Construction is basically a material handling process in that it requires the movement of materials — rock, dirt, debris, trees, shrubs, etc. — from one place to another so that materials can be moved onto the site for the construction process. There are purpose-built machines for specific types of material handling activities such as dozers, scrapers and excavators for earthmoving,...
Construction is basically a material handling process in that it requires the movement of materials — rock, dirt, debris, trees, shrubs, etc. — from one place to another so that materials can be moved onto the site for the construction process.
There are purpose-built machines for specific types of material handling activities such as dozers, scrapers and excavators for earthmoving, scrap handlers and forestry equipment to name a few. There are also machines designed specifically for moving materials around warehouses, storage facilities and/or job sites. Material handling is an extremely broad term.
Let's consider it in terms of a construction job site and eliminate warehouses, storage facilities and scrap yards. Let's also eliminate straight earthmoving applications with a basic reminder that for moving large volumes of material from a job site there are a number of choices: scrapers and dozers, loaders and/or excavators in combination with articulated haulers or trucks. Artics have become a valuable tool in the rapid movement of material on and off of the job site whether it's a dirt job or a demolition project. Artics can be matched to loaders or excavators for fast long distance material removal. They can definitely improve both efficiency and profitability on a lot of jobs. Do cost comparisons before bidding the job. With the number of machine choices available and the availability of rental equipment you don't have to bid a job on the makeup of your equipment fleet.
Optimum haul distances for the different pieces of equipment will vary depending on underfoot conditions, grade, material type production rate, and operator skills. For short distances up to 300 feet (plus or minus) dozers are the most cost effective. Wheel loaders take over when hauling materials between 250 feet and 500 feet distances. After that you graduate to the scraper zone that is from around 2,000 feet to somewhere around 5,200 feet, again, depending on the above noted factors. Articulated haulers pretty well match the optimum travel distance of the scrapers, going beyond a couple hundred feet, depending on terrain and load. For distance greater than 5,200 feet you would want to consider a rear dump or wagon.
At one time the vertical mast rough-terrain forklift was the principal jobsite material handler. In the family of rough-terrain forklifts there are three categories: the transportable vertical mast reach type, the vertical mast type and the variable reach type. Today the variable reach type forklift is the most common on the job site. It is marketed under a variety of different names such as shooting boom forklift, telehandler, 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 also 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 tool for loading and unloading flatbed trailers and for placing loads several stories up. Because of 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.
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 building 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 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 drive axles provide traction to handle tough jobsite conditions and multi-axle steering provides added maneuverability. There are suspension options that can provides 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 597 feet and boom heights at 344 feet (plus or minus).
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 — 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 negative 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. Boom tip height will peak at feet just short of 150 feet, and jib tip height will reach 208 feet.
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 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 peaks at 100 tons. There are some cranes that can reach heights up to just over 200 feet when rigged with a jib and around 135 feet without.
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 carbodys 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 them 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 boom 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.
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 a 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.
Hydraulic excavators have become adaptable to many material handling applications through quick coupler systems and a wide array of attachments. Most of the mid-size and larger hydraulic excavators have buckets equipped with lifting eyes. When you think hydraulic excavator remember that this family of machines include compact excavators, mini excavators, zero tail swing machines, and rubber-tired machines. Although not as popular in the United States 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.
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.
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 — which adds 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 does 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 a wheel loader. Check out the latest engineering innovations. They have improved on the machines.
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 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 multi-terrain 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 its 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 a recent introduction of an all-wheel steer version of the machine. This option should improve its already strong material handling characteristics.
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.
Pre-start inspections are critical and should never be glossed over. No shortcuts! Walk-a-rounds should be performed with the same level of seriousness that you want a pilot to use on your 17-hour overseas flight. Follow the manufacturer's checklist. Look for cracks, missing or loose parts and fluid leaks. No shortcuts!
On rubber-tired machines check tire air pressure. Be sure that all tires are properly inflated for the application.
Check the operating functions of all systems before moving the machine.
Don't give the material handling jobs to the newest operator. 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 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.