how waterjet cutting works

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1.2 Intensifier Based Pumps The water circuit consists of the inlet water filters, booster pump, intensifier, and shock attenuator. Ordinary tap water is filtered by the inlet water filtration system – usually comprising of a 1 and a 0.45 micron cartridge filter. The filtered water then travels to the booster pump, where the inlet water pressure is maintained at approximately 90 psi – ensuring the intensifier is never “starved for water.” The filtered water is then sent to the intensifier pump and pressurized to up to 60,000 psi. Before the water leaves the pump unit to travel through the plumbing to the cutting head, it first passes through the shock attenuator. This large vessel dampens the pressure fluctuations to ensure the water exiting the cutting head is steady and consistent. Without the attenuator, the water stream would visibly and audibly pulse, leaving marks on the material being cut. The hydraulic circuit consists of an electric motor (25 to 200 HP), Introduction Beyond cost cutting, the waterjet process is recognized as the most versatile and fastest growing process in the world. Waterjets are used in high production applications across the globe. They compliment other technologies such as milling, laser, EDM, plasma and routers. No noxious gases or liquids are used in waterjet cutting, and waterjets do not create hazardous materials or vapors. No heat effected zones or mechanical stresses are left on a waterjet cut surface. It is truly a versatile, productive, cold cutting process. The waterjet has shown that it can do things that other technologies simply cannot. From cutting whisper thin details in stone, glass and metals; to rapid hole drilling of titanium; to cutting of food, to the killing of pathogens in beverages and dips, the waterjet has proven itself unique. 1. The Pump of Waterjet One of the important part of water jet system is pump. Two types of pump can be used for waterjet machines applications first is an intensifier based pump and secend one is direct drive based pump. 1.1 Direct Drive Pump The direct drive pump operates in the same manner as a low- pressure “pressure washer” that you may have used to pressure wash a house or deck prior to repainting. It is a triplex pump that gets the movement of the three plungers directly from the electric motor. These pumps are gaining acceptance in the waterjet industry due to their simplicity. direct drive pumps can deliver a maximum continuous operating pressure 10 to 25% lower than intensifier pumps units (20k to 50k for direct drive, 40k to 60k for intensifiers). hydraulic pump, oil reservoir, manifold, and piston biscuit/plunger. The electric motor powers the hydraulic pump. The hydraulic pump pulls oil from the reservoir and pressurizes it to 3,000 psi. This pressurized oil is sent to the manifold where manifold’s valves create the stroking action of the intensifier by sending hydraulic oil to one side of the biscuit/plunger assembly, or the other. The intensifier is a reciprocating pump, in that the biscuit/plunger assembly reciprocates back and forth, delivering high-pressure water out one side of the intensifier while low-pressure water fills the other side. The hydraulic oil is then cooled during the return back to the reservoir. The advanced technology in the pump is found in the intensifier. As mentioned briefly in the description of the water circuit, the intensifier pressurizes the filtered tap water to up to 60,000 psi.

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Page 1: How Waterjet Cutting Works

1.2 Intensifier Based Pumps

The water circuit consists of the inlet water filters, booster pump, intensifier, and shock attenuator. Ordinary tap water is filtered by the inlet water filtration system – usually comprising of a 1 and a 0.45 micron cartridge filter. The filtered water then travels to the booster pump, where the inlet water pressure is maintained at approximately 90 psi – ensuring the intensifier is never “starved for water.” The filtered water is then sent to the intensifier pump and pressurized to up to 60,000 psi. Before the water leaves the pump unit to travel through the plumbing to the cutting head, it first passes through the shock attenuator. This large vessel dampens the pressure fluctuations to ensure the water exiting the cutting head is steady and consistent. Without the attenuator, the water stream would visibly and audibly pulse, leaving marks on the material being cut.

