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FM 5-499

FM 5-499

Field Manual

Headquarters

No. 5-499

Department of the Army

Washington, DC, 1 August 1997

Hydraulics

Table of Contents

Page

LIST OF FIGURES AND TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv

CHAPTER 1.

Hydraulic Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1-1. Pressure and Force. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1-2. Pascal’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1-3. Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Flow Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

1-4. Energy, Work, and Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Potential Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Kinetic Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Heat Energy and Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Relationship Between Velocity and Pressure. . . . . . . . . . . . . . . . . . . . . . . . 1-7

Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

CHAPTER 2.

Hydraulic Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2-1. Basic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Hydraulic Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Motor-Reversing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Open-Center System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Closed-Center System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited.

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2-2. Color Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2-3. Reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Ventilation and Pressurization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Line Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-4. Strainers and Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Strainers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

2-5. Filtering Material and Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

2-6. Accumulators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Spring-Loaded Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Bag-Type Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

Piston-Type Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2-7. Pressure Gauges and Volume Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

Pressure Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2-8. Portable Hydraulic-Circuit Testers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Testers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Improper Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

2-9. Circulatory Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Tubing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

Flexible Hosing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

2-10. Fittings and Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

Threaded Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

Flared Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

Flexible-Hose Couplings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

Reusable Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

2-11. Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

Internal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

External. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30

Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30

2-12. Seals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30

Static Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

Dynamic Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

Packing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

Seal Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

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CHAPTER 3.

Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-1. Pump Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Nonpositive-Displacement Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Positive-Displacement Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-2. Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-3. Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Fixed-Displacement Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Variable-Displacement Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3-4. Slippage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3-5. Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Centrifugal Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Rotary Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Reciprocating Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3-6. Gear Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

External . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Internal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Lobe Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3-7. Vane Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Unbalanced Vane Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Balanced Vane Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Double Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Two-Stage Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3-8. Piston Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Radial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Axial Piston Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3-9. Pump Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Excess Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Cavitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Operating Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

CHAPTER 4.

Hydraulic Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4-1. Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Single-Acting Cylinder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Double-Acting Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Differential Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Nondifferential Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Ram-Type Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Piston-Type Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Cushioned Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Lockout Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.2

Construction and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

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4-3. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

External Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Internal Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Creeping Cylinder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Sluggish Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Loose Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Misalignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Lack of Lubrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

Abrasives on a Piston Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

Burrs on a Piston Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

Air Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4-4. Hydraulic Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

Gear-Type Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Vane-Type Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Piston-Type Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

CHAPTER 5.

Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5-1. Pressure-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Relief Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Pressure-Reducing Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Sequence Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Counterbalance Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Pressure Switches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

5-2. Directional-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Poppet Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Sliding-Spool Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Check Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Two-Way Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

Four-Way Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

5-3. Flow-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

Gate Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

Globe Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21

Needle Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Restrictor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Orifice Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

Flow Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

5-4. Valve Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

Meter-In Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

Meter-Out Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

Bleed-Off Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

Compensated Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

5-5. Valve Failures and Remedies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

Servicing Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

Disassembling Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

Repairing Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

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Page

5-6. Valve Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

5-7. Troubleshooting Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

Pressure-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

Directional-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-32

Volume-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-33

CHAPTER 6.

Circuit Diagrams and Troubleshooting . . . . . . . . . . . . . . . . . . . . . 6-1

6-1. Hydraulic-Circuit Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6-2. United States of American Standards Institute (USASI) Graphical . . . . . . . 6-1

Symbols

Reservoir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Pressure-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Flow-Control Valves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Directional-Control Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

6-3. Typical Mobile Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

Hydraulic-Lift Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

Power-Steering Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

Road-Patrol-Truck Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

6-4. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

Causes of Improper Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

Testing a Hydraulic Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

Comparing Test Results with Specifications . . . . . . . . . . . . . . . . . . . . . . . 6-13

Slippage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15

Flow and Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15

Other Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15

Specific Troubles, Causes, and Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

CHAPTER 7.

