Equipment

What to Consider When Spec’ing Excavators

Whether renting or buying, fleets must ensure excavator specs meet the needs of the application. Fleet managers and equipment manufacturers weigh in on factors to consider.

March 2011, Government Fleet - Feature

by Stephen Bennett

The Terex TC 20 Compact Crawler Excavator has max dig depth of 8 feet 2 inches and max reach of 14 feet 4 inches.
The Terex TC 20 Compact Crawler Excavator has max dig depth of 8 feet 2 inches and max reach of 14 feet 4 inches.

You dig, right? What government fleet doesn't?

Many public works departments use a backhoe for everyday jobs, resorting to an excavator for special occasions.

Excavators are more versatile and perform better now than excavators of a decade and more ago, according to manufacturers. While this is good news, it means purchasers and renters should do more research on the equipment to ensure they make appropriate purchasing and spec'ing choices. The user has a range of factors to consider, including size, weight, reach, tail swing, horsepower, attachments, auxiliary hydraulics, and breakout force.

Whether a fleet rents or purchases an excavator, it still must ensure the machine's specs match up to the work required.

Rent or Buy?

Fleets have various ways of determining­ when to rent or buy an excavator, with many finding rental sufficient for their needs.

"When the reach and depth requirements exceed those of a backhoe, organizations will often rent an excavator, but relatively few municipal fleets actually buy one," said Chris Amos, CAFM, commissioner of Equipment Services for the City of St. Louis.

Walter Burnett, CAFM, public works director for the City of Macomb, Ill., said, "We occasionally rent an excavator when the project warrants it. Our decision on size is almost always based on when the excavator will do the job better than one of our backhoes. Often, we rent a mini excavator if the workspace is tight and sometimes larger machines are needed when the job requires greater digging depth or breakout forces than our backhoes can provide. Our most recent rental was for a 48-inch reinforced concrete culvert project across a street. In that case, the weight of the pipe sections was the determining factor."

Stephen Kibler, ACFM, fleet manager for the City of Loveland, Colo., offered a rule of thumb for fleet managers: If excavator utilization is less than 400 hours per year, rent it.

"Our standard workload does not currently justify our purchasing an excavator," Kibler said. "Most underground main leaks in Loveland involve a six-inch or smaller pipe. Access or excavation is accomplished by a backhoe 95 percent of the time. If a larger main needs accessing, a contractor would be hired to do the excavating."

Kibler added, "mid-sized, rubber-tracked units that are more maneuverable seem to be the best value in a municipal environment. Most excavating needs are predominately in the roadway, and pavement damage needs to be minimized."

The John Deere 220D W wheeled excavator allows operators to drive to a jobsite rather than loading the equipment onto a trailer.
The John Deere 220D W wheeled excavator allows operators to drive to a jobsite rather than loading the equipment onto a trailer.

Managing Specific Demands

Transporting an excavator to a jobsite is also an issue, in part because side streets aren't always large enough to allow off-loading. In Loveland, Kibler said the Water Department will drive a backhoe as far as 10 miles to a worksite, which accounts for 50 percent of the equipment wear-and-tear. (The size and weight of the machine also determine the size of a trailer and towing vehicle, and whether the driver will need a commercial driver license.)

Government fleets deal with different demands day-to-day, often shaped to some degree by geography and seasonal weather patterns, among other factors.

Flooding and mud slides come with the territory in Snohomish County, Wash.  Excavators are used to move rock and riprap into place for flood control and to clear mud slides.

The Snohomish County Department of Public Works (DPW) has 11 excavators: five crawler excavators, four mini-excavators, and two wheeled machines. They are from a mix of manufacturers, including Caterpillar, JCB, John Deere, and Komatsu, said Allen Mitchell, CPFP, fleet manager for Snohomish County DPW.

"We rent additional machines if we're busy," Mitchell said. During the construction season, the road division, which has 170 employees, hires half as many again for summer help. Seasonal employees are limited to operating pickup trucks while the full-time, experienced employees are assigned to the excavators and other more sophisticated equipment, Mitchell said.

Spec'ing the excavators for various uses requires consideration of a wide range of factors that include boom reach, maximum loading height, and swing radius.

An excavator spec'd with hydraulics to run a well-chosen variety of attachments is a very versatile machine, Mitchell said. Snohomish County's excavators are used for solid waste management, parks maintenance and construction, and road repair and construction.

At transfer stations, the County uses excavators with a hydraulic thumb attachment to sort and pack recyclables. In the County's parks, an excavator with a mower attachment replaced a traditional mower, and an excavator with a hydraulic thumb attachment is also used for parks projects such as reconfiguring drainage systems. The road crews use excavators with pavement breakers; they also use a hydraulic thumb attachment to load catch basins and culverts on and off trailers and to plant trees. Road crews use the mower attachment for drainage projects along rights-of-way and to remove debris from bridge structures to prevent flood damage.

For construction projects, a compactor attachment comes in handy for compacting soil to minimize settling once a concrete slab is poured. To dig for construction projects, the County usually specs two or three buckets of varying widths, Mitchell added.

A compact or mini excavator can cost about $95,000 and a large excavator around $350,000, Mitchell said. As for service life, Mitchell said, "We don't go beyond 10,000 hours. After that, there can be major rebuild costs." That number of hours usually translates to about 15 years, Mitchell said.

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