machinery fuel.
  • provision for thermal expansion and contraction is provided

Constructional requirements

Different types of cargo tanks should be provided with special material at maintained pressure as described in the constructional and cargo handling requirement of IGC code for both LPG and LNG ships.

LPG ship cargo carriage requirements

LPG can be carried by sea if any one of the three criteria is fulfilled:

  • It is solely under pressure maintained at ambient temperature.
  • It is fully refrigerated at its boiling point.
  • It is semi refrigerated but at elevated temperature and elevated pressure.


Other important auxiliaries that are required are:

  • A well insulated and refrigerated LPG tank to fulfil any of the above criteria
  • A compressor room compressors and refrigeration plants
  • A nitrogen bank as well as an inert gas generator with dryer system
  • The cargo temperature and environment data monitoring system
  • Tank atmosphere and temperature data is monitoring system

LNG ship cargo carriage requirements

LNG is carried at very low temperature which can cause crack in the metal structure if cargo comes in contact with the ship’s hull. Moreover,

  • LNG carrier must have a cargo tank with double layer of insulation protection.
  • Material used for tank must have very low coefficient of thermal expansion (invar).


  • To be provided with vaporiser to meet its own vapours requirements.
  • Re gasification plant should be provided(optional)

You may also like to read-Panamax and Aframax Tankers: Oil Tankers with a Difference

References: Book on Ship construction by D.J Eyres


Do you have info to share with us ? Suggest a correction

Latest Type Of Ships You Would Like:

Nuclear Vessels

What Are Nuclear Vessels?

Posted on
Nuclear power is derived from chemical reactions that involve nuclear substances that react under particular conditions. A nuclear-powered ship has many advantages over conventional vessels. Read this article to learn more about nuclear vessels.
What Is A Hospital Ship

What is A Hospital Ship?

Posted on
A hospital ship is designed and constructed to serve as a medical facility similar to hospitals, nursing homes, or other healthcare infrastructure. Read along to learn more about hospital ships.
What Are Bunker Ships

What Are Bunker Ships?

Posted on
Bunker ships are small tankers transporting and carrying bunker fuel used for ship propulsion. They can transfer fuel to a recipient’s vessel while on a voyage. Know more about these vessels and their operations in the article.

Latest Maritime Law You Would Like:

Damaged Shipping Containers – Causes And Types

Posted on
Careless or inexperienced MHE operators can cause containers to hit against each other and result in extensive damage. Let’s take a look at different causes and types of Damaged Shipping Containers.
Port Services (3)

What are Port Services?

Posted on
Port operations are normally controlled by the port authority appointed by the respective government of the country. Find out more about port services that are required to support these operations.

How is Management of Empty Shipping Containers Carried Out?

Posted on
A common challenge faced by container Carriers relates to the handling and movement of empty containers. Learn how shipping lines manage empty containers to ensure optimal returns, minimise idle time, and maximise asset turnover.

Get the Latest Maritime News Delivered to Your Inbox!

Our free, fast, and fun newsletter on the global maritime industry, delivered everyday.


  1. pls.tell me that if the LPG carrier / tanker does not have any refrigeration and only is equipped with Inert gas ,could it carry the LPG safely,
    also could you recommend LPG vessel for rent /sale

  2. Sirs
    i like to know if LNG designed vessel can carry and work also as LPG vessel
    Best regards
    Eng. T.B.Idriss

  3. Hello
    Iranian sailor
    Where is the gas training course going?
    Thank you
    Iranian sailor
    My name is Alireza Azizian
    please guide me
    Telegram number 00989379971354

  4. On LNG ships with DFDE engines, usually the DF engines are installed by pairs (on pair at stbd and other pair at port side),
    Can some of you confirmed me if a par of LNG in the same room can run different fuels?
    For instance, in stbd side, G/E#1 running in HFO and G/E#2 running on BOG + pilot,


  5. Sir I want to do a job in LNG carrier ship.. what I will do . tell me the process sir please…

  6. I would like to know impacts from LNG Carries Type C and international guidelines for LNG Carriers.

Leave a Reply

Your email address will not be published. Required fields are marked *