The hydraulic circuit consists of an electric motor (25 to 200 HP),

Introduction

Beyond cost cutting, the waterjet process is recognized as the most versatile and fastest growing process in the world. Waterjets are used in high production applications across the globe. They compliment other technologies such as milling, laser, EDM, plasma and routers. No noxious gases or liquids are used in waterjet cutting, and waterjets do not create hazardous materials or vapors. No heat effected zones or mechanical stresses are left on a waterjet cut surface. It is truly a versatile, productive, cold cutting process. The waterjet has shown that it can do things that other technologies simply cannot. From cutting whisper thin details in stone, glass and metals; to rapid hole drilling of titanium; to cutting of food, to the killing of pathogens in beverages and dips, the waterjet has proven itself unique.

1. The Pump of Waterjet

One of the important part of water jet system is pump. Two types of pump can be used for waterjet machines applications first is an intensifier based pump and secend one is direct drive based pump.

1.1 Direct Drive Pump

The direct drive pump operates in the same manner as a low-pressure “pressure washer” that you may have used to pressure wash a house or deck prior to repainting. It is a triplex pump that gets the movement of the three plungers directly from the electric motor. These pumps are gaining acceptance in the waterjet industry due to their simplicity. direct drive pumps can deliver a maximum continuous operating pressure 10 to 25% lower than intensifier pumps units (20k to 50k for direct drive, 40k to 60k for intensifiers).

hydraulic pump, oil reservoir, manifold, and piston biscuit/plunger. The electric motor powers the hydraulic pump. The hydraulic pump pulls oil from the reservoir and pressurizes it to 3,000 psi. This pressurized oil is sent to the manifold where manifold’s valves create the stroking action of the intensifier by sending hydraulic oil to one side of the biscuit/plunger assembly, or the other. The intensifier is a reciprocating pump, in that the biscuit/plunger assembly reciprocates back and forth, delivering high-pressure water out one side of the intensifier while low-pressure water fills the other side. The hydraulic oil is then cooled during the return back to the reservoir.

The advanced technology in the pump is found in the intensifier. As mentioned briefly in the description of the water circuit, the intensifier pressurizes the filtered tap water to up to 60,000 psi.

Page 2: How Waterjet Cutting Works

Intensifier pumps utilize the “intensification principle.”

Hydraulic oil is pressurized to a pressure of, say, 3,000 psi. The oil pushes against a piston biscuit. A plunger with a face area of 20 times less than the biscuit pushes against the water. Therefore, the 3,000-psi oil pressure is “intensified” twenty times, yielding 60,000-psi water pressure. The “intensification principle” varies the area component of the pressure equation to intensify, or increase, the pressure.

Pressure = Force /Area

If Force = 20, Area = 20, then Pressure = 1. If we hold the Force constant and greatly reduce the Area, the Pressure will go UP. For example, reduce the Area from 20 down to 1, the Pressure now goes up from 1 to 20. In the sketch below, the small arrows denote the 3,000 psi of oil pressure pushing against a biscuit face that has 20 times more area than the face of the plunger. The intensification ratio, therefore, is 20:1.

In the illustration below, the biscuit and plungers are in the green section and outlined in red. The biscuit contains the small arrow suggesting movement to the left. The two water plungers extend from either side of the biscuit. High-pressure water is delivered out the left side while low-pressure water refills the right. At the end of travel, the biscuit/plunger assembly sequence is reversed.

Sophisticated check valves ensure the low pressure and high-pressure water is only allowed to travel one direction. The high-pressure cylinders and end caps that encase the plunger and biscuit assembly are specially designed to withstand the enormous force and the constant fatigue.The entire unit is designed for long life, while also designed to fail in a safe way. Waterjet systems fail in a gradual, rather than instantaneous way. The seals and connections begin to leak slowly through specially designed weep holes. The operator or maintenance person can see a drip escaping from a weep hole. The location of the drip and the amount of water indicate when maintenance should be performed. Usually, the maintenance person can schedule the periodic maintenance of seals and check valves out 1 to 2 weeks into the future by simply monitoring the gradual weeping. Warning and shutdown sensors also cover the pumping unit to further safeguard against pump damage.

Troubleshooting of an intensifier is quite simple. Dripping of hot water from a weep hole indicates a high-pressure leak, cold water indicates low-pressure. In the actual image, those drops labeled hot or warm are in red, cold is in blue.

