7.pppc vs lspc

8/20/2019 7.PPPC vs LSPC

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Proportional, Priority, Pressure

Compensated Hydraulic Systems

Objectives:

• Provide students with a comparison of a basic PPPC

hydraulic system to a basic LS/PC hydraulic system

• Explain PPPC hydraulics as it is used on representative Cat

products


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ORIFICE

PRESSURE

REDUCING

VALVE

FLOW CONTROL VALVE


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ENGINE

FIXED

DISPLACEMENTPUMP

CLOSED CENTER

CONTROL VALVE

3000 PSISPRING

DOUBLE

CHECK VALVE

PRESSURE

REDUCING VALVE

50 PSI

SPRING

LOAD

PRESSURE COMPENSATION


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Definition:

Pressure CompensationA control system which results in constant

implement speed for a given lever displacement.The system does this by maintaining a

controlled pressure drop across the main

control or directional spool in each circuit.


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3000 PSI

SPRING

300 PSI

SPRING

A

B

LOAD

LOAD

ENGINE

FLOWCONTROLVALVE

RESOLVER

RESOLVER

RESOLVER

RELIEFVALVE

LOAD SENSING WITH SIGNAL NETWORK


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BOOM

PRIMARYRESOLVER

SECONDARY

RESOLVER

TO IMPLEMENT

CONTROL VALVES

SIGNAL NETWORK

SWING BUCKET STICKRIGHT

STABILIZER

LEFT

STABILIZER

3000 PSISPRING

300 PSI

SPRING

ENGINE

FLOWCONTROLVALVE

RELIEFVALVE


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Definition:

Load Sensing

A control system that maintains a pump supplypressure at a fixed value above the highest

system pressure requirement.


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VARIABLE DISPLACEMENT PUMPPUMP OUTPUT

LARGE ACTUATOR

SMALL ACTUATOR

& BIAS SPRING

SWASH PLATE

DRIVESHAFT

YOKE PAD

PRESSURE

COMPENSATOR

(PRESSURE CUT-OFF)

FLOW COMPENSATOR

( MARGIN SPOOL)


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ENGINE FIXED

DISPLACEMENT

PUMP

CLOSED CENTER

CONTROL VALVE

3000 PSISPRING

DOUBLE

CHECK VALVE

50 PSI

SPRING

300 PSI

SPRING

LOAD

LOAD SENSING / PRESSURE COMPENSATION

FLOWCONTROL

VALVE

PRESSURE

REDUCING VALVE


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ENGINE

VARIABLEDISPLACEMENT

PUMP

CLOSED CENTERCONTROL VALVE

DOUBLECHECK VALVE

PRESSUREREDUCING VALVE

50 PSISPRING

PUMPCONTROL

VALVE LOAD



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MOTOR

3000 PSISPRING

300 PSI

SPRING

A

B

LOAD

LOAD

LOAD SENSING

TWO VALVE OPERATION


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LS Only - Pressure DifferentialsFlow Needs Met

Maximum Pump Flow = 30 gpm

Valve A desired flow = 10 gpm

Valve B desired flow = 10 gpmMargin Pressure is normal

System Pressure = Valve A load plus margin pressure = 2300 psi

∆P Directional Spool

Valve A @ 2000 psi 2300 - 2000 = 300 psi

Valve B @ 1000 psi 2300 - 1000 = 1300 psi

Pressure ∆P Varies

If Valve A load stayed the same and Valve B would vary as the load on the circuit

varied, the operator would have to constantly shift the lever to maintain implement

control.


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ENGINE

3000 PSI

SPRING

50 PSISPRING

300 PSI

SPRING

50 PSI

SPRING

LOAD

LOAD

A

B


TWO VALVE OPERATION


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LS/PC - Pressure DifferentialsFlow Needs Met

Maximum Pump Flow = 30 gpmValve A desired flow = 10 gpm

Valve B desired flow = 10 gpm

Margin Pressure is normal


∆P Compensator ∆P Directional Spool

Valve A @ 2000 psi 2300 - (2000+50) = 250 psi 2050 - 2000 psi = 50 psi

Valve B @ 1000 psi 2300 - (1000+50) = 1250 psi 1050 psi - 1000 psi = 50 psi

∆P Varies ∆P the Same


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LS/PC - When Flow Demand Exceeds

