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Getting Gritty

April 2012

Recycling garnet can reduce waterjet cutting costs

If you’re a high-volume user of garnet for a waterjet, recycling garnet can payoff in a big way. In fact, it could cut your new garnet purchases in half.

“Waterjet users need to realize that only 30 percent of the jet stream coming out of a waterjet cutter is doing the cutting,” mentions Bradley Schwartz, Pacific regional sales manager at JetEdge Waterjet Systems.

“Therefore 70 percent of the garnet is not being used at all. It’s still virgin material that’s just going directly into the waterjet table,” he says. “You can use recycled garnet over and over again. Usually this is done by adding 50 percent of the recycled garnet to new material.

“Generally for a company to look at a recycling system, they need high garnet consumption,” Schwartz explains. “Recycling would also work for a company that needs to concentrate the amount of scrap or waste from the cutting process and reuse the rest or [for a company that] cuts rare earth and/or very expensive materials that need to be removed from the garnet.”

Jeff Day, sales manager for WARDJet Inc. says, “Half of the hourly costs for using a waterjet is the garnet that’s used. So a waterjet user can reduce these expenses and have a pretty significant impact on his overall operating costs. This would be a primary reason to consider recycling to reclaim a certain amount of this abrasive and use it again to bring down operating costs.

“The second reason would be a reduction in disposal costs for the abrasive,” he says. “Often it’s fairly expensive to dispose of because of the weight. You can take it out of the tank and let it dry, but it’s still heavy. Also companies look at recycling as being green and reducing their environmental footprint. Garnet will run out at some point, so some people see it as a good environmental step they can take.”

Another factor notes Day, is that there are some companies that cut expensive materials like gold that want to recapture some of it and use what would normally be considered the waste portion from the recycler to catch this expensive raw material.

When to recycle

Waterjet users that run their machines several hours a day five days a week or even less aren’t the best candidates for recycling garnet.

“When a waterjet user goes through 30,000 pounds of garnet per month, that’s when they can save money from recycled garnet usage,” says Schwartz. “These are typical shops that run one to two waterjets two shifts, six to seven days per week.”

Day says, “Generally what we find is that a company that uses 10,000 pounds of garnet a month should be recycling it. If a company is only using several thousand pounds per month, recycling probably is not justifiable for them.”

Garnet type can make a recycling difference

Garnet can split into small pieces that are too small for recycling, Day says.
“There is alluvial garnet found in river beds, which tends to be more rounded around its edges. And there’s crushed garnet that is mined and has a sharper edge. What we found is that with the alluvial garnet, after it goes through the cutting process, some of its corners break off. It will end up with sharper edges that are good for cutting.”

Therefore, if alluvial garnet is recycled, the waterjet user probably won’t see much reduction in the waterjet cutting speed, because what comes out of the recycling process probably has sharper cutting edges then what went into the hopper, Day mentions.

He adds that if the waterjet user gets alluvial garnet from Australia, generally there is an approximate 50 to 60 percent recovery rate. If alluvial garnet comes from India or China, it tends to have different fracture patterns and only about 30 percent is reusable.

“When a customer calls and is interested in recycling garnet, we ask if they are using an Indian or an Australian abrasive, and if it’s crushed or alluvial. If they aren’t doing a huge amount of cutting, at a 30 percent recovery rate, it won’t be justifiable to recycle it. At the 50 to 60 percent recovery range, then it’s much easier to justify recycling.”

Recycling equipment

WARDJet Inc. holds the patent on the abrasive recycler it sells and is the only waterjet manufacturer that makes a garnet recycling system for a waterjet.

“Our recycler can be added to any waterjet system,” mentions Day. “The recycler includes an abrasive removal system. We install a series of pipes into the waterjet’s tank and then pump the water and abrasive out of it to a hopper. From the second hopper, the abrasive would be pumped to the top of an abrasive recycler where it will go through various screens to sift out the waste. The good abrasive goes into a drying element. Then this dry abrasive can be sifted further into a course grade and a fine one that both can be reused. Some companies, if they don’t have a use for the finer mesh garnet, will sell it.”

Equipment costs are in the $60,000 to $70,000 range. WARDJet offers a calculator to help a company figure out if a recycling system is cost justifiable.

Day notes that the recycling system is pretty much all automatic. “Some periodic monitoring needs to be done by an operator, and heating elements in the system need to be checked periodically for temperature. But it’s designed to be pretty self-sufficient without much operator intervention.”

A company saves by recycling

Garnett Gerke, owner of G.O. H2O in Edmonton, AB, Canada, is a high-volume garnet user, as he runs two JetEdge waterjet tables 24/7. One is a High Rail Gantry with a 4-ft.-by-12-ft. bed. They equipped the table with two cutting heads and powered it with a 100-hp, 55,000-psi Jet Edge 55-100 Intensifier Pump with dual intensifiers.

“In 2000, our waterjet table was only 1.5 years old, and we were having trucks in and out of here every 10 to 14 days to clean out our tank,” says Gerke.

“It didn’t take long to fill the table full of garnet,” he explains. “Back then they were charging about $700 to clean the table, but we would be down for eight hours, as we had to remove all the slats and the sand from the waterjet tank. Within a year the cleanup cost went up to about $2,000.

“We bought a WARDJet recycling system, and it ended up paying for itself within seven months,” he says.

After using the WARDJet recycler successfully, Gerke added another JetEdge waterjet and designed an add-on system to recycle garnet from both waterjets.

For the second system, the company went with a Jet Edge High Rail Gantry with a 6-ft.-by-12-ft. table to accommodate larger sheet sizes. They equipped this system with two cutting heads and a 55-100 Jet Edge Intensifier Pump.

“The WARDJet recycling system works very well in every aspect,” he says. “But I think the real major challenge for us was the amount of dust created during the heating and drying cycle. So we made changes to add on a secondary dust collection unit, and we designed our system to handle both of our waterjets at the same time.”

Gerke uses about 3,200 pounds of garnet per day and recycles from 50 to 60 percent that is then added into new garnet.

“People asked how long we can recycle the garnet? Actually, we can do it infinitely, because we always mix it with new garnet,” mentions Gerke.

Garnet that’s too fine is disposed of, says Gerke, as he has no place to sell it to. Currently, however, he’s looking into some possible options.

Another way to recycle

For companies that don’t use enough garnet to make recycling feasible, they can still save costs by purchasing recycled garnet through the GMA Garnet Group. This company offers used garnet that can be recycled up to five times without compromising its performance, the company’s website notes.

Grain size distribution of GMR 80 mesh is generally finer compared to the standard GMA 80 mesh specification. But it contains mainly crushed grains with sharp cutting edges.

G.O. H2O
GMA Garnet
Jet Edge Waterjet Systems
WARDJet Inc.