Vacuum Technology Sweeps to a Tougher Standard

Tennant’s Centurion mechanical street sweeper employs
dry dust control to meet more stringent environmental requirements all year round.

by Arnie Consdorf, Contributing Editor

Tougher environmental standards, like those in Storm Water II and PM-10 rules from the Environmental Protection Agency, have caused a lot of highway departments and public works agencies to take a closer look at street-sweeping operations. A new mechanical sweeper that uses a vacuum to control dust and pick up finer materials has been the answer of choice for many of these users. Even a premium price tag, which normally accompanies new technology and often slows down acceptance, has not slowed down this machine because of its ability to meet tougher requirements and its overall features.

Such has been the relatively short life history of the Centurion street sweeper from the Tennant Company. In two years, the Centurion has gone from the new technology kid on the block to a performance-sweeping tool that matches the needs of a growing list of users across the county.

New technology can be slow to take hold because users are reluctant to risk the delivery of service on something new until it has proven itself for years. But the same users that have a well regarded sense of “no guinea pigs here please” have been quick to adopt the new technology of the Centurion.

Much of that is due to tougher demands for street sweeping. Storm water management plans and air quality rules on fine particulate matter have created a need to eliminate problems earlier. That means getting rid of the dust cloud that often accompanies dry sweeping and keeping problem materials out of storm sewers and catch basins.

A Look "Inside" the Centurion

Dust expertise

The Centurion was born out of Tennant’s desire to expand its product line. And it is backed by years of experience in indoor dust control from serving the industrial sweeping market.

“We had been looking at outdoor street machines for a long time,” says Bill Ruhr, Outdoor Market development manager for Tennant. “In the late 1990s, senior management was looking for new areas of growth. Where else could we bring our core technology — mechanical sweeping with dry dust control — to bear? With pending changes in PM-10 requirements, it looked like street sweeping. We took indoor dust control outside.”

The Centurion is a truck-mounted mechanical broom sweeper with vacuum. To control dust, Tennant closes off the pickup areas with shrouds and creates a negative pressure or vacuum through the machine’s filter and blower system. This PM-10 certified street sweeper operates with or without water to meet year round sweeping needs even in cold climates. The machine was designed to combine efficiency, productivity, and versatility with on-the-job performance.

Efficiency. Vacuum technology not only contains dust, but also reduces the need for multiple passes by more than 50%. The ability to change sweeping modes on the fly makes the machine more efficient over a full range of working conditions.

Productivity. The ability to operate wet or dry extends sweeping applications, especially in colder climates. Sweeping dry increases actual material pickup capacity and eliminates time-consuming stops at water hydrants or the need for a water truck. The truck-mounted machine is nimble on the road sweeping at speeds of up to 20 miles per hour and traveling at speeds of more than 50 miles per hour. Large hopper capacity means it can stay on the job longer.

Versatility. A computerized touch screen allows the operator to choose a custom mode or one of four pre-set sweeping modes — economy, normal route, heavy work (for sand, chip seal, and road millings), and leaves/litter.

A large air conditioned cab with a panoramic windshield and a StreetSmart sweeping system that automatically adjusts broom and conveyor performance to sweeping conditions allows the operator to concentrate more on sweeping and less on what the machine is doing. An IntelliPower system monitors brush wear and optimizes brush tip speed, which maximizes sweeping performance and minimizes brush wear and replacement.

What users say

In the final analysis, it’s what users say about their experience with the Centurion that tells you the most about the acceptance of this new technology machine.

Milwaukee County in Wisconsin, about 90 miles north of Chicago, is a good example. The county sweeps nearly 1600 miles of roads, contract sweeps all the expressways in the greater Milwaukee metropolitan area, and takes care of sweeping at Mitchell International Airport. They run three Centurions, have another one on order, and still another in next year’s budget.

“Sweeping in the winter with wet machines, when temperatures drop below freezing, has been a problem,” says George Torres, director of Fleet Management for Milwaukee County. “We are also expected to meet storm water requirements.

