About the Size of It
When it comes to fuel consumption, excavator design isn’t the only factor. “Another thing that can influence fuel economy is the contractor may not be using the right machine for the application,” says Tony McGreavy, D’Allessandro Corp.
“It only stands to reason that a contractor will want to use an excavator that he already owns rather than rent or purchase a machine matched to the application,” says Bob Fiorenza, district manager for Liebherr Construction Equipment. But this can have negative effects on both productivity and owning and operating costs.
A mismatched machine may not provide the functionality you need. “By using a bigger machine to do a task, it may allow the project to be completed ahead of schedule. But if space is limited, the bigger machine may not fit the job,” Fiorenza points out.
“On the other hand, using an excavator that is too small could result in a number of problems. It may not have the required digging depth, reach or breakout force to effectively dig the material.”
“Using a machine that is too small for the task does not have a big impact on fuel consumption,” notes Walter Reeves, product manager, Volvo Construction Equipment, “but it would have a large impact on lost production, especially if there is a time limit on the job.”
It can also shorten the service life of the machine. “When thinking about duty cycle of the smaller machines, the life expectancy will be shortened if the job requirement is always asking for 110% of the machine’s capacity,” Reeves states.
Safety is also a consideration. “Depending on the job — whether it is lifting heavy loads or digging to deeper depths — using a machine that is too small may put workers under the load or in the bottom of the trench in harm’s way,” says Reeves.
Fiorenza witnessed just such an incident a few years ago when a contractor tried to use an under-sized excavator to set sewer pipe. “The machine was able to lift the pipe up close. But when the operator tried to set the pipe, he had to stick out and exceeded the lift capacity of the machine and lost control of the load,” he describes. The machine tipping capacity was exceeded. Fortunately, workers were able to climb into another pipe for safety before the machine and pipe came to a rest in the hole.
Though less of a safety issue, using an over-sized machine for a project can be costly. “If you’re using a machine that’s too big, you’re wasting all the energy and power,” says D’Allessandro. “A big machine might burn 100 gal. [of fuel], while a small one might burn 50.”
There is also the potential for added restoration costs. “If a bigger, heavier machine is too close to a poured foundation, it could potentially crack the foundation, resulting in costly repairs,” Fiorenza comments.
Over sizing a trench can also result in higher costs for bedding materials, increasing job costs, adds Reeves.
In certain applications, zero or minimal tailswing excavators may be the answer. “We have 14 zero tailswing excavators,” says D’Allessandro. “These machines are more productive for us. I haven’t measured it, but I would almost guarantee I’m getting more fuel efficiency because they don’t have to keep walking back and forth. They can swing within their own tracks.”
Such units have the ability to work up against buildings, or in the street without blocking two lanes of traffic. You may also find you can utilize a bigger machine size class. “We are able to put a larger machine in the same footprint as a machine that is maybe two-thirds its size because of the zero tailswing,” says D’Allessandro.
Renting the right machine size is another alternative. Even with 22 excavators, D’Allessandro Corp. will rent when a job calls for it. “In the mid-range, we have everything we need,” says D’Allessandro. “But if we need to go out and rent a big one for a specific job, we will. And if it’s a real small job, we will work safely and rent a smaller one.”
D’Allessandro feels it’s easy to justify the rental expense. “If it’s a larger machine, we can get more production and it’s going to cost me less to do the job,” he says. “And the same thing if it’s a small machine. If I need three guys to hand dig a small hole between utilities, and this excavator will save me all that labor, then that’s what we need to do.”