A bucket isn’t just a bucket these days. There are now a variety of specialized models available to take on tasks well beyond digging and dumping. Particularly noteworthy are those designed to screen and/or crush materials in place. Prevalent in Europe, these attachments are starting to show up on more U.S. jobsites as contractors begin to recognize their benefits.
Apex Pipeline Services, Inc. is an oil and gas pipeline contractor working on a project for Marcellus Shale in West Union, WV. Started in April 2012, the job involves the placement of around 87 miles of gas pipelines. Apex is using REMU EX 140 screening buckets on its 21-ton Caterpillar excavators to backfill excavations.
The screener is a portable bucket with rotators turning both directions to sieve material while in use; larger particles are retained inside the bucket. The sieved material can then be reused on site for padding and backfilling.
Avoiding/reducing truck traffic on the pipeline site was very important for Apex Pipeline Services due to the very limited work space in the mountainous regions around West Union. Screening the material directly into the trench reduces truck movements. Use of the screener has also enabled the contractor to avoid purchasing new, fine material and transporting it to the work site.
“By screening on site, you save on both material costs and transportation,” says Sini Karjalainen, REMU. “On-site bucket screening increases the time that machinery is used for profitable work by eliminating downtime associated with waiting for the next truck.”
Screening buckets are available in a variety of types, sizes and configurations.
VTN Rotobec offers five models of rotary screening buckets for use on excavators from 7.5 to 38.5 tons. They’re available with a single-piece steel screen ranging in size from 3/4 to 3 in., and are suited for applications where materials from a demolition job are being used in new construction or where fill has to have specific characteristics.
Also available is the SB screening bucket, which screens material using 1- to 4-in. screens mounted longitudinally inside the bucket. Three models are available for carriers from 14 to 45 tons. This attachment is particularly suited for screening demolition material, reclaiming rocky ground and for quarry applications.
REMU USA also offers hydraulically operated screening buckets that utilize rotating blades to screen finer material out while retaining oversized material in the bucket. The attachments are available in .24 to 7.2-cu.-yd. capacities (SAE) and can be mounted on carriers up to 40 tons, including excavators, wheel loaders, backhoe-loaders and skid steers.
List prices for REMU screening buckets range anywhere from $13,500 to $80,000, depending on the size and setup. This can be quickly recouped by the time saved in separating materials on site. “In most applications, it is more effective and economical to screen materials first,” says Karjalainen. “The screening bucket is made to genuinely classify and separate materials.”
A screening bucket can be used to process existing soil into a finer product for use as fill or padding, which can reduce the volume of material that has to be trucked to and from the site. “With a screening bucket and the right blade design, it is easy to process different materials that have lumps or frozen clods,” says Karjalainen.
Blades may be available to convert the buckets for other applications, as well. “REMU screening buckets can be converted into a screener/crusher by replacing the blades with crushing and shredding blades,” says Karjalainen. “Furthermore, spiral rotators combined with crushing blades can effectively grind lumpy material. The spiral-shaped configuration also reduces needed power.”
With the proper blade choice and spacing, the buckets can be used to grind glass, tile, gypsum, grass lumps, roots, wood sticks and even asphalt (with certain limitations). The minimum particle size of screened or crushed material that can be achieved is 5/16 in. with a maximum of 2 3/4 in., depending on conditions, blade design, setup, etc. “The normally required particle size for [cable and line] padding is 5/8 in. With a REMU screening bucket, even the 5/16-in. grain size can be produced,” says Karjalainen.
Crushers to Suit Every Carrier
For those with applications that more frequently call for on-site crushing, a dedicated screening/crushing bucket is an effective choice. These attachments can handle higher crushing volumes and more varied materials.
Most screening/crushing buckets utilize counter-rotating shafts in the middle of the bucket to crush material. The buckets are typically available with different blades to adapt to the specific material-handling requirements.
ALLU D-Series screener crusher buckets are capable of processing materials ranging from topsoil and clay, to blacktop and milled asphalt, to C&D waste and even glass. Changeable wear hammers enable them to be adapted to the application.
“Universal blades are used for most applications and materials,” says Jesse Allen, ALLU Group. “Long blades are recommended for screening and aerating compost and other soft materials to increase capacity. Axle blades are ideal for crushing bark and mixing compost, while oval blades are designed for screening material with high stone content or when reduced crushing effect is needed.”
D-Series attachments are available in over 100 model configurations for use with wheel loaders, excavators, backhoe-loaders and skid steers. They are designed to screen, crush, pulverize, aerate, blend, mix, separate, feed and load materials all in one stage. “The ALLU power adjustment valve promotes powerful startup and rotation, allowing the attachment to efficiently screen and crush wet or dry material from .6- to 6-in. fragment sizes,” says Allen.
