| abstract
| - High reach removal is a demolition method that involves the use of an excavator fitted with a special Long arm to cut or crunch material from a tower block or tall structure, in order to demolish it. It is an increasingly popular method of demolition as the technology surrounding the equipment used improves. It has replaced the wrecking ball as the preferred choice of demolition. It is also used were it is not possible to Blow down a building or structure. The equipment is operated from the ground by an operative sat in a armoured cab. At the end of a long arm fitted with hydraulicly operated interchangeable attchments such as; Shears fitted with two jaws which can cut through the wall or the floor concrete. The jaws are made of special steel and fitted with replacable cutting edges that can crush the concrete or cut steel beams and wire, or with concrete pulverisers or with grabs of various types for picking up items. The Operator controls it by two Joysticks that control servo operated hydraulic valves, and give very precise control. On some the long arm is built like a mobile crane and has an extending boom that is made of special steels and profile to reinforce it. There are several joints along the arm which allow it to bend. At the working end the joint holding the attachment can move up and down as well as rotating 360 degrees. These attachments are interchangeable for different jobs. In demolition, concrete pulverisers are the preferred attachment as it is so versatile with a skilled operator. For versatility the Long reach arm and attachments can be removed, and a adapted normal digger boom and arm fitted allowing the use of buckets for moving materials, loading wagons and excavating. Drilling tools are used in buildings which are built of reinforced concrete, which is a harder material to break down using a conventional pulveriser or jaw. At the base of the arm is the control unit where the operator works from, behind a protective shield. The operator is at risk of falling debris if mistakes are made so the operator is highly skilled. Mandatory safety requirements include a cab for the operator fitted with armoured (bullet proof) glass which is 5 times stronger than normal glass. To the front and roof is a cab guard which is a metal grill in front of the glass windscreen. This grill is fitted to FOPS frame to protect the operator from falling objects. An extra counterweight is added to balance out the extra weight of the long arm and tools. Usually the arm is made from "Weldox" which is a high strength to weight ratio steel. For improved operator visibility and comfort, the whole cab can is able to tilt up along the view of the arm. This relieves the strain on the neck. Some Firms fit CCTV cameras to the arms, as well as dust suppression water jets to assist in vision and cut down dust. Most demolition contractors now include long reach excavators in their plant fleet. As the building requiring demolition get bigger so have the machines. Some excavators can exceed 50 metres in arm length, requiring a heavier and more powerful base machine. As the size has gone up the Base machine used have had to be adapted with extra counter balance weights and wider Track units to prevent a loss of balance and possible incident resulting in a fatality. This has resulted In long reach excavators with an arm length of 50 metres or more, being based on a machine weighing around 120 tons or more. The weight at the arm is increased by the attachment and further by the material it has removed from the building. The attachments can weigh 4 tons or more. Some are fitted with Outriggers to stabilise them. Transport restrictions effect the design of the machines and they are made with removable sections. As can expected, the longer the arm, the more expensive the excavator, with some machines costing several million pounds for the base machine and then up to £1/2 million to make and fit the new boom and alter the base M/C. A Japanese company built a 65m machine that weighs 325 ton and reputedly cost them $8.7million. A Dutch company is building a 90m machine from a used CAT 5110B excavator. The Boom will be a 3 section design with a triple telescopic section for the main boom. The new boom will weigh about 65 tons and to take a 5 ton tool at full height and a 10 ton tool at reduced height. An extra 25 tons of counter weight will be required as well as new longer and wide tracks. The whole machine will weigh in at 250 ton and need 4 low loaders to move. But will be able to go to work within hours of arriving on site due to the design. Due to specialist design it will not able to be used as a excavator. Source: Excavator magazine sept 2007
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