Available Pump Flow


Margin Pressure less than normal

Desired Flow Available FlowValve A @ 2000 psi 30 gpm 0 gpm

Valve B @ 1000 psi 20 gpm 20 gpm

Valve C @ 500 psi 10 gpm 10 gpm

Total 60 gpm 30 gpm


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PPPC HYDRAULIC SYSTEMTWO VALVE OPERATION / FLOW NEEDS MET

PUMP

SIGNAL

LIMITER

VALVE

2000PSI

1000PSI

50 PSISPRING

50 PSISPRING

VALVE A VALVE B

300 PSIMARGINSPRING

3500 PSICUTOFFSPRING

PRESSURECOMPENSATINGCHECK VALVE

PILOT OIL PILOT OIL

BRIDGEPASSAGE

FEEDERPASSAGE

DIRECTIONALSPOOL

30 GPM

MAXIMUM

FLOW

10 GPMFLOWREQ'D

10 GPMFLOWREQ'D

3000 PSISPRING


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PPPC - Pressure DifferentialsFlow Needs Met

Maximum Pump Flow = 30 gpmValve A desired flow = 10 gpm

Valve B desired flow = 10 gpm

Margin Pressure is normal


∆P Directional Spool ∆P Compensator



∆P the Same ∆P Varies


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PUMP

SIGNAL

LIMITER

VALVE

2000PSI

1000PSI

50 PSISPRING

50 PSISPRING

VALVE A VALVE B

300 PSIMARGINSPRING

3000 PSISPRING


PILOT OIL PILOT OIL

BRIDGEPASSAGE

FEEDERPASSAGE

DIRECTIONALSPOOL

30 GPM

MAXIMUM

FLOW

20 GPMFLOWREQ'D

20 GPMFLOWREQ'D

PPPC HYDRAULIC SYSTEMTWO VALVE OPERATION / HIGH FLOW DEMAND



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PPPC - Pressure DifferentialsFlow Needs Not Met

Maximum Pump Flow = 30 gpmValve A desired flow = 20 gpm Proportioned Flow = 15 gpm

Valve B desired flow = 20 gpm Proportioned Flow = 15 gpm

Margin pressure less than normal

System Pressure = Valve A load plus reduced margin pressure = 2200 psi




∆P the Same ∆P Varies


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PPPC - When Flow Demand Exceeds

Available Pump Flow


Margin pressure less than normal

Desired Flow Available FlowValve A @ 2000 psi 30 gpm 15 gpm

Valve B @ 1000 psi 20 gpm 10 gpm

Valve C @ 500 psi 10 gpm 5 gpm

Total 60 gpm 30 gpm


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Definition:Proportional, Priority, Pressure

Compensated Hydraulic System

Provides precise multiple circuit flow control

whenever pump flow is exceeded. This is

accomplished through post main spool pressure

compensation, which results in proportional

flow division.


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PPPC HYDRAULIC SYSTEMTWO VALVE OPERATION / CUTOFF CONTROLS MAX. PRESSURE

PUMP

SIGNAL

LIMITER

VALVE

3500PSI

1000PSI

50 PSISPRING

50 PSISPRING

VALVE A VALVE B

300 PSIMARGINSPRING



PILOT OIL PILOT OIL

BRIDGEPASSAGE

FEEDERPASSAGE

DIRECTIONALSPOOL

30 GPM

MAXIMUM

FLOW

10 GPMFLOWREQ'D

4000 PSISPRING


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PPPC - Pressure DifferentialsPressure Cutoff Controls Maximum System Pressure

