Chapter 1

1.1Introduction:-

A water jet cutter, also known as a water jet or water jet, is an industrial tool capable

of cutting a wide variety of materials using a very high-pressure jet of water, or a

mixture of water and an abrasive substance. The term abrasive jet refers specifically

to the use of a mixture of water and abrasive to cut hard materials such as metal

or granite, while the terms pure water jet and water-only cutting refer to water jet

cutting without the use of added abrasives, often used for softer materials such as

wood or rubber.

Water jet cutting is often used during fabrication of machine parts. It is the preferred

method when the materials being cut are sensitive to the high temperatures generated

by other methods. Water jet cutting is used in various industries,

including mining and aerospace, for cutting, shaping, and reaming.

Fig1.1:- Water jet cutter

1

Cutting steel, concrete, glass and marble with water - sounds a bit far-fetched doesn’t

it? Way back in the 1950s, a forestry engineer by the name of Norman Franz started

fiddling around with a high-pressure water stream to cut lumber. His aim was to

streamline the process and reduce the strain on traditional cutting equipment such as

saw blades, which easily became blunt and needed replacing. From these humble

beginnings an idea was born, and over the next couple of decades, water cutting

became an unparalleled method for cutting materials of all types, shapes and sizes.

FIG1.2:- nozzle

The end product? A water jet cutter – a machine capable of slicing metal and other

materials such as granite and marble with unbelievable accuracy. It does this by using

a jet of water at high velocity and pressure, sometimes mixed with an abrasive

substance, depending on the material that is being cut. Water jet cutters are usually

used to cut materials such as rubber, foam, plastics, leather, composites, stone, tiles,

2

metals, food and paper. However, they can’t cut tempered glass, diamonds and certain

ceramics

Fig1.3:- water jet cutter operation.

3

CHAPTER 2

2.2 HISTORY:-

While using high-pressure water for erosion dates back as far as the mid-

1800s with hydraulic mining, it was not until the 1930s that narrow jets of water

started to appear as an industrial cutting device. In 1933, the Paper Patents Company

in Wisconsin developed a paper metering, cutting, and reeling machine that used a

diagonally moving water jet nozzle to cut a horizontally moving sheet of continuous

paper.[2] These early applications were at a low pressure and restricted to soft

materials like paper.

Water jet technology evolved in the post-war era as researchers around the world

searched for new methods of efficient cutting systems. In 1956, Carl Johnson of

Durox International in Luxembourg developed a method for cutting plastic shapes

using a thin stream high-pressure water jet, but those materials, like paper, were soft

materials.[3] In 1958, Billie Schwacha of North American Aviation developed a

system using ultra-high-pressure liquid to cut hard materials.[4] This system used a

100,000 psi (690 MPa) pump to deliver a hypersonic liquid jet that could cut high

strength alloys such as PH15-7-MO stainless steel. Used as a honeycomb laminate on

the Mach 3 North American XB-70 Valkyrie, this cutting method resulted in

delaminating at high speed, requiring changes to the manufacturing process.[5]

While not effective for the XB-70 project, the concept was valid and further research

continued to evolve water jet cutting. In 1962, Philip Rice of Union Carbide explored

using a pulsing water jet at up to 50,000 psi (345 MPa) to cut metals, stone, and other

materials.[6] Research by S.J. Leach and G.L. Walker in the mid-1960s expanded on

traditional coal water jet cutting to determine ideal nozzle shape for high-pressure

water jet cutting of stone,[7] and Norman Franz in the late 1960s focused on water jet

cutting of soft materials by dissolving long chain polymers in the water to improve the

cohesiveness of the jet stream.[8] 

4

In the early 1970s, the desire to improve the durability of the water jet nozzle led Ray

Chadwick, Michael Kurko, and Joseph Corriveau of the Bendix Corporation to come

up with the idea of using corundum crystal to form a water jet orifice,[9] while Norman

Franz expanded on this and created a water jet nozzle with an orifice as small as

0.002 inches (0.05 mm) that operated at pressures up to 70,000 psi (483 MPa).[10] John

Olsen, along with George Hurlburt and Louis Kapcsandy at Flow Research (later

Flow Industries), further improved the commercial potential of the water jet by

showing that treating the water beforehand could increase the operational life of the

nozzle.[11]

Fig 2.1 old model of water jet system

2.2.1 1800:-

Hydraulic mining had its precursor in the practice of ground sluicing, a

development of which is also known as "hushing", in which surface streams of water

were diverted so as to erode gold-bearing gravels. This was originally used in the

Roman empire in the first centuries AD and BC, and expanded throughout the empire

wherever alluvial deposits occurred[2] The Romans used ground sluicing to remove

overburden and the gold-bearing debris in Las Medullas of Spain,

5

and Dolaucothi in Britain. The method was also used in Elizabethan

England & Wales (or rarel for developing lead, tin and copper mines.1

Water was used on a large scale by Roman engineers in the first centuries BC and AD

when the Roman empire was expanding rapidly in Europe. Using a process later

known as hushing, the Romans stored a large volume of water in a reservoir

immediately above the area to be mined; the water was then quickly released. The

resulting wave of water removed overburden and exposed bedrock. Gold veins in the

bedrock were then worked using a number of techniques, and water power was used

again to remove debris. The remains at Las Medullas and in surrounding areas

show badland scenery on a gigantic scale owing to hydraulic king of the rich alluvial

gold deposits. Las Medullas is now a UNESCO World Heritage site. The site shows

the remains of at least seven large aqueducts of up to 30 miles in length feeding large

supplies of water into the site. The gold-mining operations were described in vivid

terms by Pliny the Elder in his Naturalist Historia published in the first century AD.

Pliny was a procurator in Hispania Terraconensis in the 70's and must have witnessed

for himself the operations. The use of hushing has been confirmed by field survey

and archaeology at Dolaucothi in South Wales, the only known Roman gold mine

in Britain.

