The orifice assembly is a key component of the waterjet cutting process. Its function is to direct the high-pressure stream of water through the mixing tube where it draws in the abrasive and delivers it to the cutting surface. Diamond orifices are highly regarded in the industry or waterjet cutting. Ruby and sapphire orifices are also used.
Ruby and sapphire orifices are considered functional equivalents. They are commonly used in less-critical applications because they are susceptible to damage in high-pressure applications when abrasive particles impact the sides of the orifice. The impact of these particles can damage the inlet edge and compromise the quality of the waterjet stream. Ruby and sapphire orifices usually last anywhere from 1 to 40 hours.
Diamond orifices are known to produce a more cohesive stream than a ruby or a sapphire orifices. A more cohesive stream can result in longer mixing-tube life and increased cutting power. Diamond orifices are generally warrantied for 500 hours, and consistently meet or exceed the 500 hours. It is not uncommon for an operator to get 1,000 hours or more from a single diamond orifice.
Diamond orifices are recommended for use with 6,000 bar (87K to 100K PSI) equipment and are typically preferred for long-duration cuts on expensive material that might be ruined in the event of an orifice failure mid-cut. The cost of a ruined part because the cut was compromised by a damaged orifice can far exceed the initial upfront cost of purchasing a diamond orifice instead of a ruby or sapphire orifice.
Diamond orifices also result in significant cost-efficiency because they require less maintenance and wear longer, requiring fewer replacements.
Operators running multiple cutting heads can also realise the added value of using diamond orifices. Ruby and sapphire orifices have a shorter, more unpredictable usable life than diamond orifices. That shorter life cycle adds to increased downtime, especially on multi-head machines.
And while diamond orifices are preferable for a variety of reasons, there are times when less expensive ruby and sapphire orifices are often chosen. Operators who cut a wide variety of materials that do not have exacting specifications, and change orifice/mixing tube combinations often, may prefer to use less expensive ruby or sapphire orifices, since the frequent handling of the components during regular replacements creates greater potential for loss or damage. More expensive diamond orifices would present greater financial risk to the operation.
Protecting the orifice against damage is always a good strategy. Whether ruby, sapphire or diamond orifices are chosen, the useful life of any orifice assembly can be improved by adding a short-stop filter assembly in the high-pressure line before the on-off valve to eliminate the risk of contaminants entering the line and damaging the orifice. If a short-stop filter assembly is employed, periodic cleaning with an ultrasonic cleaner is recommended to remove calcium deposits and extend the life of the orifice.