Maximum Pump Flow = 30 gpmValve A desired flow = Stalled

Valve B desired flow = 10 gpm Actual Flow = 0 gpm

Margin pressure = 0

System Pressure = Controlled by Pressure Cutoff = 3500 psi


Valve A @ 3500 psi 3500 - 3500 = 0 psi 3500 - 3550 psi = -50 psi

Valve B @ 1000 psi 3500 - 3500 = 0 psi 1000 - 3550 psi = -2550 psi

∆P the Same Neg ∆P Varies = No Flow


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Telehandlers

PPPC Hydraulic System


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HYDRAULIC

PUMP

SIGNAL

LINE

TANK

FILTER

HMU

FRAME

LEVEL

CONTROLVALVE FRAME

LEVEL

JOYSTICK

FORKS

ATTACHMENT

CARRIER

ROTATE TILT

COMPENSATING

VALVE

COMPENSATING

CYLINDERS

DIRECTIONAL

CONTROL

VALVES

BOOM

EXTEND/RETRACT

BOOM

RAISE/LOWER

DIFFERENTIAL LOCKSELECTOR

VALVE MANIFOLD

IMPLEMENT AND STEERING SYSTEM

TO BRAKE

BOOST CYLINDER


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DIFFERENTIALLOCK

TO OTHER

VALVES

SIGNAL

RELIEF

VALVE SIGNAL FROM

OTHER VALVES

RETURN FROM

OTHER VALVES

BOOM

RETRACT

BOOM

EXTEND

BOOM

LOWER

BOOM

RAISE

HYDRAULIC SYSTEM

PUMP

TILT

BACKTILT

FORWARD

PRESSURE

REDUCING

VALVE

MANUAL

OVERRIDE

JOYSTICK

PILOT

CONTROL

VALVESERVICE BRAKE

BOOST CYLINDER

SELECTOR

VALVE

MANIFOLD

STEERING

VALVE

BOOM

RAISE/LOWER

CONTROL VALVE

BOOM

RETRACT/EXTEND

CONTROL VALVE

TILT

CONTROL

VALVE


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COMPENSATOR VALVESTEERING AND IMPLEMENT PUMPCONSTANT FLOW

SIGNAL

PRESSURE

TO CONTROL

VALVE GROUP

PRESSURE

CUTOFF SPOOL

MARGIN

SPOOL

BIAS

SPRING

ACTUATOR

PISTON

SWASHPLATE


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JOYSTICK

PILOT

CONTROL

VALVE

DIFFERENTIALLOCK

TO OTHER

VALVES

SIGNAL

RELIEF

VALVESIGNAL FROM

OTHER VALVES

RETURN FROM

OTHER VALVES

BOOM

RETRACTBOOM

EXTEND

BOOM

LOWER

BOOM

RAISE

HYDRAULIC SYSTEM IMPLEMENTS IN HOLD

SELECTOR

VALVEMANIFOLD

TO

HMU

TILT

BACKTILT

FORWARD

PRESSURE

REDUCING

VALVE

STEERING

PRIORITY

VALVE

PRESSURE

COMPENSATINGCHECK VALVE

RESOLVER

SERVICE BRAKE

BOOST CYLINDER

PUMP


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PORT A PORT B

FROM PILOT

SYSTEM

PRESSURE


RESOLVERVALVE

RETURN

TO TANK

BRIDGE

PASSAGE

FEEDER

PASSAGE

A B

SIGNAL

PASSAGE

FEEDER

PASSAGE

PUMP

SUPPLY

IMPLEMENT

CONTROL VALVEHOLD

DIRECTIONAL

CONTROLSPOOL

RESOLVED

SIGNALTO NEXT

VALVE


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B

PORT A PORT B

FROM PILOT

SYSTEM

PRESSURE


RESOLVERVALVE

RETURN

TO TANK

BRIDGE

PASSAGE

FEEDER

PASSAGE

A

SIGNAL

PASSAGE

FEEDER

PASSAGE

PUMP

SUPPLY

RESOLVED

SIGNAL

IMPLEMENT

CONTROL VALVESHIFT

DIRECTIONAL

CONTROL

SPOOL

TO NEXT

VALVE


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B

A B

A B

A B

PILOT OIL

SIGNAL TO

PUMP CONTROL

STEERINGVALVE

BOOM

RAISE/LOWER

VALVE

BOOM

EXTEND/RETRACTVALVE

TILT

VALVE

AUX.

