Canadian naval architect Robert Allan Ltd (RAL) reports that a pair of dual fuel (diesel and LNG) standby vessels, to the RAL RAstar 4200-DF design, have recently entered service with Hongkong Salvage and Towage (HKST).
Built by Cheoy Lee Shipyards, LNG Sentinel I and LNG Sentinel II were specifically designed for service at the Hong Kong LNG Terminal (HKLTL) import terminal.
Featuring an electric propulsion system with Z-drives that can receive power from both diesel and dual fuel (diesel and LNG) propulsion gensets, these vessels will help maintain a safety zone around the terminal and assist with berthing of LNG carriers to the jetty. They will transport personnel plus equipment between Hong Kong and the floating regasification and storage unit (FSRU) and jetty. Their standby duties may include emergency towing of the FSRU, fire-fighting, spill response, and rescue.
Working closely with both HKST and Cheoy Lee Shipyards through the design process was key to enabling RAL to develop this vessel pair that are customised for the missions for which they will be tasked. The vessels are notably the eighth and ninth LNG dual fuel tugs completed to five different RAL designs, with three classification societies, and for service on three continents, which the company considers is illustrative of its expertise in the design of workboats incorporating the use of alternative fuels and propulsion technologies for any service, class, or region.
The 1275gt RAstar 4200-DF design is 42m length overall: 16m beam with maximum draught (navigational) of 6.8m. The HKST vessels are classed by BV with Notation BV I ✠ Hull, ✠ Mach, Dual Fuel, Tug, Fire-Fighting 1 Waterspraying, Unrestricted Navigation, ✠ AUT-UMS, In Water Survey, Oil Recovery Ship Second-Line
The machinery package includes two 1500kWe Wartsila 8L20DF dual fuel gensets, two 1880kWe Wartsila 9L20 diesel gensets, a Caterpillar C4.4 diesel harbour/emergency genset of 82kWe. Propulsion is via two Wartsila WST-32 fixed pitch Z-drives, 3.3m diameter, each driven by 3000kW ABB electric motors and a Schottel STT 60 electrically driven fixed pitch bow thruster, of 125 kW. Wartsila supplied LNGPac double wall vacuum insulated IMO Type C fuel tanks, with integral tank connection space and double airlock.
Design bollard pull is about 105t astern, and speed is quoted as 14+ knots.
Image: RAstar 4200-DF standby vessel for Hong Kong Salvage and Towage (credit: Robert Allan Ltd)
