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LNG Tanks
LNG Storage Technology

For many decades DYWIDAG, a member of STRABAG Group, has been in the forefront of the development, design and construction of prestressed concrete containments for the storage of liquefied gases. The current safety standards for containment systems were to a large extent influenced by DYWIDAG’s engineering work. Various gases require storage at low temperatures e.g. from – 20°C for Propane gas to -165°C. for natural gas (LNG).

LNG is an abbreviation for liquefied natural gas and is liquefied by cooling it to around -162°C to -165°C depending on the exact chemical composition. This reduces the volume by a factor of 600. As a result, the volume required for storage and transport is reduced and LNG has become an economical solution for countries which are not connected to a gas pipeline network.
Liquefaction is a technically safe and economical solution to the problem of storing large quantities of gas and transporting them by ship over large distances.

At both ends of the transport chain storage tanks are required, i.e. prior to loading of the vessel and after off-loading at the destination. Given the size of the available vessels, the common tank size is currently 140–160.000 m³ net storage capacity. In selected markets tanks of 200.000 m³ and in future maybe 270.000 m³ will be realised.

Other markets where storage tanks for liquefied natural gases are needed are for energy suppliers using peak-shaving tanks to cover peak demands and bunker stations with truck loading facilities located at harbours for the supply of ferries and vessels. In general, the capacity of these tanks is much smaller and defined by the available space, demand and local regulations.


Storage Systems

Due to various aspects and requirements related to the storage at low temperatures and the high energy potential of liquefied gases, planning of LNG Tanks is a complex task. In the early years LNG was stored for in single wall steel tanks, as was common practice for oil. Subsequently double containment l steel tanks were introduced. Due to more demanding safety consideration and in some locations lack of space, the overall concept for liquefaction plants included full containment tanks and this has become the worldwide industry standard today. In simple terms, the tank resemble a thermos flask, with insulation between the inner and outer containments to maintain the temperature of the stored liquid at the required level.

The outer containment, a prestressed concrete shell provides the protective component as an integral part of the full containment tank. The inner tank, fabricated with special steel as a stand-alone component, forms the primary storage tank, and the thermal insulation between the inner and outer tank prevents cold loss, thus limiting the vaporisation rate. The inner and outer tanks are designed with separate hydrostatic stability.

In addition, the concept of the tank system is designed to restrict all the effects of any conceivable accident to the inner storage tank. The outer tank protects the primary tank from potential operational disturbances from external sources and, conversely, also protects people and the environment from a potentially explosive gas-air mix, forming as a result of a leak in the inner tank.

In this system the outer concrete tank has to fulfil the following protective functions:

  • Physical protection e.g. against pressure waves from explosions, impact caused by parts of the plant flying through the air, helicopter collision and (cold) liquid impact.
  • Thermal protection e.g. against fire in adjacent tanks, fire on the tank roof, cold shock
  • Collecting and retaining fluids or gases e.g. escaping from a leak in the inner tank.

These requirements mean that the outer tank must form a self-contained gas-tight prestressed concrete containment. To achieve this a multilayer liner system is required in addition on the inner face on the prestressed concrete containment.


Protection from Earthquakes

Locations with high levels of seismic activity pose special risks. Large storage tanks have a fundamental frequency of between 2 and 10 Hz and thus lie more or less within the resonance range of typical earthquakes, i.e. they will be accelerated 3 to 4 times more than the ground on which the tanks are built.

The critical condition can be largely avoided if the vibrational behaviour of the tank can be disassociated from that of the ground. Base isolation, a technique also applied to machine foundations and bridges is one method used to achieve this. The containment is placed on isolators and with a correctly designed system to taking into account the dynamic properties of the ground and the structure, the stresses on the vulnerable steel inner tank can be reduced by 80 – 90 %. For these calculations a dynamic model of the tank structure is prepared. The complex interaction between foundation, isolators, outer tank, inner tank and the liquid can be reproduced realistically with a Lump-Mass model.

DYWIDAG pioneered the worldwide systematic use of base isolators for large scale LNG tanks in the design of the Inchon LNG Receiving Terminal, using round layered elastomer bearings made of natural rubber and steel.