VALVE

SIGNAL

RELIEF VALVEPRESSURE

REDUCING

VALVE

TELEHANDLER IMPLEMENT VALVE GROUP

LINE

RELIEF

VALVE

A

PUMP SUPPLY

RESOLVER


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JOYSTICK

PILOT

CONTROL

VALVE

DIFFERENTIALLOCK

TO OTHER

VALVES

SIGNAL

RELIEF

VALVESIGNAL FROM

OTHER VALVES

RETURN FROM

OTHER VALVES

BOOM

RETRACT

BOOM

EXTEND

BOOM

LOWER

BOOM

RAISE

HYDRAULIC SYSTEM BOOM RAISE

SELECTOR

VALVEMANIFOLD

TO

HMU

TILT

BACKTILT

FORWARD

PRESSURE

REDUCING

VALVE

STEERING

PRIORITY

VALVE

PRESSURE


RESOLVER

SERVICE BRAKE

BOOST CYLINDER

PUMP


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'H' Series Motor Graders



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RIGHT

VALVE BANK

LEFT

VALVE

BANK

PUMP

COMPENSATOR

VALVEACCUMULATOR

COMBINATION

VALVE

HAND

METERING

UNIT

TANK

STEERING AND IMPLEMENT HYDRAULIC SYSTEM


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TO IMPLEMENTCYLINDERS

TO IMPLEMENTCYLINDERS

TO STEERINGCYLINDERS

LEFTVALVEBANK

RIGHT

VALVEBANK

STEERINGACCUMULATOR

HANDMETERING

UNIT

COMBINATIONVALVE

PUMP

COMPENSATORVALVE

FILTER

IMPLEMENTSIGNAL LINE

H-SERIES

HYDRAULIC SYSTEM

STEERINGSIGNAL LINE


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PUMP OUTPUTSIGNAL

REDUCED PRESSURE

PUMP AND COMPENSATOR OPERATIONCONSTANT FLOW


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FROM STEERINGHAND METERING UNIT

TO PUMPCOMPENSATOR VALVE

RIGHTBLADE LIFT

LEFTBLADE LIFT

WHEELLEAN

CENTERSHIFT

ARTICULATION

SIDESHIFT

CIRCLEDRIVE

BLADE TIP

TO

COMPENSATORVALVES

SIGNAL RESOLVER VALVE

COMBINATION VALVE

FROM PRIORITY ANDSTEERING RELIEF VALVE

TO SIGNAL BLEEDAND SIGNAL PRESSURE

RELIEF VALVES

SIGNALCHECKVALVE

SIGNAL NETWORKRIGHT BLADE LIFT


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LEFT BLADE LIFT

SIDESHIFT

BLADETIP

CIRCLE DRIVE

LEFT IMPLEMENT CONTROL VALVESHOLD


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ARTICULATION CENTER SHIFT WHEEL LEAN RIGHT BLADE LIFT

RIGHT IMPLEMENT CONTROL VALVESHOLD


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FROMPUMP

TO TANK

TO TANK

PORT BPORT A

LOCK VALVE

PISTON

LOCK VALVE POPPETLOCK VALVE

POPPET

LOCK VALVE SEATS

COMPENSATOR VALVE

SIGNALCHECK BALLCONTROL

STEM

TYPICALIMPLEMENT VALVE

HOLD

ROTARYACTUATOR

MANIFOLD

TOCOMBINATION

VALVE

COUNTERBALANCESPRING

CENTERING SPRING


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SIGNAL

CHECK BALLFROMPUMP

COMPENSATORVALVE

CONTROLSTEM

BLADE LIFT VALVE

HOLD

MANIFOLD

TO COMBINATIONVALVE

TO TANK

TOTANK

TOROD END

TOHEAD END

LOCK VALVEPISTONS

LOCK VALVEPOPPET

LOCK VALVEPOPPET

LOCK VALVE SEATS

ROTARYACTUATOR

ROD END LINERELIEF VALVE

DETENTSPRING

CENTERING

SPRING

COUNTERBALANCESPRING


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SIGNALCHECK BALL

FROM

PUMP

PORT BPORT A

COMPENSATORVALVE

CONTROLSTEM

BLADE LIFT VALVEFULLY SHIFTED TO THE RIGHT

MANIFOLD

TO COMBINATIONVALVE


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TO TANK

PORT BPORT A

COMPENSATORVALVE

CONTROLSTEM

FROM PUMP

PORT BPORT A

COMPENSATORVALVE

SIGNALCHECK BALL

(OPEN) FROM PUMP

SIGNALCHECK BALL

(SEATED)

