hydraulic devices Important project report 1

AUTOMOBILE DEPARTMENT BOARD MOUNTED HYDRAULIC DEVICES

1

P. V. P. I. T. BUDHGAON

A

PROJECT REPORT

ON

“CUT SECTION MODEL OF HYDRAULIC

DEVICES”

Submitted by:

Mr. Patil Sukhdev Govind

Mr. Shelar Shubham Vijay

Mr. Sutar Aditya Ashok

Mr. Swami Pavan Sadashiv

Under guidance of-

Prof. S.S. Mane

DEPARTMENT OF AUTOMOBILE ENGINEERING

Dr. Vasantraodada Patil Shetkari Shikshan Mandals

PADMABHOOSHAN VASANTRAODADA PATIL

INSTITUTE OF TECHNOLOGY-BUDHGAON YEAR 2014-2015


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Dr. Vasantraodada Patil Shetkari Shikshan Mandal’s

PADMABHOOSHAN VASANTRAODADA PATIL

INSTITUTE OF TECHNOLOGY

BUDHGAON-416304

CERTIFICATE This is to certify that the project work entitled

“CUT SECTION MODEL OF HYDRAULIC DEVICES”

This is to certify that, Mr. Patil Sukhdev Govind

Mr. Shelar Shubham Vijay

Mr. Sutar Aditya Ashok

Mr. Swami Pavan Sadashiv

Of T.Y Automobile class has completed satisfactory project report in the

academic year 2014-2015, is a report of their own work carried out under my

direct supervision and guidance.

Date : -

Place : - BUDHGAON

Prof. S. S. Mane Prof. S. Y. Saptasagar Prof. B. B. Patil

Guide HOD Principal


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ACKNOWLEDGEMENT

We are rather infused by Prof. S.S .mane Sir who put us in cradle of

engineering studies & evaluated us to this end & mean of our project

report without his guidance, we are sure to be orphan in vast ocean of

subject. Ultimately no tongue could describe deep sense of co-operation

and ready nature to help us even in our minute details of the write up of

the project report.

We would like to thank Prof. S. Y. Saptasagar Head of automobile

department for his valuable guidance & encouragement.

Further we are thankful to all teaching and non teaching staff of

AUTOMOBILE DEPARTMENT for their co-operation during

seminar report work. We are very grateful to those who in the form of

books and conveyed guidance in this project report work.

Finally we thank our colleagues, friends and all other who helped us

directly or indirectly.

Sr. No. Name Roll No.

1 Mr. Patil Sukhdev Govind 02

2 Mr. Shelar Shubham Vijay 04

3 Mr. Sutar Aditya Ashok 05

4 Mr. Swami Pavan Sadashiv 06


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Sr. No. Index Page No.

1 List of Figure 5

2 Introduction 8

3 Hydraulic Pump 9

3.1 Gear pump- 10

External gear pump 11

Internal Gear pump 14

3.2 Vane pump 17

3.3 Lobe Pump 19

3.4 Screw Pump 22

3.5 Piston Pump 25

4 Control Components 29

4.1 Direction Control valve- 30

Poppet Valve 31

Sliding-Spool Valve 33

Two-Way Valve 34

Three-Way Valve 35

Four-Way Valves 37

4.2 Pressure Control Valve- 45

Pressure Relief Valve 45

Direct Type Relief Valve 46

Unloading Valve 47

Sequence Valve 48


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Counterbalance Valve 49

Pressure reducing valve 50

4.3 Flow control valve- 51

Gate Valve 52

Plug or glove valve 53

Butterfly valve 54

Ball Valve 55

Balance valve 56

5 Actuator 57

5.1 Cylinder- 57

Single Acting 57

Double Acting 57

Differential Cylinder 58

Piston Type Cylinder 58

Cushioned Cylinder 60

Lockout Cylinder 61

5.2 Hydraulic Motor- 62

Gear type motor 63

Vane type motor 64

6 Fitting & connector 66

Threaded Connector 66

Flared connector 67

Flexible hose coupling 70


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Reusable Coupling 71

7 Cutting Procedure 72

Vane Pump 72

Gear pump 73

Double acting cylinder 74

Single acting cylinder 74

Flow control valve 75

Hoses 75

8 Tools & Equipment 76

9 Costing 78

10 Conclusion 79

11 References 80


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List of figure

Sr. No. Name Page No.

Fig 3.1 Gears of pump 09

Fig 3.2 An exploded view of an external gear pump 11

Fig 3.3 Working of external gear pump 12

Fig 3.4 An exploded view of an internal gear (Gerotor) pump 14

Fig 3.5 Internal gear (Gerotor) pump 14

Fig 3.6 Working of Internal gear pump 15

Fig 3.7 Working of Vane Pumps 17

Fig 3.8 Working of lobe Pumps 20

Fig 3.9 Screw pump 22

Fig 3.10 Piston Pump 25

Fig 4.1 2 / 2 DCV Poppet Design 32

Fig 4.2 Symbol of 2/2 poppet valve ( Check valve ) 32

Fig 4.3 Spool type 2 / 2 DCV 34

Fig 4.4 4.9 2 /3 DCV 36

Fig 4.5 Two- position, four – way DCV 31

Fig 4.6 2 / 4 DCV with manually operated 39

Fig 4.7 2 / 4 DCV with manually operated by hand lever 39

Fig 4.8 Working of solenoid to shift spool of valve 40

Fig 4.9 Pilot actuated DCV 42

Fig 4.10 Symbol for Pneumatic actuated 2 / 4 DCV 43

http://en.wikipedia.org/wiki/Exploded_view


http://en.wikipedia.org/wiki/Gerotor



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Fig 4.11 Pressure Relief Valve 46

Fig 4.12 Unloading Valve 47

Fig 4.13 Sequence valve 48

Fig 4.14 Counter Balance Valve 49

Fig 4.15 Pressure Reducing Valve 50

Fig 4.16 Gate valve 52

Fig 4.17 Plug or glove valve 53

Fig 4.18 Butterfly valve 54

Fig 4.19 Ball valve 55

Fig 4.20 Balanced valves 56

Fig 5.1 Piston Type cylinder 58

Fig 5.2 Double-acting, piston-type cylinder 59

Fig 5.3 Cushioned, actuating cylinder 60

Fig 5.4 Basic operations of a hydraulic motor 62

Fig 5.5 Gear-type motor 63

Fig 5.6 Vane-type motor 64

Fig 5.7 Pressure differential on a vane-type motor 64

Fig 5.8 Rocker arms pushing vanes in a pump 65

Fig 6.1 Threaded-pipe connectors 66

Fig 6.2 Flared tube connector 67

Fig 6.3 Flared tube Fittings 69

Fig 6.4 Field-attachable couplings 70

Fig 6.5 permanently attached couplings 71


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Fig 7.1 Cutting & grinding of vane pump 72

Fig 7.12 Dismantling & cutting of gear pump 73

Fig 7.3 cutting of flow control valve 75


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2) INTRODUCTION

Hydraulic machinery is very essential in industries for improving quality of parts &

reduces the time of manufacturing of new parts. Hydraulic machine are used in

industries, & it can be hydrostatic or Hydrodynamic.

Hydraulic pump is a mechanical source of Pollster that converts mechanical power

into Hydraulic energy, (Hydrostatic energy i.e. flow, pressure). It generates Row of

with rough power to overcome pressure inducted by the load at the pump outlet.

When a Hydraulic pump operates its creates a vacuum at the pump inlet, which

forces liquid from the reservoir into the inlet line to the pump & by mechanical

action delivers this liquid to the pump outlet & forces it into the Hydraulic systems.

Hydrostatic pumps are positive displacement pumps which Hydrodynamic pumps

can be fixed displacement in which the displacement (How thought the pumps per

rotation of the pump) cannot be adjusted or variable displacement pumps, which have

a more complicated construction that allows the displacement to be adjusted.

Although, Hydrodynamic pumps are more frequent in day to day life. Hydrostatics

pumps which are of various types of work on the principle of Pascal’s low. It states

that the increases in pressure in pressure at one point of the enclosed liquid in

equilibrium of rest are transmitted equally, to all other points of the liquid, unless the

effect of gravity is neglected.


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3. Hydraulic pump

Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or

hydrodynamic. A hydraulic pump is a mechanical source of power that converts

mechanical power into hydraulic energy (hydrostatic energy i.e. flow, pressure). It

generates flow with enough power to overcome pressure induced by the load at the

pump outlet. When a hydraulic pump operates, it creates a vacuum at the pump inlet,

which forces liquid from the reservoir into the inlet line to the pump and by

mechanical action delivers this liquid to the pump outlet and forces it into the

hydraulic system. Hydrostatic pumps are positive displacement pumps while

hydrodynamic pumps can be fixed displacement pumps, in which the displacement

(flow through the pump per rotation of the pump) cannot be adjusted or variable

displacement pumps, which have a more complicated construction that allows the

displacement to be adjusted. Although, hydrodynamic pumps are more frequent in

day to day life. Hydrostatics pump which are of various types works on the principle

of Pascal’s law. It states that the increase in pressure at one point of the enclosed

liquid in equilibrium of rest is transmitted equally to all other points of the liquid,

unless the effect of gravity is neglected.(in case of statics)

Fig. 3.1 Gears of pump


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Hydraulic pump types

3.1 Gear pumps:-

Gear pumps (with external teeth) (fixed displacement) are simple and

economical pumps. The swept volume or displacement of gear pumps for hydraulics

will be between about 1 and 200 milliliters. They have the lowest volumetric

efficiency (nv= 90%) of all three basic pump types (gear, vane and piston

pumps).These pumps create pressure through the meshing of the gear teeth, which

forces fluid around the gears to pressurize the outlet side. For lubrication, the gear

pump uses a small amount of oil from the pressurized side of the gears, bleeds this

through the (typically) hydrodynamic bearings, and vents the same oil either to the

low pressure side of the gears, or through a dedicated drain port on the pump

housing. Some gear pumps can be quite noisy, compared to other types, but modern

gear pumps are highly reliable and much quieter than older models. This is in part

due to designs incorporating split gears, helical gear teeth and higher precision or

quality tooth profiles that mesh and unmesh more smoothly, reducing pressure ripple

and related detrimental problems. Another positive attribute of the gear pump, is that

catastrophic breakdown is a lot less common than in most other types of hydraulic

pumps. This is because the gears gradually wear down the housing and/or main

bushings, reducing the volumetric efficiency of the pump gradually until it is all but

useless. This often happens long before wear causes the unit to seize or break down.


