Tank Insulation Work

LNG/LPG carrier vessels

The three most common types of LNG carrier tanks

LNG tankers utilize tanks with various shapes and insulation methods, but the four most common types in use worldwide are described below.
Inocrete has construction experience with all four types.

Moss-type spherical tanks

The Moss system uses plastic foam to insulate the area around aluminum spherical tanks.
Cylindrical skirts support the spherical tanks around their equatorial region, transferring load to the ship’s structure.
Due to their spherical shape, these tanks offer several advantages: structural analysis is simpler; they have the smallest surface area per unit volume, which makes external insulation effective and reduces boil-off rates; they experience lower sloshing impact pressures; and they offer increased safety in the event of collision or grounding.

GTT Mark III membrane system

The GTT Mark III membrane system uses a 1.2-mm-thick stainless-steel film as the primary insulation barrier, with corrugations designed to absorb contractions due to LNG thermal fluctuation and hull deformations during navigation. The insulation layer is glass-fiber-reinforced polyurethane foam, enhancing safety with a glass fiber and aluminum foil composite as a secondary insulation barrier.

The GTT Mark III membrane system is more space-efficient than spherical tanks, allowing for an approximately 18% increase in tank capacity for ships of the same size.

Tank insulation process

The GTT NO96 membrane system

The GTT NO96 membrane system utilizes a primary barrier made from Invar steel (0.7 mm thick, 36% nickel steel film), which has almost no thermal contraction, for insulation. The insulation is achieved by stacking plywood insulation boxes filled with expanded perlite in a brick-like fashion. The flat nature of the membrane makes welding easier, and the simple shape and structure of the insulation unit facilitate construction and scaling to larger sizes.

Compared to spherical tanks, the GTT NO96 system offers better space efficiency, allowing for an approximate 15% increase in tank capacity for vessels of the same size.

Membrane construction process for LNG vessel insulation

SPB-type rectangular tanks

The SPB (self-supporting prismatic shape, IMO type B) method features tanks comprising the tank itself (the primary barrier), insulation, and a support base, forming a structure that is independent of the ship’s hull.

SPB tanks are characterized by a robust and reliable tank structure, the prevention of sloshing at any liquid level, and high flexibility in the tank shape.

External insulation methods for SPB tanks do not subject the insulation material to load, so rigid polyurethane foam is commonly used.

Basic LNG facts

What is natural gas?

Natural gas is produced from oil and gas fields. It is a colorless, odorless, high-calorie combustible gas with methane as its main component. It is lighter than air, so it does not accumulate in low places in the unlikely event of a leak, and its natural ignition temperature is higher than other fuels, enhancing its safety. It is also a cleaner energy source than coal or oil because when burned it emits 30 to 40% less carbon dioxide, which contributes to global warming.

What is LNG?

LNG (liquefied natural gas) is natural gas that has been cooled to such a low temperature (–162 °C) that it liquefies. This process is used to efficiently transport and store natural gas from distant oil fields.

Pipelines are the primary method of globally transporting natural gas. However, in island nations like Japan that depend on imports and are surrounded by sea, transportation is mostly done by LNG carriers. When natural gas is liquefied, its volume reduces to about 1/600th that of its gaseous state, allowing large quantities to be transported at once. The tanks in LNG carriers function like a vacuum flask to maintain a temperature of –162 °C, and they are designed to withstand the temperature differences experienced during transport and when empty.

Therefore, constructing the insulation that LNG carriers rely on demands strict quality control and high technical capabilities.

What is LPG?

LPG (liquefied petroleum gas) is a general term for gases such as propane and butane that can be easily liquefied by pressure and cooling. When liquefied, its volume reduces to 1/250 that of its gaseous state. When the main component is propane, it is called propane gas, and it is called butane gas when butane is the main component. It is obtained as a by-product of refining petroleum or producing natural gasoline and is used in households and industry.

Chemical tanker vessels

Chemical tankers are ships designed for transporting liquid chemicals.
They mainly transport petrochemical products (methanol, ethylene glycol, etc.) and non-petrochemical products (phosphoric acid, sulfuric acid, palm oil, caustic soda, ammonia, etc.).
They are typically divided into multiple tanks, which may be specially coated or made of stainless steel.
The type of cargo a tank can transport is determined by its coating or material.
Tanks come in various shapes and sizes, and each ship has specific insulation specifications. Inocrete has experience in various insulation construction methods for chemical tanks, including urethane spray methods, urethane spray and injection methods, and insulation panel methods.

