TSHD UKD Orca delivered

UKD ORCA

Barkmeijer Shipyards delivers 100 % custom made dredger for port maintenance in UK

The UKD Orca was handed over to her owners on July 22nd 2010, and is currently engaged in port maintenance activities in Wales. The vessel is unique and totally custom built to match the requirements of the owners, UK Dredging. 

Principal particulars:

In November 2007, UK Dredging approached Barkmeijer Shipyards from Stroobos for the construction of a new trailing suction hopper dredger. The vessel was developed to maintain all the ports under UK Dredging's parent company Associated British Ports and to carry out dredging works in ports throughout Europe. 

The design of the UKD Orca was based on the characteristics of her working area: confined spaces in small ports, near quays and jetties. The locks and channels of the working area defined her principal dimensions, resulting in a length over all of 79 metres and a beam of 16 metres. The concept design was developed by Barkmeijer Shipyards in close consultation with the owners. The detailed technical design was entrusted to Conoship.

UK Dredging

With a hopper volume of 2.300 m3, the UKD Orca will be the second smallest vessel in the UK Dredging fleet, which now includes four TSHD's with hoppers ranging from 2.189 m3 to 3.900 m3. A grab hopper and two ploughs complete the fleet.

While the UKD Orca was intended to replace the 26-year old UKD Dolphin, the company has been so busy in the last two years that the older vessel will be kept in service for the near future. Besides the Brittish ports, the UKD vessels have been active in European ports ranging from Portugal to Estonia, in some cases chartering for Boskalis.

Diesel-electric installation

The propulsion arrangement on UKD Orca is completely diesel-electric. Three 1.200 kW Wärtsilä 6L20 diesel engines are each coupled to a Leroy Somer alternator, feeding the onboard power grid at 500 Volts. The engines run on MDO, resulting in excellent reliability and long maintenance intervals.

The power generated by these three gensets is used for the rudderpropellers, the bowthruster, the house load and the dredge pumps. Typically when sailing at speed, dredging loads are low or non-existent and vice versa, making the sharing of their power source an ideal solution. 

The advantages of a diesel-electric installation are:

- a high torque is available at low rpm's, resulting in good manoeuvrability at low speeds

- no controllable pitch propellers are needed, which would be subjected to a lot of wear in the murky waters where the ship operates

- the speed is limited by the power available, not by the maximum rpm's of the main engines. 

- during transit in ballast condition, the vessel can sail at 10 knots with only one generator running, resulting in excellent fuel economy.

During dredging activities, normally two generators are running with the third one available in standby. The power management system will automatically bring the third generator online if the loads demand more power.

The engine room was installed by Wolfard & Wessels Werktuigbouw, while Alewijnse Marine Systems took care of the electrical installation.

For emergency and harbour use, a 140 kW diesel generator is located in a dedicated room on the starboard side of the main deck. This 140 kW Cummins genset was supplied by DBR from Sliedrecht. 

Rudderpropellers

Two well-mounted Z-drive azimuthing thrusters from HRP are located in the stern. Each of these is rated at 1.500 kW and is driven by an inboard electric motor, through a cardanic shaft and a flexible coupling. The Z-drives are of the type HRP 8411 WM, with an input speed ranging from 1.200 to 1.600 rpm and a reduction ratio of 5.898/1. The 2.300 mm fixed-pitch propellers are mounted in propeller nozzles, resulting in higher thrust. A hydraulic motor on top of the drives allows the thrusters to be rotated through 360 degrees. 

In combination with the 500 kW electrical tunnel bowthruster, type HRP 5003, the manoeuvrability of the UKD Orca is such that the vessel can turn on her own axis, a very useful characteristic when operating in small ports and narrow waterways.

Dredging installation

For a description of the dredging installation, we will follow the dredge as it makes its way from the seabed to the overboard discharge. Damen Dredging Equipment supplied the dredge pipes, gantries, winches, swell compensators, degassing system, ringgate valves, jetwater monitors, telescopic overflow, bottom doors and dredging instrumentation. The hydraulic powerpack was delivered by Hycom from Apeldoorn.