Electrical Devices: Troubleshooting and Safety. . . . . . . . . . . . . . . 7-1

7-1. Hydraulics and Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7-2. Troubleshooting Electrical Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

Testing Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7-3. Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

Earth Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

Chassis or Common Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9

Zero Reference Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9

Isolation Between Earth and Chassis Ground . . . . . . . . . . . . . . . . . . . . . . 7-10

7-4. Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10

Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10

Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

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APPENDIX A. Metric Conversion Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix-1

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glossary-1

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index-1

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List of Figures and Tables

Figures

Page

Figure 1-1.

Basic hydraulic device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Figure 1-2.

Compressibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Figure 1-3.

Water column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Figure 1-4.

Pump pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Figure 1-5.

Interaction of hydraulic and atmospheric pressures . . . . . . . . . . . . . . 1-4

Figure 1-6.

Force, pressure, and area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Figure 1-7.

Pascal’s Law apparatus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Figure 1-8.

Laminar and turbulent flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Figure 1-9.

Effect of friction on pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Figure 1-10. Bernouilli’s Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

Figure 1-11. Combined effects of friction and velocity changes . . . . . . . . . . . . . . . . 1-9

Figure 2-1.

Hydraulic jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Figure 2-2.

Motor-reversing system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Figure 2-3.

Open-center system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Figure 2-4.

Open-center system with a series connection . . . . . . . . . . . . . . . . . . . . 2-4

Figure 2-5.

Open-center system with a series/parallel connection . . . . . . . . . . . . . 2-5

Figure 2-6.

Open-center system with a flow divider . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Figure 2-7.

Closed-center system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Figure 2-8.

Fixed-displacement pump and accumulator . . . . . . . . . . . . . . . . . . . . 2-7

Figure 2-9.

Variable-displacement pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

Figure 2-10. Closed-center system with charging pump . . . . . . . . . . . . . . . . . . . . . . 2-8

Figure 2-11. Design features of a reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Figure 2-12. Hydraulic-system stainers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

Figure 2-13. Full-flow hydraulic filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

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Figure 2-14. Proportional-flow filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Figure 2-15. Spring-loaded accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

Figure 2-16. Bag-type accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Figure 2-17. Piston-type accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Figure 2-18. Pressure gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

Figure 2-19. Nutating-piston-disc flowmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

Figure 2-20. Portable hydraulic-circuit tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Figure 2-21. Method of installing tubing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

Figure 2-22. Flexible rubber hose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

Figure 2-23. Installing flexible hose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

Figure 2-24. Threaded-pipe connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

Figure 2-25. Flared-tube connector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

Figure 2-26. Flared-tube fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24

Figure 2-27. Field-attachable couplings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

Figure 2-28. Hose-length measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

Figure 2-29. Hose cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

Figure 2-30. Permanently attached couplings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

Figure 2-31. Skived fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

Figure 2-32. Trimming a hose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27

Figure 2-33. Female portion of a fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27

Figure 2-34. Male and female portions of a fitting . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Figure 2-35. Tightening a fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Figure 2-36. Nonskived fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Figure 2-37. Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28

Figure 2-38. Assembly of clamp-type coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

Figure 2-39. Static seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

Figure 2-40. O-ring placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

Figure 2-41. O-ring removal tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

Figure 2-42. Backup ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

Figure 2-43. T-ring seal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

Figure 2-44. Lip seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

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Page

Figure 2-45. Cup seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

Figure 2-46. Piston ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

Figure 2-47. Face seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

Figure 2-48. Compression packing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-34

Figure 3-1.

Nonpositive-displacement pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Figure 3-2.

Reciprocating-type, positive-displacement pump . . . . . . . . . . . . . . . . . 3-2

Figure 3-3.

Positive-displacement pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Figure 3-4.

Volute pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Figure 3-5.

Diffuser pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Figure 3-6.

External gear pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Figure 3-7.

Internal gear pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Figure 3-8.

Lobe pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Figure 3-9.

