November 2020

KR's LNG Bunkering Risk Analysis and Safety Zone Setting

16 November, 2020

System Safety Research Team in R&D Center Div,KIM Chong-min

LNG is recognized by the maritime industry to be a clean alternative fuel which can effectively meet the environmental regulations proposed by the International Maritime Organization (IMO). The adoption of LNG fuel for ships offers potential economic advantages and as a result, the challenges to the development of LNG fuel systems and LNG bunkering vessels are being actively addressed. Similarly, orders to build LNG fueled ships are gradually increasing and it is anticipated that the majority of new ships in the future will be LNG fueled vessels.

"Bunkering" is the supply of solid, liquid, gaseous fuel or other energy sources as propulsion and specific-purpose energy for marine (sea) ships from a dock or dedicated ship. LNG bunkering is an operation that transports (supplies) LNG for fuel to sources, using tank-rory, onshore pipelines or ships to receiving vessels (LNG fueled vessels).

For the commercial introduction and spread of LNG fueled ships, there must be adequate LNG fuel ship bunkering infrastructure and safe operation technology. To support the LNG bunkering industry, the Korean Register (KR) provides ship to ship (STS) LNG bunkering safety procedures and risk analysis services to promote safe and efficient LNG bunkering operations.

Although, there is no domestic STS LNG bunkering, the first STS LNG bunkering will be carried out in the near future in Korea. The Korean Register conducted a risk assessment for this planned STS LNG bunkering operation, and we advise STS LNG bunkering performers on ways to strengthen their safety management for STS work and LNG transport by conducting detailed risk analysis.

The purpose of STS LNG bunkering risk analysis is:

❶ To review and understand the characteristics of STS LNG bunkering operations from the viewpoint
    of safety,
❷ To identify the nature and scale of hazards that exist in STS LNG bunkering operations,
❸ To identify the potential impact of the hazards on the people, the environment, and the asset
    associated with STS LNG bunkering operation,
❹ To review the adequacy of qualitative risk levels of STS LNG bunkering operations, and
❺ To propose additional safety actions and recommendations to improve the safety of STS LNG
    bunkering operations.

Figure 1. Ship to ship LNG bunkering

The main hazards identified in STS LNG bunkering are different depending on the bunkering location and recipient. The countermeasures for adopted by the operator for STS LNG bunkering vary depending on the “self-safety management plan” and “contingency procedure”. The analysis range can be divided into four, according to the STS LNG bunkering procedure.

The first is "ship approach and departure". For the purpose of mooring STS, we identify the risk that occurs in the process of two ships approaching and deberthing from each other after the bunkering process.

The second is “STS mooring connection and release”. It identifies the risk that may occur in the process of connecting and fixing two ships mooring lines to start the LNG transfer and in de-mooring after the LNG transfer is complete.

The third is “connecting and disconnecting bunkering hoses”. We identify possible risks when connecting bunkering hoses for LNG transfer in earnest after mooring is complete and when disconnecting the connected hoses after the LNG transfer has been completed.

Finally, “LNG transfers”. After all the preparations for STS LNG bunkering are complete, there is risk relating to the cryogenic LNG transport through the connected hose.

Severe hazards include bunkering hose LNG leaks, hose and manifold connections, LNG leaks resulting from damage to the hull and injury to workers during LNG transfer operations. STS LNG bunkering personnel must take measures to reduce the level of risk, and to identify any further risks.

Dangerous zones such as Zone 0, Zone 1 and Zone 2 are permanently established for LNG fueled ships and LNG bunkering ships and related safety equipment and countermeasures are in place.

However, proper management of the bunkering workspace can vary because it is greatly affected by the size of the receiving vessel and the surrounding environmental elements.

In addition, the “Controlled Area” is only needed for the duration of bunkering, so no permanent action is required. This is because LNG is transported through external equipment such as STS LNG bunkering hoses or loading arms. Therefore, the safety management area must be properly set around external equipment at the same time as bunkering.

In addition, proper safety management is required to prevent air LNG leakage as a result of hose damage, and to prevent deck/offshore LNG leakage. The "Safety Zone" means an area in which special safety precautions have been put in place to mitigate the risk of natural gas or LNG leakage during bunkering operations. The size of the safety zone is determined by the size of the ship, the amount of LNG leakage, the surrounding environmental conditions (weather, temperature etc.) and the geometry of the leak point. The criteria are set based on the concentration of the leaked LNG vapor below the lower flammable limit (LFL).

Safety management measures include leakage control measures, ignition sources removal, personal protective equipment, and work by appropriately qualified workers. KR conducted its research on safety zones established during STS LNG bunkering, through joint research with a domestic “anonymous company”.

In the future, KR has plans to provide a service that tailors safety management procedures and safety management zones to customers who want to bunker with STS LNG.

Figure 2. Schematic Diagram of STS LNG bunkering “Safety Zone”

• Gas jet leak - horizontal and vertically upwards dispersion (H1 and R1)
• LNG downwards dispersion onto land (H2 and R2) and onto water (H3 and R3)

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