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Schematic of LNG single containment flat bottom tank part 2 (EN 1473)

Flat Bottom Storage Tank – Different Types and Its Features

In my third LNG project, I had a chance to meet two different LNG storage tank vendors. One vendor produce vacuum insulated  storage tank (pressurized type) and the other one produce flat bottom storage tank (atmospheric type).

During the meeting I got several terms of  LNG flat bottom storage tank types, such as single containment tank, double containment tank, and full containment tank. What was that?

In this post I want to share you different types of LNG flat bottom storage tank and its special features.

Single Containment Tank

Typical feature of single containment storage tank is primary liquid containment open-top inner tank, a carbon steel primary vapor containing outer tank, and earthen dike for secondary containment.

Schematic of LNG single containment flat bottom storage tank part 1 (EN 1473)
Schematic of LNG single containment flat bottom storage tank part 1 (EN 1473)
Schematic of LNG single containment flat bottom storage tank part 2 (EN 1473)
Schematic of LNG single containment flat bottom tank part 2 (EN 1473)
Schematic of single containment LNG storage tank (source: Kawasaki Heavy Industries Ltd)
Schematic of single containment LNG storage tank (source: Kawasaki Heavy Industries Ltd)

Peru LNG selected single containment flat bottom tank due to site remoteness and enough space is available to provide secondary containment thus comply with regulations and represented safe design of installation.

Peru LNG export teminal with two single containment storage tanks
Peru LNG export teminal with two single containment storage tanks (source: http://www.cbi.com/What-We-Do/Project-Profiles/PERU-LNG-Export-Terminal)

Double Containment Tank

Double containment tanks are similar to single containment tanks except that outer tank is capable of containing liquid spill in the event of a breach in the inner tank wall. The tank design has a freestanding 9% nickel inner tank an outer tank made of either prestressed concrete or reinforced concrete. Type of LNG storage tanks in Arun, Indonesia, is double containment tank.

The outer concrete wall increases the cost of the tank, but less space is required because no need for containment dike. If the inner tank fail, the liquid will be contained and vapor will escape through the annular gap which is the space between the two tanks or tanks and the concrete wall.

Schematic of double containment LNG storage tank part 1 (EN 1473)
Schematic of double containment LNG storage tank part 1 (EN 1473)
Schematic of double containment LNG flat bottom storage tank
Schematic of double containment LNG flat bottom storage tank
LNG Storage Tanks at Arun - All of them (4 tanks) are secondary containment type storage tank
LNG Storage Tanks at Arun – All of them (4 tanks) are secondary containment type storage tank

Full Containment Tank

Full containment tank is double containment tank in which the annular gap between outer and inner tank is sealed. Typical feature of full containment tank is primary liquid containment open-top inner tank and a concrete outer tank. The outer tank provides primary vapor containment and secondary liquid containment. In the event of leak, the outer tank contains the liquid and provides controlled release of the vapor. Majority of LNG storage tanks built in the last 10 years worldwide have been designed as full containment tanks.

Full containment flat bottom storage tank
Full containment flat bottom storage tank
Full containment flat bottom LNG storage tank part 2 (EN 1473)
Full containment flat bottom LNG storage tank part 2 (EN 1473)
Full containment flat bottom LNG storage tank part 3
Full containment flat bottom LNG storage tank part 3
LNG Storage Tank at Donggi Senoro LNG is an example of Full Containment Storage Tank
LNG Storage Tank at Donggi Senoro LNG is an example of Full Containment Storage Tank (source: BG&G containment structure capability)

In-Ground Storage Tank

The advantages of in-ground storage tanks is required less space area and reduced seismic loading but are very expensive and required longer time to build – about 4 to 5 years compared to 3 years for a tank built above ground.

In-ground storage tank
In-ground storage tank (source: http://www.tokyo-gas.co.jp/lngtech/ug-tank/)
In-ground LNG Storage Tank
In-ground LNG Storage Tank (source: http://www.tokyo-gas.co.jp/lngtech/ug-tank/)
Schematic of LNG in-ground storage tank
Schematic of LNG in-ground storage tank (source: Kawasaki Heavy Industry Ltd)

References:

  1. Peru LNG : a grassroots gas liquefaction project optimized for cost in difficult times
  2. BS EN 1473
  3. Rollover in LNG storage tanks
  4. Managing LNG risks – containment

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