Basic Hydraulic

Basic Hydraulic

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Hydraulic Fluid

Check Valve

Least Resistance

Relief Valve

Pascal’s Law

Pressure Differential Relief

Application Principles

Conditioners

JIC

Open vs Closed

Pumps

Hydraulic Valve JIC

Axial Piston Pump

Hydraulic Cylinder Principles

Gear Pump

Cylinder Leakage Test

Motors

Build With JIC’s

Reservoirs Lines and Connections

Liquids Have no Shape of their own

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Liquids are Practically Incompressible

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Liquids under pressure follow what path? Path of least Resistance

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Path of Least Resistance

10 lbs

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Imperial

Pascal’s Law ■

Metric

Pressure Exerted on a Confined Fluid is Transmitted Undiminished in All Directions and Acts With Equal Force on Equal Areas and at Right Angles to Them.

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This slide illustrates one of the basic principles of hydraulics; LIQUIDS TRANSMIT APPLIED PRESSURE EQUALLY IN ALL DIRECTIONS. BUILDS: 1. When a 1 lb (.45kg) force is applied to this handle and the area of the piston is 1sq in (.65cm2), with the confined fluid, what PSI (kpa) pressure will be produced? (1psi (6.9kpa)) Note that this pressure is exerted in every direction. 2. With a 10 sq in (6.5cm2) piston, how much weight will this system lift? This principle is what allows us to multiple our work efforts. With 1 lb (.45kg) of down pressure, we are able to lift 10 lbs (4.5kg). Pressure is caused by a resistance to flow, in this case the 10 lb (4.5kg) weight. Point out that resistance to flow is what causes pressure. In this example, if there were a 100 lb (45kg) weight on the right side (in place of the 10 lb (4.5kg) weight), how much pressure would be required to lift it. (10 PSI (69kpa)).

IMPERIAL --Hydraulics is a means of power transmission --Oil is the most commonly used medium because it serves as a lubricant and is practically non-compressible (it will compress approximately 1/2 of a 1 percent per 1000 PSI). --Weight of oil varies with viscosity, but averages between 55 to 55 lbs per cubic foot. (at 100 degrees F). NOTE: A cubic foot of oil is 1728 Cu.In (12x12x12). A gallon is 231 Cu.In., so a Cubic Foot of oil is equivalent to 7.48 Gallons. --A liquid is pushed, NOT DRAWN, into a pump. Atmospheric pressure equals 14.7 PSI at sea level. --Oil takes the course (path) of least resistance. FORMULAS; 1. H.P. = GPM x Pressure x .000583 -or- H.P. = GPM x PSI / 1714 2. One H.P. = 33000 ft./lbs. per minute (33000 lbs raised 1 ft in 1 minute) One H.P. = 746 Watts, One H.P. = 42.4 BTU per minute 3. Required Area of a transmission line; Area = GPM x .3208 / velocity (ft./sec) -or- Velocity (ft./sec) = GPM / 3.117 x Area

Pascal’s Law, named after Blaise Pascal (French 1623-1662)

METRIC --Hydraulics is a means of transmitting power. --Oil is the most commonly used medium because it serves as a lubricant and is practically non-compressible (it will compress approximately 1/2 of 1 percent per 690 kpa). --Weight of oil varies with viscosity, but averages between 23 to 25 kg per cubic foot. (at 100 degrees F). NOTE: A cubic foot of oil is 1728 Cu.In (12x12x12). A gallon is 231 Cu.In., so a Cubic Foot of oil is equivalent to 7.48 Gallons. --Liquid is pushed (by Atmospheric Pressure), NOT DRAWN, into a pump. Atmospheric pressure equals 14.7 PSI at sea level. --Oil takes the path (line) of least resistance. FORMULAS; 1. H.P. = GPM x Pressure x .000583 -or- H.P. = GPM x PSI / 1714 2. One H.P. = 33000 ft./lbs. per minute (33000 lbs raised 1 ft in 1 minute) One H.P. = 746 Watts, One H.P. = 42.4 BTU per minute 3. Required Area of a transmission line; Area = GPM x .3208 / velocity (ft./sec) -or- Velocity (ft./sec) = GPM / 3.117 x Area

Pascal’s Law, named after Blaise Pascal (French 1623-1662)

Application Principles 1 lb (.45kg) Force

10 lbs (4.5kg)

10 sq in (6.5cm2) Piston Area

1 sq in (.65cm2) Piston Area 1 psi (6.9kpa)

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THE TWO MAIN TYPES OF PUMPS: 1. With a positive displacement pump, with each revolution, a specific amount of fluid is pumped somewhere. 2. The non-positive pump can rotate all day and not necessarily cause fluid to flow. Thus the positive displacement pump is used in applications that require higher pressures and the non-positive displacement pumps are used in applications that require high volumes (flow rates).