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1) External gear pump

Fig 3.2 An exploded view of an external gear pump

External gear pumps are a popular pumping principle and are often used as

lubrication pumps in machine tools, in fluid power transfer units, and as oil pumps in

engines.

External gear pumps can come in single or double (two sets of gears)

pump configurations with spur (shown), helical, and herringbone gears. Helical and

herringbone gears typically offer a smoother flow than spur gears, although all gear

types are relatively smooth. Large-capacity external gear pumps typically use

helical or herringbone gears. Small external gear pumps usually operate at 1750 or

3450 rpm and larger models operate at speeds up to 640 rpm. External gear pumps

have close tolerances and shaft support on both sides of the gears. This allows them

to run to pressures beyond 3,000 PSI / 200 BAR, making them well suited for use in

hydraulics. With four bearings in the liquid and tight tolerances, they are not well

suited to handling abrasive or extreme high temperature applications.

Tighter internal clearances provide for a more reliable measure of

liquid passing through a pump and for greater flow control. Because of this, external

gear pumps are popular for precise transfer and metering applications involving

polymers, fuels, and chemical additives.



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Working of External Gear Pumps

External gear pumps are similar in pumping action to internal gear pumps in that two

gears come into and out of mesh to produce flow. However, the external gear pump

uses two identical gears rotating against each other -- one gear is driven by a motor

and it in turn drives the other gear. Each gear is supported by a shaft with bearings

on both sides of the gear.

1. As the gears come out of mesh, they create expanding volume on the inlet side of

the pump. Liquid flows into the cavity and is trapped by the gear teeth as they rotate.

2. Liquid travels around the interior of the casing in the pockets between the teeth

and the casing -- it does not pass between the gears.

3. Finally, the meshing of the gears forces liquid through the outlet port under

pressure.

Because the gears are supported on both sides, external gear pumps are quiet-

running and are routinely used for high-pressure applications such as hydraulic

applications. With no overhung bearing loads, the rotor shaft can't deflect and cause

premature wear.

Fig 3.3 Working of external gear pump

http://www.pumpschool.com/principles/eg_ani.asp


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Advantages

High speed

High pressure

No overhung bearing loads

Relatively quiet operation

Design accommodates wide variety of materials

Disadvantages

Four bushings in liquid area

No solids allowed

Fixed End Clearances

Materials of Construction / Configuration Options

As the following list indicates, rotary pumps can be constructed in a

wide variety of materials. By precisely matching the materials of construction with

the liquid, superior life cycle performance will result.

External gear pumps in particular can be

engineered to handle even the most aggressive corrosive liquids. While external

gear pumps are commonly found in cast iron, newer materials are allowing these

pumps to handle liquids such as sulfuric acid, sodium hypochlorite, ferric chloride,

sodium hydroxide, and hundreds of other corrosive liquids.

Externals (head, casing, bracket) - Iron, ductile iron, steel, stainless steel,

high alloys, composites (PPS, ETFE)

Internals (shafts) - Steel, stainless steel, high alloys, alumina ceramic

Internals (gears) - Steel, stainless steel, PTFE, composite (PPS)

Bushing - Carbon, bronze, silicon carbide, needle bearings

Shaft Seal - Packing, lip seal, component mechanical seal, magnetically-

driven pump


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2) Internal gear pump

Fig. 3.4 An exploded view of an internal gear (Gerotor) pump

Fig. 3.5 Internal gear (Gerotor) pump

Internal gear pumps are exceptionally versatile. While they are often used on

thin liquids such as solvents and fuel oil, they excel at efficiently pumping thick

liquids such as asphalt, chocolate, and adhesives. The useful viscosity range of an

internal gear pump is from 1cPs to over 1,000,000cP.

In addition to their wide viscosity range, the pump has a wide temperature

range as well, handling liquids up to 750F / 400C. This is due to the single point of

end clearance (the distance between the ends of the rotor gear teeth and the head of

the pump). This clearance is adjustable to accommodate high temperature,

maximize efficiency for handling high viscosity liquids, and to accommodate for

wear.

The internal gear pump is non-pulsing, self-priming, and can run dry for

short periods. They're also bi-rotational, meaning that the same pump can be used to





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load and unload vessels. Because internal gear pumps have only two moving parts,

they are reliable, simple to operate, and easy to maintain.

Working of Internal Gear Pumps

Fig. 3.6 Working of Internal gear pump

1. Liquid enters the suction port between the rotor (large exterior gear) and idler (small

interior gear) teeth. The arrows indicate the direction of the pump and liquid.

2. Liquid travels through the pump between the teeth of the "gear-within-a-gear"

principle. The crescent shape divides the liquid and acts as a seal between the suction

and discharge ports.

3. The pump head is now nearly flooded, just prior to forcing the liquid out of the

discharge port. Intermeshing gears of the idler and rotor form locked pockets for the

liquid which assures volume control.

4. Rotor and idler teeth mesh completely to form a seal equidistant from the

discharge and suction ports. This seal forces the liquid out of the discharge port.


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Advantages

Only two moving parts

Only one stuffing box

Non-pulsating discharge

Excellent for high-viscosity liquids

Constant and even discharge regardless of pressure conditions

Operates well in either direction

Can be made to operate with one direction of flow with either

rotation

Low NPSH required

Single adjustable end clearance

Easy to maintain

Flexible design offers application customization

Disadvantages

Usually requires moderate speeds

Medium pressure limitations

One bearing runs in the product pumped

Overhung load on shaft bearing

Materials of Construction / Configuration Options

Externals (head, casing, bracket) - Cast iron, ductile iron, steel, stainless

steel, Alloy 20, and higher alloys.

Internals (rotor, idler) - Cast iron, ductile iron, steel, stainless steel, Alloy

20, and higher alloys.

Bushing - Carbon graphite, bronze, silicon carbide, tungsten carbide,

ceramic, colomony, and other specials materials as needed.

Shaft Seal - Lip seals, component mechanical seals, industry-standard

cartridge mechanical seals, gas barrier seals, magnetically-driven pumps.


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3.2 Vane Pump:-

While vane pumps can handle moderate viscosity liquids, they excel

at handling low viscosity liquids such as LP gas (propane), ammonia, solvents,

alcohol, fuel oils, gasoline, and refrigerants. Vane pumps have no internal metal-to-

metal contact and self-compensate for wear, enabling them to maintain peak

performance on these non- lubricating liquids. Though efficiency drops quickly, they

can be used up to 500 cPs / 2,300 SSU.

Vane pumps are available in a number of vane configurations

including sliding vane (left), flexible vane, swinging vane, rolling vane, and external

vane. Vane pumps are noted for their dry priming, ease of maintenance, and good

suction characteristics over the life of the pump. Moreover, vanes can usually

handle fluid temperatures from -32�C / -25�F to 260�C / 500�F and differential

pressures to 15 BAR / 200 PSI (higher for hydraulic vane pumps).

Each type of vane pump offers unique advantages. For example,

external vane pumps can handle large solids. Flexible vane pumps, on the other

hand, can only handle small solids but create good vacuum. Sliding vane pumps can

run dry for short periods of time and handle small amounts of vapor.

Working of Vane Pumps

Despite the different configurations, most vane pumps operate under the

same general principle described below.

Fig 3.7 Working of Vane Pumps

http://www.pumpschool.com/principles/vane_ani.asp

http://www.pumpschool.com/principles/vane_ani.asp


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1. A slotted rotor is eccentrically supported in a cycloidal cam. The rotor is located

close to the wall of the cam so a crescent-shaped cavity is formed. The rotor is

sealed into the cam by two side plates. Vanes or blades fit within the slots of the

impeller. As the rotor rotates (yellow arrow) and fluid enters the pump, centrifugal

force, hydraulic pressure, and/or pushrods push the vanes to the walls of the

housing. The tight seal among the vanes, rotor, cam, and side plate is the key to the

good suction characteristics common to the vane pumping principle.

2. The housing and cam force fluid into the pumping chamber through holes in the

cam (small red arrow on the bottom of the pump). Fluid enters the pockets created

by the vanes, rotor, cam, and side plate.

3. As the rotor continues around, the vanes sweep the fluid to the opposite side of

the crescent where it is squeezed through discharge holes of the cam as the vane

approaches the point of the crescent (small red arrow on the side of the

pump). Fluid then exits the discharge port.