“After doing our research, we found the Centurion to be the best fit for our type of operations,” explains Torres.

Out east in Westford, Massachusetts, there’s a similar story.

“I tested everything available and looked further into new technology on the sweeping market,” says Richard ‘Chip’ Barrett, highway superintendent for Westford. “I liked what I saw in the Centurion. Other users were satisfied. The advantage of being able to sweep in winter was very important to us.”

Westford, which is north of Boston near Lowell, Massachusetts, has 175 miles of roads to care for and has to meet tougher environmental standards.

“We have to keep dust down and sweep up material before it gets into the storm drains,” says Barrett. “In winter, we now can get sand up with one pass by sweeping dry.”

And that means saving money. Barrett believes the Centurion will save Westford between $20,000 and $40,000 a year.

“It costs us $25 to $30 a ton to dispose of street sweepings,” he says. “Catch basin spoils cost up to $85 a ton to dispose of. Keeping sand and other road material out of the catch basins saves money and helps us meet our storm water management plan.”

Six-machine fleet

Snohomish County in Washington state has six Centurions in service, having just recently received three additional units. Allen Mitchell is the fleet manager responsible for the more than 1600 units of rolling stock overall, 600 of which are needed to care for the county’s 1632 miles of roads and 191 bridges.

“At one point, we were looking at a sweeper fleet of 10 mechanical units,” says Mitchell. “We believe we can do the job with six Centurions because of the way they work.”

The vacuum Centurions, each with a price tag in the $150,000 to $160,000 range, are more expensive than conventional sweepers by $20,000 to $30,000, according to users. But higher efficiency and better productivity can offset these up-front costs.

“The unit picks up everything, including sand in the winter,” says Mitchell. “We think they’ll save us in overall costs — less crew time and more sweeping for the dollar. The technology allows us to sweep in half the time. The old mechanical sweepers left behind lines of material, which meant we had to make two passes. These new machines get the job done in one pass.”

Sweepers can be costly units to maintain. Mitchell says it can cost $18,000 to $20,000 a year to maintain a mechanical sweeper because of wear to parts like brooms and hydraulic hoses.

“We haven’t had the Centurions long, but we haven’t seen anything that concerns us,” he says. “With the vacuum technology, they do blast themselves a bit in the hopper area. But so far, the technology has not created any problems for us. We have a well-trained staff here and we always get the manufacturer training we need when we add something new to the fleet.”

In the west, as in other parts of the country, environmental rules are getting tougher. In Washington, there’s also the Endangered Species Act.

“Making a long story short,” says Mitchell, “the more heavy metals and other materials — chemicals, oil, and everything else that ends up on the roads — you pick up, the better it is for the environment. The Centurion picks up fines very well.”

Single-pass efficiency

In South Lake Tahoe, California, the Centurion’s ability to pick up fine materials without dust was a major reason for the purchase.

“We had been researching new street sweepers to replace our aging regenerative air sweeper,” says Jose Mercado, fleet manager. “Our City has been looking for improvements in storm water management and drainage facilities maintenance. The selection of this new sweeper is expected to be a major component in meeting our improvement goals.

“When demonstrating this machine, we had personnel from our air-and water-quality agencies in attendance, who were equally impressed with the end results. The Centurion was able to remove more debris in a single pass than the other sweepers could with multiple passes. The most impressive aspect is its ability to operate virtually dust free, removing finer particles than anything either agency has seen in the past.

“We have issues here with lake water clarity and air quality,” he says. “We need to keep road materials out of runoff and out of the air. In the winter, we put down cinders. We can pick them up with a conventional mechanical sweeper, but it leaves a trail of cinders and creates a lot of dust. The Centurion picks them up in one pass without the dust.”

“This is revolutionary”

In Glendale, Arizona, air quality issues were a major reason for their purchase of two Centurions.

“Street sweeping is covered under our air quality management plan,” says Mike Hoyt, field operations director for Glendale. “We’re required to use a machine that can help us meet PM-10 requirements.