Full Screen of this picture at final paper

Page 3: How Waterjet Cutting Works

2. Types of Waterjets

2.1 Pure Waterjet

Pure waterjet is the original water cutting method. The first commercial applications were in the early to mid 1970s, and involved the cutting of corrugated cardboard. The largest uses for pure waterjet cutting are disposable diapers, tissue paper, and automotive interiors. In the cases of tissue paper and disposable diapers the waterjet process creates less moisture on the material than touching or breathing on it.

2.1.1 Pure Waterjet Attributes

• Very thin stream (0.004 to 0.010

inch in diameter is the common range)

• Extremely detailed geometry

• Very little material loss due to cutting

• Non-heat cutting

• Cut very thick

• Cut very thin

• Usually cuts very quickly

• Able to cut soft, light materials (e.g., fiberglass insulation up

to 24” thick)

• Extremely low cutting forces

• Simple fixturing

• 24 hour per day operation

In waterjet cutting, the material removal process can be described as a supersonic erosion process. It is not pressure, but stream velocity that tears away microscopic pieces or grains of material. Pressure and velocity are two distinct forms of energy. But how is the pump’s water pressure converted to this other form of energy, water velocity? The answer lies in a tiny jewel. A jewel is affixed to the end of the plumbing tubing. The jewel has a tiny hole in it. The pressurized water passes through this tiny opening changing the pressure to velocity. At approximately 40,000 psi the resulting stream that passes out of the orifice is traveling at Mach 2. And at 60,000 psi the speed is over Mach 3. Pure waterjet orifice diameter ranges from 0.004 to 0.010 inch for typical cutting. When waterblasting concrete with a nozzle traversing back and forth on a tractor, a single large orifice of up to 1/10 th of an inch is often used.

The three common types of orifice materials (sapphire, ruby, diamond) each have their own unique attributes. Sapphire is the most common orifice material used today. It is a man-made, single crystal jewel. It has a fairly good quality stream, and has a life, with good water quality, of approximately 50 to 100 cutting hours. In abrasive waterjet applications the Sapphire’s life is ½ that of pure waterjet applications. Sapphires typically cost between $15 and $30 each.

2.1.2 Pure waterjet cutting head

As you may recall from an earlier section of this document, the basic waterjet process involves water flowing from a pump, through plumbing, and out a cutting head.

2.2 Abrasive Waterjets

The abrasive waterjet differs from the pure waterjet in just a few ways. In pure waterjet, the supersonic stream erodes the material. In the abrasive waterjet, the waterjet stream accelerates abrasive particles and those particles, not the water, erode the material. The abrasive waterjet is hundreds, if not thousands of times more powerful than a pure waterjet. Both the waterjet and the abrasive waterjet have their place. Where the pure waterjet cuts soft materials, the abrasive waterjet cuts hard materials, such as metals, stone, composites and ceramics. Abrasive waterjets using standard parameters can cut materials with hardness up to and slightly beyond aluminum oxide ceramic (often called alumina, AD 99.9).

2.2.1 Abrasive Waterjet Cutting

Heads Within every abrasive waterjet is a pure waterjet. Abrasive is added after the pure waterjet stream is created. Then the abrasive particles are accelerated, like a bullet in a rifle, down the mixing tube. The abrasive used in abrasive waterjet cutting is hard sand that is specially screened and sized. The most common abrasive is garnet. Garnet is hard, tough and inexpensive. Like the pink colored sandpaper found at the hardware store, different mesh sizes are used for different jobs:

120 Mesh – produces smooth surface

80 Mesh – most common, general purpose

50 Mesh – cuts a little faster than 80, with slightly rougher surface

Page 4: How Waterjet Cutting Works

2.2.3 Abrasive Waterjet Attributes

• Extremely versatile process

• No Heat Affected Zones

• No mechanical stresses

• Easy to program

• Thin stream (0.020to 0.050 inch in

diameter)

• Extremely detailed geometry

• Thin material cutting

• 10 inch thick cutting

• Stack cutting

• Little material loss due to cutting

• Simple to fixture

• Low cutting forces (under 1 lb.

while cutting)