Unbalanced vane pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Figure 3-10. Balanced vane pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Figure 3-11. Vane-type double pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Figure 3-12. Fluid flow from vane-type double pumps . . . . . . . . . . . . . . . . . . . . . . . 3-8

Figure 3-13. Vane-type, two-stage pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

Figure 3-14. Simplified radial piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Figure 3-15. Nine-piston radial piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

Figure 3-16. Pintle for a radial piston pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

Figure 3-17. Cylinder block for a radial piston pump . . . . . . . . . . . . . . . . . . . . . . 3-12

Figure 3-18. Pistons for a radial piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Figure 3-19. In-line piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

Figure 3-20. Bent-axial piston pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Figure 4-1.

Single-acting cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Figure 4-2.

Double-acting cylinder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Figure 4-3.

Nondifferential cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Figure 4-4.

Telescoping, ram-type, actuating cylinder . . . . . . . . . . . . . . . . . . . . . . 4-3

Figure 4-5.

Single-acting, spring-loaded, piston-type cylinder. . . . . . . . . . . . . . . . 4-3

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Figure 4-6.

Double-acting, piston-type cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Figure 4-7.

Cushioned, actuating cylinder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Figure 4-8.

Applications of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Figure 4-9.

Basic operations of a hydraulic motor. . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

Figure 4-10. Gear-type motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Figure 4-11. Vane-type motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Figure 4-12. Pressure differential on a vane-type motor . . . . . . . . . . . . . . . . . . . . . . 4-9

Figure 4-13. Flow condition in a vane-type pump . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

Figure 4-14. Rocker arms pushing vanes in a pump . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Figure 4-15. In-line-axis, piston-type motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Figure 4-16. Swash plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

Figure 4-17. Bent-axis, piston-type motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

Figure 5-1.

Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Figure 5-2.

Simple relief valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Figure 5-3.

Compound relief valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Figure 5-4.

Pressure-reducing valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Figure 5-5.

X-series, pressure-reducing valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Figure 5-6.

Internal construction of an XC-series valve . . . . . . . . . . . . . . . . . . . . . 5-5

Figure 5-7.

Sequence valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Figure 5-8.

Application of sequence valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Figure 5-9.

Counterbalance valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Figure 5-10. Pressure switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Figure 5-11. Spool valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Figure 5-12. Operation of a simple poppet valve . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Figure 5-13. Operation of sliding-spool, directional-control valve . . . . . . . . . . . . . 5-10

Figure 5-14. Swing-type check valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Figure 5-15. Vertical check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Figure 5-16. Spring-loaded check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Figure 5-17. Standard check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Figure 5-18. Restriction check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

x

FM 5-499

Page

Figure 5-19. Pilot-operated check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

Figure 5-20. Pilot-operated check valve, second type. . . . . . . . . . . . . . . . . . . . . . . . 5-13

Figure 5-21. Two-way valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

Figure 5-22. Flow conditions in a circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15

Figure 5-23. Working view of poppet-type, four-way valve . . . . . . . . . . . . . . . . . . . 5-16

Figure 5-24. Schematic of a four-way, directional-control, sliding-spool valve . . . 5-17

Figure 5-25. Closed-center spool valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Figure 5-26. Open-center spool valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Figure 5-27. Shifting spool by hand lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20

Figure 5-28. Spool shifted by pilot pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21

Figure 5-29. Solenoid-operated, sliding-spool, directional-control valve . . . . . . . . 5-21

Figure 5-30. Cross section of a gate valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Figure 5-31. Operation of a globe valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Figure 5-32. Sectional view of a needle valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Figure 5-33. Fixed restrictor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

Figure 5-34. Variable restrictor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

Figure 5-35. Orifice check valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23

Figure 5-36. Flow equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24

Figure 5-37. Typical meter-in circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

Figure 5-38. Typical meter-out circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

Figure 5-39. Spring tester. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

Figure 5-40. Valve inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

Figure 5-41. Volume-control valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

Figure 5-42. Pressure-control valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

Figure 5-43. Cartridge-type relief valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

Figure 5-44. Readings on a cartridge-type relief valve . . . . . . . . . . . . . . . . . . . . . . 5-30

Figure 6-1.

Graphical-circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Figure 6-2.

USASI graphical symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Figure 6-3.

Reservoir symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Figure 6-4.