MB America takes a different approach with its bucket crushers, replacing the counter-rotating shafts with an eccentric actuated by a hydraulic motor — a concept similar to that used in mobile jaw crushers. The bucket crushers can generate 19,000 lbs. of force per square centimeter, though the company says the buckets are capable of much higher crushing energy.
“There is a multiplier effect on the power because of the elliptical movement of the jaws,” explains Max Ravazzolo, CEO, MB America. “It grabs the material and then there is a slicing effect on the crystals. The pressure is applied in two different ways and that creates cracks inside the [material’s] structure.” This enables the bucker crushers to break even very hard materials such as basalt and granite.
MB America bucket crushers are available in size classes suited for skid steers, backhoe-loaders, wheel loaders and excavators up to 154,000 lbs. List prices can range from $36,000 for the MB-L 160 skid-steer model up to $275,000 for the BF 150.10 model for mining applications.
The larger models are capable of crushing hard material (e.g., granite or rock) up to 10-in. minus and softer material (e.g., concrete) up to 15-in. minus. Skid-steer models crush material from 8- to 10-in. minus. “The output can be adjusted so you can go anywhere from 1 to 5 in., and it takes about 10 minutes to adjust,” says Ravazzolo. “You simply regulate the opening of the jaws.”
Some screening/crushing buckets can separate out rebar from reinforced concrete by using a magnetic separator attached to the attachment or via the movements of the crusher itself. “When you apply compression, all of the concrete will crumble away and will [separate] from the rebar... In our case, the passage is straight and open, so the rebar will go through to the other side without even bending,” says Ravazzolo.
Cost-effective Attachment Alternative
Productivity of screening/crushing buckets varies depending on the model, but is notably lower than most mobile crushers. For example, Ravazzolo notes that MB America’s BF 120.10 produces about 60 to 70 cu. yds. per hour, whereas a mobile crusher may produce 200 cu. yds. per hour. Yet, there are other factors that influence overall productivity on a project.
“It’s not just what you do while you’re working, but also what you need to do in order to get that to happen,” says Ravazzolo. “It takes days in order to have a fixed crusher start operating... With our machine, it takes you 10 minutes if you have a quick coupler, 30 minutes if you do it by hand.”
This time savings adds up. Ravazzolo cites a contractor that chose to use a bucket crusher attachment to process a concrete walkway along 3 miles of road. “A 3-mile stretch of road — that’s a lot of walkway and a lot of concrete. You would maybe say that justifies a fixed crusher,” he comments.
But by using the attachment, the contractor was able to eliminate the time required to transport a mobile crusher to the jobsite, set it up, then load and transport material to and from its location. “With our machine, you can go along with the excavator, break it with a hammer, pick up the broken concrete with the bucket crusher and crush it directly where it is going to be used,” he points out.
Similar benefits can be seen on windmill and pipeline installation projects. The attachments are often used to crush base material — including rock and old concrete pipe — in place for laying miles of new cable or pipe, or for setting up haul roads for access to remote areas.
“Whenever you have a job that stretches for a certain distance, you’re better off with a machine that can follow the job instead of having to move the material back and forth,” Ravazzolo asserts.
This is also advantageous on demolition projects in urban areas. “Whenever you demolish something, you end up with a pile of rubble that you have to haul away. If you’re in downtown Manhattan or San Francisco, that means maybe 50 miles. Then you have to carry in gravel and aggregate to create the concrete for the new construction,” Ravazzolo relates. “With our machine, you take the material you demolished, crush it and you have the aggregate to use for the [new concrete]...The economic advantage is significant.
“Another important thing to keep in mind is there is no need for a license to use our crusher,” he adds. “It is an attachment, so you don’t need to ask for a permit. You just go ahead and use it.”
Under the right circumstances, the savings in trucking costs alone may offset any sacrifice in productivity. Ravazzolo points to a New Jersey-based contractor hired to repave a 1-mile stretch of road on Long Island. Factoring in traditional methods, the three-month project was bid at $140,000. By crushing material in place for the road base, the contractor was able to avoid the need to truck material to and from the island. The job was completed in just 40 days at a cost of $60,000.
“If you start to calculate, if you have one mile of road and you have to haul [material] 35 miles away, it’s almost $1,000 per trip,” Ravazzolo points out. “[With the attachment], you just use the material you have, create your own base and you’re ready to go.”
The potential savings add up quickly. “We have examples where clients have completely recovered the cost of the machine in two months,” Ravazzolo states. “The return on investment is unbelievable."
For an interactive version of this story, click here to download the Winter 2013 issue of Sustainable Construction.