Transcript Hydraulics session notes

KCPA
SAMPLE Hydraulic SYSTEMS
Tom Korder
[email protected]
Roméo et Juliette RAMP
2
1
1
1
4
2” bore x 36” stroke, double-acting, tie rod cylinders
• Two –
Flow divider - rated to 5 GPM
• One –, rated up to 5 GPM
solenoid actuated/closed center/ industrial style valve
• ½”One
–
x ¼” x ¼” npt medium pressure Tee
One
–
¼” npt x 36” 4000 psi hoses
$90 / $180
$150
$120
$40
$20 / $80
2
½” npt “pioneer” style couplers
$18 / $36
2
½” x 25’ 4000 psi hoses w/ couplers
$40 / $80
TOTAL
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$700
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16-Nov-02
Roméo et Juliette RAMP
Ramp cylinders
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16-Nov-02
Roméo et Juliette RAMP
Ramp cylinders
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Roméo et Juliette RAMP
cylinders
Hydraulics viewed from
under ramp in trap room
Flow divider
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Roméo et Juliette RAMP
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Roméo et Juliette RAMP
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Roméo et Juliette SLIPSTAGE
1
1
1
1
• Low
Two
– torque motor
speed/high
– cable
drum drive
• Stock
One
–, rated
upunit
to 5 GPM
center/ industrial style valve
• solenoid
One actuated/float
–
sandwich style flow control valve, both A&B
One
–
$250
NC
$120
$200
2
¼” npt “pioneer” style couplers
$18 / $36
2
¼” x 50’ 4000 psi hoses w/ couplers
$60 / $120
TOTAL
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$726
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Roméo et Juliette SLIPSTAGE
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Roméo et Juliette SLIPSTAGE
Slipstage in “out” position
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Roméo et Juliette SLIPSTAGE
Cable drum
Hydraulic motor
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16-Nov-02
Shop-Built Hydraulic Trainer
•
•
•
•
•
AC Power Unit (500 psi, 1-2 gpm)
Tie-rod and industrial cylinders
Low speed/high torque motor
Rotary Actuator
Industrial and Mobile valves
– different actuations and centers
• Flow, pressure, etc. valves
– sandwich and in-line style
• Pressure gauges and flow meter
• Hoses with couplers, adapters
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Shop-Built Hydraulic Trainer
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16-Nov-02
Closed Loop vs. Open Loop
pressure line
pressure line
Return line
Return line
pressure line
inlet
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pressure line
exhaust
Return line
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DESIGNING A SYSTEM
A. Determine System Parameters
B. Perform System Calculations
C. Choose System Components
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A. System Parameters
• What type of movement? (Linear or Rotary)
– actuator type
• How far does it travel?
– Stroke, degree of rotation
• How heavy is the object ?
– total weight of all materials
• What speed?
– How fast of move? safe travel speed ?
– How fast to get to full speed? , rpm
• Other needed components?
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B. System Calculations
• FORCE / TORQUE
– lbs of force
– in lbs of torque
• SPEED / FLOW
– time for stroke
– time for rotation
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AREA–PRESSURE / force
• Amount of force is determined by pressure
pump can deliver
– measured in psi – lbs per square inch
2000 lbs of force
6000 lbs of force
1000 psi
3000 psi
2”
actuator
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2”
actuator
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calculate AREA–PRESSURE
/force
load
• F=PXA
– force = pressure x area
– Area = d2 x .7854
– lb = psi x sq in
cylinder
• given a stated force needed
• start with assumed area
– pick a cylinder bore
• start with assumed system pressure
– as low as possible for safety
• experiment with numbers until you find right
combination
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examples AREA–PRESSURE /force
• Force = Pressure x Area
Force (lb.) = pressure (lb sq in) x area (sq in)
2” bore x ??
psi system pressure
• 1570 lb = 500 psi x 3.14 (2 x.7854) sq. in.
2
• 4710 lb = 1500 psi x 3.14 (2 x.7854) sq. in.
2
• 9420 lb = 3000 psi x 3.14 (2 x.7854) sq. in.
2
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Multiplication of Force
F/A=P
242 x .7854 = 452 sq. in.
