basic training hydralic

8/9/2019 Basic Training Hydralic

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basictraining

- Hydraulics -


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Hydraulic basicstopics:

- Hydraulic fluid

common sorce of contamination in a hydraulic system filtration oil analysis purity class of hydraulic fluid

- hydr. symbols according to DIN ISO 1219

types of valves

- Pump systems- Tube coupling system

- Maintenance and Assembly____________________________________________________________________________________________________________

- Introduction to the hydraulic control system of the WKP 600 S reading and understanding the hydr. diagram

technical site visiting and operation of the WKP 600 S

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pressure

force

volumespeed

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Function of the fluid in the Hydraulic system:

Transmit the force and movementHydralic power is defined as the product of pressure and flow rate

Hydralic fluid

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Hydralic fluid

Subdivision of the hydralic fluid mineral oils:

According to DIN 51524 the hydraulic oil is subclassify into 4 groups.These oils are determinated by the used additives:

Group H mineral oils without additional additives Lubricating oils

Group HL improvement of the resistance to ageing and corrosion used by system pressure to 200bar and normally thermal loads

Group HLP further improved of the resistance to wear and loadcapacity, as well as improve the viscosity-temperature characteristics

Group HLPD additional properties as dispersing (water retaining

effect) and detergent (cleaning effect)

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generally used in hydralic systems

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Hydralic fluid

chem. characteristics:

corrosion protection

low viscosity changes- viscosity pressure characteristics- temperature-dependence of viscosity

compatibility with the system- no swelling of the seal materials, paints,

flame-resistant- high flashing point

low thermal expansion coefficient rule of thumb : oils increase in volume by 0,63..0,76 % of their total

volume for each 10C temperature increase



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oxidation resistance(no acid formation)- ageing resistance

Less air input and good air output- high temperatur makes the air release property significantly

worse

good dielectric(isolating) properties

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Hydralic fluid

chem. characteristics:

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shear stability of a fluid

- mechanical load of the fluid at control edges and valve seats

lubrication ability- is indicated by the Brugger-test according to DIN 51347-2

high density-high density allow to transfer higher performances

low compressibility

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Hydralic fluid

mech. and phsical characteristics:

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low foam formation

high wear resistance to: dirt (abrasion)

cavitation (fatigue)

corrosion (e.g. by water)

dirt removal

good filterability- attention: by filteration with filterelements


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Hydralic fluid

contaminationReason of contamination:



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Hydralic fluid

contaminationReason of contamination:

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e.g. typical clearances on valves:- Servo valve => 1..4m

- Prop. Valve => 1..6m- Directional control valve => 2..8m

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Hydralic fluid

contamination

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assembly

tinder,welding spatter,

rubber particles,liquid remaining,grinding dust,metal chips,sand, fibres,etc.

missing or

inadequatemaintenance

no filter replacement

filling with non-filtered oil

lack of cleanlinessby componentreplacement

lacking inspection ofthe hydraulic fluid atregular intervals

Reason of contamination:

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Hydralic fluid

contamination

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plant operations

- inner systeminfluences inner contamination

accrue constantly

dirt particles will beproduced by wearnessor result by the aging

of the oil

plant operations- externalsysteminfluences

biggest dirtingress is cousedby cylinder

non-closed system

openings

Reason of contamination:

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Consequences of wear:

Abrasion: caused by particles between

reciprocating surfaces

effects: increase in play, external oil leak, loss of holding ability and

additional wear and contamination of the fluid

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Hydralic fluid

contamination

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Erosion: existing particles clash with high velocity against the corners

and edges of the system

effects: increase in play, leaking/damaged seat and plug, piston jamming

and


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Hydralic fluid

contamination

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Deposition by adhesion: excessive load and/or a reduction in

fluid viscosity can reduce the oil film

thickness

effects: clamping of the materials (metal-to-metal contact)

malfunction of the componentes, e.g. piston jamming at valves

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Hydralic fluid

contamination

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Surface fatigue: surfaces damaged by particles

are subjected to repeated stress

effects: smallest cracks in the surface are

hollowed out this causing a break off the material and


Oil ageing: leads to deposits, filter will clogging quickly

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Hydralic fluid

contamination

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Oil care by:

system filters

permanent offline filter units

mobile bypass filteration

Stefan Hertel Seite 17

Hydralic fluid

oil analysis and care

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Overview system filters:

suction filters=> pump protection

pressure filters=> direct protection of the components

return line filters=> filters the contamination which hasentered the system as a result of component wear

tank breather filters=> protection contamination from entering the tankduring tank breathing

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Hydralic fluid


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Oil analysis by:

oil sampling for analysis in laboratory

- detailed analysis (viscosity, Brugger,contained additives, wear components, water content, etc. )

for particle countint by oil diagnosticdevice

- immediate particle counting at place

permanent oil analysis byConditionMonitoring system

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Hydralic fluid


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Hydralic fluid

Brugger test



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Limits:- For general hydraulic: >30 N/mm

