The delicate task of moving an Australian Navy submarine from water to land for repair can be compared to that of dealing with a beached whale.
Near the western Australian city of Perth is the Australian Marine Complex (AMC), one of the most modern dockyards in the world. The AMC was designed as a repair and service centre for the submarine fleet and ships of the Australian Navy. Underwater vessels weighing more than 3,000 tonnes are regularly serviced there. At the same time, the technical equipment on board the ships must be continually upgraded to meet the latest standards.
For the work to be carried out the submarines must be transported on shore, which is not an easy undertaking in view of the size of the 80 m vessels. An especially tricky challenge is transporting from the ship lift to the service and repair centre. Although the hulls are extremely stable underwater, they must be handled with great care and attention on land. The Navy authorities contracted Scheuerle to build the transport systems to haul the fragile cargo.
As elegantly and effortlessly a submarine moves in the water, the more immovable and fragile it is when lifted ashore. It almost resembles a stranded whale lying beached helplessly on dry land. What a whale and submarine do have in common - apart from size and weight - is the acute sensitivity of each when being moved on shore.
To transport the multi-million dollar submarines as carefully as possible from the water to their designated berth on land, AMC invested in a new dockyard. The main feature is a floating dock with integrated ship-lifting system. When a submarine is taken from the water, bearing supports are arranged one behind the other on the platform of the ship lifting system in which the vessel will subsequently be positioned.
Next, the floating dock casts off and moves away from the quayside and heads for deeper water. At this point, the buoyancy chambers are flooded until the floating dock is submerged so that the submarine can move onto the U-shaped platform and over the bearing supports. When the vessel is correctly positioned, the water is pumped out of the buoyancy chambers and filled again with air. The submarine slowly lifts out of the water and the floating dock returns to the quayside.
At this point the Scheuerle transporter comes into play. The self-propelled modular transporter from the SPMT series comprises 24 vehicle units, (18 six-axle, 3 four-axle and 3 triple-axle modular transporters), coupled one behind the other in a 6-file arrangement.
The Power Pack Unit (PPU) is then coupled to the last vehicle of each group. These provide the motive power from 350 kW Daimler OM 502 LA diesel engines. Total output of the three PPUs is 1,050 kW.
Hercules on 516 wheels
The modular transporter is in three rows under the bearing supports where the submarine rests. One transporter row drives into the middle tunnel while the other two rows are positioned on the left and right under the cantilever arms in each case. The three transporter rows are then coupled electronically with one another and synchronised via a data link. All instructions are sent to the transport system by a cable or radio remote control.
The order to raise the vessel is given by the push of a button and the PPU engines start simultaneously on full load. Hydraulic pumps supply 258 hydraulic cylinders. Slowly the bearing supports are lifted off the ground and a load of more than 3,200 tonnes rests on the Scheuerle heavy load modular transporters.
The lifting procedure is controlled via allocation boxes which monitor and regulate the lifting and lowering function. If unexpected pressure loss develops in one of the cylinders, which could lead to an unintentional lowering of the vessel, check valves are actuated. This ensures that the oil circulation system is sealed off in a fraction of a second, and the platform is kept level.
The lifting procedure ends when the bearing supports have been lifted high enough off the ground so that problem-free driving around the dockyard area is possible. The remaining travel in the hydraulic cylinder is reserved for axle compensation. It is used to compensate for ground surface irregularities.
Sensitive but strong
Hydrostatic drive is the best solution for this type of operation. In each heavy load module, around a third of the pendulum axles are powered. To activate the drive, the operator moves the joystick forward, giving the order for the PPUs to begin supplying oil to the hydraulic motors in the driven pendulum axles. The entire vehicle group then starts moving and the vessel starts out on another journey, this time on land. Giving the impression of almost floating over the ground, the gigantic hull moves from the ship lifting facility onto the dockyard area supported on 516 wheels with solid - instead of pneumatic - rubber tyres.
Steering is also hydraulic. Each pendulum axle has a steering angle range of +130 degrees and -100 degrees. The electronic control system was developed by Scheuerle. Each wheel set must adopt its correct steering angle to be able to execute one of the driving programs pre-selected by the vehicle operator. Even with a simple cornering manoeuvre, the onboard computers assign the calculated steering angle to each of the 258 pendulum axle wheel sets as well as remaining fully in control of these at all times. As the steering movements are constantly changed, the calculation and control processes are done in milliseconds.
"Our SPMTs have already transported submarines and ships in many shipyards in Europe. The fact that this technology could be used also for the Collins Class submarines of the Australian Navy was the message we took with us to the negotiation table in Australia", said Andreas Kohler, Scheuerle deputy managing director.