Formal safety notice recommends actions to prevent LNG leakage from /connect hose bunkering and transfer system connections
The Society of Gas as a Marine Fuel (SGMF) issued a formal safety notice in July with recommended actions to prevent LNG leakages from /connect couplings (DD-CC) hose /transfer system connections.
The safety notice concerns LNG bunkering operations, ship-to-shore (STS), shore-to-ship and truck- or mobile-to-ship transfers. The formal safety notice was issued after SGMF received reports of LNG leakage related to the connections between hose bunker systems and gas-fuelled vessel manifolds. The main issue identified provides evidence that differential movement and applied forces between supply and receiving bunkering equipment are causing leakages where /connect couplings are employed, highlighting the need for guidance on how they should be used, said SGMF. All the reported leakages were detected and safely issues addressed.
DD-CC are manually operated mechanical devices that enable the hose bunkering system to be quickly and safely connected to, and disconnected from, the manifold of the receiving vessel without employing bolts. The coupling consists of a nozzle and a receptacle. These couplings are also known as dry-disconnect couplings or dry-break couplings.
“SGMF received reports of LNG leakage related to the connections between hose bunker systems and gas-fuelled vessel manifolds”
/disconnect couplers use a manual or hydraulic mechanical device to connect the transfer system (such as a loading arm) to the bunkering manifold presentation flange without employing bolts.
SGMF acknowledges and approves the use of ISO 21593-2019 DD-CCs as a suitable connection option. However, the society noted that DD-CCs produced before its publication of ISO21593-2019 are still in use.
SGMF points out that a DD-CC has a limited capacity to withstand external loads and 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 a loss of tightness in the connection between the DD-CC nozzle and receptacle.
Operators should refer to the maximum allowable bending loads for the vessel manifold, as described in SGMF TGN06-04 Manifold arrangements recommendations, and to DD-CC in ISO 21593-2019. These loads should be compared with the approximate weight of hoses and fittings, as reported in SGMF TGN06-06 LNG Bunkering with hose bunker systems.
Recommendations
In its notice, SGMF made a number of recommendations. First, it recommends fully supporting the DD-CC connection of a hose bunker system to a gas-fuelled vessel manifold presentation flange. This means the hoses should be fully seated on hose saddles or supported by hose buns so that the weight of the hose rests on the support for the whole duration of the operation. Additionally, the hoses should have enough slack to prevent them from lifting away from their support if there is a change of draught or tide, or if there are other relative movements between the bunkering facility and the gas-fuelled vessel. Also, when supporting the hose, operators should not restrict its movements to avoid damaging the hose.
Second, loads and forces at the DD-CC connection are recommended to be checked by design calculation against the maximum allowable DD-CC bending moment, taking into account the actual application and bunkering scenario (hose size and weight, support cantilever, etc); and the dynamic and static loads applied at the connection.
“Hoses should have enough slack to prevent them from lifting away from their support”
Third, 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 §2.3: via a flange bolting assembly where the two flanges are standard ASME B16.5 class 150 RF; or via a manual or hydraulic connect coupler, often referred to as a camlock or QC/DC to a standard ASME B16.5 class 150 RF manifold presentation flange.
Furthermore, an alternative means of connection may be allowed by the administration under the provision of an alternative design route.
Transfer hoses
As LNG bunker operations have rapidly expanded globally to meet the uptake of LNG as a fuel, international rules and guidelines have been continuously updated, based on accumulated experience to ensure the safety of these bunkering operations. Manufacturers of LNG transfer hoses use these guidelines to improve their product and system design.
One of the latest updates is EN 1474-II for LNG transfer hoses in dynamic conditions. Published in 2020, this document was revised based on 15 years of LNG transfer experience by industry professionals to ensure safe and reliable LNG transfer operations.
Last year, Gutteling Multi-LNG White STS hoses were qualified to the latest EN 1474-II 2020 standard by class societies DNV and ClassNK. Since 2005, Gutteling Multi-White STS hoses have been used in STS LNG transfer operations. These hoses are designed by Gutteling for handling cryogenic liquids such as liquid nitrogen and LNG down to temperatures of -196°C. Gutteling Multi-LNG White Hoses can be supplied in two different types: Multi-LNG White hoses for LNG bunkering, STS and industrial applications and Multi-LNG White STS hoses for STS and LNG bunker operations.
Qualification with EN 1474-II ensures that LNG bunker operators are able to work with fully certified and reliable transfer hoses, which are 100% in compliance with all new requirements issued by the LNG industry itself. These hoses can be used in combination with loading arms and flexible pipelines and are produced and certified to international standards EN 13766, IMO IGC, EN 1472-II, EN 12434 and PED regulations.
In 2021, Manntek designed and produced a custom-made LNG transfer system for the 7,500-m3Avenir Accolade and its sister ships, some of the world’s largest LNG supply and bunker vessels.
For Avenir Accolade, Manntek designed and supplied an LNG transfer system as a two-hose system of8-inch size and SIL2 compliant.
