Hydrulic accessories(exe)09 10 07

1)

ACTUATORS & IT’S SEALS

2)

ACCUMULATORS

3)

FILTERS

 HYDRAULIC ACTUATORS PERFORM THE OPPOSITE FUNCTION OF HYDRAULIC PUMPS 

THEY CONVERT THE HYDRAULIC ENERGY BACK TO MECHANICAL ENERGY TO PERFORM USEFUL WORK

 SINCE ACTUATOR PLAY AN IMPARTANT ROLE OF CONVERTING THE FLUID POWER TO MECHANICAL POWER, THIS IS OFTEN CALLED MUSCLE OF THE FLUID POWER.  ACTUATORS EXPECTED TO PERFORM A) AS A STRUCTURAL MEMBER TO GIVE SUPPORT AGAINST LOAD AND LOAD VARIATIONS B) AS A FUNCTIONAL MOTION MEMBER SATISFYING LOAD & MOTION REQUIREMENTS.

ACTUATORS ARE BRODLY CLASSIFIED AS A) LINEAR ACTUATORS B) ROTORY ACTUATORS

LINEAR ACTUATORS THE BASIC LENIAR ACTUATOR IS THE CYLINDER OR RAM a

X

AREA RADIUS Area

2

A = II R2 R

a = II R - II r

2

F(ex) = PA Normally

Y

F(re) =Pa A/a

ratio is

6/5

RADIUS area = II r

r

2

AREA

A/a ratio =

ANNULUS AREA a = A/2

A

2 :1 A

P

Fex

=

Fre

B

T

High extending force ( clamp or form an object ) but Retraction force is minimum

Volume of fluid V I I I I I I Area = A

d

The speed of the cylinder moving is determined by volume of the fluid delivered to It V = Ad If the piston moves at speed s , it moves distance d in time t t = d/s Flow rate to V f to achieve speed s V f = Ad/ t =A s

STATIC SEAL

Dynamic seals

SEAL MATERIAL

Temp Range 0

1) Neo prene (synthetic )

-

below 65

C

2)

Nitrile (Buna – N ) (The most common use & cheapest )

-50 to + 100

3)

Silicon (expensive & tends to tear)

-100 to +250

The natural rubber con not be used in hydraulic systems as it tends to swell and perish in the presence of oil

ACCUMULATORS

Weight loaded accumulators

Spring loaded accumulators

Non separated

Rigid separation

Gas loaded accumulators

separated

Flexible separation

WEIGHT LOADED ACCUMULATOR

ADVANTAGES: Heavy industrial requirements suitable for larger units High capacity at relatively low cost per unit volume Capable of handling shock loads DISADVANTAGES :Bulky & heavy Space constraint

SPING LOADED ACCUMULATORS

ADVANTAGES

: Compact in design Light in weight Can be used in any altitude

DISADVANTAGES: Suitable for low capacity and low pressure

GAS LOADED ACCUMULATOR



SUCCESFUL OPERATION OF THE HYDRAULIC SYSTEM MOSTLY DEPENDS ON THE CONTAMINATION CONTROL OF THE SYSTEM

 SYSTEM COMPONENTS ARE SENSITIVE TO SOLID PARTICULATE CONTAMINANTS BOTH IN SIZE AND QUANTITY WAYS OF ENTERING THE CONTAMINANTS IN TO SYSTEM A) Built in contaminants (fabrication residue) B) Ingression (dirt ingression from external source) C) Generation (wear particles generated over period of time) AFFECTS OF CONTAMINANTS CONTAMINANTS ENTRAINED IN THE SYSTEM FLUID CAN CAUSE FAILURE OF THE SYSTEM THEY ARE 1)TRANSIENT FAILURES 2)DEGRADATION FAILURES 3)CATASTROPHIC FAILURES

FILTRATION IS THE PROCESS OF PHYSICAL/ MECHANICAL SEPERATION OF THE SOLID PARETICULATE CONTAMINANTS FROM THE SYSTEM OF THE FLUID TYPES OF FILTRATION A) OFF- LINE FILTRATION B) ON LINE FILTRATION TYPES OF FILTERS A) SURFACE FILTERS B) DEPTH FILTERS C) EDGE FILTERS THE PARTICLE SEPERATION PERFORMANCE OF FINE FILTERS IS BASED ON B ï€ RATING. THE RATING IS ASSOSIATED WITH SPECIFIC SIZE RANGE (> X- microns) REFERS TO THE RATIO. No. of particles of size range > X per unit volume entering in to the filter (Nix)

Bx =

No of pa particles of size range > X per unit volume coming out from the filter (Ndx)

Materials used in depth type filters 1) Fibrous media- paper (cellulose) 2) cotton 3) synthetic (polypropylene , polyester, polyacrilic , micro fiber glass) ď ś Fiber ranging from 0.5 to 30 microns in diameter are compacted 0.25 to 2 mm thick sheets and then impregnated with resin for binding the fibers together and giving the structural strength and stability

Location of filters suction filter : discharge filter : return filter : breather filter :

will be located at suction of the pump located after relief valve in the discharge line located in the tank in return oil line located above the tank

Filter unit accessories : filtering unit generally have the fallowing accessories A) By- pass valve B) clog indicator

1)

ACTUATORS & IT’S SEALS

2)

FILTERS