Hydraulic excavators in the >21- to 24-metric-ton class are the go-to construction machine for small- and medium-sized contractors. Several OEMs report that machines in this class lead their annual sales volume figures.
And that makes sense: these machines are used in a multitude of applications, from light utility work to support equipment in road building and other heavy construction applications. They are large enough to handle some on-highway truck loading jobs, but small enough to be quickly and easily transported without special hauling permits.
Also, as Scott Sutherland, product manager for Link-Belt, notes, excavators in this class are reasonably priced, compared to larger machines. “That means they really appeal to the small, owner-operator contractors out there,” he says. “But they’re productive enough that they’re also a productive buy for large fleet managers – either as support equipment on large jobs or for smaller projects.”
Will zero tail swing models become the standard in this class?
These machines are also evolving. In the past few years, zero tail swing models have made significant inroads in this market, supplanting the traditional style excavators that have
longer rear sections. Zero tail swing advocates say these newly configured excavators can lift as much, or more, than conventional models, while working in much tighter surroundings.
Ron Wallace is vice president and equipment manager for George J. Igel & Company, a construction firm in Columbus, Ohio. He says his company recently bought its first near zero tail swing excavator, a Komatsu PC-228, and liked it so much the company since added two more to its fleet of 20 excavators. “Normally, I’d rather rent than buy a specialty machine like this,” Wallace says. “But these units have a lot of applications in everyday use outside of working in tight surroundings. They’re just as strong, or stronger, than a conventional excavator. And although a zero tail swing unit costs 5 or 10 percent more to buy than a conventional machine, it’s worth it for the ability to rotate inside its tracks. We do a lot of highway work and jobs in downtown Columbus and at Ohio State University and our operators really appreciate the peace of mind of not having to worry about swinging the machine into traffic or a building.”
But, Wallace says, Igel is beginning to use these units in applications formerly handled by conventional excavators. “We measured them against the conventional excavators,” he says, “and found they’re more productive when lifting over the side of the tracks because of the counterweight configuration.”
Testimonials like that lead some OEM specialists to believe the days of the conventional excavator may be numbered. “Zero tail swing models are definitely a trend in the >21- to 24-metric-ton class right now,” says Eric Wilde, product manager, Komatsu. He says Komatsu’s PC228, spec’d by Igel, out lifts the company’s conventional design PC200 excavator by more than 10 percent. “We accomplished that by a reconfiguration of the machine’s engine placement and by using a solid cast steel counterweight that is significantly heavier than the concrete and steel shot mixture versions used on conventional machines. The end result is increased lift and the same balance as a conventional machine in a tighter package.”
Given those enhancements, Wilde says he sees no downfalls for contractors who switch to zero tail swing designs. “The market is going to drive that trend,” he notes. “But in my opinion there’s no reason to even consider an old configuration machine anymore. The main knock against zero tail swing designs is tighter component placement. But we’ve found the serviceability on the PC228 to be better than that on many standard machines.”
Thanks to heavier counterweights and a more compact design, zero tail swing excavators have side-lifting abilities on par with conventional design models.
Not so fast
Ed Smola, senior project engineer, Caterpillar, takes an opposing view. “There is no doubt that zero tail swing models like Cat’s 321 excavator can get into and work in tighter, more restricted places that other excavators can’t,” he says. “But we don’t think the older style of excavator is going to become extinct. There are a lot of contractors out there who don’t work in tight spaces – maybe they’re doing site development work – and the lower cost and high productivity of a conventional design will work just fine for them.”
Smola says there are trade-offs for everything, and zero tail swing excavators are no exception. “With the reduced radius design, components are packed tighter into the machine, and in some cases the cab may be a little bit smaller than those on the previous style machines,” he notes. “And to keep the same lift capacity as the standard machine, you have to increase the weight of the counterweight. So the machine becomes heavier, and that extra weight is more demanding in terms of the machine’s structural life. And there can be transportability issues as well.”
Because of those trade-offs, Smola says a contractor should carefully consider his needs before switching to a zero tail swing machine. “There’s no doubt that zero tail swing models have huge advantages for contractors working on restricted jobsites,” he says. “If the trade-offs I mentioned are eventually accepted by the industry, then perhaps zero tail swing will become the norm in this class. But I don’t see that happening quickly. Cat still has customers that like these machines in both configurations.”
As for Ron Wallace, although he’s obviously impressed by their productivity, he says Igel currently has no plans to standardize zero tail swing throughout its equipment fleet. “We’ve got 20 excavators ranging from 10 metric tons up to 110 metric tons. And I don’t think we’ll ever see zero tail swing models take over for larger machines. But they do make a lot of sense for the smaller excavators in our fleet, and I think we’ll be adding more of them in those sizes later on.”
Matching applications and hydraulic capacity vital for excavator performance
Once you’ve decided between a conventional excavator and a zero tail swing model, excavator experts say other factors come into play if you want to spec the best machine possible for your jobs.
According to Sutherland, the type of jobs you expect to be doing with the machine should be your first consideration. “The second issue needs to be the weight of the primary attachment you’ll be using,” he adds. “And don’t forget to factor in the weight of the material it will be picking up and refer to the machine’s load chart to make sure you’re within recommended tolerances. Once you have those numbers, make sure the machine in question can handle those requirements while remaining safe and stable.”
