Building on experience

A lot has changed from the first days of LNG bunkering. As LNG-fuelled ships emerged, and needed to be supplied, the first truck-to-ship (TTS) bunkering operations were carried out. The first single truck deliveries resembled TTS bunkering operations of oil products, albeit with a lot more time spent setting up the safety measures, obtaining permission and performing the thorough LNG bunker checklist. Indeed, for early operations, the interval between the arrival of the truck and its departure from the quay could be up to four hours. When ships started increasing in size, and thus began requiring multiple truckloads of LNG in order to be bunkered to capacity, this interval would increase almost linearly, especially since each truck unloading was considered to be a separate operation. This meant that prior to each truck unloading its cargo, a complete review of the LNG bunker checklist, etc., would take place. Furthermore, on some occasions, each truck would need to take its own gear (hose, emergency shutdown (ESD) link, fire hydrant, etc.) to its next operation, which created an additional delay interval between each individual truck unloading, adding to the total length of the bunkering operation. Considering that a single operation could consist of more than 10 trucks, each needing to offload their cargo over a two hour period, one by one, it was a logical step to begin to examine options that could facilitate a multi-truck operation.

The first location to allow this type of operation was the Port of Amsterdam, with the bunkering of the Fure West, followed by Rotterdam, where, at Titan’s own permitted site at the Rotterdam Short Sea Terminal, the LNG-powered retrofit vessel Wes Amelie received six truckloads of LNG in three pairs of two trucks simultaneously. This almost halved the overall delivery time, and also provided some flexibility in the operation, in cases where a truck would arrive late due to traffic or other reasons.

With multiple trucks unloading onto one ship, the safety requirements become immediately more complex. As a result, discussions regarding this form of bunkering operation with permitting authorities included a lot more time dedicated to talking about technical issues and operational errors that could arise and how to mitigate associated risks. For example, backflow of LNG, which can result in one truck accidentally filling up another, instead of the ship’s tanks. Also, as the quantity of LNG being bunkered increases, so does the risk of an accident, which in turn enlarges the risk zone of the operation. Furthermore, with the need to efficiently switch from one truck to another mid-operation, additional cryogenic valves are required, as well as safety valves to protect against human error, and many more instruments to assist operators in managing the greater complexity of the operation. The purging system also becomes more complex with regards to this form of operation, and therefore even more valves and instruments are required.

Along with innovating the standard TTS bunkering process to facilitate multi-truck loadings, another development that needed to be made was the installation of an ESD link capable of linking multiple trucks to a ship in one overall system, where each truck, or the ship itself, had the ability to stop the operation if required. This would appear to be a simple task, but, with a variety of systems and connections in place on various trucks and ships, it was not so easy. The system in use today works with the air supply of a truck. The operation must continue even when the truck supplying the air is being changed, therefore the ESD is only triggered if the airflow is interrupted for the entire operation.

This is an abridged version of an article that was originally published in the May 2020 issue of LNG Industry. The full version can be read here.

Read the article online at: https://www.lngindustry.com/small-scale-lng/12052020/building-on-experience/