MANIFOLD

IMPLEMENT VALVE WITHHIGHEST LOAD

IMPLEMENT VALVE WITHLOWEST LOAD

TOCOMBINATION

VALVE

TYPICALIMPLEMENT VALVES


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924G/924Gz Wheel Loaders



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M300 Wheeled Excavators


BUCKETSTICK BOOM

M300 SERIES EXCAVATOR HYDRAULIC SYSTEMGENERATION 2 AND 4 MACHINES

PILOT AND IMPLEMENT HYDRAULIC SYSTEMS


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PILOT MANIFOLD

OIL

COOLER

RETURN

MANIFOLD

SWING

PUMP

MAIN

PUMP

BRAKE

AND

STEERING

PUMPS

DOZER

PILOT

VALVE

STICK

AND

SWING

PILOT

VALVE

TRAVEL

PILOT

VALVE

BOOM AND

BUCKET

PILOT

VALVE

MAIN CONTROL VALVE GROUP

SWING

MOTOR

TO DOZERBLADE/

STABILIZERS

A

WHEEL BRAKE

VALVE

STEERING

VALVE

TRAVEL

MOTOR

TRANSMISSIONTO

BRAKES

TO L

ATT

TO

SWING

PUMP

TRANSMISSION

SHIFT

PARKING

BRAKE

CONTROL

GOVERNORACTUATOR

MOTOR

ENGINE

LOAD

M312/M315/M318

MAIN PUMP CONTRO


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A

SENSING

SPOOL

LEVER

POWER SHIFT

PRESSURE PISTON

ACTUATOR PISTON

SECTION A - A

LEVER

A

MARGIN PRESSURE

ADJUSTMENT SCREW

SIGNALLIMITER VALVE

COMPONENTS

POWER SHIFT

PRESSURE

FROM MAIN

PUMP PRV

MAXIMUM ANGLE PISTON

MINIMUM ANGLE

PISTON

HORSEPOWER CONTROL SPOOL

LOAD SENSING

ORIFICE SPOOL

LOAD SENSING

ORIFICE ADJUSTMENT

SCREW

LOAD SENSING ORIFICE

HORSEPOWER

ADJUSTMENT SCREW

HORSEPOWER

CONTROL SPOOL

MAIN RELIEF

VALVE

PUMP

SUPPLY

CONT

PRES

LOAD SENSING

SIGNAL

MAIN CONTROL

VALVE

TO IMPLEMENTS

PIVOT PIN

CONTROL VALVE


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SHOCK

VA

PORT A PORT B

TRAV

S

LINE RELIEF AND

MAKEUP VALVE

COMPENSATOR VALVE

LOAD CHECK VALVE

SIGNAL

PUMP

SUPPLYFROM

JOYSTICK

FROM

JOYSTICK

CONTROL

SPOOL

LOAD SENSING

PORT

CONTROL VALVENEUTRAL

FEEDER

PASSAGE

TO SIGNALCOMPENSATOR VALVES


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HIGH CIRCUIT

PRESSURE

NEUTRAL LOW CIRCUIT

PRESSURE

CONTROL

SPOOL

FEEDER

PASSAGE

PASSAGE TO

CYLINDER

LOAD

SENSING

PORT

SUPPLYOIL

CROSS-DRILLED

PASSAGE

SIGNAL

COM

TO PUMP

CONTROLS

TO SIGNAL

LIMITER VALVECOMPENSATOR VALVES


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PUMP

SUPPLY

FROM

JOYSTICK

SHOCK REDUCING

VALVE

PORT A PORT B

LINE RELIEF AND

MAKEUP VALVE

COMPENSATOR VALVE

LOAD CHECK

VALVE

SIGNAL

FEEDER

PASSAGE

CONTROL VALVEHIGH PRESSURE

CONTROL VALVE


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PUMP

SUPPLYFROM

JOYSTICK

SHOCK R

VA

PORT A PORT B

LINE RELIEF AN

MAKEUP VALVE

COMPENSATOR VALVE

LOAD CHECK

VALVE

SIGNAL

FEEDER

PASSAGE

LOW PRESSURE


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'B' Series Telehandlers



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PHS

SOLENOID

IMPLEMENTELECTRONIC

JOYSTICK

PWMSIGNAL

CATERPILLARELECTRONIC

TECHNICIAN(ET)

% NORMALIZEDLEVER POSITION

% VALVECOMMAND

CURRENT

PHS CAN

DATA LINK

CATDATA LINK

PHS PILOT MODULE

% VALVECOMMAND

+10 V POWER SUPPLYADDRESS LINE IN

ADDRESS LINE OUT

PHS DATA LINK +

PHS DATA LINK -

+12 V BATTERY

GROUNDMACHINE

ECM PHSECM

PROGRAMMABLE HYDRAULIC SYSTEM (PHS)ELECTRICAL BLOCK DIAGRAM


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7.pppc vs lspc

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