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Presswork, stamping, fabrication Subcontracting Services
News Release from: DavyMarkham
Edited by the Manufacturingtalk Editorial
Team on 09 March 2004
1.1(GBP) Million Contract For Selby
Swing Bridge
AK Heavy Engineering, has secured the 1.1 (GBP) million contract for the design, manufacture and commissioning of the complete mechanical, hydraulic and electrical works for the Selby Swing Bridge.
AK Heavy Engineering, formerly the Manufacturing Division of Kvaerner Engineering and Construction UK, has secured the 1.1 (GBP) million contract for the design, manufacture and commissioning of the complete mechanical, hydraulic and electrical works for the Selby Swing Bridge, one of the largest of its kind in the UK The cable-stayed swing bridge will carry the new A63 bypass across the River Ouse and features a main 95m span that rotates on a central pivot, to allow the passage of river traffic
This article was originally published on Manufacturingtalk on 10 Jul 2008 at 8.00am (UK)
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AK Heavy Engineering is responsible for the main motor-driven slew ring assembly, which supports the 1200 tonne moving deck structure and enables it to be rotated and locked into the open position in just two minutes.
The Sheffield-based company is also supplying the bridge hydraulics system complete with three power packs, the main bridge deck bearings, moveable carriages and nose bolt assembly, a PLC-based control system and motor control centre, and all traffic control equipment, including road barriers, traffic signals, navigation aids and CCTV cameras.
The contract, which was awarded by bridge contractor Cleveland Bridge and specified by scheme designer High-Point Rendel, is scheduled for completion shortly.
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The 42 (GBP) million Selby bypass scheme, awarded to Skanska Construction in July 2001, runs for 10km and includes four roundabout junctions and six new bridge structures, including the Selby canal bridge and the distinctive River Ouse swing bridge, totalling 125m in length.
The river has a tidal rise and fall of five metres and carries significant marine traffic, including small commercial vessels and many recreational boats, along its 40m wide navigation channel.
To allow movement of this river traffic, the bridge's central span will swing through 90 degrees and admit passage, up to three times daily.
The rotating central structure is a cable-stayed swing bridge, comprising a main 55m span over the river and a 40m counterweighted back span, to balance the bridge deck.
This is variously supported on a central pivot pier located on the south bank of the river, an abutment at the southern end of the back span, and a landing pier on the north bank, from where a further fixed bridge span carries the road to the approach embankment.
Above the pivot pier is an elevated control room atop a central pylon, to which the cables are attached, while inside the pier is the machine room and operators' mess.
When the bridge is open to road traffic, the central span rests on pairs of pedestal bearings at the nose, tail and central pier, to support the vertical load.
The nose and tail bearings are mounted on mobile carriages, which are moved by hydraulic cylinders, while the central pier bearings are suspended from the underside of the bridge deck and rest on a sliding plate, which is also withdrawn by hydraulic rams.
When the bridge is to be opened to river traffic, hydraulic jacks raise the bridge deck at the central pier, allowing the retractable bearings to be withdrawn, then lowered onto four hemispherical thrust bearings on a transition structure, thence onto the slewing bearing itself.
Then, at the nose and tail ends, the deck is lifted clear of the bearings by jacks mounted on the landing pier and south abutment, enabling the bearing carriages to be retracted into recesses and the jacks lowered again.
With the nose and tail ends thus clear, the swing bridge is supported by the hemispherical bearings alone and can be safely slewed and locked in the 'open to shipping' position, by means of a hydraulically-activated nose bolt.
AK Heavy Engineering is responsible for designing all the mechanical, hydraulic and electrical systems that perform these opening/closing functions, as well as the PLC architecture that provides remote control of the entire operation.
Key component is the 13 tonne, 1200mm high, main slew ring assembly, which is fabricated from mild steel and incorporates a 4800mm diameter Roballo roller-type antifriction slew bearing; this assembly is bolted onto a reinforced concrete plinth, at the centre of the pivot pier.
On the upper rotating element is mounted a 50 tonne, 8700mm x 5200mm x 1500mm high, transition structure, again fabricated from mild steel, which forms an interface with the bridge deck and ensures the loading is distributed evenly across the slew ring assembly.
This entire structure was verified by AK, using advanced finite element analysis software.
The bridge's slewing motion is provided by a rack and pinion arrangement, comprising an external 263-tooth gear ring, which is integral with the upper element of the slew ring assembly, and six geared drives, each with an 18-tooth pinion that meshes precisely with the rack under all torque conditions.
Mounted on the side of the pivot pier central plinth, the six electrically-driven 30kW motor/gearbox drives are each rated for 48kNm maximum torque, so that any diametrically-approved pair of drives is capable of operating the bridge in all operating conditions, albeit at reduced speed.
AK Heavy Engineering also fabricated a total of 14 bridge bearings, including four guide bearings that ensure the bridge is firmly located in place after opening/closing, which incorporate steel pot bases and neoprene bearing pads, the largest of which are 710mm diameter and 40mm thick.
The operation of all bearing carriages/slides, bridge jacks and the nose bolt is provided by three industrial hydraulic power packs, each with 37kW motors, duplex pressure-compensated pumps and hydraulic fluid reservoirs.
Seven hydraulic cylinders and associated solenoid operated valves are being supplied, each with an 85 bar working pressure, 125mm bore and 850mm maximum stroke.
Each of the lifting jacks has a capacity of 400 tonnes and is fitted with proximity switches to indicate full travel in either direction.
In addition to a UPS (uninterruptible power supply) with three-hour battery backup, AK is installing a diesel-driven standby generating set, including controls, ducting, attenuators and fuel tank, which will provide power for all functions in the event of a mains failure.
It is also supplying a motor control centre and control panels for regulating all motor-driven devices.
The PLC-based operating system, also developed, factory tested and site commissioned by AK Heavy Engineering, is desk mounted in the elevated control room and incorporates a SCADA (supervisory control and data acquisition) screen, online printer, key-operated master locks for delegating partial control to remote positions, and all system components for barriers, lights, telephones, radio and CCTV.
The same viewing, printing and control functions are duplicated on a second PC in the computer room, while portable plug-in pendants can be attached at various locations around the bridge, for local control.
The control system is programmed to initiate a fully automated operating sequence, on push button activation.
The 120 second opening cycle, excluding time for passengers and vehicles to clear the bridge, includes playing pre-recorded audible warnings and messages to the emergency services, closing vehicle and pedestrian barriers, complete with traffic light signals, starting hydraulic pumpsets and confirming pressure levels, jacking up the bridge and withdrawing bearings, withdrawal of the nose bolt, slewing the bridge, inserting the locking bolt and switching on green navigation lights.
All this equipment, together with a CCTV river, road and bank observation system, falls within the AK Heavy Engineering scope of supply, as does site installation, testing and commissioning.
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