- For fast and proportional hydraulic: >50 N/mm

(Water has an Brugger value of about 19 N/mm)

Hydralic fluid

Brugger test

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Cleanliness requirements for hydraulic components

classification of solidparticle contaminationfollows ISO 4406/1999:

to determine the cleanlinesslevel the particles present in100 ml fluid are counted,sorted according to size &quantity and classified intoparticle ranges

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Hydralic fluid


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Elements of hydraulic

circuits

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hydraulic circuit = - muscle

electic control = - nervous system

mechanicalenergy

mechanicalenergy

hydraulic energy

pumps lines valvescylinder/motors/

rotary drives

energy converter tranporter of

energy control elements actuators

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Elements of hydraulic circuits

hydr. symbols (DIN ISO 1219)



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Valves

Characteristics connection interfaces

Standardized connection interfaces (according to DIN 24340A6/ISO 4401) allow worldwide replacement of valves byindependentce from manufacturer



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Valves

direction valves - direct operated

Characteristics the housing is mode of pressure-tight

hydraulic castings iron

the canals (P-T-A-B) are poured in withthe housing at the same time

main bore is lapped

the pistons ring groove serve as pressure balancing and for abetter the forming of a lubricating film

Important:piston-sleeve-valves show a certain leakage=> oil flow rate from range with high pressure to range withlow pressure e.g. canal P to A/B or canal A/B to T



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Operation modes:

electically4/3 direction valve; direct operated

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normal

position

Solenoid "B" actuated=> flow rate from P-A; B-T

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Valves


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Operation modes:

mechanicallyactivity takes a variety of forms. The returnes intonormal position achieved by a spring normally

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activity by cam/roles activity by

hand lever

Valves


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Operation modes:

emergency actuation a special formof mechanical actuation

in case of piston jamming or power failure, the valve(piston) can be moved.

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Valves


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Operation modes:

fluidic activitybecause of the big actuation forces direct operatingover valve size NG 10 is not useful

Operation is made by

pressurisation theauction cylinders ofthe valve piston

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Valves

direction valves pilot operated

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Operation modes:

electro-hydraulicvalve is pilot operated by an NG6valve witch is mounted on the main valve

internal pilot oil supply internal/external:

a minimum pilot pressure (7-15 bar) must be ensured for all operatingconditions of the directional valve

=> pilot pressure can be worn internal from the P-chanal orexternal by the X-port

=> in case of high dynamic pressure in the return line (T-chanal)external pilot oil drain, by the Y-port, is needed

a malefunction of pilot operated valves is often the result ofproblems in pilot oil supply

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Valves

direction valves pilot operated

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Operation modes:

electro-hydraulic

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Solenoid B" actuated=> flow rate from P-A; B-T

Solenoid A" actuated=> flow rate from P-B; A-T

Valves

direction valves pilot operatednormalposition

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Valves

direction seat valvesCharacteristics piston-sleeve-valves show a certain leakage due to their play

between piston and housing

seat valves realised the leak-tight sealling of the ports by aball or conical shape and seat

seat valves require a highly operation force, this means

particularly stong solenoid disadvantage of direct operated seat valves

is a small stroke and, as a result, the small oilvolume flow rates

large volume flow rates can be realized bypilot control of the main stage


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Functional principle

direct operated

pilot operated

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Valves

direction seat valves

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Characteristics

slip-in cartridge valves designed for compact block

installation

Leak-free valve charecteristic as:

- hydraulic controlled seat/check,

or pressure valve=> depanding of pressure build-up in the

main ports A and B

- active pilot operated 2/2-waycartridge valve=> Pilot pressure actively opens and closes themain poppet independent of pressure in the main ports

Valves

2 way slip-in cartridge


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Functional principle The varying of the valve elements;

slip-in cartridge, cover, and pilot systempermit combinations for singleand complex functions

Valves2 way slip-in cartridge

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Valves


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Valves2 way slip-in cartridge

normally closednormally open

sleeve

cone

spring

spacer ring

coverunit

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Valves


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Valvescheck valves

Characteristics

component parts: hardened ball or cone

seat

spring (generally 0,55 bar)