At that point, Sutherland says you should review the unit’s hydraulic capabilities to determine if you’ll be able to run powered attachments well. “A common mistake contractors make is to spec out the hydraulics and then put an attachment on the machine that uses most of, or all of, the hydraulic capacity of that machine,” he says. “That’s fine, but usually the contractor hasn’t taken into account the machine’s multi-performance abilities.”
What ends up happening, Sutherland says, is that when the full-capacity attachment is mounted on the excavator, it runs fine, but the operator notices the machine is running really slow when he tries to swing the carriage, lift the boom or perform other multi-function tasks. “That’s because too much is being demanded of the hydraulic system,” he says.
To avoid this mistake, Sutherland suggests using dealer or internal OEM programs to make sure all the attachments in your arsenal will work well with a new machine. “Link-Belt has an internal program that allows us to analyze attachments our customers want to use and make sure to match them with the proper machine size and hydraulic system to get their work done,” he says. “Using a program like that essentially gives you a customized machine, tailored for your specific hydraulic requirements.”
Think specifics when spec’ing hydraulic systems
Although these machines use attachments well, OEMs say most excavators they sell in this class are used as bucket machines – at least in their first life. But it’s not uncommon for contractors to wind up owning an excavator with too little or too much hydraulic capability for their needs.
“There’s a lot of confusion out there about hydraulic systems,” says Sam Wyant, product manager, Volvo Construction Equipment. “Even experts can get turned around on options and differing capabilities these systems have. Some OEMs offer auxiliary hydraulics standard. Some don’t offer anything. Some OEMs put a valve on but don’t run the piping. But as far as machines go, if an auxiliary attachment isn’t used in the first place, it’s generally used in the second life of the excavator.”
But if resell value isn’t a primary concern for you, and you’re planning on using buckets only, Komatsu’s Wilde says you can save a significant amount of money by spec’ing the proper hydraulic kit for the machine. “Many OEMs offer a multitude of kits. So if you just want to run thumbs, for example, you can spec a thumb kit instead of one designed to handle breakers and save around $4,000. Bear in mind, however, that you’re limiting that machine’s hydraulic potential on a jobsite.”
Tier 2 diesel engines are subjected to higher volumes of contaminants than older diesels. You need to pay extra attention to your engine filters to keep them running properly.
Common bucket mistakes rob you of time and money
There are productivity traps to be aware of for bucket machines as well. “Many contractors will try to put the biggest bucket possible on an excavator, thinking that will give them the most productivity,” observes Dan Wienkes, senior product developer, Caterpillar. “But they usually find out pretty quickly that too big a bucket adversely affects the machine’s reach and stability characteristics – in other words, there’s too much weight out front and the excavator gets tippy.”
Another problem oversized buckets cause is slower cycle times, usually because it takes the excavator longer to pull the bucket through the ground. “In those cases, a smaller bucket will move more efficiently through the cut,” Wienkes says. “The larger bucket may eventually haul a larger individual payload out of the ground, but you’re reducing your cycle times and fill factors and actually producing less over the course of a day.”
“Buckets aren’t understood as well as they should be,” Sutherland adds. “Contractors who really know their business know their buckets. And that starts with knowing the soil conditions you’re working in. Clay or sandy loam will determine whether you need a heavy-duty plate bucket or whether you can go with standard-duty plate. If you spec a standard-duty plate and you’re digging in tough material, you’re going to wear the bucket and its teeth out quickly. But heavy-duty plate buckets decrease the machine’s potential lift capacity because of the thicker material they’re made from.”
Fuel system maintenance crucial with Tier 2 engine-equipped machines
Finally, excavators in this class are now being fitted with Tier 2 diesel engines, which meet ever-tightening, EPA-mandated exhaust emission requirements. According to Wilde, these new engines – which began appearing on excavators in late 2001 – have fuel systems that require greater technical attention than previous generation diesels. “Timely engine maintenance is always important for productive excavators,” Wilde notes. “But with Tier 2 units, fuel system maintenance has become extremely critical for keeping machines running properly and reliably.” Wilde stresses the need to use only OEM spec or OEM-approved fuel filters on these engines. “Otherwise,” he says, “you’re going to have fuel injection problems.”
This, he says, holds true for engine oil filters as well. “Remember that there are a lot more contaminants being pumped back into the block on Tier 2 engines,” he says. “A lot of the engine’s waste gas is now recycled through the combustion process again instead of being pumped out into the atmosphere. So using high quality filters on these engines rather than off-the-shelf brands is crucial.”
Wyant has a final thought on engines: avoid hot shutdowns. “Don’t turn the machine off without letting the engine idle down,” he says. “If you’re an owner, and your excavators are equipped with ECM engine monitoring systems, you need to check the data they output and remind your operators not to do this. A hot shutdown is a sure-fire way to burn up the engine’s turbocharger. Remind your operators that when they shut the engine off, the oil pump shuts down as well. The engine’s turbo is still spinning at full speed, but it’s not getting any lubrication. It’s an expensive item to repair, but a repair job that can be easily avoided with a little diligence on your part.”