Projects:

1968 LNG Tank Stuttgart, Germany, Volume 30,000 m³
1971 LNG Tank Nürnberg, Germany, Volume 1,600 m³
1990 LNG Tank Mosselbay, South Africa, Volume 10,000 m³
1991 LNG Tanks Lumut, Brunei Darussalam, Volume 2x 65,000 m³
1993 LNG Tanks Inchon, South Korea, Volume 10x 100,000 m³
1995 LPG Tanks Ruwais, UAE, Volume 2x 43,000 m³
1997 LNG Tanks Qalhat, Sultanate of Oman, Volume 2x 120,000 m³
2000 LNG Tank No. 3 Tongyeong, South Korea, Volume 140,000 m³
2002 LNG Tanks Nos. 4 - 10 Tongyeong, South Korea, Volume 7 x 140,000 m³
2002 LNG Tank Point Fortin, Trinidad, Volume 160,000 m³
2003 LNG Tanks POSCO Gwangyang, South Korea, Volume 2x 100,000 m³
2003 LNG Terminal, Long Beach, California, Volume 2x 160,000 m³
2003 LNG Tanks Nos. 1 + 2 Sagunto, Spain, Volume 2x 150,000 m³
2004 LNG Tanks Nos. 11 - 14 Pyeongtaek, South Korea, Volume 4x 140,000 m³
2005 LNG Tanks Bal Haf, Yemen, Volume 2x 140,000 m³
2006 LNG Tanks Nos. 11 + 12 Tongyeong, South Korea, Volume 2x 140,000 m³
2006 LNG Tank No. 3 Sagunto, Spain, Volume 150,000 m³
2007 LNG Tanks Nos. 13 + 14 Tongyeong, South Korea, Volume 2x 140,000 m³
2007 LNG Tanks Design for South Korean Client, Volume 3x 140,000 m³
2007 LPG Tanks Design for South Korean Client, Volume 2x 30,000 m³
2008 LNG Tanks Nos. 19 + 20 Pyeongtaek, South Korea, Volume 2x 200,000 m³
2008 LNG Tanks Nos. 15 + 16 Tongyeong, South Korea, Volume 2x 200,000 m³
2009 LNG Tank Nynäshamn, Sweden, Volume 20,000 m³
2009 LNG Tank No. 4 Sagunto, Spain, Volume 150,000 m³
2009 LNG Tank No. 23 Pyeongtaek, South Korea, Volume 200,000 m³

2010 LNG Tank QCLNG, Queensland, Australia, Volume 2x 140,000 m³
2011 LNG Tank GLNG, Queensland, Australia, Volume 2x 140,000 m³
2013 LNG Tank BLNG, Brunei Darussalam, Volume 1x120.000cbm
Brunei LNG Tank, Brunei Darussalam
Brunei LNG Tank, Brunei Darussalam
[more...]
GLNG - Gladstone LNG Tanks, Curtis Island, Queensland, Australia
GLNG - Gladstone LNG Tanks, Curtis Island, Queensland, Australia
[more...]
QCLNG - Queensland Curtis LNG Tanks, Australia
QCLNG - Queensland Curtis LNG Tanks, Australia
[more...]
LNG Tanks 6-10, 13-16, Tongyeong, South Korea
LNG Tanks 6-10, 13-16, Tongyeong, South Korea
[more...]
LNG Tanks, Nynäshamn, Sweden
LNG Tanks, Nynäshamn, Sweden
[more...]
LNG Tanks, Sagunto, Spain
LNG Tanks, Sagunto, Spain
[more...]



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Downloads:

STRABAG LNG Technology - Brochure english
References LNG Tanks
LNG Journal: Earthquake
LNG Journal: Blast & Impact
LNG Journal: Liquid Spill
LNG Journal: Fire Hazard
SEI 1-2007: Fire Resistance
fib-symposium 2008: Design against Thermal Shock
ACI Fall 2008: Design of Outer Concrete Containments
ACI Fall 2010: Design and Construction of Tanks