Advantages

Handles thin liquids at relatively higher pressures

Compensates for wear through vane extension

Sometimes preferred for solvents, LPG

Can run dry for short periods

Can have one seal or stuffing box

Develops good vacuum

Disadvantages

Can have two stuffing boxes

Complex housing and many parts

Not suitable for high pressures

Not suitable for high viscosity

Not good with abrasives


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3.3 Lobe Pumps

Lobe pumps are used in a variety of industries including, pulp and paper, chemical,

food, beverage, pharmaceutical, and biotechnology. They are popular in these

diverse industries because they offer superb sanitary qualities, high efficiency,

reliability, corrosion resistance, and good clean- in-place and sterilize- in place

(CIP/SIP) characteristics.

These pumps offer a variety of lobe options including single, bi-wing, tri- lobe

(shown), and multi- lobe. Rotary lobe pumps are non-contacting and have large

pumping chambers, allowing them to handle solids such as cherries or olives without

damage. They are also used to handle slurries, pastes, and a wide variety of other

liquids. If wetted, they offer self-priming performance. A gentle pumping action

minimizes product degradation. They also offer reversible flows and can operate dry

for long periods of time. Flow is relatively independent of changes in process

pressure, so output is constant and continuous.

Rotary lobe pumps range from industrial designs to sanitary

designs. The sanitary designs break down further depending on the service and

specific sanitary requirements. These requirements include 3-A, EHEDG, and

USDA. The manufacturer can tell you which certifications, if any, their rotary lobe

pump meets.


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Working of Lobe Pumps

Lobe pumps are similar to external gear pumps in operation in that fluid flows

around the interior of the casing. Unlike external gear pumps, however, the lobes do

not make contact. Lobe contact is prevented by external timing gears located in the

gearbox. Pump shaft support bearings are located in the gearbox, and since the

bearings are out of the pumped liquid, pressure is limited by bearing location and

shaft deflection.

1. As the lobes come out of mesh, they create expanding volume on the inlet side of

the pump. Liquid flows into the cavity and is trapped by the lobes as they rotate.

2. Liquid travels around the interior of the casing in the pockets between the lobes

and the casing -- it does not pass between the lobes.

3. Finally, the meshing of the lobes forces liquid through the outlet port under

pressure.

Lobe pumps are frequently used in food applications because they handle

solids without damaging the product. Particle size pumped can be much larger in

lobe pumps than in other PD types. Since the lobes do not make contact, and

clearances are not as close as in other PD pumps, this design handles low viscosity

liquids with diminished performance. Loading characteristics are not as good as

other designs, and suction ability is low. High-viscosity liquids require reduced


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speeds to achieve satisfactory performance. Reductions of 25% of rated speed and

lower are common with high-viscosity liquids.

Advantages

Pass medium solids

No metal-to-metal contact

Superior CIP/SIP capabilities

Long term dry run (with

lubrication to seals)

Disadvantages

Requires timing gears

Requires two seals


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3.4 Screw pump

A screw pump is a positive-displacement (PD) pump that uses one or several

screws to move fluids or solids along the screw(s) axis. In its simplest form

(the Archimedes' screw pump), a single screw rotates in a cylindrical cavity, thereby

moving the material along the screw's spindle. This ancient construction is still used

in many low-tech applications, such as irrigation systems and in agricultural

machinery for transporting grain and other solids.

Development of the screw pump has led to a variety of multiple-axis

technologies where carefully crafted screws rotate in opposite directions or remains

stationary within a cavity. The cavity can be profiled, thereby creating cavities where

the pumped material is "trapped".

In offshore and marine installations, a three-spindle screw pump is

often used to pump high-pressure viscous fluids. Three screws drive the pumped

liquid forth in a closed chamber. As the screws rotate in opposite directions the

pumped liquid moves along the screws spindles.

Three-spindle screw pumps are used for transport of viscous fluids

with lubricating properties. They are suited for a variety of applications such as fuel-

injection, oil burners, boosting, hydraulics, fuel, lubrication, circulating, feed and so

on.

Fig 3.9 Screw pump

http://en.wikipedia.org/wiki/Archimedes%27_screw

http://en.wikipedia.org/wiki/Spindle_(tool)

http://en.wikipedia.org/wiki/Irrigation_systems

http://en.wikipedia.org/wiki/Viscosity

http://en.wikipedia.org/wiki/Fuel-injection

http://en.wikipedia.org/wiki/Fuel-injection

http://en.wikipedia.org/wiki/Oil_burner

http://en.wikipedia.org/wiki/Hydraulics

http://en.wikipedia.org/wiki/Lubrication


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Advantages of screw pump

1. Slow Speed, Simple and Rugged design

Probably the main and overall advantage of a screw pump is

its superb reliability. The simple design, open structure and slow rotation

speed makes it a heavy duty pumps with minimal wears that operates for

years without trouble.

2. Pumps raw water with heavy solids and floating debris

Because of the open structure and large passage between the

flights a screw pump can pump raw sewage without the need for a coarse

screen before the pump. Both floating debris and heavy solids are simply

lifted up. This saves considerably on equipment costs for a coarse screen or

maintenance!

3. No collection sump required = minimum head

A screw pump 'scoops' the water directly from the surface and

does not need a collection sump. This keeps the pump head to a minimum.

4. 'Gentle handling' of biological flock

The activated return sludge on STP’s is a delicate biological

substance. Because of the low rotational speed and large opening between the

flights, screw pumps do not damage this biological flock (whereas the high

speed rotating centrifugal pumps will completely shred the biological flock).

5. Long lifetime (> 20-40 years)

Screw pumps with typical lifetimes of between 20-40 years

are not unusual.

6. Pump capacity is self-regulating with incoming level


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When incoming water level goes down at dry weather flow the screw

pump 'automatically' pumps less water. Ergo: no control system required to adapt

pump performance.

7. Easy maintenance (no 'high skilled' staff required)

A screw pump requires very little maintenance. Compared to

(submersed) centrifugal pumps it is next to nothing. Besides that no ‘highly skilled’

maintenance staffs are required which makes this type of pump very suitable for

remote locations.

8. Constant high efficiency with variable capacity

The efficiency-curve of a screw pump is flat on the top. Due

to that efficiency characteristic, the screw pump offers even high efficiency

when it works at 50% of its capacity.

9. Can run without water

A screw pump can operate even when there is no water in the

inlet. Therefore it is not necessary to install expensive measures (level

control etc) to prevent 'dry-running'’. The lower bearing does not need

cooling.


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3.5 Piston pump

An axial piston pump has a number of pistons (usually an odd number)

arranged in a circular array within a housing which is commonly referred to as

a cylinder block, rotor or barrel. This cylinder block is driven to rotate about its axis

of symmetry by an integral shaft that is, more or less, aligned with the pumping

pistons (usually parallel but not necessarily).

Fig 3.10 Piston Pump

Mating surfaces.

One end of the cylinder block is convex and wears against a mating

surface on a stationary valve plate. The inlet and outlet fluid of the pump pass

through different parts of the sliding interface between the cylinder block and

valve plate. The valve plate has two semi-circular ports that allow inlet of the

operating fluid and exhaust of the outlet fluid respectively.

No. Part Name

1 Drive Shaft

2 Swash Plate Servo

Ball LH

3 Swash Plate Servo

Ball LH

4 Retainer Plate

5 Pistons

6 Retainer Plate

7 Ball Guide

8 Block Spring

9 Cylinder Block

10 Valve Plate

11 Shaft Bush

http://en.wikipedia.org/wiki/Rotor_(turbine)

http://en.wikipedia.org/wiki/Parallel_(geometry)

http://en.wikipedia.org/wiki/Valve


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Protruding pistons.

The pumping pistons protrude from the opposite end of the cylinder

block. There are numerous configurations used for the exposed ends of the

pistons but in all cases they bear against a cam. In variable displacement units,

the cam is movable and commonly referred to as a swash plate, yoke or hanger.

For conceptual purposes, the cam can be represented by a plane, the orientation

of which, in combination with shaft rotation, provides the cam action that leads

to piston reciprocation and thus pumping. The angle between a vector normal to

the cam plane and the cylinder block axis of rotation, called the cam angle, is

one variable that determines the displacement of the pump or the amount of fluid

pumped per shaft revolution. Variable displacement units have the ability to vary

the cam angle during operation whereas fixed displacement units do not.

Reciprocating pistons.

As the cylinder block rotates, the exposed ends of the pistons are

constrained to follow the surface of the cam plane. Since the cam plane is at an

angle to the axis of rotation, the pistons must reciprocate axially as they presses

about the cylinder block axis. The axial motion of the pistons is sinusoidal.

During the rising portion of the piston's reciprocation cycle, the piston moves

toward the valve plate. Also, during this time, the fluid trapped between

the buried end of the piston and the valve plate is vented to the pump's discharge

port through one of the valve plate's semi-circular ports – the discharge port. As

the piston moves toward the valve plate, fluid is pushed or displaced through the

discharge port of the valve plate.

Effect of precession.

When the piston is at the top of the reciprocation cycle (commonly

referred to as top-dead-center or just TDC), the connection between the trapped

fluid chamber and the pump's discharge port is closed. Shortly thereafter, that

same chamber becomes open to the pump's inlet port. As the piston continues

http://en.wikipedia.org/wiki/Simple_harmonic_motion


29


to presses about the cylinder block axis, it moves away from the valve plate

thereby increasing the volume of the trapped chamber. As this occurs, fluid

enters the chamber from the pump's inlet to fill the void. This process continues

until the piston reaches the bottom of the reciprocation cycle - commonly

referred to as bottom-dead-center or BDC. At BDC, the connection between the

pumping chamber and inlet port is closed.

