Ordinary water passes through an ultra-high pressure intensifier, which pressurizes the water up to 4,000 bar (60,000 psi), and then it is released through a tiny nozzle with a diameter ranging from 0.004 inches to 0.016 inches, producing a jet of water that travels at 915 meters per second (approximately three times the speed of sound). This high-speed water jet can be used for various surface treatments and cutting non-metallic materials such as paper, diapers, glass, fibers, and sponges.
For cutting metals and harder materials like various types of stone, glass, ceramics, and tiles, Flow International has developed a patented and more advanced design: mixing abrasive particles with the water jet to enhance its cutting ability. This high-speed abrasive water jet can cut almost any material.
To achieve this, there are higher requirements for the water, pipes, and nozzles. For example, the pipes must withstand extremely high pressures because the water jet is pressurized by high-pressure tools and must have enough force to cut through hard materials. The pressure in these systems far exceeds 700 megapascals (MPa), as thin steel plates themselves can withstand pressures up to 700 MPa.
Secondly, using completely pure water in water jets is not practical. Since the water pressure exceeds 700 MPa, even with excellent sealing performance, pure water will cause wear and eventual leakage on seals and other components. To address this, water used in water jets contains about 5% soluble emulsifying oil to improve the sealing effect. Additionally, some oil is added to the high-pressure pump to enhance its sealing performance.
As mentioned earlier, the nozzles for water jets are made of hard materials such as tungsten carbide or sapphire, with a diameter as small as 0.05 millimeters. The inner walls of the holes are smooth and flat, capable of withstanding pressures up to 1700 MPa, allowing the high-pressure water to cut materials like a knife. In some cases, long-chain polymers such as polyethylene oxide are added to the water to increase its "viscosity," making the water jet resemble a "fine thread."