• One jet setup for nearly all abrasive jet jobs

• Easily switched from single to multi-head use

• Quickly switch from pure waterjet to abrasive waterjet

• Reduced secondary

The mixing tube acts like a rifle barrel to accelerate the abrasive particles. They, like the orifice, come in many different sizes and replacement life. Mixing tubes are approximately 3 inches long, ¼ inch in diameter, and have internal diameters ranging from 0.020 to 0.060 inch, with the most common being 0.040 inch. Although the abrasive waterjet machine typically is considered simple to operate and ‘bullet proof,’ the mixing tube does require operator attention. A major technological advancement in waterjet was the invention of truly long-life mixing tubes. Unfortunately, the longer life tubes are far more brittle than their predecessors, tungsten carbide tubes. If the cutting head comes in contact with clamps, weights, or the target material the tube may be broken. Broken tubes cannot be repaired. Today’s most advanced systems incorporate collision detection to spare the mixing tube.

The standoff distance between the mixing tube and the target material is typically 0.010 to 0.200 inch. Larger standoff (greater than 0.080 inch) can cause a frosting to appear atop the cut edge of the part. Many waterjet systems reduce or eliminate this frosting by cutting under water or using other techniques.

The consumable items in an abrasive waterjet are the water, abrasive, orifice (usually Ruby) and mixing tube. The abrasive and mixing tube are exclusive to the abrasive waterjet. The other consumables are also found in the pure waterjet.

3. Basic waterjet principles

Waterjets are fast, flexible, reasonably precise, and in the last few years have become friendly and easy to use. They use the technology of high-pressure water being forced through a small hole (typically called the "orifice" or "jewel") to concentrate an extreme amount of energy in a small area. The restriction of the tiny orifice creates high pressure and a high-velocity beam, much like putting your finger over the end of a garden hose.Pure waterjets use the beam of water exiting the orifice to cut soft material like diapers, candy bars, and thin soft wood, but are not effective for cutting harder materials.

Typical design of a pure waterjet nozzle

The inlet water for a pure waterjet is pressurized between 20,000 and 60,000 Pounds Per Square Inch (PSI) (1300 to 6200 bar). This is forced through a tiny hole in the jewel, which is typically 0.007" to 0.020" in diameter (0.18 to 0.4 mm). This creates a very high-velocity, very thin beam of water (which is why some people refer to waterjets as "water lasers") traveling as close to the speed of sound (about 600 mph or 960 km/hr).

An abrasivejet starts out the same as a pure waterjet. As the thin stream of water leaves the jewel, however, abrasive is added to the the stream and mixed. The high-velocity water exiting the jewel creates a vacuum which pulls abrasive from the abrasive line, which then mixes with the water in the mixing tube. The beam of water accelerates abrasive particles to speeds fast enough to cut through much harder materials.

A diagram of an abrasivejet nozzle

Page 5: How Waterjet Cutting Works

The cutting action of an abrasivejet is two-fold. The force of the water and abrasive erodes the material, even if the jet is stationary (which is how the material is initially pierced). The cutting action is greatly enhanced if the abrasivejet stream is moved across the material and the ideal speed of movement depends on a variety of factors, including the material, the shape of the part, the water pressure and the type of abrasive. Controlling the speed of the abrasivejet nozzle is crucial to efficient and economical machining.

4. Advantages of waterjet

"If you need a machine and don't buy it, then you will ultimately find you have paid

for it but don't have it" - Henry Ford.

There is a reason that waterjet machining has rapidly grown in popularity since the mid-1990's. Actually there are a number of reasons, listed below, but they mostly come down to "versatility." A waterjet is a versatile and flexible machining tool. You can cut a wide variety of material efficiently and cost-effectively and can create a wide variety of parts.

4.1 Cut virtually any material

Because waterjets cut using water and abrasive, they can work with a wide variety of materials. These materials include:Aluminium, brass, copper, Pre-hardened steel, Mild steel, Exotic materials such as titanium, inconel and hastalloy, 304 stainless steel, brittle materials such as ceramic, quartz, stone, laminated materials, flammable materials

One of the few materials that cannot be cut with a waterjet is tempered glass.

