Stone World , July 1999

by Richard Ward, Richel, Inc., Tallmadge, OH

It is not possible to recycle gases used in most processes where heat is the main source of energy. Until now, abrasive waterjet cutting has suffered from the same irrecoverable consumable cost. While the concept of water slicing through stone has been an intriguing concept, it is not the water itself that is responsible for the cutting. Small grains of abrasive -- generally garnet -- are drawn into the water stream and accelerated to around 2,000 mph. It is this abrasive that is responsible for most of the erosion taking place in the material under the stream. In fact, abrasive waterjet cutting can best be described as an accelerated erosion process, under control.

Depending on the horsepower of the pump, the amount of abrasive used could be substantial. A good guide would be approximately 1.5 pounds per minute of abrasive consumed per 50 hp of pump strength. In other words, if a company is operating a 100-hp pump, up to 3 pounds per minute could be used, and 4.5 pounds per minute could be used with a 150-hp pump.

Abrasive costs vary from $0.22 to $0.40 per pound, depending on the supplier and grade used. This in turn means the abrasive cost alone of operating an abrasive waterjet could be as much as $36 per hour per 50 hp. Consequently, abrasives are the largest single cost when operating an abrasive waterjet. It is this abrasive cost that has closed the door to many opportunities. Too often, the technology has been defeated because of the cost of abrasive. If three heads are being operated simultaneously with a 150-hp pump, the abrasive cost alone could be over $100 per hour.

A self-contained, compact waterjet abrasive removal dispenser can not only reduce costs associated with emptying the tank of sludge and abrasive, but radically reduce the cost of new abrasive. A system called the WARD 24, an acronym for Waterjet Abrasive Recycling Dispenser has been introduced to the industry, and is forecasted to save on abrasive costs.

The WARD 24, which is distributed through EasiJet, is the size of a desk, and it removes waste products from the tank of an abrasive waterjet cutting system while separating it into a container. Additionally, it will wash, clean and dry the abrasive so it can be used again.

Indications are that the savings generated will more than cover the total payments on the entire waterjet system. Likewise, a busy waterjet shop could possibly save over $800 per day in abrasive costs alone. This excludes the additional savings gained through eliminating the costs of emptying the tank by other means, as well as the loss in revenue incurred through stopped production while the tank is being cleaned.