Wider adoption of alternative fuels, particularly LNG, requires regulatory support and ample infrastructure
More owners would consider LNG as a fuel for tugs in ports if there were greater financial incentives from authorities and more investment in refuelling facilities.
This was one of the key conclusions from PSA Marine senior manager for fleet engineering Jeffrey Sim’s presentation during Riviera’s Alternative fuels for powering a tug: the selection conundrum webinar on 2 September, which was part of Tug Technology Webinar Week.
Mr Sim revealed the handling and operating challenges of LNG in his presentation, noting that PSA bunkered LNG onto its harbour tugs PSA Aspen and PSA Oak in 2020.
These two tugs have dual-fuel engines, a pair of Niigata 6L28AHX on PSA Aspen and two Wärtsilä W9L20DF on PSA Oak.
Mr Sim explained there were positives from investing in LNG-fuelled tugs, particularly reduced fuel costs and reductions in emissions and noise. But there were also considerable challenges to overcome.
“We have seen a 22% reduction in CO2 and 15% lower noise levels for better crew comfort, compared with conventional diesel-fuelled tugs,” said Mr Sim.
Some of the challenges PSA Marine faces in operating LNG-fuelled tugs include additional safety and manning for truck-to-tug bunkering.
“Bunkering takes three times longer than with a conventional diesel tug, so we need to book this up to seven days in advance,” said Mr Sim.
He said the operation “needs additional crew deployment for monitoring bunkering, manning the bunker station and controls in the engineroom”.
There are additional safety protocols such as quick connect/disconnect cryogenic couplings and hoses for fuel transfer, a water curtain and drip tray and nitrogen gas supply for purging.
Crew also need training to manage bunkering operations, dual-fuel engine maintenance and to maintain onboard LNG storage and handling systems.
This was covered by PSA Marine through classroom and onboard training, bunkering courses and hazard workshops.
“Operating LNG-fuelled tug has its challenges though it is commercially ready and available,” said Mr Sim.
During his presentation, Mr Sim shared PSA’s LNG triangle to explain the decisions and challenges with operating dual-fuel tugs. This includes bunker availability, regulator support and costs – both capital and operating expenditure – in the three corners.
Mr Sim said financial and regulatory support is important to help cover the additional capital costs for building a dual-fuel tug compared with a conventional diesel vessel.
PSA Aspen and PSA Oak have similar features in overall length, gross tonnage, LNG tank capacity, maximum speed and bollard pull.
PaxOcean built PSA Aspen in 2019 to a RAmparts 2800-DF design and Bureau Veritas class. This 447-gt tug has an overall length of 28.2 m and moulded beam of 11.5 m. It has a hull depth of 5.5 m and maximum navigational draught of 4.6 m.
During sea trials PSA Aspen achieved a bollard pull of more than 56 tonnes and free running speed ahead of over 13 knots.
Its main propulsion includes two Niigata medium-speed 6L28AHX dual-fuel main engines, each generating 1,618 kW of power at 750 rpm.
These each drive a steel shaft connected to a Niigata ZP-31 Z-Peller propulsion unit, with 220-cm diameter fixed-pitch propeller, and zero-to-idle slipping clutch.
Use this link to view Riviera’s Alternative fuels for powering a tug: the selection conundrum webinar from Tug Technology Webinar Week
PSA Marine will present other tug technologies during Riviera’s virtual Smart Tug Operations Conference, on 13 October, click on this link to access more details and the proposed programme