Feature 6 | TUGS Pump up the volume
An Arabian Gulf-bound, Robert Allan RAstar 3900 class vessel has managed to combine the practicalities of a working tug with a high-powered, Fi-Fi 2-certified pump capacity.
W
hen it comes to developing hybrid fireboat / tug designs, Canada’s Robert Allan would
appear to be on a mission to extend as far as possible beyond the standard Fi-Fi 1 classification requirements that cover the bulk of these boats, and the recently launched RAstar 3900 class Mojaweb seems to be further proof of this strategy. The 39.1m vessel, which was ordered by Kuwait Fire Services for safety operations within the Kuwaiti port of Shuwaikh, has been certified by Lloyd’s Register as a Fi-Fi 2 craſt, packing a powerful punch with a combined pump capacity of 8400m3
per hour. Robert Allan was commissioned to come
up with the vessel design by Kuwait-based Al Boom Marine, while Korean builder Simulation Tech Inc. (STI) was tasked with her physical construction. Featuring a moulded beam of 13.5m, a top operating draught of 5.1m and a minimum bollard pull of 60tonnes ahead (68tonnes ahead was
TECHNICAL PARTICULARS Mojaweb
Designer
....................................Robert Allan Builder ........................................................ STI Length, oa ...........................................39.1m Beam, moulded ..................................13.5m Depth, moulded ...................................6.1m Operating draught, max .....................5.1m Operating speed ............................. 12knots Bollard pull ....................60tonnes, minimum Classification .......................Lloyd’s Register 100 A1 Escort Tug, Fi-Fi 2; LMC
Propulsion 2 x Wärtsilä 6L26 medium-speed engines @ 1946kW each 2 x Wärtsilä-Lips CS250-CP Z-drive units Fire-fighting equipment Wärtsilä 8L26 diesel engine Fi-Fi 2 centre pump, rated 2590kW@1000rpm 2 x FFS ENM 350 pumps at 2400m3 2 x FFS ENM 300 pumps at 1800m3
54
Mojaweb recorded a top speed of 13.1knots in sea trials.
recorded during her sea trials), the vessel has the capacity to carry 252m3 57m3
of potable water, 38m3 foam and just under 3m3
of fuel oil,
of fire-fighting of lubricant oil.
Mojaweb’s ballast capacity is measured at 67.8m3
and her top speed has been recorded
at 13.1knots during trials, although 12knots is her intended operating speed.
RAstar style Mojaweb has been designed to undertake ship-handling and tanker support work. Subsequently, the vessel’s deck comes equipped with a 75tonne safe working load (SWL) tow hook on the aſt deck and a hawser winch on the foredeck. Te vessel is capable of accommodating a maximum operating crew of 14, and features a total of 13 berths. According to Darren Hass, naval architect at Robert Allan and project manager for Mojaweb: “Nine of these berths can be considered dedicated for crew, while the remaining four can accommodate survivors or additional fire-fighters.” As with previous Robert Allan fi-fi
/hr each /hr each
tugs, Mojaweb incorporates the company’s signature RAstar hull form, featuring an outward sponson on the upper hull sides for increased stability. When conducting vessel- escorting duties, should the tug be heeled over as a result of the angle or influence of the towline, the sponson is submerged and acts to right the vessel. Te hull also features an extended skeg, positioned forward,
for roll-damping
purposes, and the overall hull form is intended to reduce roll amplitude and roll accelerations, for added safety and crew and passenger comfort. Te designer claims that, following a series of private model tests, the roll accelerations recorded for the RAstar concept were some 60% lower than for an equivalently sized, ‘wall-sided’ or conventional hull form. Additionally, the design of the hull is capable of guaranteeing superior fuel economy during the vessel’s operational cycle, Robert Allan claims. Te tug’s power comes courtesy of a pair
of Wärtsilä 6L26 medium-speed diesel engines, each rated 1946kW at 1000rpm, which drive a Wärtsilä-Lips CS250-CP Z-drive unit, with a 2400mm diameter propeller. Twin CAT C-18 diesel gensets, each rated 275ekW, provide the vessel’s auxiliary power. Before submitting its plans to Al Boom
Marine, Robert Allan opted for a Wärtsilä 8L26 diesel pump engine, rated 2590kW at 1000rpm. Hass tells Ship & Boat International: “The centreline Wärtsilä 8L26 auxiliary engine drives two 2400m3 FFS ENM 350 fi-fi pumps, supplied by Fire Fighting Systems AS [FFS], off each end, while the two Wärtsilä 6L26 propulsion engines each drive an 1800m3
FFS ENM
300 fi-fi pump off the front end.” Te end result would appear to be a potent means of combating fires and handling various generic vessel-escorting tasks, combined in one package. SBI
Ship & Boat International July/August 2011
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