4.2 Fast setup and programming

With waterjet machining, a flat piece of material is placed on a table and a cutting head moves across the material (although in some custom systems, the material moves past a fixed head). This simplicity means that it's fast and easy to change materials and that no tool changes are required. All materials use the same cutting head, so there is no need to program tool changes or physically qualify multiple tools.

The movement of the machining head is controlled by a computer, which greatly simplifies control of the waterjet. In most cases, "programming" a part means using a CAD program to draw the part. When you "push print," the part is made by the waterjet machine. This approach also means that customers can create their own drawings and bring them to a waterjet machine for creation.

4.3 No mechanical stresses

Waterjet machining does not introduce any stresses into the material.

4.5 Almost no heat generated on your part

What little heat is generated by the waterjet is absorbed by the water and carried into the catch tank. The material itself experiences almost no change in temperature during machining. During piercing 2" (5 cm) thick steel, temperatures may get as high as 120° F (50° C), but otherwise machining is done at room temperature.

The result is that there is no heat affected zone (HAZ) on the material. The absence of a HAZ means you can machine without hardening the material, generating poisonous fumes, recasting, or warping. You can also machine parts that have already been heat treated.

4.6 Are very safe

Obviously, you don't put any body parts in front of a waterjet machining head while it is on. Anything that can cut through 2" steel will make short work of flesh and bone. Aside from this, however, waterjets are very safe. A leak in a high-pressure water system tends to result in a rapid drop in pressure to safe levels. Water itself is safe and non-explosive and the garnet abrasive is also inert and non-toxic. One of the largest hazards is cuts from the sharp edges of material created by the waterjet.

4.7 Modern systems are now very easy to learn

Control of the waterjet head is complicated and requires careful calculation to get the proper speed that will give the best result. This means that the system needs to be controlled by a computer, which means that the user-interface for the system can be simplified and made friendlier. Modern systems are designed the same way as many other computerized CAD systems and are quickly learned.

Page 6: How Waterjet Cutting Works

4.8 Environmentally friendly

As long as you are not machining a material that is hazardous, the spent abrasive and waste material become suitable for land fill. The garnet abrasive is inert and can be disposed of with your other trash.If you are machining lots of lead or other hazardous materials, you will still need to dispose of your waste appropriately, and recycle your water. Keep in mind, however, that very little metal is actually removed in the cutting process. This keeps the environmental impact relatively low, even if you do machine the occasional hazardous material.In most areas, excess water is simply drained to the sewer. In some areas, water treatment may be necessary prior to draining to sewer. In a few areas, a "closed loop" system that recycles the water may be required.The pumps do use a considerable amount of electricity, though, so there is some additional environmental (and cost) impact due to this.

4.9 No start hole required

Start holes are only required for materials that are difficult or impossible to pierce. A few poorly bonded laminates can fall into this category, in which case pre-drilling or other special methods may be used.

4.10 Narrow kerf removes only a small amount of material

The amount of material removed by the waterjet stream is typically about 0.02" (0.5 mm) wide, meaning that very little material is removed. When you are working with expensive material (such as titanium) or hazardous material (such as lead), this can be a significant benefit. It also means that you can get more parts from a given sheet of material.When machining or roughing out expensive materials such as titanium, your scrap still has value. This is because you get chunks, not chips.

5. Advantages of waterjets compared with lasers

Laser cutting involves using a laser focused on material to melt, burn, or vaporize the material. The laser can be a gas laser (such as CO2) or a solid-state laser. The laser beam can be static, and the material moves in front of the laser, or the laser can itself be moved across the material. When the laser moves across the material, additional optics are required as the distance from the emitting end of the laser changes. Lasers have the advantage over traditional machining methods that the laser never touches the material (avoiding contamination) and the HAZ is relatively small.

Waterjets have a number of advantages over lasers. In many respects, however, the two tools are complementary and many machine shops own both of them.

1. Waterjets can machine reflective materials that lasers cannot, such as copper and aluminum. Waterjets cut a wide range of material with no changes in setup required. Also, materials which are heat-sensitive can be cut using waterjets.