Shortly thereafter, the chamber becomes open to the discharge port again and the

pumping cycle starts over.

Variable displacement.

In a variable displacement unit, if the vector normal to the cam plane

(swash plate) is set parallel to the axis of rotation, there is no movement of the

pistons in their cylinders. Thus there is no output. Movement of the swash plate

controls pump output from zero to maximum.

Pressure.

In a typical pressure-compensated pump, the swash plate angle is

adjusted through the action of a valve which uses pressure feedback so that the

instantaneous pump output flow is exactly enough to maintain a designated

pressure. If the load flow increases, pressure will momentarily decrease but the

pressure-compensation valve will sense the decrease and then increase the swash

plate angle to increase pump output flow so that the desired pressure is restored.

In reality most systems use pressure as a control for this type of pump. The

operating pressure reaches, say, 200 bar (20 MPa or 2900 psi) and the swash

plate is driven towards zero angle (piston stroke nearly zero) and with the

inherent leaks in the system allows the pump to stabilize at the delivery volume

that maintains the set pressure. As demand increases the swash plate is moved to

a greater angle, piston stroke increases and the volume of fluid increases; if the

demand slackens the pressure will rise, and the pumped volume diminishes as

the pressure rises. At maximum system pressure the output is once again almost

zero. If the fluid demand increases beyond the capacity of the pump to deliver,

http://en.wikipedia.org/wiki/Precession


30


the system pressure will drop to near zero. The swash plate angle will remain at

the maximum allowed, and the pistons will operate at full stroke. This continues

until system flow-demand eases and the pump's capacity is greater than demand.

As the pressure rises the swash-plate angle modulates to try to not exceed the

maximum pressure while meeting the flow demand.

Advantages

1. Parameter High: Rated high pressure, high speed, large power-driven pump

2. Efficiency, volumetric efficiency is 95% of the total efficiency of about 90%

3. Long life

4. Variable convenient form for

5 More unit power and light weight

6. Piston main components are compressive stress, strength of materials can be fully

utilized

7. Piston pumps have a wide pressure range, can reach high pressures and the

pressure can be controlled without an impact on the rate of flow. Piston pumps have

a continuous rate of discharge.

Disadvantages

• Piston pumps cost more per unit to run compared to centrifugal and roller

pumps. The mechanical parts are prone to wear, so the maintenance costs can be

high. The valves must be resistant to abrasives for large solids to pass through.

Piston pumps are heavy due to their large size and the weight of the crankshaft that

drives the pump.


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4) Control components

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

control components are not properly selected, the entire system will fail to deliver

the required output. Elements for the control of energy and other control in fluid

power system are generally called “Valves”. It is important to know the primary

function and operation of the various types of control components. This type of

knowledge is not only required for a good functioning system, but it also leads to the

discovery of innovative ways to improve a fluid power system for a given

application

The selection of these control components not only involves the type, but also

the size, the actuating method and remote control capability. There are 3 basic types

of valves.

1. Directional control valves

2. Pressure control valves

3. Flow control valves.

Directional control valves are essentially used for distribution of energy in a fluid

power system. They establish the path through which a fluid traverses a given

circuit. For example they control the direction of motion of a hydraulic cylinder or

motor. These valves are used to control the start, stop and change in direction of

flow of pressurized fluid.

Pressure may gradually buildup due to decrease in fluid demand or due to sudden

surge as valves opens or closes. Pressure control valves protect the system against

such overpressure. Pressure relief valve, pressure reducing, sequence, unloading and

counterbalance valve are different types of pressure control valves.

In addition, fluid flow rate must be controlled in various lines of a hydraulic

circuit. For example, the control of actuator speeds depends on flow rates. This type

of control is accomplished through the use of flow control valves.


32


4.1 Directional control valves

As the name implies directional control valves are used to control the direction

of flow in a hydraulic circuit. They are used to extend, retract, position or

reciprocate hydraulic cylinder and other components for linear motion. Valves

contains ports that are external openings for fluid to enter and leave via connecting

pipelines, The number of ports on a directional control valve (DCV ) is usually

identified by the term “ way”. For example, a valve with four ports is named as

four-way valve.

Directional control valves can be classified in a number of ways:

1. According to type of construction :

• Poppet valves

• Spool valves

2. According to number of working ports :

• Two- way valves

• Three – way valves

• Four- way valves.

3. According to number of Switching position:

• Two – position

• Three - position

4. According to Actuating mechanism:

• Manual actuation

• Mechanical actuation

• Solenoid ( Electrical ) actuation

• Hydraulic ( Pilot ) actuation

• Pneumatic actuation

• Indirect actuation


33


1) According to type of construction

1. Poppet Valves:

Directional poppet valves consists of a housing bore in which one or

more suitably formed seating elements ( moveable ) in the form of balls, cones

are situated. When the operating pressure increases the valve becomes more

tightly seated in this design.

The main advantage of poppet valves is;

- No Leakage as it provides absolute sealing.

- Long useful life, as there are no leakages of oil flows.

- May be used with even the highest pressures, as no hydraulic sticking

(pressure dependent deformation) and leakages occurs in the valve.

The disadvantages of these valves are;

- Large pressure losses due to short strokes

- Pressure collapse during switching phase due to negative overlap (connection

of pump, actuator and tank at the same time).

P. V. P. I. T. BUDHGAON 32

2 / 2 DCV (Poppet design) :-

Fig 4.1 2 / 2 DCV Poppet Design

Figure shows a ball poppet type 2 / 2 DCV. It is essentially a check valve as it allows

free flow of fluid only in one direction (P to A) as the valve is opened hydraulically and

hence the pump Port P is connected to port A as shown in fig b. In the other direction the

valve is closed by the ball poppet (note the fluid pressure from A pushes the ball to its seat)

and hence the flow from the port A is blocked .The symbol for this type of design is same as

that of check valve.

No flow

Free flow

Fig. 4.2 Symbol of 2/2 poppet valve ( Check valve )


35


2. Spool valves:

The spool valve consists of a spool which is a cylindrical member that has

large- diameter lands machined to slide in a very close- fitting bore of the valve body. The

spool valves are sealed along the clearance between the moving spool and the housing. The

degree of sealing depends on the size of the gap, the viscosity of the fluid and especially on

the level of pressure. Especially at high pressures (up to 350 bar) leakage occurs to such a

extent that it must be taken into account when determining the system efficiency. The

amount of leakage is primarily dependent on the gap between spool and housing. Hence as

the operating pressure increases the gap must be reduced or the length of overlap increased.

The radial clearance is usually less than 20 µ. The grooves between the lands provide the

flow passage between ports.


36


2) According to number of working ports

1. Two-way valve ( 2/ 2 DCV):

Fig 4.3 Spool type 2 / 2 DCV

The simplest type of directional control valve is a check valve which is a two way valve

because it contains two ports. These valves are also called as on-off valves because they

allow the fluid flow in only in one direction and the valve is normally closed. Two – way

valves is usually the spool or poppet design with the poppet design more common and are

available as normally opened or normally closed valves. They are usually actuated by pilot

(Hydraulic actuation) but manual, mechanical, solenoid actuated design are also available.

Figure 4.3 above shows Spool type 2 / 2 DCV manually actuated. In Fig 4.3) the port P is

blocked by the action of spring as the valve is UN actuated (absence of hand force). Hence

the flow from port P to A is blocked. When actuated (Presence of hand force) the valve is

opened, thereby connecting port P to A.


37


2) Three – way valve:

A directional control valve primary function is alternatively to pressurize and exhaust

one working port is called three-way valve. Generally, these valves are used to operate

single- acting cylinders. Three-way directional valves are available for manual, mechanical,

pilot, solenoid actuation. These valves may be two-position, or three -position. Most

commonly they have only two positions, but in some cases a neutral position may be needed.

These valves are normally closed valves (i.e. the pump port is blocked when the valve is not

operating). The three-way valve ports are inlet from the pump, working ports, and exhaust to

tank. These ports are generally identified as follows: P= pressure (Pump) port; A or B =

working port and T = tank port. Figure 4.4 (a) and (b) shows the two positions of the three –

way valve actuated manually by a push button.

a. Spool position 1: When the valve is actuated, the spool moves towards left . In this

position flow from pump enters the valve port P and flows out through the port A as shown

by the straight- through line and arrow .In this position, port T is blocked by the spool.

b. Spool position 0: when the valve is un-actuated by the absence of hand force, the

valve assumes this position by the action of spring in this position, port P is blocked by the

spool. Flow from the actuator can go to the tank from A to T as shown by straight – through

line and arrow.


38


Three way valve: P to A connected and T is blocked

Three way valve: P to A connected and T is blocked

Fig 4.4 2 /3 DCV

Symbol 2/ 3 DCV: -

0 1


39


3. Four - way DCV: -

These valves are generally used to operate cylinders and fluid motors in both

directions hydraulically. The four ways are Port P that is connected to pump, tank port T,

and two working ports A and B connected to the actuator. The primary function of a four

way valve is to alternately to pressurize and exhaust two working ports A & B. These

valves are available with a choice of actuation, manual, mechanical, solenoid, pilot &

pneumatic. Four-way valve comes with two or three position. One should note that the

graphical symbol of the valve shows only one tank port even though the physical design

may have two as it is only concerned with the function.