“If you think about it, this is revolutionary. Street sweeping, in the past, was primarily used to keep roads safe and free of debris, not to pick up 10-micron dust. I’m now part of an environmental service that is more important than it has ever been before.”

Glendale sweeps a lot of five-lane streets with two lanes in each direction and a fifth center lane for turning.

“In the past, the center lane was where all the left behind material ended up after sweeping,” says Hoyt. “Now I drive down our streets and see really clean streets, even the center lanes.”

Glendale and other cities and agencies out west have been able to obtain environmental grant money to help pay for the new Centurions.

As with all new technology, there is a learning curve with the Centurions. But it hasn’t proven to be a big hurdle.

“You have to retrain your drivers,” says Glendale’s Hoyt. “The driver was taught to focus on picking up debris. If you want to pick up dust, you need to slow down and use as little water as possible.

“Our operators love the new machines. Cabs are comfortable and you can really see what you’re doing. We just haven’t had the start-up problems you sometimes get with new technology. Tennant did their homework in talking to users and responding with the unit’s design and operation.”

Learning curve issues and concerns encountered include:

In a western application, the gutter broom shroud kept the unit from picking up pine cones easily. The user took off the shroud when picking up that kind of debris and hasn’t had a problem. Tennant also says it is working on improved gutter reach and pickup.

One user had early concerns that a single engine machine like the Centurion might lug when slowing down under load compared to two engine machines (one engine for travel and one for sweeping). But the Centurion automatically sequences power away from unnecessary tasks as it slows down. Engine lugging hasn’t been a big issue.

Another user had some early problems with clogged filters. One shift would clean the machines and hose off the filters. The next shift would take the machines out with wet filters and cake them up. Blow-drying the filters when the units were going right back to work solved the problem.

One user had some early issues picking up leaves until they learned how to properly adjust the machine.

Whatever the issues or concerns, users have given Tennant very high marks for their responsiveness and technical assistance, which is a critical factor in gaining acceptance for any really new machine. While most of the machines in use are still relatively new, major maintenance problems have not surfaced and problem solving has not dealt with the same issues over and over.

Environmentally friendly and user friendly, the Centurion’s new technology has gained acceptance at a faster than normal pace. As a result, the street sweeping industry may never be the same again.

Centurions Take On the Dirty Work at Airports

Centurion street sweepers have been showing up at airports around the country, where sweeping operations encounter rough duty

In Milwaukee County at Mitchell International Airport, a Centurion keeps field operations — runways, taxiways, aprons, and ramps — clear of dust, dirt, and debris year round.

“You can’t be pushing up dust clouds with planes landing on adjacent runways,” says Bill Tietjen, fleet services coordinator for Milwaukee County.

The ability to sweep dry without dust in winter was an important issue for the county. In freezing temperatures, the county had to use glycol in place of water for dust control to be able to sweep. Eliminating glycol and sweeping dry without dust in cold weather represents a “substantial savings.”

At John F. Kennedy International Airport, a Centurion handles both air-side and passenger-side sweeping at Terminal 4. Terminal 4 is the largest terminal at JFK, serving 46 air carriers, all but one of them being international carriers. Facilities Manager Doug Mandart oversees care and maintenance of the 162-acre complex.

He contracts out sweeping applications for roadways, parking lots, taxiways, aprons, and the ramp area to Laro Service Systems.

“They talked to us about adding the Centurion unit,” says Mandart. “We believe in economies of scale. I would rather they invest in the right piece of equipment than tie up people that can be better used doing other things. We encouraged them to bring on the Centurion.”

Laro began using the new sweeper at JFK about six months ago.

“We have two sweepers out there,” says Bob Francis, project manager for Laro. “When you’re out on the ramp, there’s a lot of debris that accumulates around the planes. There are pretty stiff rules about keeping the ramp area clean. The Centurion picks up the debris in one pass, where it could take as many as three passes with the old machine.”

For more information go to:
Tennant Company

Reprinted from Better Roads Magazine
October 2003

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