The Society for Gas as a Marine Fuel (SGMF) has received several reports of issues and LNG leakages related to the connection and connectors used between hose bunker systems and the gas-fuelled vessel manifolds.
The main issue identified is evidence that differential movement and applied forces between supply and receiving bunkering equipment are causing leakages where dry disconnect/connect couplings (DDCCs) are employed, highlighting the need for guidance on how they should be used.
All reported leakage cases have been detected and dealt with safely.
Dry-Disconnect/Connect Coupling (DD-CC)
SGMF acknowledges and approves the use of ISO 21593-2019 DD-CCs as a suitable connection option. However, it is noted that DD-CCs produced before its publication of ISO21593-2019 are still in use. The following points are deemed applicable to all types of DD-CC.
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A DD-CC has a limited capacity to withstand external loads/forces. This requires the hose and, in general, the connection to be supported, to minimise the lateral stress on the DD-CC and to avoid the loss of tightness in the connection between the DD-CC nozzle and receptacle.
Recommendations
- Hoses should be fully seated on hose saddles or supported by hose buns so that the weight of the hose is rested on the support for the whole duration of the operation;
- Hoses should have enough slack so that they do not lift away from their support if there is a change of draft or tide or if there are other relative movements between the bunkering facility and the gas-fuelled vessel;
- When supporting the hose, care should be taken not to restrict its movements, to prevent damage to the hose;
- Loads and forces at the DD-CC connection are recommended to be checked by design calculation against the maximum allowable DD-CC bending moment;
- Wherever a DD-CC connection is not deemed suitable because of an unacceptable risk of leakage based on a load calculation, the connection from a hose bunker system to a gas-fuelled vessel manifold presentation flange should be achieved by one of the following alternative connection means, approved under the alternative design clause of the IGF Code.
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