3.1. Three positions, four way valves:

These type of DCV consists of three switching position. Most three- position valves

have a variety of possible flow path configurations, but has identical flow path configuration

in the actuated position (position 1 and position 2) and different spring centered flow paths.

When left end of the valve is actuated, the valve will assume 1 position. In this position the

port P to connected to working port A and working port B is connected to T (in some design

P is connected to B, and A to T when left end is actuated ). Similarly when the right end is

actuated, the valve will assume 2 positions. In this position port P is connected to B and

working port A to T. When the valve is un-actuated, the valve will assume its center

position due to the balancing opposing spring forces. It should be noted that a three-position

valve is used whenever it is necessary to stop or hold a actuator at some intermediate

position within its stroke range, or when multiple circuit or functions must be accomplished

from one hydraulic power source.

Three- position, four- way DCV have different variety of center

configurations. The common varieties are the open center, closed center, tandem center,

floating center, & regenerative center with open, closed and tandem are the three basic

types A variety of center configurations provides greater flexibility for circuit design.


40


3.2 Two- position, Four – way DCV:

These valves are also used to operate double acting cylinder. These valves are

also called as impulse valve as 2 / 4 DCV has only two switching positions, i.e. it has no

mid position. These valves are used to reciprocate or hold and actuating cylinder in one

position. They are used on machines where fast reciprocation cycles are needed. Since

the valve actuator moves such a short distance to operate the valve from one position to

the other, this design is used for punching, stamping and for other machines needing fast

action. Fig a and b shows the two position of 2 / 4 DC

Fig 4.5 Two- position, four – way DCV:

Symbol

1 2


41


3) Actuation of Directional control valves:

Directional control valves can be actuated by different methods.

1. Manually – actuated Valve:

A manually actuated DCV uses muscle power to actuate the spool. Manual

actuators are hand lever, push button, pedals. The following symbols shows the DCV

actuated manually

1 2

Fig 4.6

Fig 4.6 shows the symbol of 2 / 4 DCV with manually operated by roller tappet to 1

and spring return to 2.

1 2

Fig 4.7

Fig 4.7 shows the symbol of 2 / 4 DCV with manually operated by hand lever to 1 and

spring return to 2. In the above two symbols the DCV spool is returned by springs which

push the spool back to its initial position once the operating force has stopped e.g., letting

go of the hand lever


42


2. Mechanical Actuation:

The DCV spool can be actuated mechanically, by roller and cam, roller and

plunger. The spool end contains the roller and the plunger or cam can be attached to the

actuator (cylinder). When the cylinder reaches a specific position the DCV is actuated. The

roller tappet connected to the spool is pushed in by a cam or plunger and presses on the

spool to shift it either to right or left reversing the direction of flow to the cylinder. A

spring is often used to bring the valve to its center configuration when deactuated.

3. Solenoid-actuated DCV :

A very common way to actuate a spool valve is by using a solenoid is

illustrated in Fig 4.8. When the electric coil (solenoid) is energized, it creates a magnetic

force that pulls the armature into the coil. This caused the armature to push on the spool rod

to move the spool of the valve.. The advantage of a solenoid lies within its less switching

time.

Fig 4.8 Working of solenoid to shift spool of valve

Figure 4.8 shows the working of a solenoid actuated valve when left coil is

energized, its creates a magnetic force that pulls the armature into the coil. Since the

armature is connected to spool rod its pushes the spool towards right. Similarly when right

coil is energized spool is moved towards left. When both coil is de-energized the spool will

come to the mid position by spring force Figure a shows a symbol for single solenoid used

to actuate 2- position, 4 way valve and b) shows symbol for 2 solenoids actuating a 3-

position valve, 4 way valve.


43


1 2

Fig 4.8 a) Symbol for Single solenoid-actuated, 2- Position,

4-way spring centered DCV

1 0 2

Fig 4.8b) Symbol for Solenoid actuated, 3- position,

4- way spring centered DCV


44


4. Hydraulic actuation:

This type actuation is usually known as pilot- actuated valve. The hydraulic

pressure may directly used on the end face of the spool. The pilot ports are lo cated on

the valve ends. Fig 4.9a shows a directional valve where the rate of shifting the spool

from one side to another can be controlled by a needle valve. Fluid entering the pilot

pressure port on the X end flows through the check valve and operates against the

piston. This forces the spool to move towards the opposite position. Fluid in the Y end

(right end ,not shown in the figure) is passed through the adjustable needle valve and

exhausted back to tank. The amount of fluid bled through the needle valve controls how

fast the valve will shift. Fig 4.9b shows the symbol of pilot actuated 2 / 4 DCV.

Fig 4.9a Pilot actuated DCV

A B

Y

X P T

Fig 4.9b Symbol for pilot actuated 2 /4 DCV


45


5. Pneumatic actuation :

Directional control valve can also be shifted by applying air pressure against a

piston at either end of the valve spool. When air is introduced through the left end

passage (X), its pressure pushes against the piston to shift the spool to the right. Removal

of this left end air supply and introduction of air through the right end passage (Y) causes

the spool to shift to the left. Figure 4.10 shows the symbol for pneumatic actuated 2 / 4

DCV. Note that the shaded arrow represents the pilot actuation as in fig 4.9 and the

unshaded arrow represent pneumatic signal.

A B

X Y

P T

Fig 4.10 Symbol for Pneumatic actuated 2 / 4 DCV


46


6. Indirect actuation of directional control valve :

We have seen that a directional valve spool can be positioned from one

extreme position to another by actuated it by manually, mechanically, electrically

(solenoid), hydraulic (pilot) and pneumatic. The mode of actuation has no influence on

the basic operation of these switching circuits. However since there is usually not a lot

of force available, direct actuation is restricted to use with rather smaller valves.

Especially with direct actuation, the greatest disadvantage is that the force which can be

developed by them to shift a directional valve spool is limited. As a matter of fact, the

force required to shift a directional spool is substantial in the larger size.

Larger valves are often indirectly actuated in one after the other sequence. First the

smaller valve is directly actuated. Flow from the smaller valve is directed to either side of

the larger valve when shifting is required. The main DCV is referred as pilot actuated

DCV.

The control oil can come from a separate circuit or from the same system’s pressure line.

Pressure for pilot valve operation is usually supplied internally from the pressure passage

in the main valve. These two valves are often incorporated as a single unit. Therefore one

may find it hard to see that it is an indirectly controlled valve. These valves are also

called as Electro-hydraulic operated DCV.


47


4.2 PRESSURE CONTROL VALVE

These are the units ensuring the control of pressure. A throttling orifice is present in the

valve and by variation of orifice, the pressure level can be controlled or at a particular

pressure, a switching action can be influenced.

Different types of pressure control valves:

Pressure control valves are usually named for their primary function such as

relief valve, sequence valve, unloading valve, pressure reducing valve and counterbalance

valve.

Pressure Relief valve:

The pressure relief valves are used to protect the hydraulic components from

excessive pressure. This is one of the most important components of a hydraulic system and

is essentially required for safe operation of the system. Its primary function is to limit the

system pressure within a specified range. It is normally a closed type and it opens when the

pressure exceeds a specified maximum value by diverting pump flow back to the tank. The

simplest type valve contains a poppet held in a seat against the spr ing force as shown in

Figure 4.16 the fluid enters from the opposite side of the poppet. When the system pressure

exceeds the preset value, the poppet lifts and the fluid is escaped through the orifice to the

storage tank directly. It reduces the system pressure and as the pressure reduces to the set

limit again the valve closes. This valve does not provide a flat cut-off pressure limit with

flow rate because the spring must be deflected more when the flow rate is higher. Various

types of pressure control valves are discussed in the following sections:


48


1. Direct type of relief valve

Figure 4.11 Pressure Relief Valve

Schematic of direct pressure relief valve is shown in figure 4.11 .This types of

valves has two ports; one of which is connected to the pump and another is connected to the

tank. It consists of a spring chamber where poppet is placed with a spring force. Generally,

the spring is adjustable to set the maximum pressure limit of the system. The poppet is held

in position by combined effect of spring force and dead weight of spool. As the pressure

exceeds this combined force, the poppet raises and excess fluid bypassed to the reservoir

(tank). The poppet again reseats as the pressure drops below the pre-set value. A drain is also

provided in the control chamber. It sends the fluid collected due to small leakage to the tank

and thereby prevents the failure of the valve.


49


2. Unloading Valve

Figure 4.12 Unloading Valve

The construction of unloading valve is shown in Figure 4.12 This valve

consists of a control chamber with an adjustable spring which pushes the spool

down. The valve has two ports: one is connected to the tank and another is

connected to the pump. The valve is operated by movement of the spool. Normally,

the valve is closed and the tank port is also closed. These valves are used to permit

a pump to operate at the minimum load. It works on the same principle as direct

control valve that the pump delivery is diverted to the tank when sufficient pilot

pressure is applied to move the spool. The pilot pressure maintains a static pressure

to hold the valve opened. The pilot pressure holds the valve until the pump delivery

is needed in the system. As the pressure is needed in the Hydraulic circuit; the pilot

pressure is relaxed and the spool moves down due to the self-weight and the spring

force. Now, the flow is diverted to the hydraulic circuit. The drain is provided to

remove the leaked oil collected in the control chamber to prevent the valve failure.

The unloading valve reduces the heat buildup due to fluid discharge at a preset

pressure value.


