A closer look at the ‘Vortex’

At the time, Vortex had paid just a fleeting visit to its home port of Southampton before being deployed in the North Sea on the offshore industry ‘spot market’.

The tug has now returned to the UK and has taken up escort and shiphandling duties at Fawley on Southampton Water, a role far removed from its offshore duties in the North Sea.

With that in mind, your correspondent paid has a visit to Vortex to see the implications of this versatility.

Vortex is the fourth high performance Voith tractor tug to be built for Solent Towage in six years. Unlike its predecessors, the tanker handling escort tugs Apex, Phenix and Tenax, this latest addition to the fleet is designed to perform a wide variety of tasks, including ship handling, tanker escort, salvage, fire fighting, pollution control, deep sea towage and anchor handling duties.

Designed by Robert Allan Ltd of Vancouver BC, as an AVT 37/80, the primary aim was versatility The new vessel is very little different in size and hull form to the 38.7m Tenax class but is very different in configuration and is more powerful, with an increase in bollard pull from 65 to 73 tons. Externally the most obvious change is the high forecastle, broad open stern and a stern roller. Below the waterline, the skeg is a little smaller and has no ‘Turbo-fin’. The bow and forward quarters are well fendered to facilitate offshore barge handling operations.

As described in the earlier report, Vortex has Wärtsilä 8L26 diesel engines, each rated at 2,650 kW running at 900 rpm MCR for a total of 7,208 bhp. Each main engine drives a Voith 32R5/265-2 cycloidal propulsion unit with a blade orbit of 3.2m and slightly longer blades than in the earlier tugs.

It is the working deck aft and towing gear that is of special interest. The tug has a typical offshore configuration aft and an impressive inventory of deck equipment that enables the change of role from tanker handling to offshore to be undertaken quickly and efficiently.

The open stern is fitted with a stern roller and heavily fendered to enable shiphandling operations to be carried out in the normal way. A central steel plate extends the length of the deck and provides a mounting for a set of Karm pins and a line handling fork, a small rectangular hatch to the hold below and a unique hydraulically operated, retractable fairlead. The latter is specially shaped and polished on the inside surfaces for use with high performance HMPE synthetic towline during all ship handling and escort operations. Lugs on either side of the fairlead can be used to as an additional means of ‘trapping’ a work wire while anchor handling. Cargo rails are provided on each side of the deck and the remaining areas have a protective hardwood covering.

Vortex has a hydraulically powered, twin drum, Karmoy M361783 towing winch with a maximum brake holding load of 300 tons. Each drum is controlled independently and capable of a 200 tons line pull. Both drums can accommodate up to 1,000m of 57mm diameter steel wire rope (SWR). In normal use a 1,000m towline is carried on one drum and a 150m work wire of 51mm SWR on the other. When necessary the latter can be changed for 200m of high performance synthetic HMPE towline for ship handling. Separate spooling gear, operated by hydraulic rams, is provided for each drum and can be controlled automatically or manually.

A synthetic towline, pennants or spare gear is conveniently stored on a twin drum powered reel on the deck above. Likewise a large powered drum in the stowage hold below deck carries a spare towline of up to 1,200m SWR. The careful positioning of the powered storage drums above and below deck, with their associated leads and rollers, allows changes in towing gear to be made as simple as possible.

Two 9 ton tugger winches are mounted on the deck above the winch, one on either side, with fairleads neatly positioned to allow the wires to be deployed at deck level. A powered reel at main deck level on the starboard side carries 200m of 950mm deep oil spill containment boom for deployment through a hatch on the vessel’s side.

The Effer 44000-3SL, 36 ton/metre hydraulic knuckle boom deck crane can be used for the deployment of a skimmer, to handle the rescue boat or stores and equipment. A skimmer can be used with the onboard oil retrieval equipment and tanks.

The masters and crew aboard Vortex now have experience with the tug, both offshore and during escort operations, and speak highly of their new charge and its equipment. I owe them my sincere thanks for their willingness to show off its various attributes.