The modern form of hydraulic mining, using jets of water directed under very high

pressure through hoses and nozzles at gold-bearing upland paleo gravels, was first

used by Edward Matteson near Nevada City, California in 1853 during the California

Gold Rush.[3] Matteson used canvas hose which was later replaced with crinoline hose

by the 1860s.[4] In California, hydraulic mining often brought water from higher

locations for long distances to holding ponds several hundred feet above the area to be

mined. California hydraulic mining exploited gravel deposits, making it a form

of placer mining.

Early placer miners in California discovered that the more gravel they could process,

the more gold they were likely to find. Instead of working with pans, sluice boxes,

long toms, and rockers, miners collaborated to find ways to process larger quantities

of gravel more rapidly. Hydraulic mining became the largest-scale, and most

devastating, form of placer mining. Water was redirected into an ever-narrowing

channel, through a large canvas hose, and out through a giant iron nozzle, called a

6

"monitor." The extremely high pressure stream was used to wash entire hillsides

through enormous sluices.

By the early 1860s, while hydraulic mining was at its height, small-scale placer

mining had largely exhausted the rich surface placers, and the mining industry turned

to hard rock (called quartz mining in California) or hydraulic mining, which required

larger organizations and much more capital. By the mid-1880s, it is estimated that 11

million ounces of gold (worth approximately US$7.5 billion at mid-2006 prices) had

been recovered by hydraulic mining in the California Gold Rush.

2.2.2 1850:-

High-pressure vessels and pumps became affordable and reliable with the advent of

steam power. By the mid-1850s, steam locomotives were common and the first

efficient steam-driven fire engine was operational.[12] By the turn of the century, high-

pressure reliability improved, with locomotive research leading to a six fold increase

in boiler pressure, some reaching 1600 psi (11 MPa). Most high-pressure pumps at

this time, though, operated around 500–800 psi (3–6 MPa).

7

High-pressure systems were further shaped by the aviation, automotive, and oil

industries. Aircraft manufacturers such as Boeing developed seals for hydraulically

boosted control systems in the 1940s,[13] while automotive designers followed similar

research for hydraulic suspension systems.[14] Higher pressures in hydraulic systems in

the oil industry also led to the development of advanced seals and packing to prevent

leaks.[15]

These advances in seal technology, plus the rise of plastics in the post-war years, led

to the development of the first reliable high-pressure pump. The invention

of Marlex by Robert Banks and John Paul Hogan of the Phillips Petroleum company

required a catalyst to be injected into the polyethylene.[16] McCartney Manufacturing

Company in Baxter Springs, Kansas, began manufacturing these high-pressure pumps

in 1960 for the polyethylene industry.[17] Flow Industries in Kent, Washington set the

groundwork for commercial viability of water jets with John Olsen’s development of

the high-pressure fluid intensifier in 1973,[18] a design that was further refined in 1976.[19] Flow Industries then combined the high-pressure pump research with their water

jet nozzle research and brought water jet cutting into the manufacturing world.

8

2.2.3 1935:-

While cutting with water is possible for soft materials, the addition of an abrasive

turned the water jet into a modern machining tool for all materials. This began in 1935

when the idea of adding an abrasive to the water stream was developed by Elmo

Smith for the liquid abrasive blasting.[20] Smith’s design was further refined by Leslie

Terrell of the Hydro blast Corporation in 1937, resulting in a nozzle design that

created a mix of high-pressure water and abrasive for the purpose of wet blasting.[21] Producing a commercially viable abrasive water jet nozzle for precision cutting

came next by Dr. Mohamed Hashish who invented and led an engineering research

team at Flow Industries to develop the modern abrasive water jet cutting technology.[22] Dr. Hashish, who also coined the new term "Abrasive Water jet" AWJ, and his

team continued to develop and improve the AWJ technology and its hardware for

many applications which is now in over 50 industries worldwide. A most critical

development was creating a durable mixing tube that could withstand the power of the

high-pressure AWJ, and it was Boride Products (now Kennametal) development of

their ROCTEC line of ceramic tungsten carbide composite tubes that significantly

increased the operational life of the AWJ nozzle.[23] Current work on AWJ nozzles is

on micro abrasive water jet so cutting with jets smaller than 0.015 inch in diameter

can be commercialized

9

2.2.4 1990:-

As water jet cutting moved into traditional manufacturing shops, controlling the cutter

reliably and accurately was essential. Early water jet cutting systems adapted

traditional systems such as mechanical pantographs and CNC systems based on John

Parsons’ 1952 NC milling machine and running G-code.[24] Challenges inherent to

water jet technology revealed the inadequacies of traditional G-Code, as accuracy

depends on varying the speed of the nozzle as it approaches corners and details.[25] Creating motion control systems to incorporate those variables became a major

innovation for leading water jet manufacturers in the early 1990s, with Dr John Olsen

of OMAX Corporation developing systems to precisely position the water jet

nozzle[26] while accurately specifying the speed at every point along the path,[27] and

also utilizing common PCs as a controller. The largest water jet manufacturer, Flow

International (a spinoff of Flow Industries), recognized the benefits of that system and

licensed the OMAX software, with the result that the vast majority of water jet cutting

machines worldwide are simple to use, fast, and accurate.[28]

10

CHAPTER 3

3.1 Working:-

At its most basic, water flows from a pump, through plumbing and out a cutting head.

It is simple to explain, operate and maintain. The process, however, incorporates

extremely complex materials technology and design.

To generate and control water at pressures of 87,000 psi requires science and

technology not taught in universities. At these pressures a slight leak can cause

permanent erosion damage to components if not properly designed.

Thankfully, the water jet manufacturers take care of the complex materials technology

and cutting-edge engineering. The user need only be knowledgeable in the basic water

jet operation.

Flow machines are designed to operate as both pure and abrasive water jets.  A pure

water jet is used to cut soft materials, and within just 2 minutes the very same water

jet can be transformed into an abrasive water jet to cut hard materials. With any type,

the water must first be pressurized.

Fig 3.1 horizontal water jet cutter

11

3.1.1 High pressure water jet cutting:-

Water is pressurized to very high pressures, in excess of 50,000 psi.  This

pressurization is accomplished with the use of pumps of various designs, discussed

next in this chapter.

The high pressure water is transported through a series of stainless steel tubes to a

cutting head.  Depending upon the material being cut, the cutting head can be either a

"pure water cutting head" or an "abrasive cutting head."