50


3. Sequence valve

Figure 4.13 Sequence valve The primary function of this type of valve is to divert flow in a

predetermined sequence. It is used to operate the cycle of a machine automatically.

A sequence valve may be of direct-pilot or remote-pilot operated type. Schematic of the sequence valve is shown in Figure 4.13 its

construction is similar to the direct relief valve. It consists of the two ports; one

main port connecting the main pressure line and another port (secondary port) is

connected to the secondary circuit. The secondary port is usually closed by the

spool. The pressure on the spool works against the spring force. When the pressure

exceeds the preset value of the spring; the spool lifts and the fluid flows from the

primary port to the secondary port. For remote operation; the passage used for the

direct operation is closed and a separate pressure source for the spool operation is

provided in the remote operation mode.


51


4. Counterbalance Valve

Figure 4.14 Counter Balance Valve

The schematic of counterbalance valve is shown in Figure 4.14. It is

used to maintain the back pressure and to prevent a load from failing. The

counterbalance valves can be used as breaking valves for decelerating heavy loads.

These valves are used in vertical presses, lift trucks, loaders and other machine tools

where position or hold suspended loads are important. Counterbalance valves work

on the principle that the fluid is trapped under pressure until pilot pressure

overcomes the pre-set value of spring force. Fluid is then allowed to escape, letting

the load to descend under control. This valve is normally closed until it is acted

upon by a remote pilot pressure source. Therefore, a lower spring force is sufficient.

It leads to the valve operation at the lower pilot pressure and hence the power

consumption reduces, pump life increases and the fluid temperature decreases.


52


5. Pressure Reducing Valve

Figure 4.15 Pressure Reducing Valve Sometimes a part of the system may need a lower pressure. This can be

made possible by using pressure reducing valve as shown in Figure 4.15. These valves

are used to limit the outlet pressure. Generally, they are used for the operation of

branch circuits where the pressure may vary from the main hydraulic pressure lines.

These are open type valve and have a spring chamber with an adjustable spring, a

movable spool as shown in figure 4.15. A drain is provided to return the leaked fluid

in the spring (control) chamber. A free flow passage is provided from inlet port to the

outlet port until a signal from the outlet port tends to throttle the passage through the

valve. The pilot pressure opposes the spring force and when both are balanced, the

downstream is controlled at the pressure setting. When the pressure in the reduced

pressure line exceeds the valve setting, the spool moves to reduce the flow passage

area by compressing the spring. It can be seen from the figure that if the spring force is

more, the valve opens wider and if the controlled pressure has greater force, the valves

moves towards the spring and throttles the flow.


53


4.3 Flow Control Valves

Flow-control valves are used to control an actuator’s speed by metering

flow. Metering is measuring or regulating the flow rate to or from an actuator. A water

faucet is an example of a flow-control valve. Flow rate varies as a faucet handle is

turned clockwise or counterclockwise. In a closed position, flow stops. Many flow-

control valves used in fluid-powered systems are similar in design and operation to

water faucets.

In hydraulic circuits, flow-control valves are generally used to control the speed

of hydraulic motors and work spindles and the travel rates of tool heads or slides.

Flow-control valves incorporate an integral pressure compensator, which causes the

flow rate to remain substantially uniform regardless of changes in workload. A no

pressure, compensated flow control, such as a needle valve or fixed restriction, allows

changes in the flow rate when pressure drop through it changes.

Variations of the basic flow-control valves are the flow-control-and-check valves

and the flow-control-and-overload relief valves. Models in the flow-control-and-

check-valve series incorporate an integral check valve to allow reverse free flow.

Models in the flow-control -and- overload-relief-valve series incorporate an integral

relief valve to limit system pressure. Some of these valves are gasket-mounted, and

some are panel-mounted.


54


1 Gate Valve

In this type of valve, a wedge or gate controls the flow. To open and close a passage, a

handwheel moves a wedge or gate up and down across a flow line. Figure 4.16, shows

the principal elements of a gate valve. Area A shows the line connection and the

outside structure of the valve; area B shows the wedge or gate inside the valve and the

stem to which the gate and the handwheel are attached. When the valve is opened, the

gate stands up inside the bonnet with its bottom flush with the wall of the line. When

the valve is closed, the gate blocks the flow by standing straight across the line where

it rests firmly against the two seats that extend completely around the line.

A gate valve allows a straight flow and offers little or no resistance to the fluid flow

when the valve is completely open.

Sometimes a gate valve is in the partially open position to restrict the flow rate.

However, its main use is in the fully open or fully closed positions. If the valve is left

partly open, the Valve's face stands in the fluid flow, which will act on the face and

cause it to erode

Fig. 4.16 Gate valve


55


2. Plug or glove valve

Fig. 4.17 Plug or glove valve

The plug valve is quite commonly used valve. It is also termed as glove valve.

Schematic of plug or glove valve is shown in Figure. This valve has a plug which can

be adjusted in vertical direction by setting flow adjustment screw. The adjustment of plug alters the orifice size between plug and valve seat. Thus the adjustment of plug

controls the fluid flow in the pipeline. The characteristics of these valves can be

accurately predetermined by machining the taper of the plug. The typical examp le of plug valve is stopcock that is used in laboratory glassware. The valve body is made of

glass or Teflon. The plug can be made of plastic or glass. Special glass stopcocks are made for vacuum applications. Stopcock grease is used in high vacuum applica tions to

make the stopcock air-tight.


56


3. Butterfly valve A butterfly valve is shown in Figure. It consists of a disc which can rotate inside the

pipe. The angle of disc determines the restriction. Butterfly valve can be made to any

size and is widely used to control the flow of gas. These valves have many types which have for different pressure ranges and applications. The resilient butterfly valve

uses the flexibility of rubber and has the lowest pressure rating. The high performance

butterfly valves have a slight offset in the way the disc is positioned. It increases its sealing ability and decreases the wear. For high-pressure systems, the triple offset

butterfly valve is suitable which makes use of a metal seat and is therefore able to withstand high pressure. It has higher risk of leakage on the shut-off position and

suffers from the dynamic torque effect. Butterfly valves are favored because of their

lower cost and lighter weight. The disc is always present in the flow therefore a pressure drop is induced regardless of the valve position.

Fig. 4.18 Butterfly valve


57


4. Ball Valve The ball valve is shown in Figure 4.19. This type of flow control valve uses a ball

rotated inside a machined seat. The ball has a through hole as shown in Figure. It has

very less leakage in its shut -off condition. These valves are durable and usually work

perfectly for many years. They are excellent choice for shutoff applications. They do

not offer fine control which may be necessary in throttling applications. These valves are widely used in industries because of their versatility, high supporting pressures (up

to 1000 bar) and temperatures (up to 250°C). They are easy to repair and operate.

Fig 4.19 Ball valve


58


5. Balanced valve

Schematic of a balanced valve is shown in figure 4.20. It comprises of two

plugs and two seats. The opposite flow gives little dynamic reaction onto the actuator

shaft. It results in the negligible dynamic torque effect. However, the leakage is more

in these kind of valves because the manufacturing tolerance can cause one plug to seat

before the other. The pressure-balanced valves are used in the houses. They provide water at nearly constant temperature to a shower or bathtub despite of pressure

fluctuations in either the hot or cold supply lines.

Figure 4.20 Balanced valves


59


5) Actuators:-

A hydraulic actuator receives pressure energy and converts it to

mechanical force and motion. An actuator can be linear or rotary. A linear

actuator gives force and motion outputs in a straight line. It is more

commonly called a cylinder but is also referred to as a ram, reciprocating

motor, or linear motor. A rotary actuator produces torque and rotating motion.

It is more commonly called a hydraulic motor or motor.

5.1 Cylinders A cylinder is a hydraulic actuator that is constructed of a piston or

plunger that operates in a cylindr ical housing by the action of liquid under

pressure. Figure shows the basic parts of a cylinder. Cylinder housing is a

tube in which a plunger (piston) operates. In a ram-type cylinder, a ram

actuates a load directly. In a piston cylinder, a piston rod is connected to a

piston to actuate a load. An end of a cylinder from which a rod or plunger

protrudes is a rod end. The opposite end is a head end. The hydraulic

connections are a head-end port and a rod-end port (fluid supply).

a. Single-Acting Cylinder.

This cylinder only has a head-end port and is operated

hydraulically in one direct ion. When oil is pumped into a port, it pushes on a

plunger, thus extending it. To return or retract a cylinder, oil must be

released to a reservoir. A plunger returns e ither because of the we ight of a

load or from some mechanical force such as a spring. In mob ile equipment,

flow to and from a single-acting cylinder is controlled by a reversing

directional valve of a single-acting type.

b. Double-Acting Cylinder.

This cylinder must have ports at the head and rod ends.

Pumping oil into the head end moves a piston to extend a rod while any oil

in the rod end is pushed out and returned to a reservoir. To retract a rod,

flow is reversed. O il from a pump goes into a rod end, and a head-end port is

connected to a llow return flow. The flow direction to and from a double-

acting cylinder can be controlled by a doub le-acting directional valve or by

actuating a control of a reversible pump.


60


c. Differential Cylinder. In a differential cylinder, the areas where pressure is applied on a

piston are not equal. On a head end, a full piston area is availab le for applying

pressure. At a rod end, only an annular area is availab le for applying pressure.

A rod’s area is not a factor, and what space it does take up reduces the volume

of oil it will hold. Two general rules about a different ial cylinder are that. With

an equal GPM delivery to either end, a cylinder will move faster when

retracting because of a reduced volume capacity.

