Leaking flexitank containers and cross-pumping surveys.

Article of leaking flexitank containers and cross-pumping by constellation’s cargo surveyors.

Leaking flexitank containers and cross-pumping surveys: Nowadays there are many types of flexitanks to carry liquid and grain cargo in containers. Flexitank is actually a bag which is placed inside a shipping container and thereafter filled-up with a liquid cargo. Constellation Marine Services has carried out several surveys of such flexi-tanks due to reported leakages, usually followed with cross pumping into new flexitank.

Constellation surveyors who have been involved in such cargo surveys report that leaking flexi-tanks are quite common. Below listed are the most common causes of leaking flexi-tanks noted by Constellation marine surveyors:

  • Leakage at the double patch around the manifold at top or the bottom of the flexi-tank. This can be the reason of manufacturing problem.
  • Leakage caused by puncturing of the flexi-tank, by sharp edges or parts (nails, screws etc) inside the shipping container, (not properly cleaned and not thoroughly inspected container).
  • Leaking seams. This is probably a manufacturing problem if the same type of flexi-tank has been found with the same sort of leakage several times.
  • Securing belts (some flexi-tanks) pulling off lashing eyes of the shipping container which thereafter puncturing the flexi-tank.
  • No over-pressure valve fitted when carrying the liquid which may give off gas.

Leaking flexitank containers and cross-pumping surveys-Preparation of flexi-tank for loading/cross-pumping.

Constellation surveyor’s experience shows that correct installation of the flexi-tank is the most essential part in transportation of flexi-tank containers by sea, rail and/or road. Installation of a new flexi-tank is quite simple and it can be done at the consignee’s warehouse or at the container yard. Generally it takes about half an hour to install a flexi-tank into a twenty-foot container.

The following precautions must be taken before the new flexi-tank is placed in the shipping container:

  • The inside of the shipping container must be carefully inspected, any protruding nail or other sharp/protruding part in the floor must be removed, sweep up the inside.
  • The floor and lower half of the container should be covered with properly fixed cardboard.
  • Sharp edges should be covered with tape.
  • Bulkhead must be installed in way of the doors, to prevent the flexi-tank bulging out and thereafter no possibility to close the door upon completion of loading of flexi-tank. If force it, the doors can damage the valve.
  • Over-pressure valves should be installed if the cargo may give off gas while in transit.
  • The flexi tank should be full if securing bands are used, to avoid damaging/loosing of the container lashing eyes by excessive stress from belts.
  • It is not recommended to use expired storage products.

To load the flexi-tank, a hose is connected to the manifold and the liquid is pumped in or cross-pumped from other damaged/leaking flexi-tank. Depending on the type of cargo, it takes about from half an hour to one hour to fill up the flexi-tank, and upon completion the manifold and flexi-tank to be inspected for any signs of leakage. Upon sealing the manifold and closing container door, the flexi-tank manufacturer provided signs to be posted on the container door.

Leaking flexitank containers and cross-pumping surveys-Damage to the containers.

Flexi-tanks when filled causing sideways pressure on the shipping container, especially at the side panels. This pressure may exceed the pressure for which the container is designed. Constellation’s marine surveyors have surveyed several instances where the containers have been bulged out causing deformation of the side panels. This usually happens due to “rough” handling with container (“hard landing” on board the vessel, trailer or at the stack yard.)

Leaking flexitank containers and cross-pumping surveys-Conclusion:

Constellation Marine have trained surveyors who are able to investigate the cause, nature and extent of damage of the leaking flexi-tank container, supervise the cross-stuffing, if required, and support it with the full detailed report. It is important to ensure that the flexi-tank is properly packed and secured inside the shipping container. Appointed cargo surveyor will make sure that all the required practices are followed. Leaking flexi-tanks causes not only a loss of cargo, but can also cause damage to other cargo within the same cargo hold. Such leakages may also cause sea pollution when entering bilge systems. Often there is a need to clean the ship’s cargo hold.

View of corrugated paper on floor plate and sides of lower part of the container, rolled out flexi-tankLeaking flexitank containers and cross-pumping surveys- View of corrugated paper on floor plate

View of installed bulkhead (Bottom valve) flexi-tankLeaking flexitank containers and cross-pumping surveys - view of bulk hold

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