In Depth: Jun Yang 1

In August 2016, after successful completion of sea trials, Trailing Suction Hopper Dredger (TSHD), Jun Yang 1, was handed over to her new owners.

Built at the Royal IHC’s shipyards in Kinderdijk, the Netherlands, the TSHD was developed for CCCC Guangzhou Dredging Company Ltd (GDC), which is based in the People’s Republic of China. The official transfer of the ownership to GDC was performed upon the ship’s arrival in China.

The naming and launch ceremony for the TSHD was celebrated on Saturday, 19 December 2015. Ms. Li Wen Ci, spouse of His Excellence Ambassador Wu Ken of the People’s Republic of China in the Netherlands, performed this ceremony at the IHC facilities. Looking closer at the name itself, the jùn means ‘dredge’, while the yáng means ‘ocean’; the translation would read ‘Dredge the Ocean’.

Royal IHC has developed the design of Jun Yang 1 in close collaboration with GDC, with whom they have a long-standing relationship, to create the largest TSHD to date in China. The contract for the design, construction and delivery of the vessel was signed on 1 November 2012, whilst the keel of the vessel was laid on 16 January 2015. With the last vessel delivered twelve years ago by IHC, Jun Yang 1 is their 19th vessel built for GDC over the last 40 years. In the past four decades, IHC has developed a diverse portfolio of dredging vessels, ranging from TSHDs to Cutter Suction Dredgers (CSDs) and wheel dredgers. These dredgers were erected either on the IHC slipways in the Netherlands or in partnership with shipyards in China.

This latest addition to their fleet will enable GDC to efficiently carry out capital dredging and land reclamation jobs on the local and international market.

Building for the People’s Republic of China 

Working for clients in the People’s Republic of China provides the opportunity for Royal IHC to build according to their own corporate style and identity, but it is important to incorporate the client’s requirements in the design. This is nothing new to Royal IHC. Having built multiple vessels for the Chinese government, as well as for this particular client and others, a mutual respect has been formed between the various parties. Being a subsidiary of China Communications Construction Company (CCCC), the market-orientated Guangzhou Dredging Company was established on 18 October 2006, as a modified continuation of the Guangzhou Channel Bureau, which had a history of more than 50 years. GDC’s main activities are focused on offering high-quality services for the constructions of ports and waterways. GDC’s services primarily consist of maintenance dredging, capital dredging, reclamation, marine engineering, irrigation and environment works, cofferdam and harbour, soft soil treatment, aggregate reclaiming, underwater rock blasting, and dredging for power plants. In addition, they can also undertake other business ventures, such as geological prospecting, offshore and land surveying, building construction and civil engineering, warehousing, and towing transportation. GDC are convinced that capacity (in quality and quantity) in equipment is the most important resource to a dredging contractor. For that reason they operate a modern and well-balanced dredger fleet, consisting of over 80 different kinds of large and medium dredgers, as well as auxiliary vessels including TSHDs, CSDs, bucket type dredgers, hopper barges, and many other various service equipment.

With their accumulated experience of over 60 years to date, the specialists of GDC are interlocutors who know what they want and understand what they talk about. After an intensive preparatory phase with a significant group of stakeholders, a solid base was laid for the design of a fully integrated TSHD, which is to be deployed internationally. The primary design assumptions were based on reliability and performance.

Versatile employability 

The Jun Yang 1 is primarily designed and equipped for dredging medium sand with a grain size of up to 1.5 millimetres. The TSHD is equipped with two suction tubes with integrated submerged pumps, with which a dredging depth of 40 to 60 metres can be achieved. The starboard tube can be extended so that a dredging depth of even 90 metres can be reached. Each suction tube accommodates an IHC Wild Dragon drag head, equipped with two rows of durable teeth, and fitted with high-pressure jets through the teeth. The injected jet water results in dilatation of the sand around the teeth’s surface. The cohesion of the sand is reduced in this way, whilst the teeth are simultaneously flushed, resulting in a decreased resistance and subsequent drag head forces.

The Jun Yang 1 has a central pump room, just forward of the hopper, in which the two dredge pumps are installed. The dredged spoil is dispensed into the vessel’s single hopper of 21,393 cubic metre capacity by means of a diffuser system. When the hopper is full, the TSHD sails to a disposal area and either dumps the material through the bottom valves, or rainbows it via the nozzle on the bow. Alternatively, the vessel can remain stationary on the dredge location and pump the material ashore through a floating pipeline. In the port and starboard double bottom of the hopper, a jet supply line has been fitted so that the jet pumps can inject water into the hopper to dilute the hopper load during shore delivery, or when dumping the hopper load through the bottom valves. The dumping system is the quickest way to discharge the material through two rows of conical valves that are vertically mounted in the hopper area. The valve discs, which are cone-shaped steel parts, are mounted in the bottom of the hull. Double-acting hydraulic cylinders operate the flush mounted bottom valves.

The pump ashore discharge system consists of two suction channels, through which the liquidised material can be pumped to the bow discharge unit. This process typically requires a floating pipeline to shore, linked to the vessel with a bow coupling. The IHC bow coupling also accommodates a rainbow nozzle for direct controlled discharge to the shore without floating lines.

The dredging process is controlled from the aft side of the wheelhouse; the suction tubes and the drag heads are handled by means of three gantries and winches each. This configuration can be found on starboard as well as on port side. When extending the starboard side suction tube, one gantry from portside is moved to starboard, to provide additional assistance.