With equal pressure at e ither end, a cylinder can exert more force

when extending because of the greater piston area. In fact, if equal pressure is

applied to both ports at the same time, a cylinder will extend because of a

higher resulting force on a head end.

d. Piston-Type Cylinder.

In his cylinder, a cross-sectional area of a piston head is referred to

as a piston-type cylinder. A piston-type cylinder is used mainly when the push

and pull functions are needed.

A single-acting, piston-type cylinder uses fluid pressure to apply force in

one direction. In some designs, the force of gravity moves a piston in the

opposite direct ion. However, most cylinders of this type apply force in both

direct ions. Fluid pressure provides force in one direction and spring tension

provides force in the opposite direction.

Fig 5.1 Piston Type cylinder

Figure shows a single-act ing, spr ing- loaded, piston-type cylinder. In this

cylinder, a spring is located on the rod s ide of a piston. In some spring- loaded

cylinders, a spring is located on a blank s ide, and a fluid port is on a rod end of a

cylinder.

Most piston-type cylinders are doub le-acting, which means that

fluid under pressure can be applied to either s ide of a piston to provide

movement and apply force in a corresponding direction. Figure shows a double-

acting piston-type cylinder this cylinder contains one piston and piston-rod

assemb ly and operates from fluid flow in e ither direct ion. The two fluid ports,

one near each end of a cylinder, alternate as an inlet and an outlet, dependin g

on the directional-contro l valve flow direct ion. This is an unbalanced cylinder,


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which means that there is a difference in the effect ive working area on the two

sides of a piston. A cylinder is normally installed so that the head end of a

piston carr ies the greater load; that is, a cylinder carr ies the greater load

during a piston-rod extension stroke.

Figure shows a balanced, double-acting, piston-type cylinder. The

effective working area on both sides of a piston is the same, and it

exerts the same force in both directions.

5.2. Double-acting, piston-type cylinder


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e. Cushioned Cylinder.

To slow an action and prevent shock at the end of a piston

stroke, some actuat ing cylinders are constructed with a cushioning

device at either or both ends of a cylinder. This cushion ids usually

a metering device built into a cylinder to restrict the flow at an

outlet port, thereby slowing down the motion of a piston .Figure

shows a cushioned actuating cylinder

Fig 5.3 Cushioned, actuating cylinder


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f. Lockout Cylinders.

A lockout cylinder is used to lock a suspension

mechanism of a tracked vehic le when a vehic le functions as a

stab le platform. A cylinder also serves as a shock absorber when

a vehicle is moving. Each lockout cylinder is connected to a road

arm by a control lever. When each road whee l moves up, a

control lever forces the respective cylinder to compass..

Hydraulic fluid is forced around a piston head through

restrictor ports causing a cylinder to act as a shock absorber.

When hydraulic pressure is applied to an inlet port on each

cylinder ’s connecting eye, an inner control-valve piston is forced

against a spr ing in each cylinder. This act ion closes the

restr ictor ports, blocks the main piston’s motion in each

cylinder, and locks the suspension system


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5.2 Hydraulic Motors

Hydraulic motors convert hydraulic energy into

mechanical energy. In industrial hydraulic c ircuits, pumps

and motors are normally combined with a proper valving and

piping to form a hydraulic-powered transmission. A pump,

which is mechanically linked to a prime mover, draws fluid

from a reservoir and forces it to a motor. A motor, which is

mechanically linked to the workload, is actuated by this flow so

that mot ion or torque, or both, are conveyed to the work.

Figure 4-9 shows the basic operations of a hydraulic motor.

Figure 5.4 Basic operations of a hydraulic motor

The princ ipal ratings of a motor are torque, pressure, and

displacement. Torque and pressure rat ings indicate how much

load a motor can handle. Displacement indicates how much flow is

required for a spec ified drive speed and is expressed in cub ic

inches per revo lutions, the same as pump displacement.

Displacement is the amount of oil that must be pumped into a

motor to turn it one revolution. Most motors are fixed-

displacement; however, var iab le-displacement piston motors are

in use, mainly in hydrostatic drives. The main types of motors are

gear, vane, and piston. They can be unidirectional or reversib le.

(Most motors designed for mobile equipment are reversib le.)


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Fig 5.5 Gear-type motor

a. Gear-Type Motors.

Figure shows a gear-type motor. Both gears are dr iven gears, but

only one is connected to the output shaft. Operation is essentially the

reverse of that of a gear pump. Flow from the pump enters chamber A

and flows in e ither direction around the ins ide surface of the casing,

forcing the gears to rotate as indicated. This rotary motion is then

availab le for work at the output shaft.


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Fig 5.6 Vane-type motor

b. Vane-Type Motors.

Figure shows a vane-type motor. Flow from the pump enters the

inlet, forces the rotor and vanes to rotate, and passes out through the

outlet. Motor rotat ion causes the output shaft to rotate. S ince no

centrifugal force exists unt il the motor begins to rotate, something,

usually spr ings, must be used to init ia lly ho ld the vanes against the

casing contour. However, spr ings usually are not necessary in vane-type

pumps because a drive shaft init ia lly supplies centrifugal force to ensure

vane-to-casing contact.

Fig 5.7 Pressure differential on a vane-type motor


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Vane motors are balanced hydraulically to prevent a rotor from side-

loading a shaft. A shaft is supported by two ball bearings. Torque is

deve loped by a pressure difference as oil from a pump is forced through a

motor. Figure shows pres-sure different ial on a s ingle vane as it passes

the inlet port. On the trailing side open to the inlet port, the vane is

subject to full system pressure. The chamber leading the vane is subject

to the much lower outlet pressure. The difference in pressure exerts the

force on the vane that is, in effect, tangent ial to the rotor. This pressure

difference is effective across vanes 3 and 9 as shown in Figure. The other

vanes are subject to essentially equal force on both sides. Each wil l

deve lop torque as the rotor turns. Figure shows the flow condition for

counterc lockwise rotation as viewed from the cover end. The body port is

the inlet, and the cover port is the outlet. Reverse the flow, and the

rotation becomes clockwise.

In a vane-type pump, the vanes are pushed out against a cam ring by

centrifugal force when a pump is started up. A design motor uses stee l-

wire rocker arms to push the vanes against the cam r ing. The arms pivot

on pins attached to the rotor. The ends of each arm support two vanes

that are 90 degrees apart. When the cam ring pushes vane A into its s lot,

vane B slides out. The reverse a lso happens. A motor’s pressure plate

functions the same as a pump's. It seals the side of a rotor and ring

against internal leakage, and it feeds system pressure under the vanes to

ho ld them out against a ring. This is a simple operat ion in a pump

because a pres-sure plate is right by a high-pressure port in the cover.

Fig 5.8 Rocker arms pushing vanes in a pump


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6) Fittings and Connectors Fittings are used to connect the units of a fluid-powered system,

including the individual sections of a circulatory system. Many

different types of connectors are availab le for fluid-powered systems.

The type that you will use will depend on the type of circulatory system

(pipe, tub ing, or flexib le hose), the fluid medium, and the maximum

operating pressure of a system. Some of the most common types of

connectors are described below:

a. Threaded Connectors. Threaded connectors are used in some low-pressure liquid-powered

systems. They are usually made of stee l, copper, or brass, in a var iety

of designs. The connectors are made with standard female threading

cut on the inside surface. The end of the pipe is threaded with outside

(male) threads for connecting.

Fig 6.1 Threaded-pipe connectors


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Standard pipe threads are tapered slight ly to ensure tight

connections.

To prevent se izing (threads sticking) apply a pipe-thread

compound to the threads. Keep the two end threads free of the

compound so that it will not contaminate the fluid. Pipe

compound, when improper ly applied, may get inside the lines and

harm the pumps and the control equipment.

b. Flared Connectors. The common connectors used in circulatory systems consist

of tube lines. These connectors provide safe, strong, dependab le

connect ions without having to thread, weld, or solder the tub ing. A connector consists of a fitting, a sleeve, and a nut

Fig. 6.2 Flared tube connector

Fittings are made of steel, aluminum alloy, or bronze. The fittings

should be of a material that is similar to that of a sleeve, nut, and

tubing. Fittings are made in unions, 45- and 90-degree elbows, Ts, and

various other shapes. Figure shows some of the most common fittings

used with flared connectors.

Fittings are available in many different thread combinations.

Unions have tube connections on each end; elbows have tube connections

on one end and a male pipe thread, female pipe thread, or a tube

connection on the opposite end; crosses and Ts have several different

combinations.

Tubing used with flared connectors must be flared be fore be ing

assembled. A nut fits over a sleeve and, when t ightened, draws the

sleeve and tub ing flare tight ly against a male fitting to form a seal. A

male fitting has a cone-shaped surface with the same angle as the


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ins ide of a flare. A s leeve supports the tube so that vibration does not

concentrate at the edge of a flare but that it does distr ibute the

shearing action over a wider area for added strength. Tighten the

tub ing nuts with a torque wrench to the value specified in applicab le

regulations.

If an aluminum alloy flared connector leaks after tightening to the

specified torque, do not t ighten it further. Disassemb le the leaking

connector and correct the fault. If a steel connector leaks, you may

tighten it 1/6 turn beyond the spec ified torque in an attempt to stop

the leak. If you are unsuccessful, disassemble it and repair it.

Flared connectors will leak if—

· A flare is distorted into the nut threads.

· A sleeve is cracked.