2. Waterjet cutting does not heat your part. There is no heat-affected zone (HAZ) or thermal distortion, which can occur with lasers. Waterjets do not change the properties of the material.

3. Abrasivejets typically use garnet as the abrasive material. Garnet is a non-reactive mineral that is biologically inert. The only issue with waterjets is when you are cutting a material that is potentially hazardous (such as lead), since small pieces of the material will be abraded and mix in with the spent garnet.

4. There are no noxious fumes, such as vaporized metal, and no risk of fires. The distance between the end of the waterjet nozzle and the material is typically very small, although caution is needed when the waterjet nozzle is raised.

Page 7: How Waterjet Cutting Works

5. The cost of a waterjet machine is generally much lower than that of a laser. For the price of a laser, you can purchase several waterjet machining centers.

6. With lasers, the material needs to be relatively uniform. In particular, when cutting over uneven surfaces, the laser can lose its focus and cutting power. A waterjet will retain much of its cutting power over uneven material. Although the material may deflect the cutting stream, it typically has a negligible effect.

7. How thick you can cut is a function of how long you are willing to wait. Waterjets easily handle 2" (5cm) steel and 3" (7.6 cm). Although some people have used waterjets at thicknesses of up to 10" (25 cm) in steel, it is difficult to maintain precision in materials thicker than 2" (5 cm). Lasers seem to have a maximum practical cutting thickness of 0.5" (12 mm) to 0.75" (19 mm).

8. Maintenance on a waterjet is simpler than that of a laser 9. Waterjets are computer controlled, so that the operator does not have to be highly skilled and

trained. 10. Material cut by waterjets have a fine, sand-blasted surface because of the way the material was

abraded, which makes it easier to make a high-quality weld. Material cut by laser tends to have a rougher, scaly edge, which may require additional machining operations to clean up.

6. A Research and design the nozzle of water jet Crusher [4,5,6,7,8,9,10,11,15]

The nozzle is the core engine of the water jet crusher and can launch a fan-shaped water jet and control the density of water jet (that is, the distance between water molecules). If the needs of smaller particles, the distance between water molecules should be smaller. If the biological needs of larger particles, the distance between water molecules should be bigger, with direct proportion of its function: y = f (x). The fan-shape water jet is fired through nozzles.

In this picture, we can see from d4, d3, d2, d1 the water density is different. We summarised the distance between water molecules expansion multiplier formulation[6,7,8] in accordance with the relevant principles of mathematics.the expansion of multiples ηn where dn,

The expansion formula of the distance between water molecules [6,7,8] rn= r0×ηn

rn denotes the distance between water molecules after expansion, r0 denotes the original distance between water molecules before expansion, r0 = 0.4 [7] nm; ηn for the expansion of multiples. According to last picture and calculation we can know r1 <r2 <r3 <r4,and r controls particle size for r denotes the size of the place where water jet fail to impact of microbe cells, as for the control of the production of biological particles broken the basis of data. Now, living examples of diameters of biologic particles obtained by the machine were illustrated. Structure of the spray nozzle was presented in last picture, Water jet in left and right spray pipes where the interval between the water molecules r0, r0=0.4 nm, was interfused 10%-12% of microbe cells and given strong pressure P which was strong enough to crush microbe cell. The size of obtained biologic particles was calculated as follows: With the practical measuring values: d=1.2mm, d1=2.4mm, d2=4.8mm,d3=9.6mm, d4=19.2mm. The interval between the water molecules at the position d1 may be calculated: r1, By the same way we can know, r2=6.4nm, r3=25.6nm, r4=102.4nm.

When ηn =1, rn =0.4 nm, the size of particle is under nano-grade. When ηn =2.6~ 250, rn =1~ 100 nm, the particles are just nanograde. When ηn﹥ 250, rn﹥ 100 nm, the particles are upper nano-grade.

