When someone says "Material handling," you have to wonder what they're talking about. It's a confusing term that says nothing but means a lot. Everyone knows that every construction project involves some type of material handling function. On a site prep job you could be moving trash, debris, brush trees, and earth. As the job progresses you could be installing sewers, roads, parking areas, footings, foundations, and a host of other utilities.
On building sites it can be steel, concrete panels, windows ... you name it. It's always a challenge to get the materials to where they are needed when they are needed. It sounds simple enough but often isn't. Navigating the job site often poses challenges, let alone trying to run the gauntlet of obstacles that commonly adorn a typical job site — any kind of job site.
Safety is always a primary consideration when operating equipment. With material handling equipment the safety aspects are more important, because once the load is up and in the air, any mishap will mean the load is coming down ... in some cases in a controlled descent, in other cases outside of all control. The results can be catastrophic.
Pre-start inspections are critical and should never be glossed over: no short cuts! Walk-arounds should be performed with the same level of seriousness that you want a pilot to use on your 17-hour overseas flight. On all equipment the formula is simple: follow the manufacturer's recommended checklist. Look for cracks; missing or loose parts; fluid leaks; missing, cracked or cloudy mirrors; broken, missing or burned out lights; cracked windshields; bad wiper blades ... in short, anything that could interfere with the safe, smooth operation of the machine. There are no short cuts!
- Check tire air pressure on rubber-tired machines. Be sure that all tires are properly inflated for the application. Make sure the tires are in good — no, make that excellent condition.
- Check the operating functions of all systems before moving the machine.
- Don't give the material handling jobs to the newest man. It takes experience and know-how to manage and handle a load, not matter what it is. Make certain the operator knows the machine, how it operates, its lifting or handling characteristics and its capacity limitation.
- Never exceed manufacturer's load limits.
It's too easy to make mistakes when moving around the job site. It's always better to be overly cautious than even a little careless.
- And don't forget to check the weather. High winds, lightning, sleet, rain, snow, and fog can all take a normally safe job site and turn it into a hazardous work zone.
- Remember that wearing proper apparel is as important as every other aspect of the job: hard hats, safety shoes, safety glasses when called for, gloves if necessary, and safety harness when and where required. This isn't the full list of safety gear you might need or use on the job; that will vary from job to job. If you're in doubt about what's required, check with the jobsite safety director.
Let's take a look at some of the equipment commonly used for material handling applications.
Hydraulic excavators have become adaptable to many material handling applications through quick coupler systems and a wide array of attachments. Most excavator manufacturers have "material handler" configurations in both their crawler models and rubber-tired versions. The big difference is the reach which can be considerably greater, the hydraulics and the operating weight. Several of the manufacturers offer "pop-up" cabs or tilt-back cabs. These machines are usually used in scrap- or waste-handling applications and are usually equipped with grapples or magnets.
Back to the standard excavator, most of the mid-size and larger hydraulic excavators have buckets equipped with lifting eyes. When you think about hydraulic excavators, remember that this family of machines includes compact excavators, mini-excavators, zero-tail swing machines, and rubber-tired machines. Although not as popular in the U.S. as they are in Europe and Asia, the rubber-tired excavator is a very adaptable material handler. Put a highway-barrier clamp on a wheeled excavator and see just how efficiently you can move and place otherwise troublesome barriers. Because of its mobility, a wheeled excavator can move about a job site or from one job site to another quickly and quite often without having to be moved by truck. Its versatility is limited only by your imagination.
Additionally, you can put a quick coupler on any of the excavators. This will enable you to change from one type of bucket to another without leaving your seat; or change to a grapple or thumb. Try a clamshell bucket and see how broadly you have expanded your material handling capabilities. In addition to these lifting-type attachments, there are other tools that can help you demolish buildings, crush concrete, pulverize pavement, and chomp on steel beams.
The variable reach type of forklift is the most common on the job site. It is marketed under a variety of different names such as shooting boom forklift, telehandler and material handler, and it is also available in a toolcarrier version. The toolcarrier rendition indicates that the machine is equipped with a quick coupler and has been engineered to handle an array of attachments. This usually implies that the piece of equipment has been balanced to accommodate the additional weight of the coupler and attachments. It will also indicate that the machine has a higher performance hydraulic system.
Telescopic handlers are excellent tools for loading and unloading flatbed trailers and for placing loads several stories up. Due to their reach, they can also place loads in difficult-to-reach places on the job site. Typically they come with forks, but most manufacturers offer a broad selection of attachments that make these machines versatile material handlers.
Several types of buckets are available including multipurpose buckets, general-purpose buckets, light material buckets, and others. As you can guess, there are any number of forks and grapples available. Most equipment manufacturers or attachment manufacturers can provide you with lifting hooks, truss jibs, material handling arms, and self-tipping hoppers. To complete the versatility package you can add a rotating or side-shifting carriage.
