An aerial work platform (AWP) is a mechanical device used to provide temporary access for people or equipment to inaccessible areas, usually at height. AWPs may also be known as a lift table, lift platform or cherry picker.
They are generally used for temporary, flexible access purposes such as maintenance and construction work or by firefighters for emergency access, which distinguishes them from permanent access equipment such as elevators. Maintenance repair and operations or maintenance repair and overhaul (MRO is fixing any sort of mechanical or Electrical device should it In the fields of Architecture and Civil engineering, construction is a process that consists of the Building or assembling of Infrastructure An emergency is a situation which poses an immediate risk to Health, Life, Property or environment. An elevator or lift is a Transport device used to move people or goods vertically from one floor to another They are designed to lift limited weights (usually less than a tonne, although some have a higher safe working load (SWL)[1]), distinguishing them from most types of cranes. A crane is a lifting machine equipped with a Winder, Wire ropes or Chains and sheaves that can be used both to lift and lower materials and to They are usually capable of being fully operated (including setup) by a single person.
Regardless of the task they are used for, aerial work platforms may provide additional features beyond transport and access, including being equipped with electrical outlets or compressed air connectors for power tools. Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed A power tool is a Tool powered by an Electric motor, a compressed air motor or a gasoline engine They may also be equipped with specialist equipment, such as carrying frames for window glass. [1]
Contents |
Lifting mechanisms
There are several distinct types of aerial work platform, which all have specific features which make them more or less desirable for different applications. The key difference is in the drive mechanism which propels the working platform to the desired location. Most are powered by either hydraulics or possibly pneumatics. Hydraulic machinery are machines and tools which use Fluid power to do work Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed The different techniques also reflect in the pricing and availability of each type.
Articulated
Articulated lifts, also known as boom lifts or hydraulic platform are almost exclusively hydraulically powered, and are the closest in appearance to a crane. This article is about a Vehicle. For the historical British Regiment, see 11th Hussars. They consist of a number of jointed sections, which can be controlled to extend the lift in a number of different directions, which can often include 'up and over' applications.
This type of AWP is the most likely of the types to be known as a 'cherry picker', owing to its origins, where it was designed for use in orchards (though not just cherry orchards). An orchard is an intentional planting of Trees or Shrubs maintained for Food production. This article is about the Cherry berry also classified as fruit for the ornamental tree See Cherry Blossom. It lets the picker standing in the transport basket pick fruit high in a tree with relative ease (with the jointed design ensuring minimum damage to the tree). The term fruit has different meanings dependent on context and the term is not synonymous in Food preparation and Biology. The term 'cherry picker' has become generic, and is commonly used to describe articulated lifts (and more rarely all AWPs).
This type of AWP is now widely used for maintenance and construction of all types, including extensively in the power and telecommunications industries to service overhead lines, and in arboriculture to provide an independent work platform on difficult or dangerous trees. Electricity distribution is the penultimate stage in the delivery (before retail) of Electricity to end users Arboriculture ('ɑːbərɪkʌltʃə is the cultivation of trees and shrubs A specialist type of the articulated lift is the type of fire apparatus used by firefighters worldwide as a vehicle to provide high level or difficult access. A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting Fires by transporting Firefighters Firefighters are rescuers extensively trained primarily to put out hazardous Fires that threaten civilian populations and property to rescue people from car accidents collapsed These types of platforms often have additional features such as a piped water supply and water cannon to aid firefighters in their task. A water cannon is a device that shoots a high- Pressure stream of Water.
Some articulated lifts are limited to only the distance accessible by the length of each boom arm, however, by the use of telescoping sections, the range can be vastly increased. Telescoping in mechanics describes the movement of one part sliding out from another lengthening an object (such as a Telescope or the lift arm of an Aerial work platform Some large hydraulic platforms mounted on a lorry can reach heights of over 100 metres. This article is about the semi-truck For the North American use of the word see Pickup truck. [2]
The majority of articulated lifts require a wide supportive base to operate safely, and most models have extending legs/struts to help accomplish this. These legs can be manual or hydraulic (usually depending on size and price of the machine). Some AWPS are classified as 'spiders' due to the appearance of these legs. Spiders are also available in especially compact form, to fit through doorways for use inside buildings.
Scissor
A scissor lift is a type of platform which can usually only move in the vertical plane. 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). A leadscrew is a screw specialized for the purpose of translating rotational to linear motion A rack and pinion is a pair of Gears which convert rotational motion into linear motion 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.
