Vessel Launch: Hepworth complete Afon Las for use in the Caspian

Afon Las is the eighth multipurpose tug to be completed for the Holyhead Towing Company Ltd by Hepworth Shipyard Ltd at Paull on Humberside. The close relationship between shipyard and owner has resulted in a variety of vessels, tailored specifically to meet the precise needs of the business at the time.

As the Holyhead Towing Company and its associates continue to expand and diversify, the fleet can be called upon to support dredging, coastal improvement, offshore wind farm construction, cable laying, and a host of other marine civil engineering projects. Previous vessels delivered by Hepworth have varied in size from 22.5m to 35m in length and the design process has increasingly become the responsibility of Holyhead’s own technical and operations staff and in-house designer Dennis Newboult. Afon Las was built from scratch at Hepworth’s Paull facility, without recourse to sub-contracting for the hull or other major steelwork.

This latest vessel was built to perform a very specific role and is an almost identical sister ship to the previous tug completed by the yard, the Ak Bars. The shallow draft, twin screw, ice class vessel is capable of fulfilling a wide range of services in the oilfields of the Caspian Sea. A true multi-purpose vessel, the tug is designed and equipped for towing, pushing, anchor handling, cargo and personnel transportation, and the delivery of fuel and water in and around the shallow waters of the oilfields. Afon Las, also bearing the name Aboh Mac in Cyrillic script, will be operated by Holyhead Towing’s joint venture company, Caspinsky Buksir, based in the Republic of Kazakhstan under the Kazakhstan flag, with Russian crews.

Afon Las differs from its predecessor in a number of small details and a slight increase in power. The tug was designed and constructed to meet the requirements of Lloyds Register + 100A1 Tug, Ice Class 1B, +LMC, Unrestricted service. The single chine hull has an overall length of 25.00m (excluding fenders), a substantial moulded breadth of 9.50m, a moulded depth of 3.25m and a loaded draft of 2.50m. An important feature of the design is the large amount of equipment and facilities built into a relatively small tug, yet retaining a very large work deck aft.

In order to meet the shallow draft requirement and maintain maximum buoyancy for anchor handling and load carrying, the propellers and fixed nozzles of the twin screw propulsion system are located in tunnels beneath the stern. The broad flare of the chine in the bow incorporates a transverse bow thruster and a substantial ‘push knee’ is built into the stem. When viewed from the engine room and aft compartments, the impression is one of enormous strength thanks to the heavy framing and steel sections built into the vessel.

The all important fendering includes steel rubbing strakes of half-round section around the bow and on each forward shoulder, overlaid with vehicle tyres. A square section rubber moulding encircles the sides and aft quarters, at deck level. An open stern incorporates a substantial stern roller and the bulwarks have openings, just aft of amidships, to allow hoses, etc to be taken across the deck. The latter are closed when not in use by wooden shutters.

The large after deck is clear of major obstructions and offers both an ample space to work and considerable cargo capacity. A hardwood overlay protects the deck and ‘Twist-Lock’ fastenings are provided for the carriage of standard ISO containers. Integral tanks are provided for 100cu/m of fuel, 45 cu/m of fresh water and 9 cu/m of sewage. The necessary high performance transfer pumps are provided for the delivery of fuel and water to vessels or plant.

Two Cummins KTA 38 M1 engines power the propulsion system in Afon Las. The engines are rated 1,300bhp at 1,800 rpm each, a total increase of just 400bhp over its predecessor. Power is transmitted to twin fixed pitch propellers via ZF W7500 ice class 1B gearboxes with a reduction ratio of 4.939:1. The four blade propellers measure 1,600mm in diameter and rotate within fixed Kort nozzles. A high lift fishtail, rudder is mounted aft of each nozzle and is given some protection by a small ‘ice knife’ located in the top of each tunnel. The steering gear was supplied by WK Hydraulics. To aid manoeuvrability a 150hp hydraulically powered Kort KT150 transverse bow thruster is installed. Kort Propulsion Ltd supplied the propellers, nozzles, seals and bushes for the stern gear, the bow thruster, and Weka box coolers for the main and auxillary engines. European Marine & Machinery Agencies supplied Kobelt electronic control for the vessel's propulsion system.

