Before a trained operator starts working, the aerial work platform (AWP) has already been selected to provide him or her temporary access to work at height. The operator’s safety and efficiency depends on the quality of that decision. Selecting AWPs for your next project requires more planning than renting a car for your next trip. While cars’ creature comforts may vary, their basic functionality is the same, and they are intended to operate only on roads designed to safely support their travel. AWPs, on the other hand, vary significantly. They can have many different options and are used in all types of work environments. When selecting the most appropriate AWP for a task, a workplace analysis must be conducted to determine how the task can be completed safely. For example, an AWP may be chosen to work on a new construction site or in a shopping mall, in a manufacturing plant, or on a drill rig out at sea. While the basic need to reach work at 50 ft. may be consistent in each, the specifics of each work place can require completely different equipment.
In early 2013, the American Rental Association (ARA), Association of Equipment Manufacturers (AEM), Scaffold and Access Industry Association (SAIA), and International Powered Access Federation (IPAF) trade associations released a new guide to best practices for workplace risk assessment and aerial work platform selection. A copy of the Statement of Best Practices for Workplace Risk Assessment and Aerial Work Platform Equipment Selection can be downloaded, free, from each association’s website. This article summarizes the key points.
1. Required elevation
The primary reason for using an AWP is to access work at height. One of the first considerations in choosing the right unit is determining how high the worker needs to reach. The required height can vary both with worker’s height and the task to be performed.
Some tasks may require the worker to lift relatively heavy objects or make fine adjustments to equipment. These situations may limit the worker’s overhead reach and require an AWP with a higher maximum elevation.
It is important to be aware of the difference between platform height (vertical distance from ground to platform floor) and working height (platform height plus the vertical height of the worker, generally assumed to be six feet). You can specify a lift using either measurement. The important point is to be sure you know which one you are talking about. If you mix them up, you may come up short of the height you need.
2. Required horizontal reach
Knowing the vertical height is sufficient if the work is directly above the base of the AWP. If, however, the work area is beyond the base of the AWP, you will also need to figure out how much horizontal reach is needed.
The same basic questions must be answered regarding the nature of the task and the worker’s ability to reach the work area while his feet remain firmly on the platform floor. You also must carefully review all locations where the AWP can be set up. If obstacles on the ground prevent the AWP base from being set up near the worksite, be sure to consider the extra horizontal distance when calculating how much reach the AWP will need to provide.
When horizontal reach is required or obstacles stand in the way, consider whether a telescopic or articulating boom lift provides better overall access. Articulating boom lifts offer an “up-and-over” capability that provides access in areas where a straight boom may not.
3. Required capacity
Government regulations require AWP manufacturers to state a rated working load (RWL) for each AWP they build. The RWL is the total weight allowed on the lift’s platform. It includes everything on the platform: people, tools, equipment, materials, safety gear, and even the worker’s cooler, or lunch box.
Machines are typically rated as having one-, two-, or three-person capacity. To select the right AWP, you need to consider how many people will need to be lifted at once. If a job takes three workers and you want them all in one lift, you need to pick an AWP rated for three people.
Knowing an AWP’s weight capacity alone is sometimes not enough. If an AWP has a platform capacity of 900 lbs. but is rated for only two people, you cannot lift three 180-lb. workers—even though their total weight is only 540 lbs.
Material size matters, too. Most platforms are designed to have the lifted material inside the platform. This must be addressed when selecting the correct size of work platform required for the task.
Also, platforms are designed for the total load to be uniformly distributed on the platform floor. Even if you do not exceed the RWL, putting the entire load on one side or end of the platform may create a stability hazard.
Some options, such as glaziers’ packages, allow material to be transported outside the platform guardrails. Pipe holders provide a way to secure the load without placing weight on the guardrails (which could cause damage). They also allow unobstructed access in the platform. In order to pick the right AWP and options for a specific task, be sure to clearly define the job’s material-handling needs.
4. Adequate ground support
The weight of AWPs goes up significantly as their size, height, and outreach increase. Also, a boom lift displaces its weight over its tires or outriggers differently as the platform elevates, the turret rotates, and the boom extends.
It is critical to identify the maximum ground-bearing pressure a fully loaded AWP will impose, and also to make sure that every surface on which it will work or travel can support the maximum potential load.
Don’t assume that the ground or a concrete slab will support the load put on it by an AWP. Parking garages have collapsed under the weight of a large boom lift, despite many cars driving and parking safely in the same area.
An AWP imposes a concentrated loading significantly greater than a car’s. That must be considered in AWP selection. Details about an aerial work platform’s point loadings can be found in its operation manual. Underground vaults or utilities may not be able to support the weight of an AWP. Be sure to find out whether any lie beneath the area where you will drive or set up a lift.
There are a wide variety of AWPs to select from. Generally, AWPs that require outriggers to be deployed before the platform can be raised impose lower loading on the supporting surface than AWPs that can drive with the platform elevated. Tracked AWPs offer reduced point loadings and increased gradeability. There is likely to be an AWP option for almost every application.
5. Suitable driving conditions
When you drive an AWP, whether to the work location or during an elevated task, it is vital to make sure the AWP can move safely while staying within the manufacturer-specified limits for slope and support.
In addition to adequate support, suitability for driving must address slope, levelness, irregularity, unevenness, roughness, wetness, frozenness, and other ground conditions. Knowing everywhere that an AWP will need to travel and the surface conditions in each of those areas is essential in selecting the right rig. AWP features like two-wheel drive, four-wheel drive, oscillating axles, outriggers or stabilizers, and crab steering may be required for the task.
6. Working indoors
Indoor environments present conditions that may limit your AWP options. The potential for buildup of carbon monoxide could eliminate lifts powered by internal-combustion engines. Proper access to adequate ventilation will be required for battery charging. Auxiliary lighting options may be needed to provide adequate illumination for the work.
As always, adequate ground support must be addressed. Conditions may require the selection of lighter AWPs to avoid damage to floor coverings, such as tile. Interior work may also present potential crushing hazards, which may require smaller platforms or a lift equipped with anti-crushing safety devices.
7. Work area access
Workplace logistics must be evaluated when selecting an AWP. In addition to considering the machine’s weight and the floor’s strength, as mentioned earlier, you must also evaluate its height and width. Will it fit into traveling and work areas?
Site conditions, such as the ability to offload the equipment at ground or dock level; entrance opening width and height; and the presence of slopes, stairs, ramps, and narrow turning areas may also significantly affect which lift you choose.
8. Other factors
There are many other factors to consider when selecting the proper AWP for a task. How close is the work to electrical conductors? Are there confined overhead areas or obstacles? What are the expected weather conditions, such as high winds? Is there pedestrian or vehicular traffic in the work area? Are there hazardous atmospheric conditions in the work area?
There may be many more questions to review, depending on the specific work situation. It is vital to think ahead and anticipate what may arise, so that you select an AWP that gives the user the safest means of performing his or her work.
Source: Lift and Access Magazine