In the cutting head, the high pressure water is forced through a small diameter orifice. 

The diameter of this orifice is anywhere from 0.004" to 0.020". This step converts the

pressure of the water jet stream into speed. We go from potential energy to kinetic

energy.  Coming out of the orifice, the water jet stream is moving at 2200 mph or

faster. Higher pressure results in higher speed. Smaller diameter orifices yield a faster

water jet stream, but also a stream with less kinetic energy since there is not as much

water available to accelerate abrasive grains to full speed.

In a pure water cutting head, the water immediately exits the cutting head after

passing through the orifice. The speed and power of the water jet stream is enough to

cut soft or thin materials like foam, rubber, soft wood, plastics, carpet, food, car

headliners, circuit boards and more.

In an abrasive cutting head, a very hard abrasive, typically garnet, is fed into the water

jet stream.  The abrasive particles are accelerated to near the speed of the water jet

stream. This gives the abrasive particles much power. The abrasive water jet stream

now travels down through an abrasive nozzle, or mixing tube, approximately 3 inches

long with an inner diameter of between .030" and 0.050". The mixture of water and

abrasive exits the abrasive nozzle and will cut hard materials like metals, stone,

acrylic, ceramic, composites, phenolic and porcelain.

A CNC control will move the cutting head in up to 6 axes of motion to cut the

targeted work piece.

12

3.2 Types of pumps:-

3.2.1 Intensifier

Intensifier pumps are called intensifiers because they use the concept of pressure

intensification or amplification to generate the desired water pressure.

If you apply pressure to one side of a cylinder and the other side of the cylinder is the

same surface area, the pressure on the other side will be the same. If the surface area

of the smaller side is half, then the pressure on that side will be doubled. Generally

with intensifier pumps there is a 20 times difference between the large surface area

(where the oil pressure is applied) and the small surface area (where the water

pressure is generated). The following picture shows this concep

Ultimately, there must be a restriction in the flow of water in order for the pressure to

be generated.  This restriction is generated by the orifice in the cutting head. Pressure

is maintained until the orifice diameter exceeds the limits for water output of the

pump.

For very small diameter orifices, in order to maintain pressure, the pump only needs

to cycle very slowly to maintain pressure. As the orifice gets larger, the pump must

work faster to maintain pressure and water flow. If the orifice gets too large, the pump

tries to cycle too fast for the design specification. An "over stroke" situation is sensed

by the control and the pump is stopped with an error message.

If there are leaks in the water circuit between the pump and the cutting head, this can

also result in a pump "over stroke" situation. The leaks effectively rob water available

to go to the cutting head. The same as putting in too large of an orifice, the pump runs

faster to maintain pressure until it reaches its limit.

Typically, intensifiers stroke at around 50 - 60 strokes per minute when working at

full capacity

13

fig 3.2 Intensifier pump

3.2.2 Direct Drive

A direct drive pump works like a car’s engine. A motor turns a crankshaft attached to

3 or more offset pistons. As the crankshaft turns, the pistons reciprocate in their

respective cylinders, creating pressure in the water. Pressure and flow rate are

determined by how fast the motor turns the crankshaft. Direct drive pumps cycle

much faster than intensifiers, on the order of 1750 revolutions per minute. Direct

drive pumps generally are found in lower pressure applications (i.e. 55,000 pounds

per square inch and under). Maintenance on the direct drive pump tends to take longer

than an intensifier pump. Direct drive pumps can only run more than one cutting head

only if all cutting heads are cutting the same part at the same time. With an intensifier

pump, you could have cutting heads on multiple machines, cutting different parts,

cycling the various cutting heads on and off in any sequence. The intensifier pump

will need to only vary its stroke rate accordingly to maintain flow and pressure.

14

Fig 3.3 direct drive pump

3.3 Principles of water jet cutting

There are two types of water jet cutting processes; pure water cutting, in which the

cutting is performed using only an ultra-high pressure jet of clean water, and abrasive

15

water jet cutting in which an abrasive (typically garnet) is introduced into the high

pressure stream.

Pure water cutting can be employed to profile a huge variety of materials, these will

typically be 'soft' materials such as gaskets, rubber, foam & plastics. Filtered tap water

is fed into an intensifier pump where it is pressurised to (typically) 60,000psi. This

ultra-high pressure water is forced through a tiny (0.15mm) orifice jewel which is

normally manufactured from sapphire. This has the effect of focusing the beam of

water into a fine, accurate stream travelling at speeds of up to 900m/sec, capable of

accurate cutting of a wide range of soft materials.

In order to cut 'harder' materials or any material containing glass or metal, then

abrasive water jet cutting would be employed. The principles of abrasive water jet

cutting are similar to pure water jet cutting, but once the stream has passed through

the orifice it enters a carbide nozzle. Within this nozzle is a mixing chamber within

which a partial vacuum is created as the water passes through. Garnet is introduced

under gravity into the nozzle and the partial vacuum within the mixing chamber has

the effect of dragging the abrasive into the water stream to create a highly abrasive

cutting jet. Abrasive cutting would typically be used on materials such as stainless

steel, aluminium, stone, ceramics & composite materials.

Fig 3.4 mouth piece of jet

In both processes the head is controlled by a CNC controller, this offering great

accuracy and repeatability. The CNC controller is programmed by first drawing the

part to be manufactured using proprietary software, and then converting this drawing

into a G code format – CNC language.

16

Fig 3.5 vertical water jet

Water jet cutting is a cold grinding or cutting process. It combines the advantages of

laser – precision – with those of water: water jet cutting is thermoneutral. In addition

to laser cutting, water jet cutting is becoming increasingly important in Switzerland

and Germany. No thermal stresses occur with water jet cutting. The microstructure of

the material and the material strength remain. There are no cures, distortions, dripping

slag, melting or toxic gases.

In all processes, the cutting heads with the focusing nozzles are integrated in a

guiding machine (robot, 2D or 3D portal). The controlled CNC axes enable 2D, 2.5D

or 3D cutting processes. These processes can cut almost all materials – hard like steel

and glass, but also fragile and extremely soft materials – without stress forces. Water

jet cutting has three principles: the pure water jet principle “WJ”, the abrasive water

jet principle “AW” and the suspension jet principle, which is still at development

stage.

