C O N C R E T E C A S E S Dock s Owners Turn to CSDA Member for Precision Cutting It has almost been a hundred years since civil engineers Easton, Gibb and Son started construction of Rosyth Dockyard in Scotland in 1909, strengthening the Royal Navy s presence along the East coast of Great Britain. In 1984, Rosyth was chosen as the sole location for refitting the Royal Navy s nuclear submarine fleet, a role in which it was already specializing, and in 1986 extensive rebuilding commenced to facilitate this position. However, in 1993 the then-conservative government switched the refitting role to Devonport. Aerial view of Rosyth Dockyard, circa 1919.
The huge caisson required cutting in order to be widened.
Diamond wire sawing ensured a clean and precise cut through steel and concrete. The caisson is used to dry dock vessels entering Rosyth Dockyard. Thanks to our expert staff, we managed to successfully complete the job on time and on budget. Babcock Thorn, a consortium operated by Babcock International and Thorn EMI, was awarded the management contract for Rosyth Dockyard in 1987, after which they were a government-owned, contractor-run facility. In 1993, the Ministry of Defense announced plans to privatize Rosyth. Babcock International (who had bought out Thorn s share of the original Babcock Thorn consortium) was the only company to submit a bid, and after protracted negotiations purchased the yard in January 1997. Early last year, as part of the Rosyth Dockyard infrastructure upgrade, Babcock Marine approached CSDA member Core Cut Ltd. of West Lothian, Scotland with the challenge of cutting a huge caisson in two. The caisson, already measuring 33 meters wide, 5.8 meters deep and 15.5 meters high, needed to be widened and a new piece welded in place. Therefore, an accurate and clean cut was paramount. An extension piece had been prefabricated to fit exactly between the two sections of the existing caisson, and required
Did You Know? The HMS CHURCHILL Currently, there are seven decommissioned nuclear submarines stored at Rosyth Dockyard, one of which is the HMS Churchill. HMS Churchill was the first of three Churchill-class nuclear fleet submarines that served with the British Royal Navy. The three nuclear-powered fleet submarines served with the Royal Navy from the 1970s until the early 1990s, of which the lead ship was named after the former British Prime Minister and First Lord of the Admiralty, Winston Churchill. The Churchill-class was based on the older Valiant-class, but featured many internal improvements. The Churchills carried a crew of 103 and had a full load displacement of 4,900 tons when submerged. They were 86.9 meters long, had a beam of 10.1 meters, a draught of 8.2 meters and could achieve a maximum speed of 28 knots when submerged. The submarines were fitted with one Kelvin-type 1008 surface-search radar and a type 2001 sonar array, which was replaced in the late 1970s with a type 2020 array and a type 2026 towed array. Weapons included Mark 24 Tigerfish torpedoes and sub-harpoon, antiship missiles. Six 21-inch (533-mm) torpedo tubes fired from the bow. Like all nuclear powered submarines, the Churchill-class could remain submerged almost indefinitely, with supplies of food being the only limiting factor. The HMS Churchill evaluated both the American Mark 48 torpedo and the UGM-84 harpoon missile during its service, though only the latter was adopted by the Royal Navy. The HMS Churchill was decommissioned in 1990 at Rosyth and is currently awaiting disposal. The setting up and cutting process took ten days. welding together without the need for any infill metal. Being specialists in the fields of drilling and cutting, Core Cut were keen to accept this challenge. In a dockyard, a caisson performs a similar task to lock gates on a canal. The big difference is that a caisson is moveable and floats like a ship. When a vessel needs to be dry docked, the dock is first flooded and the caisson is removed by pumping out the water inside of it. When afloat, it is moved by capstan and cables to the outside wall leaving the entrance to the dock clear. The vessel is then towed into the dock and the caisson is returned to the entrance and guided into position. Water is then pumped into tanks to sink it and form a watertight seal. The caisson is then used as a walk and roadway. The water in the dock is pumped out, with the vessel being docked on oak blocks at the same time. The structural makeup of the caisson meant Core Cut needed to make two distinct cuts. The first was to the lower ballast section standing 3.5 meters high that included concrete and steel. The second, and much larger cut, was of the remaining 12 meters. Additional concerns of
C O N C R E T E C A S E S Core Cut were that the interior of the caisson contained various ballast tanks and internal bracing, all of which had to be cut with the same degree of accuracy as the mass concrete ballast to the keel section. The cuts also had to be wedged as the team progressed to prevent the natural expansion and contraction of the steel affecting the cutting process by snagging the wire. For Core Cut, cutting the caisson in two was not going to provide any problems, but cutting it accurately to allow for a successful weld was going to be the real challenge. Fortunately with 30 years in the sawing and drilling industry, and a team of highly skilled workers, Core Cut s director Finlay Crocker was confident of success, Like most jobs it was all in the setting up and our skilled operators are known for their attention to detail no matter how large or challenging the task. Core Cut spent over 24 hours setting up and preparing the task, checking and re-checking using a Hilti PR25 rotating laser to ensure accuracy before commencing the wire sawing. They employed a Hilti WS 15E 15 kw electric wiresaw system. Hilti also supplied the 10 and 4 noise-reducing pulley sets required for the project, and Core Cut made some modifications that would allow the position of the pulley wheels to be adjusted without the need for repeated set-ups. Power was supplied by a 70 KVA Super Silent 145-volt mobile generator. The set up was overseen by Finlay Crocker and Ernst Siegenthaler, Hilti s global key account manager of the Diamond Systems Business Unit, and carried out in conjunction with engineering staff from Babcock Marine. Core Cut s wire sawing was accomplished using a 50-meter length of 100% specification steel diamond wire supplied by Hilti Great Britain. Core Cut has found diamond wire sawing to be the fastest and most versatile means outcome of both the cuts and the project as a of cutting heavily-reinforced concrete and whole, Thanks to our expert staff, we managed to successfully complete the job on time steel. The wire saw easily handles the thickest sections of all construction materials with cutting rates in excess of one square meter-per- In addition to these works, Core Cut was and on budget. hour achievable, and the ability to cut circular awarded a separate job on the same project, openings up to 2.5 meters in diameter leaving and was subcontracted by Edmund Nuttall to clean, straight and smooth cut surfaces with no help with the dock-widening program. Core damage to the remaining structure. Cut s job was to make preparatory cuts of the The work was carried out over ten days concrete and granite to facilitate the easy and during July 2008, in which time the cutting tidy removal of the alters (large dock steps). team mobilized, set up the equipment, performed the cut and broke out the mass concrete ballast from the keel section. Since Core Cut completed their work, Babcock Marine has now successfully welded in the extension piece to the caisson. Crocker was pleased with the COMPANY PROFILE Core Cut joined CSDA in 1996 and is based in Broxburn, West Lothian, Scotland. The company is a family owned and run business celebrating 30 years in the concrete drilling and cutting industry. During this time, Core Cut has built an enviable reputation within the UK construction industry and is a specialist in diamond drilling, sawing and controlled demolition. The company is proud to have achieved ISO9001 accreditation. RESOURCES General Contractor: Babcock Marine Sawing and Drilling Contractor: Core Cut Ltd., West Lothian, Scotland Phone: 44-1506 854710 Fax: 44-1506 853068 Email: finlay@corecut.co.uk Website: www.corecut.co.uk Methods Used: Core Drilling, Wire Sawing and Controlled Demolition REVIEW AND COMMENT ON THIS ARTICLE AT WWW.CSDA.ORG/FORUM.cfm