These machines are used extensively in landscaping operations. Their reach enables them to place loads in areas that would be difficult to reach by machine without damaging turf, flowerbeds, water treatments, or other similar landscaping arrangements.
Cranes represent another family of material handlers that are common on many job sites. They are used for lifting and placing such things as heavy steel beams, pre-stressed concrete sections for buildings or bridges, materials and supplies to the upper stories of a high rise, unloading trucks, and a host of other essential jobsite material handling tasks. For our purposes we will look at the basic type of cranes found on many job sites.
All Terrain Cranes
All terrain cranes have become a very popular construction tool. They offer the highway travel speeds of the truck crane and share off-road characteristics with rough terrain cranes. Multiple axles — steer drive and tag — distribute the load. Multiple driven axles provide traction to handle tough jobsite conditions, and multi-axle steering provides added maneuverability. There are suspension options that can provide added off-road clearance and enhance driving characteristics, making a crane that is easy to take on the road from job to job no matter how far the trek. All terrains have been moving into areas traditionally held by truck-mounted and rough terrain cranes, pushing both just a little. Capacity on these machines can reach 1,000 tons. Jib tip heights can be measured at over 600 feet and boom heights at 400 feet (plus or minus).
Rough Terrain Cranes
Even with the advances being made by all terrain cranes, rough terrain cranes remain king of the job site. They handle tough off-road conditions with four-wheel drive and with various types of steering for maneuverability. They are simple — a two-axle configuration and have only one cab from which the operator controls all functions.
They are relatively inexpensive in comparison to other types of cranes. Since they don't have to travel at highway speeds, they don't require the horsepower or drive train components. The two-axle configuration is another major cost saver. Their biggest drawback comes from the fact that they have to be transported between jobs. Once on the job, they excel at pick-and-carry operations. They are a sound economic investment for a contractor who does a lot of lifting on the job. Construction is moving more and more in the direction of "complete or nearly complete" components as part of the building process. Poured in place structures and tilt-up panels are only a couple of examples.
Typical units on job sites range from 30 tons to 70 tons with the largest unit in regular production having a 100-ton capacity. Today boom tip height will exceed 150 feet, and jib tip height will reach beyond 200 feet. Again, with every show there are new cranes that constantly change the spec charts.
Truck Mounted Cranes
Truck mounted cranes sit on a commercial truck chassis. The truck engine is used to power the crane operation. Telescopic boom models perform the same functions as their all terrain and truck crane siblings although they are limited to ratings of about 40 tons, the limitation imposed by the commercial truck chassis itself.
These cranes may come with fixed operator control stations and cost less than an all terrain crane or truck crane. There are models where the cab swings with the crane. Another variation is an articulating boom unit; usually these are specialized horizontal boom units designed to load/unload the truck's payload. They are normally not used as general-purpose cranes.
Truck cranes can travel safely at highway speeds. They use purpose-built carriers with separate cabs for the carrier and crane operations. The hydraulic boom units are designed for quick setup. The smaller and mid-range models generally carry boom, jib and counterweight on board. Some of the larger units may require separate transport arrangements to carry any additional counterweights or boom extensions.
Lattice boom truck crane models offer high lifting capacities and hook heights and are designed to handle the big lifting jobs. By their nature, lattice boom cranes require more setup time than hydraulic boom models.
Truck mounted cranes are not as agile on rough underfoot conditions and shouldn't be taken onto undeveloped job sites unless there are good roads and work platforms. Capacity for these machines exceeds 100 tons. There are some cranes that can reach heights over 200 feet when rigged with a jib.
Lattice Boom Cranes
Lattice boom cranes are both truck-mounted and crawler-mounted. With truck-mounted cranes, the crane's upper structure is mounted on a truck-style carrier, which can travel at highway speeds. Major sections of the crane usually have to be removed and transported separately on some of the larger units. The advantage over crawler cranes, which must be disassembled, is that the carrier is mobile and erection time is usually faster.
Crawler-mounted cranes are mounted on car bodies and are propelled on tracks. This design yields superior on-site mobility and lifting capacities. Crawler cranes are not easily transported and require considerable setup time. All of the modular components of a crawler crane have to be moved by trucks.
Crawler cranes do offer a great deal of versatility, particularly for heavy lifts or long-term lifting projects. From pick-and-carry capabilities to heavy duty or severe duty applications, such as pile driving and dragline, crawler cranes offer a great deal of application versatility.