3.3.1 Water jet cutting with pure water:-

17

With pure water jet cutting “WJ”, a pure water jet with a diameter of 0.1 mm cuts the

material at up to three times the speed of sound (at speeds of up to 200 m/min). These

materials include textiles, elastomers, fibers, thin plastics, food, paper, cardboard,

leather, thermoplastic materials or food. The water is pressurized to 1,000–6,000 bar

(standard approximately 3,800 bar). After flowing through a high-pressure needle

valve, the water enters a 200 mm long and 3 mm in diameter wide collimation tube

(calming section). It is then pressurized by a water nozzle or a dynamic pressure

nozzle and accelerated. The jet speed varies according to geometry and pressure. The

small diameter of the water nozzle produces a very high local energy density, which

remains constant on a relatively long section in the direction of the water jet and cuts

cleanly and accurately when hitting the material.

Fig3.6 half section view of water jet

18

3.3.2 Water jet cutting with abrasives:-

With abrasive water jet cutting, compact and hard materials such as metals (including

steel), hard stone, glass (including bullet-proof glass) and ceramic are separated.

Before the concentrated jet of water hits the material, a cutting material of the finest

grain size (abrasive) is added in the required dose in a mixing chamber, which ensures

micro cutting. The water serves as an accelerator for the abrasive particles and hits the

material with an impact speed of 800 m/s, thereby removing it with precision. Until

the water jet is produced, abrasive water jet cutting is identical to pure water jet

cutting. The difference is that the pure water jet is no longer used just for cutting, but

as a carrier material for the abrasive particles. The pure water jet flows into a mixing

chamber, into which the abrasive particles are then introduced. At the end of the

mixing chamber is the focusing tube, in which the abrasive grains in the water jet are

accelerated and confined to a specific cross-section.

19

3.3.3 Water jet cutting with suspension jet

With the suspension jet principle or water abrasive suspension jet cutting, a pre-

prepared mixture of abrasive particles and water is discharged under high pressure

from a cutting nozzle. However, the abrasive agent is not added at the nozzle but is

pressurized under the exclusion of air. Therefore, a water-abrasive mixture (a

suspension) is expelled from the cutting nozzle under high pressure. This enables

higher cutting performance, allows greater thicknesses and almost all materials to be

cut. However, there is a delay in the start and stop of the cutting operation, since the

abrasive feed cannot be switched on and off as rapidly as in injection cutting. This is

one disadvantage when high-precision cutting is required. The wear on the valves and

nozzles is also much larger and attainable pressures are smaller. Therefore, this

principle is only seldom used on an industrial scale.

Fig 3.7 suspension jet

20

3.4 PARTS OF WATER JET CUTTER:-

3.4.1. Electric motor and hydraulic pump

The electric motor and hydraulic pump (number 1 in picture above) create the oil

pressure needed for the oil side of the intensifier. This assembly is normally in the

lower portion of the pump cabinet. The electric motor and pump are rated in HP (or

kW for metric). Typical pump sizes are 30 HP, 50 HP, 75 HP, 100 HP and 150 HP As

discussed in the previous chapter, each pump will have an associated water output

volume (gallons per minute) and pressure (psi). 

Again it is important to remember that HP is not necessarily an indication of pressure.

A 150 HP pump doesn’t necessarily create more pressure than a 50 HP pump.

Horsepower is more directly related to water output, since more HP will be needed to

create enough power to move the piston/plunger assembly in the intensifier at the

required stroke rate.

Fig3.8 Intensifier pump cabinet (150 HP)

21

3.4.2. Directional control valves

One of the most important considerations in any fluid power system is control. If

control components are not properly selected, the entire system does not function as

required. In fluid power, controlling elements are called valves. There are three types

of valves: 1. Directional control valves (DCVs): They determine the path through

which a fluid transverses a given circuit. Pressure control valves: They protect the

system against overpressure, which may occur due to a sudden surge as valves open

or close or due to an increase in fluid demand. 2. Flow control valves: Shock

absorbers are hydraulic devices designed to smooth out pressure surges and to

dampen hydraulic shock. In addition, the fluid flow rate must be controlled in various

lines of a hydraulic circuit. For example, the control of actuator speeds can be

accomplished through use of flow control valves. Non-compensated flow control

valves are used where precise speed control is not required because the flow rate

varies with pressure drop across a flow control valve. It is important to know the

primary function and operation of various types of control components not only for

good functioning of a system, but also for discovering innovative methods to improve

the fluid power system for a given application. 1.2Directional Control Valves A valve

is a device that receives an external signal (mechanical, fluid pilot signal, electrical or

electronics) to release, stop or redirect the fluid that flows through it. The function of

a DCV is to control the direction of fluid flow in any hydraulic system. A DCV does

this by changing the position of internal movable parts. To be more specific, a DCV is

mainly required for the following purposes: To start, stop, accelerate, decelerate and

change the direction of motion of a hydraulic actuator. To permit the free flow from

the pump to the reservoir at low pressure when the pump’s delivery is not needed into

the system. To vent the relief valve by either electrical or mechanical control. To

isolate certain branch of a circuit. 2 Any valve contains ports that are external

openings through which a fluid can enter and exit via connecting pipelines. The

number of ports on a DCV is identified using the term “way.” Thus, a valve with four

ports is a four-way valve A DCV consists of a valve body or valve housing and a

valve mechanism usually mounted on a sub-plate. The ports of a sub-plate are

threaded to hold the tube fittings which connect the valve to the fluid conductor lines.

The valve mechanism directs the fluid to selected output ports or stops the fluid from

22

passing through the valve. DCVs can be classified based on fluid path, design

characteristics, control methods and construction

Fig 3.9 Directional Control Valve

3.4.3. Intensifier

The intensifier proper (3 in Figures 4 and 2) consists of the hydraulic cylinder (4),

high pressure cylinders (7), and check valves (8) and end caps (9). Not visible from

the outside are the piston and plunger.