Leak-free valve charecteristic as:- line mount check valve

- cartridge designe for

block installation

- flange design for directly mount on

surfaces


Valves


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direct operated check valve- provide free flow in one direction (1->2)

and block the flow in the counterdirection (2->1)

pilot operated check valve

- provide free flow in direction (3->2).The flow in the counter direction (2->3) is

only given when pilot pressure is appliedon port 1

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Valvescheck valves

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Valves


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Valvespressure valves

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Function types

pressure relief valve- primarily protection of system pressure

- pump control of variable displacenemt pumpswith pressure compensator

pressure reducing/control valve

- the secondary pressure is limited to thepreset pressure value independently of the input pressure

pressure switching valves- a hydralic switching operation will be

triggered when it reaches the adjustablepressure value=> e.g. pressure dependent shut off valve,

pump venting valve,

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Pumps


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The choise of a pump type depends on the applicationand the cycle as well as:

combination of possible pump controller

necessity of simultaneous motions

-> pump controls with double pumps or pumpcombination of different pump designs

system pressure

availability and ease of maintenance maximal sound pressure level

price

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Pumps

selection

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Pumps


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Pumps

Overview pump types

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Pumpdesign

max. pressurerange[bar]

Flow rateDisplacement

Speed range[U/min]

Sound pressurelevel

[dB(A)]

external gearpump

160..250 fixed 800..3000 < 60

internal gearpump

160..210fixed

800..3000< 50

vane pump 160..210fixed/

variable600..3000

< 60

axial pistonpump 350

fixed/variable

500..2500 < 75

Radial pistonpump 280/350

fixed/variable

500..2500 < 70

screw pump 80fixed

3000..5000 < 50

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Pumpen


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Pumpenaxial piston pump

Parker PVplus

component parts

1. servo piston

2. rolling bearing

3. shaft drive4. drain port

5. swash plate

6. piston and slipper

7. barrel

8. pump body

9. pump compnesator

10. servo spring

3

9

1

2

8

4

5

6

7

10


Pumpen


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Rotating group

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cylinder block

piston andslipper

valve plate

Pumpenaxial piston pump

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Pipe fitting system


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The centre unit - effects thetransition from the 24taper ofthe fitting body to the 37flare

connection

24taper

37flareconnection

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the Walterscheid flare fitting design consists of fourcomponents:

fitting body according to DIN 2353 centre unit Ioose collar

nut

Pipe fitting systemWalterscheid flare tube fitting 37


Pipe fitting system


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The clear advantage for the user:

Higher assembly safety than cutting ring

Lower starting torque

High precision tightness due to elastomer sealingfor both points of separation

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Pipe fitting systemWalterscheid flare tube fitting 37

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M i t d A bl


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Maintenance and Assembly

The most important basic principles of a hydraulictechnician are:

pay attention to meticulous cleanliness in his surroundings andduring assembly work (even if it is sometimes difficult).

never install a component that is dirty or damaged.

never do any assembly work on a unit if the electric motor isrunning (not even in bypass!!) or if the accumulator is filled.

never dismantlea component or loosen a screw connection ifthe plunger is not supported mechanically, or if any other

dangerous movement can occur.

Never mix different media.




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The most important basic principles of a hydraulictechnician are:

The first step when switching the electric motor on is to check thedirection of rotation while bleeding the pressure line simultaneouslyusing suitable connections (the pump can be damaged already byrunning 10 sec in the wrong direction of rotation).

After that a static pressure test follows without activating valves andwithout switching on the accumulator.

Then the air bleeding of the pipes and the components such ascylinders and motors follows.

First start is always at lowest pressure (set pressure relief valve or

pump controller to minimum), slowest speeds (choke valves and setvalues of prop. valves set at minimum) and always without theaccumulator being switched on.




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yAvoid contaminations

In order to obtain perfect performance and the longest possiblelife span of a hydraulic system, the assembly andcommissioning are of decisive importance, as well as perfect

project planning.

The component gap widths of sometimes less than 2mmrequire the cleanest working manner during assembly.

Sources of contamination during interim storage are: dust, shavings, fibers, remains of paint, sand, remains of

packaging, water, means of preservation, rust

Compulsory: Check every component visually beforeinstallation and pay attention to the exact closure of theconnections.




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yAvoid contaminations

Sources of contamination are: During unit assembly (flexible tubes, piping, oil, cleaning rags

welding, grinding, drilling, etc.) scaling, welding beads, rubber parts, caustic and flushing agents,separating and wheel wharf, drilling chips, sealing component,paint, fibers

Compulsory: Connections of every component must be kept closed until theyare about to be installed.

No mechanical work during hydraulic assembly Clean piping and flexible tube lines also when fitting and clean

thoroughly before final assembly Use cleaning cloths that are free of fibers and fluff Never do any subsequent welding on pipes or tanks Clean oil tanks thoroughly before filling with oil only fill in finely strained oil




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Avoid contaminations

Dismantling Sources of contamination are: pipes and

connections left open Compulsory: in the case of unit dismantling

the oil should be drained off the oil tank should be cleaned thoroughly

change the filter elements (include spare elements in the listof pieces)

close connections of every component immediately do not do any more mechanical processing

close pipe and hose lines never do any welding on pipes or tanks afterwards pack the oil tank dust-free


basic training hydralic

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