Hydraulic line symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

xi

FM 5-499

Page

Figure 6-5.

Crossing lines A and B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Figure 6-6.

Pump symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Figure 6-7.

Motor symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Figure 6-8.

Cylinder symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Figure 6-9.

Pressure-control-valve symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Figure 6-10. Relief-valve symbol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Figure 6-11. Sequence-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Figure 6-12. Check-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

Figure 6-13. Counterbalance-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

Figure 6-14. Pressure-reducing-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

Figure 6-15. Flow-control-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

Figure 6-16. Unloading-valve symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9

Figure 6-17. Four-way, directional-control-valve symbol . . . . . . . . . . . . . . . . . . . . 6-10

Figure 6-18. Mobile directional-control-valve symbol . . . . . . . . . . . . . . . . . . . . . . . 6-10

Figure 6-19. Fluid-conditioner symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

Figure 6-20. Accumulator symbol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

Figure 6-21. Hydraulic-lift circuit in neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

Figure 6-22. Manual-steering-gear layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

Figure 6-23. Power-steering layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12

Figure 6-24. Semi-integral power-steering system . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13

Figure 6-25. Hydraulic circuit diagram for a road-patrol truck. . . . . . . . . . . . . . . 6-14

Figure 6-26. Hydraulic tester connected to a pump’s output . . . . . . . . . . . . . . . . . . 6-15

Figure 7-1.

Common electrical schematic symbols . . . . . . . . . . . . . . . . . . . . . . . . . 7-2

Figure 7-2.

Comparison of electrical and hydraulic components . . . . . . . . . . . . . . 7-3

Figure 7-3.

Comparison of electrical and hydraulic circuits. . . . . . . . . . . . . . . . . . 7-4

Figure 7-4.

Schematic diagrams illustrating zero reference point . . . . . . . . . . . . . 7-9

Figure 7-5.

Battery installed between earth ground and chassis ground. . . . . . . 7-11

xii

FM 5-499

Tables

Page

Table 2-1.

Figure colors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Table 5-1.

Classifications of directional-control valves . . . . . . . . . . . . . . . . . . . . 5-16

Table 6-1.

Problems and solutions with pump operations . . . . . . . . . . . . . . . . . 6-17

Table 6-2.

Problems and solutions with actuating mechanism . . . . . . . . . . . . . 6-19

Table 6-3.

Problems and solutions with heating oil . . . . . . . . . . . . . . . . . . . . . . 6-20

Table 6-4.

Problems and solutions with fluid motors . . . . . . . . . . . . . . . . . . . . . 6-21

Table 6-5.

Problems and solutions with accumulator operation. . . . . . . . . . . . . 6-21

Table A-1.

Metric conversion chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix-1

xiii

FM 5-499

Preface

This field manual (FM) serves as a guide for personnel who operate and maintain military

equipment using hydraulic-powered control systems. It includes general information cover-

ing basic hydraulics and describes the properties and characteristics of fluids and several

types of pumps, motors, valves, and controls. This manual also deals with piping, tubing,

and hoses used to convey fluid under pressure. It describes the functions and types of reser-

voirs, strainers, filters, and accumulators. It discusses the purposes and types of seals and packings used in fluid power systems.

The contents of this manual are applicable to both nuclear and nonnuclear warfare.

The Appendix contains an English to metric measurement conversion chart.

ACKNOWLEDGEMENTS

Acknowledgment is gratefully made to the organizations listed below for permitting the use

of copyrighted material in preparing this manual.

Deere & Company

Moline, Illinois

Hydraulics. "Reproduced by permission of Deere & Company. c 1997. Deere & Company. All rights reserved."

Vickers, Inc.

Rochester Hills, Michigan

Industrial Hydraulics Manua l, Third Edition 1993.

The proponent for this publication is Headquarters (HQ), United States Army Training and

Doctrine Command (TRADOC). Submit changes for improving this publication on Depart-

ment of the Army (DA) Form 2028 (Recommended Changes to Publications and Blank

Forms) and forward it to Commandant, USAES, ATTN: ATSE-TD-D-P, Fort Leonard Wood,

MO 65473-6650.