Suction pipes

The UKD Orca is equipped with two dredging pipes. Although only one can be used at any time, this configuration allows the vessel to dredge in every corner of a harbour. For the same reason, the dredge pipes are located far abaft, with the dragheads very near to the stern of the vessel. The 700 mm diameter suction pipes are long enough to dredge to depths of 25 meters. The pipe and the draghead are lowered alongside the vessel by gantries, powered by hydraulic winches, which include swell compensators for a maximum swell of 3 meters. A hull guide construction guides the upper elbow piece of the dredge pipe and jetwater pipe into alignment with the hull-throughs, which can be closed with a gate valve. The dredge arm is articulated in two spots: a cardanic coupling is situated about halfway and a single hinge is located just below the waterline. A short length of flexible pipe connects the lower and upper dredging pipe. 

Jet water can be injected into the draghead to loosen up the soil for better production.

The outboard part of the suction pipe is made of thick-walled steel, so it can be easily replaced when needed. The inboard part of the dredge pipe, which is much harder to renew, is made of Creusabro, a high performance wear-resistant type of steel.

Inside the vessel, the dredge pipe continues to the dredge pump room, aft of the hopper.

Pump room

The 800 kW dredge pump is a new type from Damen Dredging Equipment, named BP7065LD. This single-walled pump is electrically driven by an electric motor through a reduction gearbox, which are both located in the engine room. A double-walled pump is not needed in this case, as there are only a few pumps in the pump room which would be damaged in case of a leakage. The shaft leads from engine room to pump room through a watertight shaft seal from Promac. The shafts between electric motors and pumps or thrusters are made of composite. 

On the port side in the pump room is the jet pump from Nijhuis. This pump can discharge 1.500 m3/h during dredging at a pressure of 10 bar. During discharging from the hopper, the jet pump can discharge 2.500 m3/h of seawater at 5 bar. The jetwater piping has a nominal diameter of 350 mm. The pump is driven by an electric motor which is located in the engine room. The jet water is also used for filling the forepeak ballast tank and to power the ejector of the degassing system. When dredging material with high organic matter content, biogas can be dredged along with the spoil. The degassing system removes the gas safely from the spoil before it reaches the dredge pump. The gas is blown off to the atmosphere above the main deck.  

Discharge

From the dredge pump, the spoil is led to a line on deck. A branch at the beginning of the line allows the first very low density spoil - almost pure water - to be discharged overboard through a vertical pipe which leads to the bottom of the vessel. Once the specific density of the spoil is achieved, the valve closes and the spoil is either discharged into the hopper or through one of the overboard discharge lines on starboard and port side. The UKD Orca does not have a rainbowing nozzle at the bow, as this feature is typically used in land reclamation projects and not in the pure dredging work.

In the hopper, the spoil is allowed to settle, while the water on top is drained overboard through a telescopic overflow, which can be adjusted in height. When fully loaded, the UKD Orca will sail to a different location for discharging. The spoil can be discharged through the bottom doors, assisted by jetwater sprayed from nozzles all around the hopper compartments. Alternatively, the spoil can be discharged through the overboard connection. For this purpose, a dredge pipe leads from the bottom of the hopper to the dredge pump. The suction connections for this pipe are located right next to the bottom doors.

Accommodation

The wheelhouse features a central U-shaped console facing forward, and two completely equipped control stations - including a helmsman chair - on the sides. The navigation and communication equipment was supplied by Radio Holland Netherlands. 

Centered around the stairwell are a chart table and communications desk. A few steps down towards the aft is the dredgemaster's control station in a semi-circular protrusion offering 180-degree visibility. On top of the wheelhouse are a central mast for navigation lights and radars, as well as dredging masts on either side with the necessary dredging lights.

Below the wheelhouse, we find the captain's cabin, chief engineer's cabin and two officers' cabins, each with a private bathroom. Also on this level is the ship's office.

Another eight crew cabins are located on the deck below. 

At the main deck level, we find the messroom, galley, provision store, a recreation room, a laundry with adjoining drying room and a dedicated wet gear store & drying room with direct access from the main deck.

Below the accommodation in the foredeck is the bowthruster room and spare parts store, which contains various equipment such as the chiller for the airconditioning, the boiler, the hydrofore, and the sewage treatment unit, which is of the bio compact type from Technisch Bureau Uittenbogaart.

Future projects

Barkmeijer Shipyards is currently working on a series of four 8300-ton multi-purpose general cargo ships for Wagenborg Shipping and has signed an order for three 81-metre pilot boats for the Dutch pilot organisation "Nederlands Loodswezen BV". With this new order, the order book of the shipyard stretches well into 2014.