Fig 3.10 Intensifier

23

3.4.4. Hydraulic cylinder

The hydraulic cylinder (4 in Figures 2 and 5) houses the piston and is the area where

the hydraulic oil does its work. The directional control valves control the flow of oil

into and out of each side of the hydraulic cylinder.

At each end of the hydraulic cylinder is an end plate that is used to connect the

hydraulic cylinder to the high pressure cylinder. The two end plates for the hydraulic

cylinder are connected and pulled tightly in place with 4 tie rods and bolts.

Fig 3.11 Hydraulic cylinder

3.4.5. Piston

The piston (number 5 in Figures 2 and 6) is the larger diameter cylindrical part

located within the hydraulic cylinder (4 in Figures 2 and 5). The piston effectively

splits the hydraulic cylinder into a left side and a right side. Oil cannot pass from one

side to the other past the piston. It must exit and enter the hydraulic cylinder through

the hoses attached to the directional control valve. The hydraulic oil pressure is

exerted onto either side of the piston in an alternating fashion so that a back-and-forth

movement of the piston and plunger assembly is generated.

24

Fig 3.12 Piston (5) and plunger (6) assembly

3.4.6. Plunger

The plungers (6 in Figure 7) are the two smaller diameter shafts that are connected to

each side of the piston. The attachment point is inside of the hydraulic cylinder. The

other ends of the plungers extend into the left and right high pressure cylinders. Seals

are placed around the plunger shaft to keep oil from seeping into the water side of the

pump, and vice versa. The plungers are made out of either stainless steel, or, more

recently, ceramic.  Ceramic is used because of its ability to handle heat and high

pressure with little thermal expansion.

Fig 3.13 Ceramic plunger

25

3.4.7.   High pressure cylinder

The two high pressure cylinders (7 in Figures 8 and 2) are where the water is

pressurized. They are usually referred to as "left hand side" and "right hand side." The

high pressure cylinders are machined out of very thick stainless steel and treated in

order to withstand the extreme pressures they are put under on a continual, cyclical

basis.

Fig 3.14 High pressure cylinder (7)

3.4.8. Check valve

There is one check valve (number 8 in Figures 10 and 8) at the end of each high

pressure cylinder at the end opposite from the hydraulic cylinder. The check valve

allows fresh water to enter the high pressure cylinder and high pressure water to exit

the intensifier. The check valve is designed to only let water flow in one direction.

Fresh water comes in though channels machined in the sides and exits through one or

more holes in the face of the valve. Various seals, poppets and springs are used to

maintain this water flow. Over several hundred hours these components will wear,

allowing pressurized water to flow out the water inlet path, or allowing pressurized

water to seep back into the high pressure cylinder. The symptoms and diagnosis of

these various situations will be discussed later in the "Maintenance" chapter.

26

Fig 3.15 View of upper portion of intensifier cabinet

Fig 3.16 Check Valve Body cross-section

27

3.4.9. End Cap

The end cap (number 9 in Figures 11 and 2) is either a cylindrical or square item. The

cylindrical version screws onto the output end of the high pressure cylinder. The

square type is held in place with tie rods and bolts.  The end cap has a hole in the

center for the check valve and outlet body. It will also have a connection point for the

incoming fresh water. The water flows through holes machined through the cap to line

up with inlet holes in the check valve

Fig 3.17 fillets caps

28

3.4.10. High pressure tubing

High pressure 304 or 316 stainless steel tubing (number 10 in Figure 11) is attached to

the outlet of each check valve. Common outer diameters are 0.25", 0.313", 0.375" and

0.563". Inner diameters range from 0.062" to 0.312". There is usually a flexible

protective covering around the tube.

The high pressure tubing from the left hand high pressure cylinder will join together

at some point with the high pressure tubing from the right hand cylinder. The high

pressure tubing carries the pressurized water to the pressure attenuator. Additional

high pressure tubing will channel the high pressure water to the cutting head.

The length, number of bends and other obstructions to flow (e.g. hand valves) in the

high pressure tubing path must be taken into consideration when designing a high

pressure water jet system. Pressure will drop with each bend in the tubing. Also, as

the distance between the pump and the cutting head increases, internal friction of the

water as it drags against the inner walls will generate heat resulting in a loss of  water

pressure. This topic will be discussed in more detail in the Chapter 5 "Pressure Drop

in Tubing."

3.4.11. Pressure attenuator

The pressure attenuator (number 11 in Figures 13 and 2) smoothest out variations in

pressure after the high pressure water has exited the intensifier. With each reversal of

cycle of the intensifier, there is a slight delay in the increase of water pressure in the

opposite high pressure cylinder. This delay is due to: 1) reversal of motion where

instantaneous velocity at the end of the stroke equals zero, and 2) mechanical delays

of reversal. All of these factors can result in a drop in water pressure. Some

manufacturers do use proprietary technology to reduce this pressure drop, which we

suggest you investigate when selecting a pump. Generally, if a 50 HP pump can

sustain a 0.014" orifice at 60,000 psi continuous operating pressure, the implication is

that this hydraulic pressure drop challenge will have been addressed.

Figure 14 shows the pressure fluctuations in the high pressure water line prior to the

pressure accumulator. This shows a pressure change from high to low of almost

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22,000 psi. So, for a 60,000 psi system, the high pressure water would be going from

60,000 psi to 40,000 psi after every stroke of the intensifier.

If this pressure fluctuation were not smoothed out by the pressure attenuator, cutting

results at the work piece would be undesirable. There would be a significant line in

the part with every stroke of the intensifier. Recall that any change in pressure results

in a change in speed of the water jet stream at the cutting head. This change in speed

changes the speed at which the abrasive particles are moving and, therefore, the

amount of force they will impact on the work piece. Lower pressure leads to less

speed of the water which leads to less force of the abrasive which leads to slower

cutting, or rougher edge quality.

