Weighing and Manipulation System for Ship's Hull Sections

Irene Kremer, Enerpac BV,
Special Collaboration


Enerpac's PLC-controlled synchronous lifting system ensures that the desired load paths into the ship's hull structure are maintained during transport.

Six Daring Class Type 45 anti-air warfare destroyers are being assembled, launched and outfitted for the UK Royal Navy at BAE Systems Surface Fleet Solutions' Govan & Scotstoun shipyards in Glasgow. The bow sections, masts and funnels for all six ships are being built in Portsmouth. These destroyers will have an overall length of 152.4 m, space for a crew of 235, a displacement of 7350 t, a top speed greater than 27 kt and its range greater than 7000 NM. The first one is HMS Daring and is to enter service in May 2009.

The ship's hull is manufactured in sections or "blocks" in a fabrication shop adjacent to the berth and slipway. Five blocks are moved in total to build one ship of which the heaviest block weighs over 1400 t.

Hydraulic lifting and load transfer
Each block is transported to the slipway and aligned longitudinally to the slipway on multi-wheeled transportation vehicles. During this procedure the slide-tracks on the slipway are removed so that the vehicles can drive the blocks into position.

The Enerpac Synchronous Lifting System is now used to lift the block free from the transport so that they can be driven away. During the lifting procedure the 16 points PLC-controlled synchronous lifting system operates within strict load and stroke constraints to ensure that the desired load paths into the ship's hull structure are maintained. With the transport removed and the hull segments supported by the hydraulic system, the blocks are weighed with the synchronous lifting system to confirm the design calculations.

Slide-track installation, lowering and block manipulation
The next step is the slide-track installation. The slide-tracks on the berth's slipway can then be re-installed. The block is lowered synchronously and the load is transferred on to the slide-tracks. The hydraulic lifting system permits the manipulation of the blocks prior to welding to the adjoining section. This manipulation ­ lifting, lowering and rotation, is a PLC-controlled hydraulic movement.

Hydraulic System Integration
In the use of hydraulics in heavy lifting projects, application knowledge and expertise are very important. Accurate lifting, lowering, pushing or weighing has a significant effect on structures. Very accurate manual control and monitoring is complex and very time consuming. And more ­ accuracy is more important than speed ­ the advantage of PLC controlled integrated hydraulic systems is enormous. Every step of the lifting process can be monitored via the display of the PLC control unit. Apart from the very accurate and stress-free movement of steel structures, concrete segments, etc. Enerpac provides a safe, easy to manage, cost- and laboursaving solution.

The Type 45's weight must be optimised and consequently the hull skin is relatively thin when compared with a commercial ship. Therefore when lifting and lowering, the load paths must be strictly controlled and this would be almost impossible with manually controlled systems. Controlled hydraulic movement brings safety to the structure. The second advantage is the increase of productivity where hundreds of man hours were saved against traditionally controlled lifting methods. Moreover, this versatile lifting system is employed on various other lifting and weighing operations around the shipyard.

Enerpac hydraulic system integration, of high force hydraulics and advanced control technology, nowadays play an important role in the controlled movement of large-scale engineering projects, like the launching of the French Millau Viaduct, and lifting and weighing of these heavy ship's hull segments.

Source: Enerpac BV


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