Proven technology - new methods

 

lnt45 cargo2 infoboxes newSelf-supporting prismatic tanks is a proven and reliable technology - it has been successfully used for more than 50 years in the seaborne transportation of liquefied gas.

By adopting a prismatic shape in the sectional configuration, the cargo tanks fit neatly into the hold spaces. This ensures an almost entirely closed flat upper deck area, which makes low wind resistance and excellent visibility from the bridge possible.

Inside the tanks, bulkheads are installed as structural members and to curb movements of the liquid, eliminating sloshing problems regardless of the liquid levels in the tanks. Furthermore, the solid tank framework structure prevents vacuum problems in the tanks, simplifying pressure control and cargo handling work. This provides flexible route planning, making multiple loading and unloading stops during a voyage possible.

The thermal insulation with the secondary barrier is moved to the inner hull to facilitate visual access of the secondary barrier system, including support structures and tank shell. The hold space is protected from sloshing loads, allowing arrangement of a flexible cold insulation system with outstanding thermal properties.

The LNT A-BOX® containment system is without exception designed on well-proven and recognised elements and technologies.

Traditional and proven tank-supports

The cargo tank support system is based on conventional design principles, but with modified thermal details to provide a strong and thermally efficient connection to the secondary barrier system. The support system comprises recognized laminated compressed wood material to efficiently keep the tanks in place, and to act as thermal breaks between the cold cargo tank and the hull. 

The support structure has sliding surfaces to permit free expansion and contraction of the tanks from the handling of the cryogenic temperature cargo. This to prevent generation of high thermal stresses within the tank structure to minimise the time required for cooldown and cargo handling.

Superior insulation

lnt45 cargo2 detailMoving the insulation to the hull gives multiple benefits

  • An independent type A tank supported by the hull structure prevents the insulated hold spaces from extensive sloshing impulses, allowing the use of insulation materials with outstanding thermal properties.
  • Avoidance of sloshing loads allows simplified corner panel geometries enabling more volume efficient and slender ship hulls for improved transport efficiency. The thickness of the insulation system can easily be adjusted to achieve the required boil-off rates.
  • The insulation system is made of pre‐manufactured polyurethane foam panels, fastened to the inner hull with stud‐bolts through an anchoring system. The panels are bridged together by flexible liquid-tight reinforced aluminium with proven track record.
  • For condition monitoring, LNT A-BOX® is provided with access space for periodical visual inspections of the secondary barrier. Arrangement and procedures for local and global tightness tests have been developed and tested as secondary means for condition monitoring.

A smart and functional gap

The primary and secondary barrier are arranged with access space in-between allowing periodical visual inspections of the thermal insulation with the secondary barrier, including support structures and the cargo tank shell – without gas freeing the tanks.

Any potential deterioration can be detected visually and repaired on site. Insulation panels can be temporarily removed in order to identify their condition and potential damages.