220 lb. / 452 sq. in. =
.48 psi
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1442 x .7854 = 16286 sq. in.
.48 psi x 16286 sq. in. =
7817 lb. of force
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16-Nov-02
FLOW / Speed
• rate of flow determined by pump delivery
• flow determines speed of devices
– measured in GPM - gallons per minute
5 seconds
2”
actuator
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10 seconds
5 gpm
2.5 gpm
2”
actuator
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16-Nov-02
calculate –FLOW / Speed
To Find Needed GPM
• Flow = Area x stroke length x .26
time for stroke
• gal./min. = sq. in. x in. x .26
sec.
•
Flow (gal./min.) = (area (sq in) x stroke length (in) x .26) / time for stroke (sec)
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16-Nov-02
examples –FLOW / Speed
• Flow = Area x stroke length x .26
time for stroke
Flow (gal./min.) = (area (sq in) x stroke length (in) x .26) / time for stroke (sec)
2” bore x 36” stroke cylinder ; 30 seconds, 15 seconds, 10 seconds
• .97 gpm = 3.14 (2 x.7854) sq. in. x 36 in. x .26
30 sec.
2
• 1.95 gpm = 3.14 sq. in. x 36 in. x .26
15 sec.
• 2.93 gpm = 3.14 sq. in. x 36 in. x .26
10 sec.
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Motor Shaft Speed
• Speed of the motor output shaft.
Speed =___flow x 231_____
motor displacement
–
–
–
–
shaft speed in RPM
flow in GPM
displacement in cubic inches per revolution
231 = cubic inches in a gallon
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C. System Components
DCV (Directional Control Valve)
Other control devices
(pressure,flow, etc)
Power unit
Actuator
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(cylinder)
(pump)
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MOBILE vs. INDUSTRIAL
• Industrial
– closer tolerances, more expensive, valves are
modular
• Mobile
– also known as agricultural, rugged/basic
construction, more plumbing/hoses, less
expensive
• Suggestion
– Mobile actuators, Industrial valves
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POWER UNIT
• Preassembled vs. Shop assembled
• System Flow
– GPM – gallons per minute
• System Pressure
– psi – pounds per square inch
• Voltage
– 110vac or 220vac
– 1 or 3 
• Reservoir size
– gallons
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DCV directional control valve
• Actuation method
– manual, electrical, or fluid
• Rating
– flow and pressure
• Center style
– closed, open, float, or tandem
• Style of construction
– mobile or industrial
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CENTER CONFIGURATIONS
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CENTER CONFIGURATIONS
• Closed or Blocked
– when operating 2 or more branch circuits from one pump, where
more than one must operate at one time
• Float
– cylinder is free to "float", piston can be pulled or pushed by an external
force, sometimes used for Hydraulic motors
• Open
– motor" spool , minimizes circuit shock when controlling a motor,
not recommended for cylinders
• Tandem
– popular for low power systems, provides free flow path for "pump
unloading", simple/economical way to unload, holds cylinder against drift
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Mobile (Ag) style valves
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Industrial (Manifold) style valves
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ACTUATOR
• Action Needed
– Linear, Rotary limited motion, Rotary continuous motion
• Amount of action needed
– stroke length, degree of rotation, speed
• Force in both directions or only one
• Force / Speed
– Bore/Displacement, Pressure, GPM rating, Port sizes
• Mounting Method
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Mobile (Ag) style cylinders
Tie-Rod Cylinder
Welded Cylinders
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Industrial (NFPA) Cylinders
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OTHER CONTROL DEVICES
• Pressure Control (force)
• Flow Control (speed)
• Additional controls
–
–
–
–
–
Safety Devices
Additional filtering
Electrics/Electronics
Counterbalancing
Flow dividing
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Recommended– HIGH LEVEL $4000-
$5000
Power Units
1
power unit 5-7 GPM
1000–3000 psi
1
hand pump
5000 psi
3 Ø 240 AC volts
$1300
$200
Valves
1 ea
tandem, closed, open centers
industrial style
manual actuation
$360
1 ea
tandem, closed, open centers
industrial style
solenoid actuation
$360
Actuators
1
High Torque, Low Speed Motor
$250
1 ea
Tie-rod cylinder
Min. 3000 psi
2” bore x 24” stroke
2” bore x 36” stroke
$70
$90
1
Telescoping cylinder
Min. 3000 psi
Equal to trap depth
$700
4
Single-acting cylinders (ram)
1” bore x 2” stroke