On trials Afon Las achieved a bollard pull of 28 tons and a free running speed of 11 knots.

Electrical power is supplied by two 78kW generating sets, both powered by Cummins 6B5.9D2(M) engines. One engine is radiator cooled and the other via box coolers along with the main engines and other auxiliaries. Also located in the engine room is a Cummins 6CT8.3 D (M) diesel rated at 188bhp at 1,800rpm and used to power the hydraulic pump supplying the deck machinery and bow thruster.

Every square metre of space in the engineroom is utilised and included in the equipment installed is a WWT 1 Biopur sewage treatment plant supplied by RWO Marine Water Technology and a H208A fresh water maker supplied by Seafresh Desalinators Ltd.

North Sea Winches supplied most of the deck machinery including the main towing and anchor handling winch. The hydraulic winch has a single ‘spilt’ drum with a maximum line pull of 50 tons and a maximum brake holding capacity of 80 tons. The largest partition on the drum can carry up to 500m of 38mm diameter steel wire towline and the remainder a shorter ‘work’ wire. Hydraulically operated spooling gear is fitted and can be operated automatically or manually. 

A spare towline or work wire is stored on a hydraulically powered reel in the equipment hold, just aft of the engineroom. The wire can be deployed via a hatch in the deck above and strategically located rollers.

Located aft of the winch are ‘Dutch’ style bitts which act as a fairlead for the winch wires and form part of the deck crane mounting. Adjacent to the towing and anchor handling winch on the starboard side is a 9 ton hydraulically powered tugger winch and it’s associated fairlead.

The open stern incorporates a stern roller, neatly faired into the bulwarks on either side to prevent fouling of the towline or work wire. One full set of Triplex hydraulically operated tow pins and a ‘Sharks Jaw’ are installed on the centre line forward of the stern roller. A quick release tow hook is also fitted for auxiliary or emergency use.

In common with all multipurpose work vessels of this type, a deck crane is fitted for handling stores, equipment and providing lifting services on site. Afon Las is equipped with a HS Marine hydraulic crane type AKC 115 HE4, with four telescopic jib sections and a maximum outreach of 14.01m. The crane is rated at 90 ton s/m, can lift 18 tons at 4.5m and 6 tons at 12.5m, and can be operated by remote control. North Sea Winches also supplied the anchor windlass on the fore deck and installed the entire hydraulic system for deck machinery, crane and bowthruster.

In keeping with almost all of the tugs and workboats of any size in the Holyhead fleet, provision is made to provide fuel and fresh water to other vessels or plant. Dedicated tanks can accommodate 100 cu/m of fuel, 45 cu/m of fresh water and 9 cu/m of sewage. High capacity electric pumps and hose reels are installed to facilitate this service.

Accommodation is provided for a maximum of 12 persons in six cabins fitted with heating and air conditioning suitable for operation during the north Caspian winter, where temperatures can go down to –40 degrees C. Insulation, wall boards/deckheads, furniture and outfitting was supplied by Promat UK.

The wheelhouse is a compact structure surmounting the single storey accommodation block and affording very good all round visibility. A series of windows overlooking the after deck extend to floor level and give a particularly good view of the work deck and winch.

Navigational equipment installed includes two radar sets, a magnetic compass, auto-pilot, electronic chart plotter, GPS, and echosounder. Large multi-functional display screens allow a variety of vital information from various sources to be displayed in the most convenient manner. A communications outfit is installed to the appropriate GMDSS level for the operational area and includes the normal VHF radios, MF/HF single side band radio, Imarsat C, Navtex and an Iridium satellite telephone with Email.

Afon Las will operate in the Kashagan oil field working alongside other vessels in the Caspinsky Buksir fleet. They include the multi-purpose work vessel AK Tue, shallow draft tug AK Sunkar, the 35m tug AK Burkut and the Ak Bars, delivered by Hepworth last year.

By Jack Gaston