Page 8: How Waterjet Cutting Works

Ordinary tap water is used to feed the water jet systems. 90% of all water jet and abrasive water jet users require only water softening prior to sending that water through the pump’s inlet water filters and then to the intensifier. Reverse Osmosis (RO) and De-Ionizers (De-I) tend to make the water so pure that it becomes "ion starved." This aggressive water seeks to satisfy its’ ion starvation by taking ions from surrounding materials, such as the metals in the pump and high-pressure plumbing lines. RO and De-I can greatly extend orifice life,while simultaneously performing very expensive damage to the intensifier and plumbing. Orifices are rather inexpensive. High-pressure cylinders, check valves, and end caps damage will far outweigh orifice life improvements. A high concentration of total dissolved solids (TDS) in your shop’s water supply causes accelerated wear of pump components. If maximum values for TDS silica content and pH are exceeded, then water treatment - ranging from water softening to deionization or reverse osmosis - is required. 8. REQUIRED WATER QUALITY

Firs step in the process of making decision of hether water preparation system is needed or not is to analyze a sample of local water on certified laboratory and make a treatment recommendation. Water should be lean top water. Although the water passes though a filtering system before it reaches the pump, the cleaner the water the less frequently you will need to service the filter. If you are using a separate water filtering system, you should make sure you service the filters at the recommended intervals. The water should not be hard or contain large quantities of dissolved iron and silica. These materials cause problems in both the pump and the nozzle. The water circuit consists of the inlet water filters, booster pump, intensifier, and shock attenuator. Ordinary tap water is filtered by the inlet water filtration system – usually comprising of a 1 and a 0.45 micrometer cartridge filter. For these reasons the original 5 micrometer fiber cartridge filter fitted to the first machine has not always been adequate to protect the pump and jet delivery system, even though, in that installation, no erosion of the seals and shafts had occurred after the first six months of operation. In these circumstances, slight changes in water chemistry can significantly affect the erosion resistance of some of the components within the pump mechanism.

Water quality required for an Ingersoll-Rand Water jet Cutting System

7. WATER PREPARATION SYSTEM

All too often, issues such as power requirements and water quality are overlooked. When high pressure water jet cutting machines were first installed in factories it was anticipated that the equipment would be able to operate for a considerable period of time without needing a great deal of maintenance and upkeep. However, as equipment began to be installed in factories in different regions, a particular and unexpected problem arose form the water. The problem is that local water is not all of the same quality. The standards which the water must meet, may make the water acceptable for drinking and normal use, but can sometimes give problems in equipment where the water is subject to pressures above 350 MPa and where it is moving in excess of 700 m/sec. The presence of small amounts of solid material in the jet fluid can cause an accelerated wear of either the nozzle body or other points within the circuit where jet velocities are high. Also, slight changes in water chemistry can significantly affect the erosion resistance of some of the components within the pump mechanism. The problem of water quality has been recognized and addressed by the vendors of the equipment. As a result it has been found necessary to set water quality standards in order to operate high-pressure water jet cutting systems effectively. Many localities do not have water sources that satisfy these requirements. It has been found that if the water supply is inadequate then the result is equipment malfunction. A solution was found through water preparation system.

There are several ways to treat the water prior to use. The simplest is a water softening treatment similar to that used in the household. The second method is reverse osmosis, which consists of passing the water through a very fine membrane which filters out the impurities on the molecular level. And the third is de-ionizing circuit.

Page 9: How Waterjet Cutting Works

9. Water jet can cutting alloy steels with out change the properties. Look at the diagram, minimum heat for transforms ferrite to austenite is around 730 digree. And maximum heat that waterjet creat is around 120 digree. It means waterjet can cutting alloy steels with out change the properties.

9.1 Low alloy steels can cutting with waterjet

Low alloy steels contain alloying elements as Ni, Mn, Cr, Si, Mo, Nb, Cu. The percentage of all alloying elements does not exceed 5%.

9.2 High alloy steels can cutting with waterjet

High alloy steels contain alloying elements as Ni, Mn, Cr, Mo, Nb, W, V, Cu. The total percentage of all alloying elements is higher than 5%.

9.3 Stainless steels can cutting with waterjet

Stainless steels are high alloy steels. Their chromium content is at least 12%. for example if cut stainless steels with laser cutting machines then chromium will be burn.

Page 10: How Waterjet Cutting Works