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CRYOVISION innovates for its services for Vacuum Testing

Since 2012, the operators of CRYOVISION (GTT's first subsidiary) have sailed on more than 150 LNG vessels around the world, thus transforming their position of pioneers into a position of leader for the thermographic control of tanks equipped with membrane technologies.

Today, in order to be able to provide a complete offer to its customers, CRYOVISION has carried out the qualification process to provide SBTT, PBGT, Helium Test and Vacuum Box test services, all known as “vacuum tests”.

With their in-depth knowledge of GTT technologies, CRYOVISION operators are now working to provide these services, at sea, at repair shipyards or at new construction shipyards.

True to its DNA (inherited from GTT), CRYOVISION has developed innovative tools and procedures to improve or accelerate these "classic" services.

A good illustration of these innovative procedures is the new SBTT (Secondary Barrier Tightness Test) performed at sea (in gassed up conditions).

The test is made by establishing a pressure difference between primary (inter barrier space) and secondary spaces (insulation space between secondary barrier and double hull) and then by recording the variation of the pressure difference in relation to time.

SBTT1

SBTT2

In order to compare test results with reference values obtained previously during ship’s operational life, the test conditions should be close to the standardized conditions of a dry dock.

Tank stripping and warming-up before the test is therefore required although the tanks may be kept in Natural Gas conditions.

Even if the test could be performed in navigation conditions, it is recommended to perform it in calm sea conditions so that any hull deformations (due to ballast acceleration or wave bending moments) remain low and the test conditions remain comparable with the standard test.

Thanks to this more complicated but well-structured and innovative procedure, the Classifications Societies recognize that the SBTT “at sea” is an equal to the SBTT in the shipyard, even though the test is perform with tanks under Natural Gas conditions.

With CRYOVISION’s experience in on-board testing, a choice of light, autonomous and explosion proof equipment has been made to optimise the logistics.

SBTT3

This test is a real alternative to the classic process which consists in waiting for the dry-dock to perform the SBTT.

With this “at sea” procedure, the condition of the secondary barrier may be known prior to dry dock. In case of adverse results, mitigation actions (such as TAMI inspection) could be taken in due time or dry-dock mobilization plan could be modified accordingly.

This is a new opportunity in term of predictability and optimization of Special Survey

With this new opportunity, CRYOVISION can now support its customers throughout all the validation / revalidation process of tanks using membrane technologies.