Pump Types ■

Positive Displacement -With each revolution a specific amount is pumped somewhere – Low Volume, High Pressure

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Non Positive (IE: Water Pump) – High Volume, Low Pressure

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JIC Symbols ■

Joint Industry Council

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Symbolic Drawings used in Schematics to Represent Components.

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J I C Symbols Joint Industrial Council 2139 Wisconsin Ave, NW Washington, DC 20007 This organization was founded in 1965. JIC standards replaced those written by the Joint Industrial Conference (mostly auto manufacturing) BUILDS 1. Circle, the major components in a JIC schematic are circles. For a pump with start with a circle. 2. Then we add an arrow head. The arrow pointing out of the circle signifies the direction of the fluid flow. OUT, indicating a pump 3. Continue to build showing two arrows heads, meaning this pump is capable of pumping oil in two directions 4. The arrow signifies that this pump is capable of varying the amount of flow, so it is a variable displacement pump.

Pumps (JIC Symbols) ■

■

Constant Displacement Single Direction

Arrow Showing Oil Flow OUT

Bi-Directional, Variable Displacement

Pumps convert mechanical power into hydraulic force

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“Heavy Duty” applications that require variable displacement bi-directional pumps, typically use axial piston pumps. POINT OUT THE: 1. Rotating group 2. Swash plate 3. Pistons

Axial Piston Pump ■

Neutral Position Vertical Swashplate

Pressure Oil Each Piston

Piston Engine

Shaft Piston

Pumps

Piston Swash Plate

Rotating Group Typically 9 Pistons

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SWASHPLATE ANGLE, FORWARD POSITION: 1. As the hydro linkage is slowly moved forward (swashplate angle changes) the vehicle starts to move forward. 2. The movement of the swashplate controls the direction of the motor rotation. 3. When the swashplate is moved further forward (swashplate angle increases), the piston assemblies start to travel further, generating more flow, more oil is being pumped and the speed of the vehicle is increased. 4. Flow rate is determined by length and frequency of strokes. When full swashplate travel is reached (maximum swashplate angle), the maximum volume of oil is being discharged from the pump, then the speed of the motors are at maximum.

Axial Piston Pump ■

Forward Position Angled Swashplate Charge Oil

Pressure Rotating Group Typically 9 Pistons

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Axial Piston Pump ■

Reverse Position Angled Swashplate Pressure

Charge Rotating Group Typically 9 Pistons

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Before going back into JIC symbols, lets show another very popular type of pump or motor. 1. What clues might we have to determine whether this device is a pump or a motor? NOTE: Typically, a pump will have a larger INLET opening. 2. If this were a Pump and with the pump turning in the direction illustrated by the arrows, which side is the inlet and which side is the outlet? Build shows inlet and outlet.

Gear Pump or Motor

In

Out

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BUILDS: 1. Circle; as mentioned some of the major components in the hydraulic schematic are shown as circles. 2. Add an arrow head, but note how this arrow head differs from the pump shown earlier .. it points “IN”. 3. Second circle with arrowhead. This arrowhead comes down from the top. Does this signify any difference? (NO). 4. Second arrowhead. What type of motor is this? (bi-directional) 24

Motors (JIC Symbols) ◆

Single Direction

◆

Bi-Directional

Arrow Showing Oil Flow IN Motors converts hydraulic force into mechanical power

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Reservoirs

1. Vented

3. Return Above Fluid Level

2. Pressurized

4. Return Below Fluid Level 26

Lines and Connections Working Line (Main)

or Crossing Lines

Pilot Control Line Drain Line

Flow Direction

Connecting Lines Flexible Line 27

Check Valve Checked Flow

Free Flow

Spring Assisted Pilot Operated

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Relief Valves Protects the Pump and Lines from excessive pressure Returns fluid back to the reservoir

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Relief Valve

Supply

Return to Reservoir

Pilot supply 30

Pressure Differential Valve

Supply

Senses the DIFFERENCE in Pressure

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Manual On/Off Valve

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Fluid Conditioners

Filter Oil Cooler

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Filters Internal Filter Bypass Valve (Optional)

Micron ■ 1 Millionth of a Meter or 1 Thousandth of a Millimeter ■

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Types of Hydraulic Systems Open Center Closed Center The control valve that regulates the flow from the pump determines if system is open or closed. Do not confuse Hydraulics with the “Closed Loop” of the Power Train. (Hydro) 35

Hydraulic Valve JIC Closed Open Center Center Hydraulics Flow in Neutral

Trapped Oil

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OPEN CENTER VALVE: 1. Hydraulic flow continually moves through the system. 2. The hydraulic pump is constantly pumping fluid. 3. The control valve is open to return in neutral to allow the fluid to circulate.

