Mini Excavators, Robots Hold Profit Promise for Interior Demolition

While interior demolition is a niche, it is also an area of opportunity. “It is growing very rapidly,” says Kendall Aldridge, national sales manager, IHI Compact Excavator Sales. Many buildings, such as hospitals and grocery stores, need to be repaired and brought up to code. “Contractors have realized there are tools that speed up the process, which allows them to bid more work and be more efficient.”

Among them is Donley Concrete Cutting Co., Pickerington, OH, which uses IHI 9VX electric mini-excavators for concrete removal and excavation in interior applications. “Our business is cutting and drilling concrete,” says Dave Donley.

The company performs work in basements preparing trenches for utility installations. “We remove the concrete with the mini-excavator. Then we put an 8- or 12-in.-wide bucket on the excavator and dig a trench so a contractor can run the electrical or plumbing,” Donley explains. “The excavator replaces four or five guys digging with a shovel.” Because it is a specialty tool, the utilization rate will vary. “It does not go out every day, but when you need it, you need it.”

The single-phase 208- or 220-volt and three-phase 480-volt electric units offer an advantage over diesel. “We do a lot in hospitals and other buildings where you just can’t have any fumes,” says Donley. “It is a machine that we definitely value.”

The units also provide ready accessibility. “The tracks on this machine will move in (retract) to go through a regular door,” notes Donley.

Find the right fit

Once inside a building, mini-excavators offer much higher productivity compared to a hand-held tool, and reduce operator fatigue.

“If a job needs more demolition than one person can handle in a day, it is worth bringing in an excavator with a hydraulic breaker,” says Marcus Auerbach, director of compact equipment, Wacker Neuson Corp. “A mini-excavator is really the best carrier for a breaker. It is much better suited than a skid steer because it allows positioning the tool in many different angles and can complete jobs on walls and structures, while a skid steer can only break up concrete on the floor.”

Gaining access to the building is often the highest hurdle. “If it’s a garage door, you can get a larger (wider) machine in. But if it’s a smaller door, that limits your choices to something that retracts to about 32 in. wide,” says Greg Rostberg, marketing manager, Bobcat Co. “Many machines have strict height criteria limitations, and that’s typically around 8 ft. [for getting under a garage door]. Gaining access is always the biggest restriction. Once you are inside, you just have to maneuver the machine.”

Demolition robots fit into tight spaces, as well. “Each of Husqvarna’s three DXR demolition robots is 31 in. wide, so they fit through most standard doorways,” says Johan Ekstrm, product manager, Husqvarna. “When in use, the machines’ track extends from under the body for stability and individually controlled outriggers (available on most models) allow the machines to be sturdy on uneven surfaces and when close to walls.”

Machine weight and dimensions are extremely important when planning demolition jobs. “The floor in a building could be deteriorating and therefore unsafe,” says Ekstrm. “Knowing the weight of the machine enables contractors to know whether or not it will safely operate on a particular surface. Knowing the dimensions enables contractors to ensure the unit will be able to fit through doorways and make it up stairs and elevators, as well as other areas in the building.”

Also consider the tailswing of the machine. “Many times, getting through the door is the main issue. Conventional tailswings are typically narrower and best for that,” says Rostberg. “Once you’re there and operating, if you are concerned about hitting other objects, a zero tailswing machine would be best. A retractable undercarriage provides the best of both worlds.

“Often, you will be working right up against or parallel to an object,” he continues. “An in-track swing frame enables you to work without having to worry about the swing arm hitting anything.”

Fold-down TOPS, such as found on the model 418, Bobcat’s smallest unit, can also be beneficial when working in confined spaces. “The 418 has controls that can be pulled in to go through doors and tight spaces, and then let out to give the operator more leg room and comfort,” Rostberg points out.

Emissions are always a major consideration when working in confined spaces. “We stock a scrubber or exhaust purifier,” says Aldridge. “It is a muffler replacement. It allows you to take diesel equipment indoors. The muffler replacement eliminates roughly 98% of the fumes when you are going to be working inside a building. Depending upon the size of the machine, you are looking at $600 to $800.”

Consider whether you will be working on finished floors. “We have contractors requesting non-marking tracks,” says Aldridge. “If you are going into an existing building such as a hospital, where they already had the floors down, you don’t want to scar or mark up the floors.”

It is usually more productive to use the largest machine possible. “If you can get a larger excavator... in the working space, be sure to use a hydraulic breaker and clamp options (if applicable) to save on manpower and provide additional efficiency,” says Rostberg.

Maximum machine size is often dictated by the floor load. “In today’s world of floor-to-floor demo, floor loads are huge,” says Mike Martin, Brokk Inc. “The magic number is about 125 lbs. per sq. ft. That is the number that we try to stay under.”

It is also the number most often used for general construction in public buildings, though it can be less for specific applications such as high rises.

It’s often difficult to determine the actual floor load of the machine, since it depends on how it’s measured. For instance, the load measured while the machine is on its tracks is much less than when measured using point loading, where the machine is raised up onto its outriggers. “If it is a single 12” x 12” pad, now you are dividing that weight by 4 ft., because you have four pads at 1 sq. ft.,” says Martin.

Most mini-excavators offer very small floor loadings. Take the IHI 15VX, for example. It weighs in at 3,500 lbs., yet both it and the 9VX, its smaller sibling, exert only 3.5 psi of ground pressure.