Beauty and brains 

In response to the high level of demand for an optimal presentation of the working position of dredgers on the hydrographical chart, IHC installed a Dredge Track Presentation System (DTPS) on the TSHD. The DTPS System enables, amongst other things, the dredge operator to see on-line, with the highest possible accuracy, the dredging tool in the profile, and the actual updates of the dredge on the electronic chart in absolute position, in real-time.

Dynamic Positioning/Tracking (DP/DT) is also accommodated to ensure extremely accurate maneuvering, resulting in less over dredging (outside the tolerances), and reduced chance of collisions at trailing speed.

Nowadays, TSHDs are similarly involved in making trenches and pits for the offshore industry. For this purpose, Jun Yang 1 is also outfitted with a complete trenching and automated trench control system.

Furthermore, the vessel is provided with a Motion Compensator (DeiCo = Dutch abbreviation for Deiningscompensator), to compensate the ship’s motions. The most important goal of the compensator is to maintain the contact between the seabed and the ship, which may be disrupted due to either ship motions or irregularities of the bottom contour. The system is positioned in the hoist-cable system of the drag head winch gantry and prevents uncontrolled slackening and re-tensioning of the hoist cables. Moreover, it maintains an almost constant pressure of the drag head on the seabed.

When the hopper is being filled with spoil, the dredge pump starts to pump the mixture to the deck line. Right after the dredge pump, the density and flow of the mixture are measured. When the density is too low, typically when starting dredging, the mixture is discharged over the side of the vessel (AMOB system). This avoids the hopper filling up with mainly/only water. As soon as a suitable density of the mixture is measured, the overboard discharge valve closes automatically, and the dredged material can be led to the hopper.

Additionally, Jun Yang 1 is equipped with a continuous adjustable overflow system, to discharge the redundant water overboard. The overflow system is designed to optimise the efficiency of the dredging process by ensuring the maximum retention of solids in the hopper. With the solid components of the dredged slurry sinking to the hopper bottom, and the water draining overboard through the overflow, the overflow system encourages separation of solids and water. Reducing mixture turbulence and giving the solids maximum time to settle helps to achieve this.

Fancy footwork 

The engine room is situated in the aft part of the ship and has a funnel above. In the engine room, two main engines, each producing 10,800 kW, drive two Controllable Pitch Propellers (CPPs) through a gearbox. The advantage of CPPs is to be found in the method of operation. On the one hand, the ship needs enough propulsion power at relatively slow speed of one to three knots to drag the suction pipes over the seabed. On the other hand, the free sailing speed to and from the borrow area should be as high as 16 knots. To fulfill both requirements, the propellers are placed within nozzles. Additionally, the concept of double propellers with adjustable pitch strongly improves the manoeuvrability.

As a TSHD surely requires good maneuverability, two free hanging fish-tail rudders are fitted aft of the two nozzles with the propellers. Likewise, the bow area of the vessel comprises two bow thrusters, each driven by an electric motor. The speed control of the bow thrusters (as well as the electric motors of the dredge pumps) is by means of a variable frequency converter.

Besides driving the propellers, each gearbox also powers a shaft generator coupled to the rear. The shaft generators in turn feed 10,000 kVA to the medium voltage switchboard. This provides ample power to drive all electric components for maneuvering purposes and the inboard dredge pumps.

The Jun Yang 1 features two generator sets of 1,200 kW, which are located on tween deck in the engine room. These sets feed the 400 V switchboards for providing power during harbour conditions.

The emergency or harbour generator set is accommodated to portside aft on main deck level, in a dedicated compartment behind the casing containing the ventilation components and the exhaust lines to the engine room.

International crew accommodation arrangement

The superstructure with the accommodations is set at the far forward end of the TSHD, with the pump room underneath. Under the accommodations are technical spaces, the bow thruster room, and the forepeak.

The wheelhouse forward area contains the main navigation consoles on centreline, with all the usual navigation and ship control facilities; this is the ‘captain’s area’ and designated for sailing in the conventional sense. The radio console and chart table are more to the sides of the wheelhouse. The aft part of the bridge is the operational area for dredging activities and is home to the ‘dredge master’. The two bridge parts are separated in the middle by a kitchenette and the stairs to lower decks.

Below the wheelhouse is a converter room housing most of the electrical junction boxes and control units to support the bridge. The HVAC system, providing air conditioning to the bridge as well as the complete accommodation, is installed on main deck level. The crew and officers accommodations are to be found on the lower superstructure decks, between the wheelhouse and the technical spaces in the hull. The vessel has a crew of 45 people, residing in individual single-berth cabin above main deck and shared twin-berth cabins below main deck. Furthermore, these decks accommodate offices, a crew mess, officer’s mess, hospital, and changing room. The hotel amenities further comprise of a gymnasium, galley, laundry, food storage space, and cool and freeze storage rooms.

The area below the superstructure, on the same level as tank top and tween deck, contains the technical spaces, comprising the domestic machinery and equipment, providing facilities for the accommodation.

Tipping the scales 

Although the quality of the vessels and equipment, alongside Royal IHC’s reputation of delivering on time, and their long-term relationship with this client, were an important selection criterion, being able to provide more than just a hopper dredger gave IHC the competitive edge. GDC and IHC will correspondingly invest in the further development of the Chinese crew and equipment, enabling training at the IHC simulator facilities and providing extensive lifecycle support after delivery.

Tom Oomkens

This article was previously published in Maritime Holland edition #5 – 2016.

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