$200
flow, pressure
$500
Accessories
stack style valves
Hoses with connectors
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counterbalance
$250
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Recommended– LOW LEVEL $2000-$2500
Power Units
1
AC power unit 1-2 GPM
500–1000 psi
1
hand pump
5000 psi
1 Ø 120/240
$500
$200
Valves
1 ea
tandem, closed, open centers
Mobile style
manual actuation
$240
Actuators
1
High Torque, Low Speed Motor
1 ea
Tie-rod cylinder
4
Single-acting cylinders (ram)
$250
Min. 3000 psi
2” bore x 24” stroke
2.5” bore x 48” stroke
$70
$110
1” bore x 2” stroke
$200
Accessories
inline style valves – 1 flow, 1
pressure, 1 counterbalance
$250
Hoses
$250
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Recommended Systems – ADD-ONS
• Combine two systems
• Power Unit
– Second power unit
• Additional Valves
– Industrial-solenoid proportional w/ electronic card
• Actuators
– Additional cylinders
– Rotary actuator
• Accessories
– Flow divider
– More hoses
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SAFETY RULES
– Understand the basic principle and be familiar with
components of the system.
– The pressure in the system should never exceed the rated
pressure of the lowest rated component.
– Be certain all interfaces to the fluid power system are
adequate in strength.
– Never work on system under pressure.
– Test all circuitry with low pressure before the load is
attached.
– Use only the pressure required to achieve the effect.
an obstruction, overload, or added friction will stall the system until
you fixed the problem
– Use common sense!!!
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Jack Miller
(following this slide are new slides that address these topics,
these were not included in original workshop presentation)
– Pump does not produce pressure.
– Always use a Counterbalance valve if you have a load over
the cylinder.
– Be certain all interfaces to the fluid power system are
adequate in strength.
–…………………………………….
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PRESSURE
load
• pressure is created
whenever the flow of a
fluid is resisted
A
– A. load on actuator
– B. resistance or orifice in
the piping
B
• pump DOES NOT create
pressure
– it has the ability to push
against a certain pressure
actuator
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COUNTERBALANCE VALVE
• counterbalance valve is an improved pilot
operated check valve
• the opening pressure of a pilot operated check
valve depends on the pressure (applied by the
load) behind the valve
• the opening pressure of a counterbalance valve
depends on the spring pressure behind the valve.
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Counterbalance Valve
• dynamic performance of balance valve is many times
better than the performance of a pilot operated check valve
• balance valve is applied as a 'brake valve' in order to get a
positive control on a hydraulic cylinder or motor with a
negative load
pilot
– small crane systems
out
– elevator
– scissor lifts
in
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pilot
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Counterbalance
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Counterbalance valve
Left side of DCV is activated, cylinder will
make its 'OUT-stroke‘, oil flows through
integrated check valve.
To lower cylinder, the right side of DCV is
activated. From that moment on pressure is
built up at the rod side of the cylinder. This
pressure opens the balance valve & the oil at
the bottom side of the cylinder flows through
the balance valve & DCV back to reservoir.
out
pilot
in
pilot
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Counterbalance valve
To lower cylinder, the right side of DCV is
activated. From that moment on pressure is
built up at the rod side of the cylinder. This
pressure opens the balance valve
The oil at the bottom side of the cylinder
flows through the balance valve & DCV back
to reservoir
As the load helps lowering the cylinder, the
cylinder might go down faster than the oil is
applied to the rod side of the cylinder (the
cylinder isn't under control at that moment).
However, the pressure at the rod side of the
cylinder and therefore the pilot pressure on
the balance valve will decrease and the spring
moves the balance valve to the direction
'close' as long as it finds a new 'balance'. .
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Counterbalance Circuit #1
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“An Introduction to Hydraulics”
USITT- Minneapolis 2003
Notes available at
http://www.nwmissouri.edu/%7Epimmel/usitt/tech_pr
od/TECH_PROD_INDEX.HTM
Contact me at:
[email protected]