Examine available features

In interior applications, anything that can aide access, increase visibility and enhance reliability should be considered.

“Good light is very important for an accurate, quality job and it quickly pays to have additional working lights on the excavator,” says Auerbach. “Enclosed cabs provide better protection from dust and noise, but some contractors seem to prefer open machines because they can see better.”

Rostberg notes, “The operator will probably be more productive and comfortable in a machine with a cab. So if the machine will fit, then a cab is best. However, if there is an overhead height restriction to get into a space, then a machine with a foldable or removable TOPS/ROPS might be best.”

A heavy built excavator is a benefit when it comes to frequent demolition applications. “Check the arm and frame for thickness of the steel and the quality of the welds,” says Auerbach. “Look for ‘fishtail’ shape reinforcements at high stress areas and look for a one-piece boom. That means a boom does not have a weld across, but rather is cut out of one piece of sheet metal.”

Probably the most important feature is heavy-duty pins and bushings. “Unfortunately, this is difficult to see from the outside, so contractors have to ask [at the dealer service desk] or look at the parts manual,” says Auerbach. “Hardened steel bushings are better than brass or other softer material.”

Auerbach adds, “Heavy, hardened steel bushings last longer and can be simply replaced without having to line bore the arm and weld it, which is very expensive. A great test is to lift the bucket of a used excavator (500 hours or more) off the ground and then try to move the dipper arm left and right with your hands. There should not be any play or noise; the fit should be nice and tight. Sound or play indicates the potential need for a repair.”

Robots built for demo

Demolition robots add a new dimension to interior demolition. West Bend, WI-based Interstate Sawing used its Brokk demolition robots to transform its business. “Our specialty is confined space demolition,” says Duke Long. “We are not just concrete cutters.”

The machines allow the company to complete projects that most concrete cutters could not accept. “I bought my first Brokk four years ago. Now I have four of them,” says Long. “They really give us a very competitive edge. We have grown our customer base tremendously.”

The demolition robots allow Interstate Sawing to handle difficult jobs, such as removal of 30-in.-deep concrete before digging 1,000 ft. of trench in a weekend. They also allow the contractor to re-think conventional demolition methods.

For example, floors in buildings and stairways can be removed without shoring and with less saw cutting required. Plus, the robots can be sent into trenches without shoring, since there is no need for a person in the trench. The ability to mount a camera on the unit opens up even more possibilities. “When you do a walk through, you have all of these different options in your arsenal and you become more competitive,” says Long.

Demolition robots have a more narrow application focus and can cost significantly more than a mini-excavator, but there are advantages that make them the most effective choice in certain applications. “Unlike mini-excavators, demolition robots are unmanned and allow the operator freedom to move around the jobsite,” says Ekstrm. “Husqvarna’s demolition robots are operated by a remote control feature with Bluetooth technology.”

The company’s models include the DXR 310, DXR 250 and DXR 140. “From the smallest model to the largest, our machines can lift 700 to 2,000 lbs.,” says Ekstrm. “This number varies depending on how the machine is positioned and how far out the lifting point is from the machine. The robots are able to climb stairs, and the outriggers, on various models, allow the robots to fit in tight spaces while still ensuring stability.”

Brokk currently offers six models from 900 up to 12,000 lbs. “We look at it from a 100-ft.-lb. breaker up to a 1,500-ft.-lb. breaker,” says Martin. The three smallest models, the Brokk 50, 90 and 160, are best suited for interior demolition where you need to drive through a 30-in.-wide door and down a hallway. “The benefits of the machine are you can drive it up a flight of stairs. You can put it in a standard freight elevator and take it up to the third floor.”

Because you don’t need to have an operator in the cab, you can potentially run the machine suspended from a crane on the outside of a building, while the operator is in an aerial lift operating the robot via remote controls. “Just being away from the body of the machine sometimes gets you out of harm’s way,” says Martin.

Interstate Sawing just completed a job at the Kohl Center in Madison, WI, where maneuverability was critical. A 170-ft. section at the top of the stadium stairway needed to be removed for installation of luxury boxes. Using the robots to climb up a stairway, the contractor was able to reduce sawing by two-thirds.

The contract originally called for cutting the stairway into 1’ x 1’ cubes, with each cube weighing about 150 lbs. “We cut them into 1,200-lb. pieces,” recalls Long. The Brokk was able to handle these larger sections. “That concrete was 6,000 psi, loaded with steel. To cut that into 1’ x 1’ cubes would have been insanely expensive. I came in with a lower price, yet my margins were better because I used less labor and fewer consumables — fewer diamonds and less diesel in the generator.”

But the biggest productivity enhancement is allowing the operator to position the machine where he or she can best see the work. The operator is not sitting in a cab where the view can be blocked by the cab body or boom.

“It’s a precision job, especially if it’s a hard piece of concrete or rock,” says Martin. “[If] the operator is able to get close to the work and see what he is doing, he is being more productive, because he is staying tight to the work. He is able to place the machine very quickly and get the tool back in the hammering mode.” He also stays out of dangerous situations.

By moving the operator away from the machine, manufacturers can increase available boom force, as well. “We try to build a boom that will support the biggest tool we can put on the end of it and still keep the machine in balance,” says Martin. “Breakout forces are not going to be critical, because if you don’t knock our machine over every once in a while, you are probably not working it hard enough.”