Practical Winery
58-D Paul Drive, San Rafael, CA 94903-2054
phone:415/479-5819 · fax:415/492-9325

September/October 2003

BY Penny Hastings

Reducing repetitive motion injuries during grape harvest is an increasingly high priority in the grape industry. Robert Mondavi Winery (Napa, CA) has taken a lead role in that effort by developing a machine that helps grape pickers in high-density vineyards avoid injury.

Robert Mondavi Winery has used a Box Retrieval System (BRS) for the past three harvests in selected blocks of its Napa Valley vineyards (vines spaced 4-ft x 4-ft). The system spares workers the traditional burden of lifting and carrying grape-laden boxes weighing 40 to 50 pounds as many as 40 times each day.

Michael Christensen, Mondavi technical operations manager, reports that while the BRS system is still too new to yield hard data, early anecdotal reports from the field are encouraging. The system seems to be reducing repetitive motion injuries.

Collaborative effort
“The idea for the Box Retrieval System was spawned in 1999 during discussions between our staff and Mathews Mechanical in Newark, CA,” says Christensen. “We were looking for a mechanical way to lift and carry the boxes to reduce the incidence of back injuries.”

In Napa Valley, where grapes are mostly handpicked, rising worker’s compensation premiums are a serious concern. Employers are looking for every possible means to lower their premiums, which are influenced by the number of employee injury claims.

Dr. John Miles, professor in Biological and Agricultural Engineering at the University of California, Davis, reports that most injuries in vineyards are caused by lifting and carrying.

At the UC Agricultural Ergonomics Research Center, Miles and his colleagues have been studying the effects on workers of repeatedly lifting heavy boxes of grapes and carrying them to the end of a vine row, where they either stack boxes on a trailer or dump them overhead into a large gondola. Mondavi began consulting with the UC ag research group early on in its plans to develop the mechanized equipment.

High-density vineyard implement
The BRS fits on a French-made Bobard 896 over-the-row tractor. The Bobard was purchased for Mondavi’s high-density vineyards, where there is not enough room to run even the smallest conventional tractor down the four-foot wide tractor rows. The Bobard can operate in tractor rows as narrow as 40 inches wide. Mondavi has more high-density acreage planted than any other winery in California.

“We didn’t buy the Bobard tractor for harvest,” says Christensen. “It was an existing machine in our fleet and is a common tractor in France for high-density vineyards. We use the Bobard tractor for spraying, cultivation, and vine trimming throughout the year, then we attach the BRS for the harvest season.”

Christensen is also hopeful that the BRS will apply to conventional (six feet and wider) rows. Mitchell Klug, director of the Napa Valley operations for Mondavi, believes it will. “After we did the ergonomic studies and decided to go forward, Michael seized the idea and tackled high-density vineyards first, where injuries were higher,” Klug notes.

How it works
The BRS equipment is 26 feet long and 10 feet at its broadest width. It consists of three conveyors, a hydraulically actuated box ejector mechanism, a roller table, and a work platform. Conveyors are powered using the tractor’s auxiliary hydraulic power. The work platform can accommodate two workers and two full pallets of fruit (approximately two tons) or two half-ton bins and two workers.

During harvest, workers on the Bobard tractor distribute empty boxes to every other tractor row. When boxes are full, pickers leave them in the middle of the tractor row. Arms on the BRS guide each box onto the lift conveyer. The lift or incline conveyor delivers boxes up to the roller conveyor at the rear of the machine. After each box ascends the incline conveyor, the hydraulic ejector is actuated, and the box is automatically transferred to a roller table, which has a slight decline.

Each box is hydraulically propelled down the roller table toward the front of the machine at chest height. A worker removes the box and stacks it on a pallet or empties it into the larger bin. Full pallets or half-ton bins are then off-loaded on the vineyard headland and moved to a staging area via conventional vineyard tractor and trailer, while the Bobard returns to the picking area.

During the first couple of off-seasons, the BRS was returned to fabricator Mathews Mechanical for fine-tuning. Owner Jeff Mathews, whose company specializes in custom material handling, says the latest modification was the addition of an elevator that lowers empty boxes to the ground. “Before, if the worker on the platform emptied boxes into the half-ton bin, he would have to find somewhere to put them. The elevator takes care of that problem.”

Grape picking crews in Mondavi’s To Kalon and Huichica Hills vineyards, where the BRS is used, don’t exclusively work with the machine. Instead, they move between machine-assisted blocks and vineyards with larger spacing where they must carry loaded boxes to the ends of rows or to tractors. It’s no surprise, Christensen reports, that workers say they feel better and that the job is easier for them when they work with the BRS.

UCD’s “Grapemover” prototype
In the Ag Ergonomics Research Center’s vineyard injury study, the UCD staff took a two-step approach. “We wanted to eliminate most of the lifting and carrying activities,” says Miles. “We collected considerable data that showed we could reduce the persistent pain among the workers by 50% just by reducing the weight of boxes from 57 to 46 pounds.” In the next step, they created a machine similar in concept to Mondavi’s BRS, but designed for wide tractor rows rather than high-density vineyards. The “Grapemover” was tested in a prototype in 2001 and with a production run in 2002.

“Our data from 2002 is being studied but is not quite ready for release yet,” reports Miles. However, he expects that, through the use of the Grapemover, new injuries will be reduced to almost none.

“We have not completed the data analysis, but I believe the number of people reporting persistent pain is going to be a small number. It will not be zero, because the data show that something between 10% and 20% of the workers report persistent pain before the season starts. I think our data for picking the grapes, but only doing very limited lifting and carrying, will show similar numbers [to the pre-harvest reports of pain] at the end of the season (10%–20%).”

Cost factors
The BRS has cost Robert Mondavi Winery about $50,000 to develop, manufacture, and modify. “We know we’re on the right track,” explains Christensen, “But at this point, the benefits just haven’t been documented.”
One reason is that only 15% of the harvest in the high-density blocks is carried out utilizing the BRS. “It would require multiple machines to take care of all the 4x4 spaced vineyards,” Christensen adds. “We have only one and it is still being refined.”

In addition, expenses are approximately $50 higher per ton in vineyards using the BRS. But this minimal added expense is offset by a number of other considerations, Christensen suggests. Among them is the winery’s broad view of what encompasses good stewardship.

“We have a lot of long-term workers, many of whom work year-round,” notes Christensen. “We are always looking for ways to mechanize and take the burden off them. We believe this machine is one of those ways. We just have to make it more efficient and economical.”

Klug believes the BRS is successful in helping to mitigate the physicality of the harvest. “This machine allows pickers to make harvest decisions, pick the fruit, pull boxes into the center of the row and walk away. That is clearly better for them than carrying the boxes and lifting them over their heads and dumping them into containers.
“This kind of machine may well allow people to pick for a longer period of time in their lives. Right now you need a strong person. With the BRS, vineyards could potentially expand the pool of people they can use. We’re a sustainable winery. Being sustainable means maximizing potential earnings and employee safety.”