Recycling Comes to Abrasive Waterjet Operations
By: Editors of Gear Technology
Gear Technology, September/October 2000
Abrasive waterjet, an alternative cutting process that utilizes abrasive particles in a highly directed, extremely high-pressure stream of water to cut metal and other materials without some of the drawbacks associated with other processes, has traditionally had some high waste and disposal costs associated with it. In fact, according to Richard Ward, president of EasiJet, Inc. of Tallmadge, OH, abrasive is the single largest consumable cost borne by all abrasive waterjet cutting customers. However, Ward and the folks at EasiJet think they have come up with an answer to those costs: their Waterjet Abrasive Recycling Dispenser, the WARD 24.
How it Works. The WARD 24 removes waste product from the tank in an abrasive waterjet cutting system. It separates the poor product into a container for removal and then washes and dries the remaining abrasive particles so they can be used again. The abrasive is removed from the tank using patented nozzles that have no moving parts. Even if they have been buried under the abrasive for several days, the nozzles can be activated to begin delivering the sludge to the WARD. The sludge is sent to the top of a series of vibrating screens where usable abrasive is separated. This recovered abrasive is then dried and readied for reuse. This results in two products: waste and recycled abrasive.
The waste is made up of sludge and fine particles. These waste products are typically well compacted and have very little water in them since the water used for washing the abrasive is returned to the tank. The recycled abrasive is washed and dried. It is then ready to be reused.
Maintenance Issues. In general, all alloys, steels and harder materials work well without clogging the machine. Test cutting of several plastics has also proven to work well. Small particles that found their way into the dryer were bonded, melted together with a grain of abrasive and removed during the final screening. This is not to say that clogging cannot happen. If materials being cut break down into frayed particles, these could cause screen clogging, which is easily fixed by removing and cleaning the clogged screen.
Clogging is not the only potential problem associated with the WARD. A number of parts on the machine – all parts in contact with the abrasive – are considered consumables and need to be watched and replaced as needed.
Recovery Rates. A number of variables need to be taken into account when considering recovery rates of recycled abrasive. These variables include the material being cut by the waterjet, the speed and quality of the cut specified (this determines the amount of abrasive contacting the abrasive stream’s cutting face), the type and mesh size of the abrasive used, the placement of the abrasive removal nozzles in the tank, and the amount of operator attention given to the machine. Given these variables, field tests have achieved recovery rates of up to 70% in a general job shop environment. This reduces costs associated with waste removal and hauling, saving users up to 40% of the cost normally associated with abrasive waterjet.
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