On 14th February 2019 Damen Shipyards Group was awarded a contract by WSA Rhine-Koblenz (Waterways and Shipping Office) for a rather unusual form of vessel, a new diving bell ship. The modern, 21st century diving bell newbuild succeeds an existing vessel, the Carl Straat, which had been in operation since 1963. Like her predecessor, the new vessel is for operation on the European trade artery that is the River Rhine, and its tributaries. The Dive Bell Vessel 7012 (DBV 7012) will be used to search for and recover lost cargo or wreckage. In addition, she will be used for important river bed work and for construction inspections. Other duties include the production of barrel anchors in gravel or rocky areas, obtaining samples by drilling with liquid nitrogen, inspecting lock gates and buoy anchor points and even the removal of unexploded ordnance. This sub-surface maintenance system makes it possible for the little ship to travel and operate on the Rhine and Moselle Rivers (and other waterways such as the River Main) without the need to lower the water level for any such maintenance.
Unique to Europe
Ordered in February 2019, the highly unusual nature of the Dive Bell Vessel makes her unique to Europe thus far. The keel laying ceremony was announced on 25th October 2019 having taken place at Europoort Construction in Hendrik Ido Ambacht. This company had been subcontracted by Damen Shipyards to fabricate the hull. Damen’s piping department executed the main piping works during the block building stage at the company’s premises. With its proven track record in the offshore industry, Damen was confident that Europoort Construction would meet its high expectations for the project, and was not disappointed of course. Launched in July 2020, completion of the Dive Bell Vessel was announced on 11th January. The final construction and fitting out works of the ship were carried out at Damen Shipyards Hardinxveld located on the north bank of the River Merwede, and at Damen’s headquarters, Damen Shipyards Gorinchem. The Damen Shipyards Group needs no introduction to regular readers of Newbuild of the Month, a global company offering a vast range of newbuild designs whilst its family routes remain firmly in The Netherlands, being founded in 1927 in Hardinxveld-Giessendam by Jan and Marinus Damen. This location is just 10km from the present-day headquarters. Originally the €23 million vessel replacing the 1963-built TGS Carl Straat was to take on the name TGS Carl Straat. However, a change of heart occurred along the way and the name bestowed on the vessel was, rather appropriately, Archimedes. Archimedes of Syracuse lived from 287 B.C to 212 B.C and was a famous mathematician, physicist, engineer, astronomer and inventor. Leaving the “Eureka!” story aside, it is perhaps Archimedes’ principle of buoyancy that is the most relevant to the Dive Bell Vessel and her daily tasks. Archimedes not only determined that an object submerged in water displaces a volume of water equal to that of the object, he also found that the buoyant (lifting) force on that submerged object is equal to the weight of the displaced water. For divers, there is no escape from the principles that Archimedes so cleverly employed. For most purposes in diving, neutral buoyancy is preferred, to neither sink nor float. That said, the vessel now known as Archimedes allows diving operations in up to 10m-deep waters while providing a dry working environment. The application of overpressure in the steel bell blocks the passage of water, allowing the removal of obstacles, checks to be made etc in completely dry conditions at the river bed. The more general working depth will be 4m-7m but, even working at depths of up to 10 metres, no surface decompression is required. There is however a pressure chamber where the diving crew waits until the pressure is equalised to that in the diving bell. On return to the surface, the process is conducted again in reverse. For every metre of draught, 0.1 bar pressure is required. So, working at a maximum depth of 10 metres, the Archimedes’ diving bell requires 1 bar of pressure. The new diving bell system on board integrates the HAUX-Starcom and the HAUX-Bellstar hyperbaric chambers. Founded in 1980, HAUX Life-Support is based in Germany with over 1,500 chambers for various purposes delivered to date. The diving bell components include an entry lock, a lock conduit with a stairway, and a watertight caisson (dive bell) chamber, which is the main working area, with the capacity to accommodate 6 personnel. The caisson is 4m long, 6m wide and 2.7m high. A pull rod above the immersion tube creates a force parallelogram that holds the entire system in position. This ensures that the diving bell, which is reminiscent of an upturned margarine container in shape, always remains horizontal to the ship’s hull. The workers stand on a footbridge at the bottom of the bell and look for obstacles on the riverbed using long poles. For the recovery of items, the caisson is placed on the river bed and the pressure is increased again so that the remaining water is pushed out. After that, the dive team can walk on the river floor to work in the dry with the necessary equipment for the task being undertaken. Three crane systems attached to the chamber ceiling and several anchor points with a load capacity of up to 15 tonnes are also available to the dive team. There is also a side door in the caisson for loading equipment. Compared to the 1963-built version, the improved diving bell assembly is far more capable of handling the influence of underwater current forces and is also equipped with a HAUX-Fire extinguishing system. Construction, design and strength calculations of the system were carried out in the HAUX design office in Karlovy Vary, Czech Republic. The diving bell system has a total weight of approximately 160 tonnes. A 15-metre-long immersion tube connects the lock chamber via a long and fully enclosed staircase to the caisson. This is visible as a large steel tube that runs from behind the deckhouse to the diving bell and provides the crew with access to the pressure chamber. Large compressors direct air into the chamber and the immersion tube to build up the overpressure required for the respective working depth. This equipment is supported by a high-performance breathing air system, which also includes heating and insulation for the bell chamber. A single compressor is more than enough to prevent the chamber from flooding when submerged, but a second compressor is in place as a back-up. This applies to all onboard systems with everything being 100% redundant. In order to safely overcome the buoyancy of the diving bell system, 55 tons of ballast weight was also required, and this was supplied by Ancofer Stahlhandel GmbH in Cuxhaven and sister company JEBENS. In total, 33 parts with 7 different ballast weights in different formats were provided but no single ballast weight could exceed 2.5 tonnes. The diving bell assembly is raised and lowered hydraulically, with the supporting arm passing through a cut-out in the stern section of the vessel’s hull. The diving bell is suspended level with the ship’s hull at the stern whilst not in use. To hold position whilst working, an anchor system is provided by way of two 900g D’hone anchors situated forward and two 450kg anchors located aft, one each side of the bow/stern respectively. The vessel also uses a Spud Pole System for stability, one forward and one aft. These 15.90m long telescopic poles are hydraulically powered and lower beneath the keel to a maximum of 7 metres. When not in use, the poles can be stowed on deck so as not to create clearance issues with any bridges over the river.
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