Mechanical
There are a number of smaller lifts which use mechanical devices such as rack and pinion or screw threads to extend. A rack and pinion is a pair of Gears which convert rotational motion into linear motion A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw These often have juxtaposed sections which move past each other in order to create the movement, usually in a vertical direction only. This lifts usually have limited capability in terms of weight and extension, and are most often used for internal maintenance tasks such as changing lightbulbs. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general
Motive mechanisms
AWPs, by their nature, are designed for temporary works and therefore frequently require transportation between sites, or simply around a single site (often as part of the same job). For this reason, they are almost all designed for easy movement.
Unpowered
These usually smaller units have no motive drive and require external force to move them. Dependent on size and whether they are wheeled or otherwise supported, this may be possible by hand, or may require a vehicle for towing or transport. Small non-powered AWPs can be light enough to be transported in a pickup truck bed, and can usually be moved through a standard doorway.
Self propelled
These units are able to drive themselves (on wheels or tracks) around a site (they usually require to be transported to a site, for reasons of safety and economy). A wheel is a circular device that is capable of rotating on its axis facilitating movement or transportation whilst supporting a load ( Mass) or performing labour in machines Continuous tracks are large (modular tracks used on the so-called caterpillar Tanks construction equipment and certain other off-road vehicles In some instances, these units will be able to move whilst the job is in progress, although this is not possible on units which require secure outriggers, and therefore most common on the scissor lift types. The power can be almost any form of standard mechanical drive system, including electric or gasoline powered, or in some cases, a hybrid (especially where it may be used both inside and outside).
Vehicle mounted
Some units are mounted on a vehicle, usually a truck, though other vehicles are possible, such as railway cars. This article is about the semi-truck For the North American use of the word see Pickup truck. A railroad car or railway carriage is a Vehicle on a rail transport system (railroad or railway that is used for the carrying of Cargo or This vehicle provides mobility, and may also help stabilize the unit - though outriggers are still typical, especially as vehicle-mounted AWPs are amongst the largest of their kind. The vehicle may also increase functionality by serving as mobile workshop or store.
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 remote control is an electronic device used for the remote operation of a Machine. 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. A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling 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 licence and/or insurance may be required to operate some or all types of AWP. Most protocols advocate the giving of training to every operator, whether mandated or not. Before usage, most operators also prescribe a range of pre-usage checks on the unit itself, and manufacturers recommend regular maintenance schedules.
Most AWPs are fitted with safety or guard rails around the platform itself, in order to help contain operators and passengers. This is supplemented in most models by a restraining point, which designed to secure a harness or fall arrestor. Some work platforms may 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.
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 may additionally feature counterweights, which extend in order to offset the danger of tipping the machine inherent in extending items like booms or bridges. A counterweight is an equivalent counterbalancing weight that balances a load 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 potentially dangerous mechanical devices, almost all AWPs are fitted with an emergency stop button or buttons for use in the event of a malfunction or potentially dangerous occurrence. Best practice indicates 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 may not have sufficient power to complete its tasks (which will result in it refusing to operate for safety).
Business model
AWPs are often bought by equipment rental companies,[3] who then rent them out to construction companies or individuals needing these specialised machines. The market for these machines is known to be marked by especially strong boom and bust cycles, and after a great demand in the 1990s (with up to 70,000 AWPs sold per year in the US) the market crashed in the early 2000s, leading to a strong contraction amongst the manufacturers. In Economics, the term boom and bust refers to the movement of an economy through Economic cycles. [3][4]
See also
References
- ^ a b Specialized Aerial Work Platforms Stretch Makers' Market Share (from www. A crane is a lifting machine equipped with a Winder, Wire ropes or Chains and sheaves that can be used both to lift and lower materials and to A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting Fires by transporting Firefighters The long reach excavator or high reach excavator is a development of the Excavator with an especially long boom arm that is primarily used for Demolition constructionequipment. com, Thursday 1 February 2007)
- ^ Bronto Skylift (Industrial applications: HLA Range) (from the Bronto Skylift website, Retrieved 28 April 2007)
- ^ a b Sales of aerial work platforms have gone up! up! and away! over the last three years - Diesel Progress, North American Edition, August 1997
- ^ Things looking up for aerial work platforms - Diesel Progress, North American Edition, January 2005
External links
- Aerial Work Platform Specifications and Comparisons
- Aerial Work Platform Training (a website of the IPAF)
- International Powered Access Federation (official IPAF website)
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic