Technical Supervisor and Associate Professor
LATTICE Technology and KAIST
09:45 - 10:15
Wednesday, 18 September 2019
T1.3 Lattice prismatic pressure vessels for commercial use
The lattice pressure vessels (LPV) have significant advantages regarding space efficiency, improved safety, reduced weight, and cost efficiency compared with conventional pressure vessels. During the end of 2018 the first LNG fuel tank was delivered for a port cleaning ship by the Ulsan Port Authority, South Korea. The ship was planned as part of the Korean Government’s initiative to promote eco-friendly vessels running on LNG. The concept design was faced with two constraints relating to the tank installation space: One was the IGF Code’s requirement for distance between the hull plate and the LNG fuel tank shell plate to be no less than one fifth of the ship’s breadth. The other problem was that the space for the fuel process room in this case turned out to be as big as the LNG storage room; thereby severely limiting the available space for the tank. The maximum capacity achievable by a cylindrical tank was about 10 m3, providing only 10 hours of operation between bunkering. As alternative, three options for LPVs were considered: flat wall LPV (FW-LPV), round corner LPV (RC-LPV), and round wall LPV (RW-LPV). Weighing trade-off between weight and capacity, the RW-LPV was finally chosen because it provides 15 m3 volume; this capacity was acceptable to the ship owner, and the cost turned out to be as low as for the cylinder without sacrificing functional performance. The RW-LPV was fabricated by Sunbo Industry and by Answer who delivered the tank in January 2019. With the RW-LPV on board, the ship is expected to be in operation from early 2019.
Fabrication of large-scale LPVs has proven to be straightforward. Hyundai Heavy Industries has followed the development of the LPV technology since its beginning, and during 2018 they built an open mock-up of a corner part of a very large LPV. All the fabrication steps of material handling, forming, welding, and non-destructive tests were successfully implemented for the mock up. Another milestone of technology acceptance was that LPVs received a principal approval from USCG (United State Coast Guard); this was significant since USGC is considered internationally as leader in setting safety standards. In an official letter of October 31, 2018, USCG stated that LPVs can be used as pressurized cargo tanks as well as fuel tanks in the U.S. without further requirements based on receiving ASME U2 stamp. Approval will thus be rather straightforward since two out of the four LPV proto-type tanks were designed, built, and tested in full compliance with ASME U2.
The LPV technology provides significant benefits over cylindrical type C tanks, not only more space-efficient and economic storage, but also allow for improvements in the overall ship design with more environmentally efficient hull and higher cargo capacity. In short, a LPV tank is designed to fit the ship, and not the other way around. Such advantages are also valid for land or vehicular storage of LNG, LPG, and liquid hydrogen; this technology may thereby contribute significantly towards achieving a more environmentally friendly, low carbon future.