Air casters: 7 reasons to take a fresh look at an existing technology
If you’re looking for high maneuverability, safety, and ease of use when it is time to move heavy loads, take a look at air casters.
In any facility, there are a number of ways to move heavy equipment. Riggers and plant personnel may turn to the equipment they've used before-cranes, roller equipment or lift trucks-to transport and inch massive machines and oversized loads into place. But more and more, crews are embracing the ease of use and safety advantages of air casters for these challenging tasks.
Although air caster technology was originally developed in the mid-1950s, recent changes in the industrial landscape are making them a modern means to consider for moving machinery, equipment, product and cargo.
Today, the layout of the typical plant floor has become dynamic and requires adjustment as production needs arise. Manufacturing equipment simply doesn't stay in one place like it used to. As technology advances, and management looks to increase the productivity of each machine, teams are being asked to rearrange equipment on the plant floor to increase throughput.
It's not just machinery and processing equipment that are on the move either. In some operations, large assemblies need to be gently inched through tight quarters as they make their way through the process. These applications are ideal for air casters.
Air casters: The basics
Compressed air inflates a donut-shaped tube beneath the square air caster aluminum plate that is under the load being moved. When the tube completely inflates, it creates a pocket of pressurized air beneath the plate. Air leaks out from under the tube, creating a 0.003 to 0.005-in. layer of air.
Like a hovercraft, the load floats on this nearly frictionless layer and can be moved in any direction. Depending on the size of the air caster, it can lift the load up to 3.5 inches. The size and weight of the load will determine the number and size of air casters needed.
The requirements for compressed air depend on the weight of the load, the size and number of air casters and whether a standard or heavy-duty system is used. Most plant air systems operate at sufficient pressure to support a typical air caster system, operating at 25 psi (1.75 kg/cm2) or 50 psi (3.51 kg/cm2) for the heavy-duty system.
As an example, a 28,000 lb/12700 kg air caster rigging system on a normal smooth sealed concrete floor uses as little as 48 scfm at 25 psig. A representative from an air caster company can determine the airflow requirements for the system that best fits your needs.
Recent improvements to this technology include caster designs that can handle higher pressures to move heavier loads. Here are seven ways they can provide productivity and safety benefits:
1. Maneuverability: Loads carried on air casters are much easier to navigate in place than those moved on traditional wheeled casters. On most floors, a 5,000-lb load on air casters can be moved with only 5 to 25 lb of force. Better be prepared to exert more with wheeled casters taking 300 lb of force to move the same load.
Changing course with air casters is as simple as applying force in the direction you want to go, thanks to their omnidirectional travel. With wheeled casters and rollers, changing directions may require multiple redirects to position the wheels to move in the right direction.
Even those wheeled casters touted as "heavy duty" with low friction and little start-up resistance or equipped with vibration damping are difficult to maneuver when loaded. In fact, often the load has to be lifted to turn the wheeled casters. Air casters, on the other hand, enable the load to be precisely positioned and aligned, regardless of its size or weight.
2. Sensitive loads: Air casters glide along on any smooth, nonporous surface, including vinyl, linoleum, raised tiles, and smooth concrete, like that found in most factories. They will also work on porous surfaces, provided a sheet metal or plastic overlay is laid down first.
For floors with gaps, steps, machine tool bases with slots and wood-planked floors, a specially designed air caster with a membrane enclosure to meter the rate of airflow will accommodate the unevenness.
Some loads are sensitive to vibration and jarring. The inflated balloon (or caster bag) is flexible and conforms to imperfections in the floor, providing a compliant suspension. Caster wheels are much less flexible and transfer every bump in the floor to the load.
Air casters can even carry loads across wet floors and sheets of water, as long as the liquid doesn't degrade any air-caster components. There are also air casters that use water or machine-tool coolant as the working fluid in the air caster.
Should the air supply suddenly shut off, all the air inside the air caster takes time to bleed out. Thus, the load is not subject to shock from a sudden drop in pressure. Keep in mind that once the air has escaped the air caster and the load is resting on landing pads, the load is no longer moveable.
3. Moving in tight spaces: Air casters can fit where forklifts, cranes and overhead lifts cannot. Because the air cushions can easily change direction, they can be used in certain material handling operations, such as paper reformers involving large rolls and other applications where large products make their way through the operation. For example, a major manufacturer of agricultural equipment uses air casters to move the chassis and the axle along the assembly line of what will eventually be an 81 HP machine. Here, the floor space is too tight to enable other means of material handling. In addition, the absence of traditional material handling equipment provides greater safety for the workers.
The axle subassemblies ride on air casters, and the assembly employee controls their movement. Once the assembly operations are completed, the axle is mounted onto the chassis.
4. Ergonomics and safety: Air casters enable a single person to safely move and control a load weighing up to 5,000 lb-which is more than the weight of an average car. For heavier loads, power traction drives are available for extra steering and force.
The force required to move a load is calculated by multiplying the load weight by a surface factor between 0.001 to 0.005. Surface factor is determined by evaluating surface levelness and smoothness. A perfect surface would use 0.001. Most surfaces require a factor of 0.005.
There is a potential issue, however; one that air casters share with traditional wheeled casters, and that is traversing slanted or sloped floors. The rule of thumb for safety is that a person can move 5,000 lb on a shop floor with a 0.25-in. slope over 10 ft. Conceivably, one person on an air caster system can move a heavier load, but because of the risk poised by the load size, that would not be advisable.
5. No Damage to flooring: Because loads supported by air casters ride on a cushion of air, there is no floor contact when loads are being moved. Air casters also spread the load out over a larger area so there's less risk of structural damage to floors. Moving heavy loads on wheeled casters or rollers, either routinely as part of production, can damage floors. Wheeled casters can wear grooves in concrete and ruin expensive epoxy floors.
6. Minimal maintenance: Air casters are remarkably easy to maintain. They have no moving parts, require no lubrication and have no maintenance schedule. If they get dirty, they can be cleaned with mild soap and water. If a substance accumulates on the air caster fabric, simply wipe it off using a rag dabbed with acetone. Once cleaned, make sure that the air caster completely dries before any air or load pressure is applied.
7. Cleanroom applications: Wheeled casters can break through the raised flooring found in many clean rooms and in data centers that have large servers. In contrast to wheeled casters, air casters distribute the load's weight over a larger surface area to reduce stress on these floors.
Though air casters are by no means a complex technology, air caster representatives can advise you on the number of air casters you will need, how to position them and what kind of support systems you'll need. If you're looking for high maneuverability, safety and ease of use, when it is time to move heavy loads, take a look at air casters.
-John Massenburg is CEO of AeroGo.
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