Insulation installation process for chemical tanks

Refrigerated transport vessels

As Japan’s food consumption increased during its era of post-war recovery and high economic growth, mass transportation of fruits, meats, and fish from overseas began. Inocrete’s technology supported the construction of thermal insulation for refrigerated transport vessels, which played a crucial role in this transportation.

Overview

A refrigerated carrier (“reefer”) can be defined as a ship that transports cargo while maintaining an optimal environment for preserving its quality.

The environment we’re referring to here includes temperature and humidity conditions, as well as fresh air ventilation.

The cargo can include frozen goods (frozen foods and processed products including meat and fish) and fruits and vegetables, each of which must be transported under suitable temperature and environmental conditions.

Refrigeration equipment air-conditions the cargo hold to create an optimal environment, economic operation of the equipment maintains that optimal environment, and the cargo hold is thermally insulated to prevent the ship’s steel plates from cooling and causing damage. Thermal insulation construction for cargo holds differs from that for other applications (such as insulation for land-based refrigerated warehouses, plant facilities, or residential buildings) in two main aspects.

First, the equipment necessary for cargo transportation and handling must be installed in the hold. The second point is that the ship’s steel plates surround the thermal insulation layer.

These two characteristics of a refrigerated carrier make thermal insulation installation more akin to equipment and, conversely, simplify it as compared to other types of thermal insulation work.

Transported items

Ultra-low temperatures	(–60 to –30 °C) Tuna
Low temperatures	(–30 to 0 °C) Beef, pork, poultry, primary processed foods
Chilled	(–4 to 0 °C) Oranges, apples, grapefruits, kiwis, pineapples, spinach, cauliflowers, onions, ripe tomatoes, asparagus
Higher temperatures	(0 to +15 °C) Lemons, potatoes, unripe tomatoes, cucumbers
	(+12 to +14 °C) Bananas

The temperature range thus varies depending on what is being transported, as the optimal environment for preserving freshness differs from one item to another. Particularly, tuna requires storage at temperatures below –50 °C, and ships that transport it at such ultra-low temperatures are distinguished as ultra-low temperature vessels.

Furthermore, fruits and vegetables are still alive after harvest, meaning they continue to breathe and will spoil if left unattended. However, reducing oxygen and increasing carbon dioxide levels in the atmosphere allows long-term preservation. This method is called “controlled atmosphere” (CA) storage.

Employing CA storage throughout the cargo hold of refrigerated carriers enables long-distance mass transportation.

Cargo hold equipment

Let’s take a look at the cargo hold of a refrigerated carrier for transporting large quantities of fruits and vegetables.
One characteristic of these ships is that the cargo hold is equipped with devices for transportation and cargo handling.

Upper deck hatch cover

Lower deck hatch cover

Cooler

Ventilation grating

 
 

Wood liner construction

This construction involves the installation of conditioning materials (wood liners) for placing IMO type-C tanks on the ship’s tank saddles.
Materials processed according to the tank specifications, such as durable and water-resistant Apitong and high-strength beechwood impregnated with phenolic resin, are laid or adhered using a special mastic material.

Wood liner installation process

 
 

Piping insulation installation

Ships are equipped with various types of piping. A rigid urethane board insulation material is used for pipes that must be kept cold, which are protected with fiber-reinforced plastic (FRP) or metal jackets.
FRP is a composite material made by combining reinforced fibers (glass or carbon fibers, etc.) with resins (unsaturated polyester, vinyl ester, or epoxy resins, etc.). It is lightweight and has excellent strength, corrosion resistance, and moldability, so it is used in applications like small boat hulls, aircraft equipment, bathtubs, corrugated sheets, and safety helmets.

Piping insulation construction process

 
 

Fireproofing, insulation, and soundproofing installation for living quarters and engine rooms

These installations involve attaching rock wool to areas like living quarters and engine rooms, which require fireproofing, insulation, and soundproofing. Rock wool is a synthetic mineral fiber produced by mixing materials like basalt or blast furnace slag with limestone and melting them together at high temperatures. Rock wool is a safe material with excellent insulation, fire resistance, and sound absorption properties, widely used as insulation material in ships and buildings. Fire disasters on ships can lead to serious accidents involving human deaths, so fireproofing work is crucial.
Insulation pins are installed on walls and ceilings to secure and finish the rock wool.

The fireproofing, insulation, and soundproofing (rock wool) construction process

 
 

Refrigerator equipment installation

This work involves installing a refrigerator inside the ship for food storage. This refrigerator stores the crew’s food ingredients during voyages. Its floor, walls, and ceiling are enclosed with insulation panels, and the floor is equipped with resin grates, insulated doors, and shelves, along with (separately installed) cooling equipment and lighting to maintain a constant temperature.

Refrigerator equipment construction