Fortunately the pressure attenuator smoothest out these pressure spikes so that the

water at the cutting head maintains a steady pressure, speed and cutting power

Fig3.18 Pressure Attenuator

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Fig3.19 Pressure fluctuation prior to accumulator

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3.4.12. Inlet water

Prior to entering the pump cabinet, water may have to be treated to get the water

within the water jet manufacturer’s specifications. Within the pump cabinet, usually

in the lower portion, the water will typically go through one or more final filters just

prior to entering the intensifier (number 12 in Figures 15 and 2).

The inlet water must be able to maintain a specified flow rate and pressure to ensure

that the intensifier receives enough water. Incoming water must also meet certain

requirements with respect to Total Dissolved Solids (TDS), pH, organic matter,

temperature, etc. Poor water quality will result in drastically reduced high pressure

component life (i.e. anything the high pressure water comes in contact with).

Different pump manufacturers require different inlet water pressures, with some

needing as little as 30 psi, and others mandating a water pressure booster pump to

maintain 100 psi. Water quality will be discussed in more detail in the chapter 4

"Water QUILITY

Fig 3.20 water inlet system

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3.5 Controls and PLC

The controls and PLC (not pictured) control the valves in the hydraulic circuit to

determine the pressure and flow of the hydraulic oil to and from the intensifier.

Various sensor and proximity switches can also be integrated into the controls to

monitor the entire pump to verify things like stroke rate, oil temperature and pressure,

inlet water pressure and flow rate and more. This capability makes working with and

troubleshooting the modern day intensifier much easier.

3.5.1 On-Off Valve

The pneumatic On-Off valve controls the flow of water to the cutting head. The On-

Off valve at the cutting is "normally closed." That is, when there is no compressed air

supplied to the On-Off valve, a needle fits tightly against a seat to stop any high

pressure water from getting to the cutting head. When compressed air is supplied to

the On-Off valve (i.e. "tool on" command from the control), the needle is forced up

from its seating location and the high pressure water can flow through the orifice to

the cutting head.

In, or near, the high pressure pump cabinet is another On-Off valve that works in

tandem with the On-Off valve at the cutting head. The On-Off valve in the pump is

typically called the Safety Relief valve. This Safety Relief valve in the pump is

"normally open." This valve will stay open when there is no air supplied to it. When

the On-Off valve at the cutting head closes ("tool off" command by control or no

power to the system), the Safety Relief valve in the pump will open, relieving all

water pressure from the high pressure tubing. When the "tool on" command is issued

by the control, the Safety Relief valve closes so that all high pressure water will go to

the cutting head. Note, not all manufacturers of new pumps have the Safety Relief

valve as standard. We strongly suggest you ask your pump manufacturer if they

supply this standard, and when it is activated. Again, some pump manufacturers will

only activate the Safety Valve when an E-Stop is pressed; when the pump stops, high

pressure lines are still pressurized.

Both of these On-Off valves must be in good working order to protect against

accidental high pressure water discharge at the cutting head that could severely injure

someone working on or near the cutting head or any of the high pressure lines.

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Periodic replacement of the needle, seat and associated parts is required to maintain

these valves.

Fig 3.21 on/off valve

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3.6 Abrasive feeding system

3.6.1 Pressurized Bulk hopper:-

Abrasive is transported via tubing and pressure from a large bulk hopper located near

the water jet cutting system to a mini-hopper near the cutting head. Bulk hoppers will

normally hold anywhere from several hundred pounds of abrasive to 2200 pounds.  If

you are cutting with one head and 1.4 pounds per minute of abrasive, then you are

consuming about 84 pounds per hour. An 1100 pound hopper would last about 13

hours of operation. This would mean that the machine could run for well over a shift

before it needed to be refilled. Most water jets are provided with approximately 600

pound hoppers, which would equate to about 7 hours of operation. So, at least once

during an 8 hour shift the hopper would need to be reloaded. The costs associated

with the additional downtime over the course of a year should be evaluated.

Fig 3.22 bulk hopper

3.6.2 Mini-hopper

A mini-hopper is typically mounted near and above the cutting head. Most of these

mini-hoppers allow for a gravity feed of abrasive down to the cutting head. Many

mini-hoppers control the amount of abrasive that can go down to the cutting head with

the use of a slide with different size holes in it. The operator can change the position

of the slide to change the amount of abrasive to the cutting head.

A recent advance in technology is remote CNC-control of the amount of abrasive

released from the mini-hopper. Having this capability allows for optimum feeding of

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abrasive to the cutting head in relation to the water pressure at the pump for the

following desirable capabilities:

Piercing of fragile materials like glass or stone. Typically a lower

water pressure will be used with a smaller amount of abrasive

Changing abrasive amount for different abrasive nozzle sizes to

optimize part cost. This can be done automatically if the mini

hopper is set up to do this.

Fig 3.23 abrasive material feeding

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CHAPTER 4

4.1 WATER QUALITY:-

4.1.1 Overview

This chapter will discuss water quality requirements for high pressure water jet

cutting and why it is crucial to maintain proper water quality.

Note: See "Recommendation for water treatment" at the end of this chapter for a

potential solution to everything you are about to read in this chapter about water

treatment.

4.1.2 Water specifications

Every manufacturer has specific requirements for water quality. Check with the

manufacturer to get the specifications for your particular machine.

The water supplied to the intensifier is critical to water jet cutting due to its direct

influence on the service life of the equipment components such as check valves, seals

and orifices. A high concentration of Total Dissolved Solids (TDS) causes accelerated

wear of any components that come in contact with the high pressure water because of

the increased abrasiveness of the water from the TDS.

As part of the installation planning, a water quality analysis should be performed by a

commercial company that specializes in water conditioning equipment. The minimum

information that should be supplied by this analysis is TDS, silica content and pH

value. Companies like Culligan can perform these tests, or you can search "water

quality testing" on the internet.

Inlet water should be treated for either the removal of hardness of the reduction of

TDS. Water softening is an ion exchange process that removes scale forming minerals

such as calcium. TDS reduction can be accomplished with either deionization (DI) or

reverse osmosis equipment. Generally, DI or RO provides better component life than

water softening.

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A water purification supplier should be consulted to supply the most suitable

equipment for special conditions. It might be a good idea to ask any company that you

are considering using if they have supplied systems for any other high pressure water

jet cutting systems and check their references.

