LNG import terminal operators must assess how LNG reloading operations impact their facilities
LNG import terminals are designed and built to unload LNG from carriers into storage tanks, where it can be regasified and injected into pipeline networks. Over the last decade, more LNG import terminals have broadened their services, offering the capability to reload LNG carriers, providing more flexibility in the LNG market. These reloading operations, however, involve a number of challenges and risks that might not have been considered in the original design of a purpose-built LNG import terminal.
Recognising this, a task force at the International Group of Liquefied Natural Gas Importers (GIIGNL) undertook a study to develop a reference guideline to help LNG import terminal operators better understand the challenges and technical risks associated with reloading operations and to develop best practices.
National Grid Grain LNG technical development manager Goke Phillips, who headed up the GIIGNL study task force, says LNG import terminal operators that offer reloading operations need to conduct risk and process safety assessments, methodically examining all of the terminal’s assets and equipment. “You need to understand how changing your operation will affect your original design intent,” Mr Phillips told delegates at Riviera’s LNG Ship/Shore Interface Conference in November. “You need to look at the worst-case scenarios and their likelihood, carry out an analysis and implement mitigation measures,” he added.
“You need to look at the worst-case scenarios, assess their likelihood, carry out an analysis and implement mitigation measures”
Mr Phillips believes terminal operators should conduct technical studies that assess risks associated with surge, terminal boil-off gas (BOG) facilities, in-tank pump operating curves, LNG loading arm arrangements, increased jetty usage and LNG carriers.
For example, typical terminal loading transfer rates can be up 12,000 m3/hr. However, reloading rates, transferring LNG to the LNG carrier, are significantly slower, perhaps between 2,000 to 4,000 m3/hr. As a result, an LNG carrier might spend two to six days at a jetty. These are marine structures that were originally designed for loading operations that might take just 24 to 36 hours. “What’s the impact of that on the integrity of your loading arms, fender panels, mooring hooks, gangways and structure?” said Mr Phillips. He noted that assessments need to be carried out on the mechanical integrity of the loading arms, the condition of the berthing equipment, mooring hooks, gangway and jetty structure.
Another example, Mr Phillips cited was the non-return valve (NRV), which is used to prevent LNG backflow to the ship in a loading operation. NRVs can prevent backflow of LNG in case of a carrier pump trip which may cause loss of pressure and reverse flow potential. Another instance would be during recirculation, as an additional layer of protection (after isolation valves) to prevent LNG leaks to the environment.
During a reload operation, both LNG and vapour flow direction will be reversed compared to the original design intention. If NRVs are installed on the liquid transfer arms, operators must determine how to achieve flow through (or around) the NRVs.
Possible solutions, said Mr Phillips, are the temporary removal of the internal components of the NRV, use of retractable NRVs, or installation of an NRV by-pass line.
Mr Phillips emphasised that all stakeholders, the import terminal operator, LNG carrier operator, emergency services personnel and port authority must have clear responsibilities to ensure a safe operation. The GIIGNL Technical Study Group report, Guidelines for Reloading LNG Carriers at Importation Terminals is available for download on the GIIGNL website.
CNG loading arm for FSRUs
LNG importers have increasingly looked at floating storage and regasification units (FSRUs) as ‘plug and play’ solutions for import terminal development. FSRUs can offer greater flexibility, lower capex and shorter timelines to importing LNG-sourced natural gas. In 2019, FSRUs were used for new import terminals in Bangladesh, Jamaica and Turkey. Of the current operational fleet of 34 FSRUs, 24 were used as full-time import terminals, according to the International Gas Union (IGU). There are another 12 FSRUs under construction.
Germany’s SVT GmbH, which has been designing marine loading arms for over 50 years, has now launched a hydraulically operated high-pressure compressed natural gas (CNG) marine loading arm designed to meet the requirements of high pressure CNG berth and FSRU applications.
The SVT CNG marine loading arm contains a newly developed high-pressure safety release coupler (HP QCDC) for CNG service. The HP QCDC is certified by class society Lloyd’s Register and OCIMF requirements.
One of SVT’s latest LNG marine loading arm installations is at Tacoma LNG at the Port of Tacoma in Tacoma, Washington. Located at the first LNG bunkering pier on the US west coast, an SVT Arctic series triple-swivel assembly fuel marine loading arm will be used to refuel two US-flag roro vessels.
In a multi-phase conversion, Tote Maritime Alaska is refitting Midnight Sun and North Star, two coastal roro vessels, to burn LNG as a fuel. Making the conversion unique in North America is the fact that the two Orca-class sister ships will undergo much of the required work while they remain in operation.
LNG bunkering of the vessels will be handled once a week at a marine loading pier at the Port of Tacoma. While SVT’s Arctic marine loading arm is designed to reach the bunker station on the Tote vessels, accounting for a large tidal variance, it will also be able to load LNG onto bunker barges or other vessels at a rate of 10.5 m3 per minute. The LNG will be supplied to the bunkering pier by an underground LNG pipeline.
Being developed by Puget Sound Energy and Puget Sound LNG, Tacoma LNG will enter commercial service in Q1 2021.
Unique hydrogen loading arm
With its eye on a decarbonised future, Japan is committed to developing low-cost utilisation of hydrogen as energy and the supply chain to support it. In December, Suiso Frontier, the world’s first liquefied hydrogen carrier was launched in Japan by Kawasaki Heavy Industries (KHI).
The 2,500-m3 liquefied hydrogen carrier is part of the Shell-backed Hydrogen Energy Supply-Chain Technology Research Association (HyDYSTRA) demonstration project. Brown coal in Australia will be used to produce H2, which will be liquefied and shipped to Japan.
Working with KHI, Japan Aerospace Exploration Agency, and Japan Ship Research Association, Tokyo Boeki Engineering developed the world’s first loading arm for transferring liquefied hydrogen (LH2) from a carrier to an onshore storage facility. The 11.5-m LH2 loading arm will have a double-walled vacuum insulation structure, a highly flexible swivel joint that permits 360-degree rotation and an emergency release system (ERS) that safely halts LH2 transfer by quickly shutting the valves of the pipes and safely disconnecting them in the event of an emergency.
Since the temperature of LH2 is lower than the liquefaction temperature of air, using loading arms designed for LNG would run the risk of fire. During LH2 transfer, liquid oxygen may be generated on piping surfaces. To prevent such generation, a structural design was developed that provides high thermal insulation performance and ensures safety, says Tokyo Boeki Engineering.
The loading arm’s swivel joints and ERS were tested at Noshiro Rocket Testing Centre in Akita Prefecture, Japan, which is operated by JAXA, an aerospace research and development institute with ample knowledge of LH2 as a rocket fuel. The tests involved disconnecting the ERS filled with LH2, as well as 400,000 sequential rotations of the swivel joint, to ensure a high level of safety and durability over time.
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