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wel com to my own home page website.. - Scissor Lift
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Seisser Lift
A scissor lift is a type of platform which can usually only move vertically. The mechanism to achieve this is the use of linked, folding supports in a criss-cross 'X' pattern. The upward motion is achieved by the application of pressure to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the work platform vertically. The Platform may also have an extending 'bridge' to allow closer access to the work area (because of the inherent limits of vertical only movement).
The contraction of the scissor action can be hydraulic, pneumatic or mechanical (via a leadscrew or rack and pinion system). Depending on the power system employed on the lift, it may require no power to enter 'descent' mode, but rather a simple release of hydraulic or pneumatic pressure. This is the main reason that these methods of powering the lifts are preferred, as it allows a fail-safe option of returning the platform to the ground by release of a manual valve.
Control:
The power assisted drive (if fitted) and lift functions of an AWP are controlled by an operator, who can be situated either on the work platform itself, or at a control panel at the base of the unit. Some models are fitted with a panel at both locations or with a remote control, giving operator a choice of position. A control panel at the base can also function as a safety feature if for any reason the operator is at height and becomes unable to operate his controls. Even models not fitted with a control panel at the base are usually fitted with an emergency switch of some sort, which allows manual lowering of the lift (usually by the release of hydraulic or pneumatic pressure) in the event of an emergency or power failure.
Controls vary by model, but are frequently either buttons or a joystick. The type and complexity of these will depend on the functions the platform is able to perform. The controls can control features such as: • Vertical movement • Lateral movement • Rotational movement (cardinal direction) • Platform / basket movement – Normally, the system automatically levels the platform regardless of boom position, but some allow overrides, tilting up to 90 degrees for work in difficult locations. • Ground movement (in self propelled models)
Safety:
The majority of manufacturers and operators have strict safety criteria for the operation of AWPs. In some countries, a license and/or insurance is required to operate some types of AWP. Most protocols advocate training every operator, whether mandated or not. Most operators also prescribe a range of pre-usage checks on the unit itself, and manufacturers recommend regular maintenance schedules.
Work platforms are fitted with safety or guard rails around the platform itself to contain operators and passengers. This is supplemented in most models by a restraining point, designed to secure a harness or fall arrestor. Some work platforms also have a lip around the floor of the platform itself to avoid tools or supplies being accidentally kicked off the platform. Some protocols require all equipment to be attached to the structure by its own lanyard.
Extreme caution must be taken when using AWPs in the vicinity of overhead power lines as electrocution may result if the lift comes in contact with energized wiring. Non-conductive materials, such as fiberglass, may be used to reduce this hazard.
AWPs often come equipped with a variety of tilt sensors. The most commonly activated sensor (especially with two people on a lift), will cause the machine to refuse to raise the platform beyond a certain height. Sensors within the machine detect that weight on the platform is off balance to such a point as to risk a possible tip-over if the platform is raised further. Another sensor will refuse to extend the platform if the machine is on a significant incline. Some models of AWPs additionally feature
counterweights, which extend in order to offset the danger of tipping the machine inherent in extending items like booms or bridges. Some lifts are also fitted with sensors which will prevent operation if the weight on the platform exceeds the safe working load.
As with most dangerous mechanical devices, all AWPs are fitted with an emergency stop button or buttons for use in the event of a malfunction or danger. Best practice dicates fitting of emergency stop buttons on the platform and at the base as a minimum. Other safety features include automatic self checking of the AWPs working parts, including a voltmeter, which detects if the lift has insufficient power to complete its tasks (which will result in it refusing to operate for safety). Some AWPs provide manual lowering levers at the base of the machine, allowing operators to lower the platform to the ground in the event of a power or control failure or deliberate use of the machine (e.g. by unauthorized persons).
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