The best treatment process for a specific application is a function of the original water

quality and the desired service life of the affected components. Sixty to 70 ppm of

TDS is optimum. Any water treatment producing TDS content of less than 0.5 part

per million (ppm) should be avoided since the aggressiveness of such purified water

will damage pump components.

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4.2 Water treatment guidelines

Criteria Values Recommended

Treatment

Total Dissolved

Solids (TDS)

Low TDS (<100

ppm)

Moderate TDS (100

- 200 ppm)

High TDS (>200

ppm)

Good water, requires only

softening

Can be treated by

softening, DI or RO

Poor water, should be

treated with RO or DI

Silica Content High content (>15

ppm)

Dual Bed Strong Base DI

pH Value Treated water must

have a value of 6 - 8

 

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4.3 Suspended solids

In addition to the treatment described above, the water must be filtered for the

removal of suspended solids. Different manufacturers supply differently sized final

filters for this purpose, typically down to 0.45 nominal. See "Recommendation for

water treatment" at the end of this chapter for an alternative to this.

Water supply

The initial water supply should be at least 5 gallons per minute at 40 pounds per

square inch. The water may be boosted by a small pump to the 80 psi required by

most intensifiers. Some intensifiers do not require pressure boosters, requiring only 30

psi for the incoming water. This removes a potential failure point from the system.

Hydraulic Oil Cooling

Intensifier pumps have hydraulic oil that must be cooled. Typically there are three

options:

1. Water-Cooled through a heat exchanger

2. Air-Over-Oil Cooler

3. Closed-Loop Chiller

4.

4.3.1 Heat exchanger - For water cooled pumps

1. A heat exchanger is primarily used for cooling the hydraulic fluid of the

intensifier pump. Typically the hydraulic oil temperature must be kept below

120° F (49° C). The heat exchanger will require a consistent water flow of 0 to

8 gpm (0 to 30 liters per minute) at an inlet temperature not exceeding 70° F in

order to keep the hydraulic fluid at the proper temperature. Actual volume of

water will depend on the pump selected. As many pumps are thermostatically

controlled, when the pump is cool, it may be that no water is required.

2. This cooling water must go to drain. The cost of this water must be balanced

against the costs of the other two cooling options (air-over-oil and chiller),

which would not have any water going down the drain.

3. Public utility water is usually acceptable for cooling purposes. In situations

where the water contains heavy mineral deposits, the exchanger tubes may

40

eventually become restricted by particle buildup. If this is a chronic problem,

pre-filtration and/or water softening may be necessary.

4. Depending upon plant setup, ambient temperature can also be a factor in

cooling the hydraulic fluid. Additional cooling may be required if the

intensifier and/or heat exchanger is confined to a small, high-temperature

space.

Fig 4.1 heat exchanger

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4.3.2. Air-Over-Oil Cooler

Some pumps will use an oil-air cooler to remove heat from the hydraulic oil, so no

heat exchanger is required. In the summer, the unit can be vented outside the building

to remove the heat from the building. In the winter it can be vented inside the building

to help out with heating the building.

Fig 4.2 oil cooler

4.3.3. Chiller

A chiller can be used to re-circulate the cooling water that is used by the intensifier's

heat exchanger. It cools the water and then sends it through the heat exchanger again,

creating a closed loop. A chiller is most effective in worth considering in a few

situations in particular:

Warmer climates where the efficiency of the heat exchanger may be reduce

Facilities that cannot send any water to a drain,

Parts of the country where there is a water shortage, or if the cost of water is high,

because a 50 HP pump can use up to 5 gpm for cooling the hydraulics.

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The chiller will only reuse the cooling water; you will still be putting approximately 1

gpm with a 50 hp pump of fresh water through the cutting head, which will not be

reused with the chiller.

Incoming water for the intensifier should also be maintained at 70° F (21° C) or

cooler for best high pressure seal life. If this temperature cannot be maintained, then

the chiller can also be used for this water.

Fig 4.3 chiller

Water circuit options

Water circuit options

Following are 4 different scenarios for the water flow through a water jet cutting

system.

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Option 1 - Heat exchanger in pump, all water runs to a drain.

fig 4.4 Heat exchanger in pump, all water runs to a drain.

Option 2 - Air-Over-Oil cooler

fig 4.5 Air-Over-Oil cooler

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Option 3 - Chiller and heat exchanger. Water for heat exchanger re-circulates; used

water from cutting runs to drain.

Fig4.6 water from cutting runs to drain.

Option 4 - Heat exchanger, chiller and WRS-3000 water recycling unit. No water to

drain. Only water required is make-up water to replace evaporation and spillage.

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4.4 Recommendation for water treatment

WARD Jet has found that the use of a good quality water softener in conjunction with

a 0.2 absolute final filter to be successful for treatment of water for the intensifier.

This setup can be used as long as the water from the cutting tank is not being recycled

for use through the intensifier. In the worst case, if seal life does not seem to be living

up to expectations, then a DI or RO system can be installed

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4.4.1 Benefits of Water jet Cutting

As one of the fastest growing machine tool industries, water jet cutting has proven to

save time and money on countless applications such as metal cutting and stone

cutting. See the advantages of water jet cutting and view our photo album of different

uses for the tool. Whether it's cutting sheet metal, titanium, granite, marble, or steel -

water jet might be the answer for you.

Benefits of Water jet Cutting

Let's Take a Look... Water jet cutting is best described as an accelerated erosion

process that we are controlling. For this reason, water jet can cut or erode through

virtually any material known, making it one of the most versatile machines available.

As one of the fastest growing machine tool industries, water jet cutting has proven to

save time and money on countless applications. Please take a look at the advantages

below to see if water jet could be for you.

Tolerances

Tolerances tighter than +/- 0.005" are achievable,

especially in thinner materials such as 1" stainless

steel. However, high tolerances come with a price,

sometimes up to 500% higher than if the same part

had been specified with a tolerance of +/- 0.015".

By being more flexible with tolerances, prices will plummet as cutting speeds

increase. Water jet cutting has the ability to vary tolerances in different locations on a

part, ensuring the best pricing and quality.