Hydraulic Valve JIC

Extend

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Hydraulic Valve JIC

Retract

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Hydraulic Valve JIC

Neutral Again

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Let’s examine what happens when a cylinder is extended. Pressure oil is routed to the piston end. Oil from the rod end is allowed to return to the reservoir.

Lift Cylinder ■

Extend

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When cylinders “leak down” over a period of time, it is commonly believed that the cylinder piston “packings” (O-ring seals) are the cause of the problem. This IS NOT TRUE!! So where does the hydraulic oil go?

Lift Cylinder Leak Down ■ Where Does the Oil Go?? ■

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This illustration goes beyond the practical but makes the point. Because of the volume of oil trapped in the cylinder, the rod CANNOT retract any further unless the trapped oil is allowed to escape somewhere. In this case and always with cylinders that leak down by retracting, the control valve is leaking allowing the oil out of the cylinder. Remember, this rule applies only when the cylinder rod retracts (oil leaking from the piston end to the rod end and out through the control valve). Oil can leak from the rod side to the piston side (allowing the rod to extend) because the rod side with less volume of oil can leak into the piston side with a greater area.

Lift Cylinder ■

Is it Possible for This Rod to Retract Even With the Piston Removed??

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Cylinder Hose Failures ■

Effects On Line Pressure When a Cylinder Piston Packing is Leaking

15000 lbs of Down Force 1.5” Diameter Rod .75 x .75 x 3.1416 = 1.77 sq.in. Results in 8475 PSI 3” Diameter Piston 1.5 x 1.5 x 3.1416 = 7.07 sq.in. Results in 2122 PSI 47

To test a cylinder for internal leakage (past the piston seals), remove the cylinder pin from the rod (what ever the cylinder works on will have to be supported). Either extend or retract the rod completely. Then remove the oil line closest to the cylinder’s internal piston. Connect a hydraulic hose to the cylinder where the line was removed. Place the other end of the hydraulic hose in a clean bucket. Pressurize the opposite side of the cylinder with hydraulic oil. Measure leakage into the bucket. If excessive leakage is observed into the bucket, replace cylinder piston seals. NOTE: On some systems, such as the John Deere light weight fairway mowers, the line returning the lift valve will need to be capped to prevent return oil from flowing out the line.

Hydraulic Cylinder Leakage Test Depending on the System, You May Have to Cap This Line To Prevent Return Oil From Leaking Out

Retract

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JIC Symbols Would This Hydraulic Drive System Work?

PM

Yes, In one direction Common Reservoir

Common Reservoir

Hydraulic Drive Does NOT Provide Dynamic Braking ■

Build the System 50

JIC Symbols

PM

Hill Simulation

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Closed Loop Hydrostatic Transmission 51

JIC Symbols

PM

Hill Simulation

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Closed Loop Hydrostatic Transmission 52

JIC Symbols

Oil Filter

Inlet Check

PM Common Reservoir

Inlet Check

■ Oil Cooler

Common Reservoir

Build the System 53

Both the Oil Cooler Bypass and Oil Filter Bypass are “Differential Relief Valves” which have the capability of comparing pressures on the inlet side and the pressure on the outlet side; On the 3365 WARM, these reliefs open: 1. Oil cooler bypass will open with a differential of 80-130 PSI 2. Filter bypass will open with a differential of 20-30 PSI Leak off lines are NOT shown, but are required to provide; 1. Lubrication 2. Cooling 3. Cleaning

JIC Symbols

Oil Filter

Oil Cooler Bypass Valve

PM

Charge Relief Valve

Filter Bypass Valve

■ Oil Cooler

Build the System 55

This slide shows normal oil flow; 1. Hydro turns providing oil flow to motors. 2. Motors turn, some oil is lost to case drain 3. Charge pump provides oil flow through; Cooler Filter Inlet Check Valves

JIC Symbols

Oil Filter

Oil Cooler Bypass Valve

PM

Charge Relief Valve

Filter Bypass Valve

■ Oil Cooler

Hydrostatic Transmission Components

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