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UNIT 3 HYDRAULICS PUMP

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2 1. (Non positive displacement pump)

( Hydrodynamics)

PUMP Non-positive displacement pump Positive displacement pump

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2. (Positive displacement pump)

( Hydrostatics)

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2 (Hydraulic pump) 3

HYDRAULIC PUMP

GEAR PUMP ROTARY VANE PUMP PISTION PUMP

EXTERNAL GEAR PUMP INTERNALLY PRESSURIZED RADIAL PISTION PUMP

INTERNAL GEAR PUMP EXTERNALLY PRESSURIZED AXIAL PISTION PUMP SCREW PUMP

RING GEAR PUMP

CONSTANT PUPM CONSTAN, ADJUSTABLE AND VARIABLE CAPACITY PUPM

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Externally toothed gear pump

Internally toothed gear pump

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3 () 1. Y N ..1) ..2) 2 - (Non-Positive displacement) - (Positive splacement) ..3) - ..4) - ..5) (Centrifugal pump) (Impeller) - ..6) -

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2. ..1) 1. 2. ..2) 3. ..3) 4. ..4) 5. 6. ..5) 7.

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3. 3

Hydraulic pumps 1. 2. 3.

CONSTANT PUPM CONSTAN, ADJUSTABLE AND VARIABLE CAPACITY PUPM

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Exercise sheet 3 1. 1) N

2) Y 3) N 4) Y 5) Y 6) Y

2. 1) 2

2) 5 3) 4 4) 7 5) 3

3. 1. Gear Pump

2. Rotary vane pump 3. Piston pump

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Ring gear pump

(Screw pump)

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5 (Work piece Slide)

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System pressure p 15 20 25 30 35 40 45 50 bar Floweret q Vmin

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Solution description Once the hydraulic circuit has been assembled, valve (3) should be fully opened. Now close this valve slowly to set the first p value as shown on the pressure gauge (2). The maximum attainable pressure is 60 bar, governed by a pressure relief valve built into the pump which is set to this value.

Evaluation System pressure p 15 20 25 30 35 40 45 50 bar Floweret q 2.33 2.31 2.29 2.28 2.26 2.24 2.22 2.20 Vmin Conclusions As the pressure rises, the pump delivery falls slightly. In theory, the characteristic curve for the pump should be a straight line. The decrease in pump delivery is due to internal leakage losses, which become greater as the pressure increases. The ratio of the measured pump delivery and theoretical pump delivery is the effective volumetric efficiency of the pump. Note For technical reasons, the actual value recorded in this exercise is the power consumption of the electric motor or the premature opening of the pressure relief valve. The pump is dimensioned for a maximum pressure of 250 bar (see data sheet). An electric motor with an appropriately high rating would be required to achieve this. This would not, however, be meaningful, since the exercises are carried out with a maximum pressure of 60 bar.

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Q P -

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(Variable displacement vane pump)

(Pressure compensate displacement vane pump)

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(Unbalanced vane pump)

(Piston pump) - 1. (Radial piston pump)

2. (Axial piston pump)

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(Axial piston pump)

()

Maximum angle

Less angle

No angle

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(Swashplate piston pump) - FN = Friction bearing force FT = Torque force F = Output force

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(Swashplate)

Maximum swashplate angle Decreased swashplate angle Zero swashplate angle Maximum displacement Partial displacement Zero displacement

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(Pump selection) , , , , , , 1. (actuator) 2. 3. 4. 5. 6. 7. 8. (Hydraulic tank) - - - -

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() 15 30 45 60 100 150 200 350 500 A 26 29 26 445/8 54 60 64 721/8 96 B 17 24 24 27 30 321/2 34 401/2 40 C 18 20 22 231/8 251/2 29 33 411/2 34

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baffle plate

Inlet & Return

Inlet & Return

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Accessories Hydraulic Components (filter), (Heater, Cooler), (Accumulator), (Pressure gauge, Flow meter) (filter) 1. (strainer)

(strainer)

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check valve 100 2 1. (mesh) 1 2. (micron) 1 1/1000 1/1,000,000 40 (100 ) (70 ) 2. (pressure filter)

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3. (return line filter)

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Filtering of the main flow By-pass flow filtering

Return flow filter Pump inlet filter Pressure line filter Advantages economical

simple maintenance protects pump from contamination

smaller pore size possible for valves sensitive to dirt

smaller filter possible as an additional filter

Disadvantages contamination can only be checked having passed through the hydraulic components

difficult access, inlet problems with fine pored filters result : cavitation

expensive low dirt-filtering capacity

Remarks frequently used can also be used ahead of the pump as a coarse filter

requires a pressure-tight housing and contamination indicator

only part of the delivery is filtered

/

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(Coolers and Heaters) ( 25 ) 1. (Air-blast heat exchanger)

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2. (Shell and tube water-cooled head exchanger)

(tube) 2 2 4 (shell) -

Air cooler Water cooler Description The hydraulic fluid flows from

the return through a pipe which is cooled by a fan

Pipes conveying oil are by-passed by coolant

Advantages Low running costs Easy installation

Larger heat losses can be diverted No disturbing noises

Disadvantages Disturbing noise Higher operating costs Susceptible to contamination and corrosion (coolant)

/ Air Cooler Water cooler

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3. (Heating element)

(Heating element)

Estimated hydraulic fluid temperatures Stationary system : 35-55C in the oil reservoir

Mobile system : 45-65C in the oil reservoir

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4 () 1.

. . . .

2. . . . .

3. . . . 2 .

4. . . . .

5. 3 . . . .