· A flare is cracked or split.

· A flare is out-of-round.

· A flare is eccentric to the tube’s OD.

· A flare's inside is rough or scratched.

· A fitting cone is rough or scratched.

· The threads of a fitting or nut are dirty, damaged, or broken.


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Fig 6.3 Flared-tube fittings


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c. Flexible-Hose Couplings. If hose assembly is fabricated with d attachab le couplings (Figure ),

use the same couplings when reacting the replacement assembly, as

long as the fa ilure (leak) did not occur at a coupling. Failure occurred

at a coupling, card it.

Fig 6.4 Field-attachable couplings

When measuring a replacement hose assemb ly for screw on a

pings measure from the edge a retaining bolt.

Hose in hose b locks and n in a bench vice for effective

cutt ing, a blade should have 24 or 32 teeth per inch. To remove an

old coupling on a hose assemb ly that is fabricated with

permanently attached couplings, you just discard the ent ire

assembly.


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d. Reusable Fittings. To use a skived fitting you must strip (skive) the hose to a length

equal to that from a notch on a fitting to the end of the fitting. (A

notch on a female portion of a fitting in Figure indicates it to be a

skived fitting.) To assemble a conductor using skived fittings—

Fig. 6.5 permanently attached couplings

· Determine the length of the skive.

· Make a cut around the hose with a sharp knife. Make sure

that you cut completely through the rubber cover of the hose.

· Cut lengthwise to the end of the hose. Lift the hose flap and

remove it with pliers.

· Repeat the process on the opposite end of the hose.

· Place the female portion of the fitting in a bench vice and secure it in place.

· Lubricate the skived portion of the hose with hose

lubricant (hydraulic fluid or engine oil, if necessary).

· Insert the hose into the female socket and turn the hose counterclockwise until it bottoms on the shoulder of the female socket, then back off 1/4 turn.

· Place the female socket in an upright position (Figure 6.5)

and insert the male nipple into the female socket.

· Turn the male nipple clockwise (Figure 6.5) until the hex is within 1/32 inch of the female socket.

· Repeat the above process on the opposite end of the hose.


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7) CUTTING PROCEDURE

1. Hydraulic Vane Pump:-

1) First of all the vane pump oil is drained.

2) After washing the marking is done

3) Then the cut the cover on the marking part with the help of hacksaw.

4) After then we cuts the spring assembly in pump & also the body by using hand

grinder.

5) The grinder is used to finish the rough cutting surface. In small area finishing

the files are used.

6) After the finishing clean & paints with the color to inner & outer side & also

paint & dry in the air.

7) After this process all the removed part assemble it.

8) Then we paint the parts with various shades of color.

Fig. 7.1 Cutting & grinding of vane pump


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2. Gear Pump:-

1) First of all the Gear pump oil is drained.

2) The gear pump cover is open, it clean with cotton, & kerosene. Then foam

water is used to washing.

3) After washing the marking is done on the gear pump.

4) Then the cut the cover of marking point with the help of hacksaw.

5) Then we cut the body of pump by using hand grinder.

6) The grinder is used to finish the rough cutting surface in small area & for

finishing the file is used.

7) After finishing it clean & paints with the color & to inner & outer side.

8) After this process both the gears are assemble in casing.

Fig. 7.2 Dismantling & cutting of gear pump


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3. Double Acting Cylinder:-

1) First cleaning the double acting cylinder in outside.

2) Then we remove connector from cylinder, bolt or stud & dismantle all part of

cylinder like piston, piston rod, oil seal etc.

3) Then we again clean the all part with kerosene.

4) Then we cut cylinder block by using grinder.

5) After cutting us removes the sharp edges by using file.

6) Then we paint it.

4. Single Acting Cylinder:-

1) First cleaning the single acting cylinder in outside then we remove connector

from cylinder, bolt or stud & dismantle all part of cylinder like piston, piston

rod, oil seal etc.

2) Then we again clean the all part with kerosene.

3) Then we cut the cylinder block by using hacksaw & grinder.

4) Then we paint with red color on cutting edge.

5) After drying the color we assemble the all parts & then mount on a board

with the help of clamps.


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5. Flow Control Valve:-

1) First cleaning the flow control valve in outside.

2) After cleaning the throttle position & diverting position by kerosene.

3) Marking is done on flow control valve.

4) Then cut the flow control valve block by using grinder.

Fig. 7.3 cutting of flow control valve

6. Hoses:-

1) Firstly clean the hoses outside by using cloth.

2) Then we cut the hoses by using of hacksaw.

3) Then paint it with red color.

8) TOOLS AND EQUIPMENT

Grinders and Grinding Machines Information:-

Grinders and grinding machines use an abrasive that is bonded to a wheel, belt

or disc to remove material and improve surface finish. Dev ices can be pneumatically

driven or powered by a combustion engine or electric motor.

Grinders and grinding machines can use single phase or three phase power and

are available in a range of voltages 60 Hz power is used in North America. 50 Hz

power is used internationally.

Features:-

Optional features include

Cabinets and enclosures


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Double sided disks

Dressing systems

Dust collection or filtration systems

Related Products & Services:-

Honing, Lapping, and super finishing Machines

Honing, lapping and super finishing equipment are used to improve surface

finish or geometry to tight tolerances.

Hacksaw:-

A hacksaw is a fine tooth hand saw with a blade held under tension in a frame,

used for cutting materials such as metal or plastics. Hand held hacksaws consist of a

metal arch with a handle, usually a pistol grip, with pins for attaching a narrow

disposable blade. A screw or other mechanism is used to put the thin blade under

tension. Te blade can be mounted with the teeth facing toward or away from the

handle, resulting in cutting action on either the push or pull stroke.

On the push stroke, the arch will flex slightly, decreasing the tension on the

blade, often resulting in an increased tendency of the blade to buckles and crack.

Cutting on the pull stroke increases the blade tension and will result in greater control

for the cut and longer blade life.


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Blades: -

Blades are available in standardized lengths, usually 10 or 12 inches for a

standard hand hacksaw. Junior hacksaws are half this size. Powered hacksaws may

use large blades in a range of sizes, or small machines may use the same hand blades.

Electric hacksaw:-

A power hacksaw (or electric hacksaw) is a type of hacksaw that is powered

either by its own electric motor or connected to a stationary engine. Most power

hacksaws are stationary machines but some portable models do exist. Stationary

models usually have a mechanism to lift up the saw blade on the return stroke and

some have a coolant pump to prevent the saw blade from overheating.


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9) Costing

Sr. no. Object Amount

1 Gear Pump 2,500

2 Vane Pump 3,500

3 Single Acting cylinder 1,500

4 Double Acting cylinder 3,000

5 Flow control valve 950

6 Direction Control Valve 3,000

7 Connectors 600

8 Hoses 600

9 Coupler 900

10 Boards 850

11 Nut &bolt 60

12 Fabrication 600

13 Color 500

14 Painting 500

15 Kolhapur visit 1,000

16 Traveling 200

Total 20,150


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10) CONCLUSION

The main purpose of our project is to collect all information about hydraulic

devices. In this project we show all internal parts of gear pump and vane pump, as

well as try to show Direction control valve, flow control valve, single and double

acting cylinder, Hose pipes. With its mechanism in board mounted condition. & it’s

works properly.

This project is good collection of Gear pump, vane pump and other parts. We

try to develop our automobile lab, hence we select this project.


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11) Reference

1. Chapter2_Hydraulics_control_in_machine_tools nptel.

2. Hydraulic Pumps – pumpschool.com

3. en.wikipedia.org/wiki/Hydraulic pump

4. Field Manual, No. 5-499, Headquarters, Department of the

Army.

5. BASIC HYDRAULIC SYSTEMS AND COMPONENTS,

Sub course Number AL 0926, EDITION A,US Army Aviation

Logistics School Fort Eustis, Virginia 23604-54394, Credit

Hours, Edition Date: September 1994

6. Collage library.

7. McNeil, Ian (1990). An Encyclopedia of the History of Technology. London: Rout ledge. p. 961. ISBN 0-415-14792-1.

8. Jump up Housel, David A. (1984), From the American System to Mass

Production, 1800-1932: The Development of Manufacturing Technology in the United States, Baltimore, Maryland: Johns Hopkins University Press, ISBN 978-0-8018-2975-8, LCCN 83016269

9. Jump up to: Hunter, Louis C.; Bryant, Lynwood (1991). A History of Industrial Power in the United States, 1730-1930, Vol. 3: The Transmission of Power. Cambridge, Massachusetts, London: MIT Press. ISBN 0-262-08198-9.

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB0QFjAA&url=http%3A%2F%2Fscience.howstuffworks.com%2Ftransport%2Fengines-equipment%2Fhydraulic3.htm&ei=QJEZVdjyH4ezuASqh4HADg&usg=AFQjCNGdf98EKCP6jMRR59dtAO8sURvtdg&bvm=bv.89381419,d.c2E

http://en.wikipedia.org/wiki/International_Standard_Book_Number

http://en.wikipedia.org/wiki/Special:BookSources/0-415-14792-1

http://en.wikipedia.org/wiki/David_A._Hounshell


http://en.wikipedia.org/wiki/Special:BookSources/978-0-8018-2975-8

http://en.wikipedia.org/wiki/Library_of_Congress_Control_Number

http://lccn.loc.gov/83016269


http://en.wikipedia.org/wiki/Special:BookSources/0-262-08198-9

hydraulic devices Important project report 1

Engineering

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