GTT - Gaztransport & Technigaz)

GTT is a French marine engineering compagny specialised in the design of membrane containment systems for the maritime transportation and storage of LNG (Liquefied Natural Gas).

Leader on the market of Cargo Containment Systems (CGS), GTT provides solutions for all the major steps of the LNG chain: LNG Carriers, Subsea Cryogenic Pipeline, Land Storage.

GAZTRANSPORT & TECHNIGAZ

LAND STORAGE

GST® membrane design

GST® is a cryogenic containment system directly positionned on the bottom

slab and on the walls of the concrete structure.



Membrane technologies are referenced in the european (EN 1473, EN 14620) standards as one of the four main existing categories of containment systems for LNG storage.

With a safety level equivalent to full containment tanks, GST® membrane tanks maintain the same principle (two containers separated by an insulation layer) while optimizing the choice of materials as well as the general design.

A double barrier protection

In addition to the stainless steel membrane, a secondary barrier made of a composite laminated material is placed inside the insulating panel.
In the event of a failure of the primary barrier, it limits the stress concentration on concrete corner, as required by European standards.


Separation of the main functions

The GST® concept is based on a clear separation of the main functions of the containment system: the membrane inner container provides tightness; the insulating panel ensures thermal protection; and the concrete walls permit structural resistance to inner and outer loads.
This separation allows for the optimization of each function and avoids simultaneous multiple failures. This enhances the reliability and efficiency of the membrane.


A cost-effective solution

As the membrane has no structural function, its thickness does not increase with the tank capacity. Thus, a GST® tank is less sensitive to the high price of nickel, and the bigger the tank is, the higher the relative cost-savings.

AN ATTRACTIVE CONCEPT

A COST AND TIME SAVING TECHNOLOGY

Prefabricated modular elements

The GST® concept consists in combining a limited number of modular basic shaped components, widely available by normal industrial processes.
The elements composing the membrane layer as well as the insulating panels are prefabricated and are fitted together on site.
The dimensions of the elements (roughly 1m * 3m) were designed for ease of handling.

Automatic welding process

The membrane elements are positionned so that the welding process is automated as far as possible. Specific welding machines have been developped to reduce erection time.

A flexible construction planning

The assembly methods allow different tasks to be carried out at the same time. The general planning of the building ¬process is thus relatively flexible.

A SAFE AND RELIABLE SOLUTION

A COST AND TIME SAVING TECHNOLOGY

Numerous controls throughout the erection of the tank

The materials chosen for GST® containment system are provided by approved suppliers only.
Moreover, each element composing or having a potential interface with the containment system, is controlled several times, from its prefabrication to the final erection phase.

Among the numerous tests carried out, a hydrotest checks the settlement of the foundation and the structural functionality of the concrete container. This test is usually performed after application of the moisture barrier, before erection of the insulating panels.
Performed after containment system erection, an NH3 test and a global test verify the tightness of the GST® containment system.

An efficient monitoring process

The membrane is tightly connected with the steel dome liner, such that the insulation space constitutes a closed cell.

This technological choice presents two main advantages:

  • a permanent control of the integrity of the inner containment by gas analysis of the nitrogen atmosphere in the insulation space, which is under a lower pressure than that of the inner tank ; breathing is ensured by N2 intake or exhaust.
  • a quicker decommissioning phase: as the insulation space is closed, there is no need to gas-free it for decommissioning. This way, inspection and repair can be easily carried out if necessary.

A flexible technology

As it is constituted of standard modular elements, GST® technology can be adapted to every structure, whatever its form or size, without any major changes in the design and dimensions.
The proportions of a GST® membrane tank depend only on the capacity and the geometry (prismatic or cylindrical) required for the storage unit.

A wide range of configurations are available, from above-ground to in-ground tanks, as well as Gravity Based Structures (GBS) and cryogenic caverns.

GTT and YOU

The GTT attractive offer to EPC contractors and sub-contractors includes:

a standard and non-exclusive Licence Agreement,
allowing a fair and equal competition

and a full package of services covering the whole tank lifetime :

- Pre-project studies and assistance during the bidding phase
- Basic and detailed engineering for containment and handling systems
- Material specifications and approval
- Assistance and consulting services during construction and tank maintenance
- Training

GST® Containment System

GST® Pavement


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