Thickness And Kerf

Materials ranging from 10" stainless steel to

0.010" acrylics can be cut by water jet, making it a

very versatile tool. Stacking of very thin materials

to increase productivity is possible. Kerf ranges

from 0.020" to 0.050".

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Taper and Edge Finish

Taper and edge finish are directly related to cut speed.

The greater the speed, the more taper and the coarser

the edge finish. As the water jet slows down, taper can

be eliminated and the finish of about 120 achieved.

Again, slower means an increase in time...and price.

For a finer edge finish, use a finer abrasive.

No Heat Affected Zone (HAZ)

Water jet cutting is a natural erosion process involving no

chemicals or heat. Because of this, warping and distortion

typically associated with laser, plasma and oxy-fuel

cutting is eliminated, therefore minimizing the need for

secondary processing.

Nesting And Common Line Cutting

Unlike laser, plasma and oxy-fuel cutting, water jet

lends itself to common line cutting. WARDJet offers

optional state-of-the-art nesting software, allowing you

to nest multiple shapes together and cut them with

multiple heads. Tracking of remnants and nesting into

these odd shapes later, helps save precious material and can contribute toward

reducing your operating costs.

Cutting Speeds

The speed at which the water jet can cut through material will vary based on a variety

of parameters. In the charts below you can see that the orifice/nozzle combination you

select will have an influence on your cut speed. Generally when cutting with a single

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head and a 50 hp pump the chart with the 14/40 orifice/nozzle combination is the

closest guide for cut speed. When cutting with two heads and a 50 hp pump use the

chart with the 10/30 orifice/nozzle combination to indicate the cutting speed of each

head.

After selecting the correct chart find the material and the thickness that you will be

cutting. This will then give you an idea of your straight line cutting speed based on

the quality of edge finish and tolerance you need for your parts. These cutting speeds

are only a guide to estimate cutting speeds achievable. We recommend that test

cutting is done to determine actual feed rates on different materials and thicknesses.

4.5 Water jet in Any Industry

The versatility of the water jet allows it to be used in nearly every industry. There are

many different materials that the water jet can cut. Some of them have unique

characteristics that require special attention when cutting. As you can see in the chart

below each material you cut will have some unique characteristics that have to be

taken into account.

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The information below explains some of the cutting techniques we've used when

cutting these materials. We recognize that there are many materials not listed so if

you have a specific question about your material feel free to contact us at (330) 677-

9100.

4.5.1Alloys 

Inconel, Hastalloy, Wasp alloy, Titanium, Aluminum, Stainless etc. No heat effected

zone or change in the molecular structure occurs in the alloy material. There is no

distortion as seen with typical heat cutting methods. Generally, cutting with water jet

costs less than traditional machining or cutting methods. In many cases, no secondary

removal of slag or damaged material is necessary, and minimal to no burring is seen.

4.5.2Steels

Water jet is not always the most cost effective method to cut steels. As a rule, if the

finished product is presently being cut using laser, plasma or oxyfuel, and no

secondary work is needed to the part after being cut, it is unlikely water jet will be an

economical solution. However, as soon as any secondary work, closer tolerances or

removal of the Heat Affected Zone (HAZ) is needed, water jet is probably the

solution. With the use of the WARD (Water jet Abrasive Recycling Dispenser)

companies are able to reduce their operating cost substantially, reducing the gap

between laser and water jet cutting. In many cases, water jet now costs less than laser!

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4.5.3Laminates

Water jet, in most cases, does not see any difference between laminated materials -

e.g. acrylic, aluminum, stainless and honeycomb section all laminated as one. Many

aircraft parts consist of laminated materials where water jet is the only solution.

4.5.4Composites

many composites are very difficult to machine as the cutting tool tips 'gum' up and

quickly becomes inefficient. Water jet has no gumming at all and can leave a good

clean surface requiring no additional work.

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4.5.5Plastics/Acrylics

It is possible to not only cut these materials effortlessly, but also drill start holes using

specialized low-pressure options available with certain systems.

4.5.6Rubber

Depending on the durometer value, rubber can be cut with water only or with

abrasive. Tests will quickly reveal what the best option is for your application.

52

4.5.7Gaskets

By using water jet for cutting gaskets, it is possible to automatically nest various sized

and shaped gaskets on one sheet effortlessly. There is no longer any need for stacks of

dies. Software will keep track of all remnant sheets allowing off cuts to be put back

into inventory and used for smaller parts. Specialized software is available to track

materials through the entire process.

4.5.8Fiberglass

When cutting materials that are typically associated with hazardous fine airborne

materials, water jet is an ideal solution. Particles and materials removed are

transported by the water away from the surface into the tank, reducing this risk and

hazard.

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4.5.9Glass

Intricate cutting and shaping of glass is easy with water jet. The water jet can

generally drill all its own start holes, making it a highly versatile tool. Glass from

1/32" to 10" thick can be cut, even when laminated in multiple layers.

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CHAPTER 4

CONCLUSION:-

As a conclusion, the experiment that have been carried out were successful, even

though the data collected are a little bit difference compared to the theoretical value.

The difference between the theoretical value and the actual value may mainly due to

human and servicing factors such as parallax error. This error occur during observer

captured the value of the water level. Besides that, error may occur during adjusting

the level gauge to point at the white line on the side of the weight pan. Other than that,

it also maybe because of the water valve. This error may occur because the water

valve was not completely close during collecting the water. This may affect the time

taken for the water to be collected. There are a lot of possibilities for the experiment

will having an error. Therefore, the recommendation to overcome the error is ensure

that the position of the observer’s eye must be 90° perpendicular to the reading or the

position. Then, ensure that the apparatus functioning perfectly in order to get an

accurate result.

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REFERENCE

1.http://www.cee.mtu.edu/~dwatkins/ce3600_labs/impact_of_jet.pdf

2. http://www.eng.ucy.ac.cy/EFM/Manual/HM%2015008/HM15008E-ln.pdf

3.http://staff.fit.ac.cy/eng.fm/classes/amee202/Fluids%20Lab%20Impact%20of%20a

%20Jet.pdf

4. WIKIPEDIA

5. http://www.wardjet.com/water jet-university

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