LNG – or Liquified Natural Gas – is fast becoming an essential part of the global energy market. LNG is principally used for transporting natural gas to hard-to-reach markets, where it is ‘regasified’ and then distributed as pipeline natural gas.
LNG starts life as an approximately 95% methane natural gas (predominantly methane, CH4) that is then cooled down (through a cycle of compression, condensation, expansion and evaporation) to -160°C, at which point it transforms to a liquid form.
The liquefication process involves the removal of particular components, such as dust, acid gases, helium, water, and heavy hydrocarbons, that would potentially create difficulties later down the line.
Not only is transportation of LNG easier in liquid format, but it is also more practical as once it has been liquified, natural gas is less voluminous and can be stored in a volume 1/600th as large. This allows it to be stored and transported safely in very large quantities.
Efficient transportation of LNG is essential. The easiest and most economical method of transportation is to ship it via LNG tankers that have thermally insulated tanks, that have been specially designed to maintain the natural gas in a liquid form.
As an example of the benefits of using LNG as opposed to other fuel supplies, in 2019 the AIDA Nova cruise ship was fitted with low-temperature tanks for liquefied natural gas. By converting from heavy oil to LNG propulsion, the ships emission of CO2 is reduced by up to 25% and other emissions are also lowered significantly.
Nickel Steel Alloys and the LNG Industry
The specialist materials used to transport LNG have to be carefully sourced to ensure that they can safely contain it. During transportation, it is vital that the benefits of natural gas being non-corrosive and non-toxic when it is in its liquid form are maintained. If LNG is vaporised, then it potentially could become explosive or emit thermal radiation hazards. To prevent this, the materials used to transport and store the liquid gas must be reliable and have the ability to maintain the extremely low temperatures required.
Most steel is disposed to crack at low temperatures. This is because of the brittle-ductile transition; an occurrence that causes materials to shatter, rather than deform in extremely low temperatures. However, it has been found that steel produced with 9% Nickel is different: it has a low brittle-ductile transition temperature, resulting in it being able to remain ductile even when extremely cold.
Nickel steel alloys are therefore the most effective metals for the production, containment and storage of liquefied natural gas (LNG) and other cryogenic substances.
These same nickel alloy levels also present strong weldable properties. Where welds are used, they have to be able to be extra tough and resilient to fracture; again, research has found that nickel alloys can withstand temperatures of -196°C without losing toughness.
Nickel is not the only critical material in a nickel steel alloy – the use of stainless steel is also very important as it has a number of advantages of its own. It is highly weldable, has a high resistance to corrosion and does not undergo phase transformations during welding processes. The ability to withstand the impact of very low temperatures comes from a higher ferrite level that is found in high quality stainless steel.
Special Piping Materials and the LNG Market
Special Piping Materials’ global network of experienced mills and manufacturers allows us to source the most high-performing products in the market. Whether it is storage tanks, pipes or other essential items that are required, we are able to source it.
As the LNG industry continues to develop, manufacturing companies that build storage and transportation facilities, such as tanks and tankers, for LNG will need to source large amounts of nickel stainless steel alloys. Special Piping Materials will continue to work closely with both our clients and suppliers to ensure that this need is met.