Choosing a specific crane is typically based on job requirements. A lattice crane is typically the best choice when the job requires long, vertical reaches, significantly large lifts, or long-term work. Both truck and crawler-mounted lattice boom cranes are well adapted for lifting and moving large quantities of steel, constructing large tilt-up concrete panels, and for making very high and far-reaching picks. The design of lattice booms is inherently stronger and more stable at greater distances than telescopic boom cranes, plus lattice boom cranes utilize larger-diameter wire rope, requiring fewer parts of line for faster line speeds. Typically, a lattice crane yields higher capacity picks at a nominal base capacity unit, making a 100-ton capacity lattice crane outperform a 200-ton capacity telescopic crane.
The Hydraulic-Crawler-Mounted Crane is the latest innovation in crane design and technology. It's available as a telescopic or lattice boom crane mounted on a crawler excavator carrier and offers yet more versatility in your choice of lifting device.
In the final analysis, determining which crane to use for which job comes down to the same parameter we apply to any equipment selection: What is the application? For cranes, the main application considerations are how high do you have to lift the load, how far out must it be placed and what does it weigh? The bulk of the load can also be a factor in that a bulky load may require a larger crane to handle physical dimensions in order to obtain lift height required at a given radius.
Other considerations include the terrain and if the crane will be working on- or off-road, pick-and-carry considerations, single or repetitive lifts, travel time and distance, and other factors. Cost considerations also enter into the equation and will be viewed differently depending on the end user.
Please note that we haven't mentioned tower cranes. These lifting wonders are extremely popular in Europe and are becoming more popular in major metropolitan areas. Big cities don't have the room for large-capacity cranes on the ground over extended periods. This is where the tower crane excels. It has a relatively small footprint and can be erected to unbelievable heights and has tremendous lifting capacity. Today's technology has added to the functionality of tower cranes so that even though it is fixed in one place, it has the ability to cover a lot of ground.
If you have a job in a downtown area, you may want to investigate the advantages that a tower crane might offer.
There are a number of manufacturers that produce portable conveyor systems. Most job sites aren't laid out with conveyors in mind; however, there are times when they offer the best solution to a material handling requirement.
I recall visiting Atlanta's Hartsfield-Jackson Airport during its recent expansion and remember listening to the contractor talk about the important role an elaborate conveyor system played in that project. In that case, the job was long enough that the conveyor system was fixed rather than portable; however, some segments were moveable. The net result was that tons of materials were moved economically and efficiently.
If you have a job that requires the movement of high volumes of loose materials like sand, gravel, dirt, chips or the like, you may want to investigate the use of a portable conveyor system. You might be surprised by the amount of money you drop to the bottom line.
Backhoe loaders are primarily earthmovers ... or are they? They are designed for digging and loading, which makes them great material handlers. Recently the toolcarrier design has been applied to these machines as well as others. The result is a very flexible material handler. You have a wide variety of sizes from which to choose and also several drive configurations. Although these machines started their existence on the farm, it didn't take long for them to become a major piece of equipment for construction.
You can put a quick coupler on both ends of this machine. On the loader side you have a selection of buckets that can satisfy any applications as well as loader forks, material-handling arms, bale spear, and other material handling devices. On the loader end, add a quick coupler so you can easily and quickly change buckets and/or other attachments.
Integrated toolcarriers and quick coupler-equipped wheel loaders are kissing cousins, but that's about as close to each other as they get. The toolcarrier is designed and engineered to be a multipurpose work tool/work platform/power source. No matter what you think, the most important part of any machine is the part that gets the job done. You can dig holes, push dirt, lift things any variety of ways; your interest is getting a specific job done. The toolcarrier is designed and balanced to accommodate the quick coupler — adding several inches to the front of the machine — and engineered to handle additional hydraulic flow. Yes, you can put a quick coupler on a wheel loader and put forks on it, but it will not have the same lifting capacity as a tool carrier. Wheel loaders are great material handlers but are purpose built; so are toolcarriers.
There is a variety of lifting arm configurations available on the market today. You may want to do a little research before deciding on a wheel loader. Check out the latest engineering innovations, since the machines have improved.
Integrated toolcarriers and wheel loaders have a broad selection of attachments designed to meet most material handling jobs. In addition to all the various buckets there are many different types of forks available that are designed to make material handling on the job site easier, faster and above all else safer.
Skid-steer loaders and compact track loaders (also called all terrain vehicles and multiterrain vehicles) definitely belong in the material handling equipment category. There are two types of lifting arm configuration on these machines: radial arms and vertical lift arms. The difference is that the vertical lift machines move the load straight up from the ground to the top of the travel path, keeping the bucket or pallet fork level through the cycle. This configuration is a better choice if you are going to use the machine more as a material handler than an earthmover. Many of the ground engaging tools operate more efficiently with the radial arm configuration, as it tends to exert a greater downward pressure.
There are numerous buckets, hooks, lifting arms, and fork attachments available for skid-steer loaders and compact track loaders. The skid steer's already dominating jobsite appeal has been enhanced with the recent introduction of an all-wheel-steer version of the machine. This option should improve its already strong material handling characteristics.