Unless otherwise stated, masculine nouns and pronouns do not refer exclusively to men.

xiv

index-16_1.png

FM 5-499

CHAPTER 1

Hydraulic Basics

Hydraulics is the science of transmitting force and/or motion through the medium of a

confined liquid. In a hydraulic device, power is transmitted by pushing on a confined liquid.

Figure 1-1 shows a simple hydraulic device. The transfer of energy takes place because a quantity of liquid is subject to pressure. To operate liquid-powered systems, the operator should have a knowledge of the basic nature of liquids. This chapter covers the properties of liquids and how they act under different conditions.

1-1. Pressure and Force. Pressure is force exerted against a specific area (force per unit area) expressed in pounds per square inch (psi). Pressure can cause an expansion, or resistance to compression, of a fluid that is being squeezed. A fluid is any liquid or gas (vapor).

Force is anything that tends to produce or modify (push or pull) motion and is expressed in

pounds.

a. Pressure. An example of pressure is the air (gas) that fills an automobile tire. As a tire is inflated, more air is squeezed into it than it can hold. The air inside a tire resists the squeezing by pushing outward on the casing of the tire. The outward push of the air is pressure. Equal pressure throughout a confined area is a characteristic of any pressurized fluid.

For example, in an inflated tire, the outward push of the air is uniform throughout. If it

were not, a tire would be pushed into odd shapes because of its elasticity.

There is a

major difference

between a gas and a

liquid. Liquids are

Weight

slightly compress-

ible (Figure 1-2,

page 1-2). When a

Confined liquid is

confined liquid is

subject to pressure

pushed on, pressure

builds up. The

pressure is still

transmitted

equally throughout

the container. The

fluid's behavior

makes it possible to

transmit a push

through pipes,

around corners, and

up and down. A

hydraulic system

Figure 1-1. Basic hydraulic device

uses a liquid

Hydraulic Basics

1-1

index-17_1.png

FM 5-499

because its near incompressibility makes the action instantaneous as long as the system is

full of liquid.

Pressure can be created by squeezing or pushing on a confined fluid only if there is a

resistance to flow. The two ways to push on a fluid are by the action of a mechanical pump

or by the weight of the fluid. An example of pressure due to a fluid's weight would be in an ocean's depths. The water's weight creates the pressure, which increases or decreases,

depending on the depth.

By knowing the weight of a cubic foot of water, you can calculate the pressure at any

depth. Figure 1-3 shows a column of water 1 foot square and 10 feet high, which equates to

10 cubic feet. (One cubic foot of water weighs 52.4 pounds.) The total weight of water in this column is 624 pounds. The weight at the bottom covers 1,445 square inches (1 square foot).

Each square inch of the bottom is subject to 1/144 of the total weight, or 4.33 pounds. Thus, the pressure at this depth is 4.33 psi. You can also create an equal pressure of 4.33 psi in a liquid using the pump and figures shown in Figure 1-4, page 1-4.

Before pressure, head was the only way to express pressure measurement. It was

expressed as feet of water. Today, head is still the vertical distance between two levels in a fluid. In Figure 1-3, the head between the top and bottom of the water is 10 feet, which is

equivalent to 4.33 psi. Therefore, each foot of water is equal to 0.433 psi.

The earth has an atmosphere of air extending 50 miles up, and this air has weight. This air

creates a head of pressure that is called atmospheric pressure. A column of air 1 square inch in cross section and the height of the atmosphere would weigh 14.7 pounds at sea level. Thus,

the earth's atmospheric pressure is 14.7 psi at sea level. The role of atmospheric pressure in A gas is compressible

A liquid resists compression

Figure 1-2. Compressibility

1-2

Hydraulic Basics

index-18_1.png

FM 5-499

most hydraulic systems is significant. Fig-

ure 1-5, page 1-4, shows the interaction of

hydraulic and atmospheric pressures under

the three sets of conditions listed below:

(1) Diagram A. In the diagram, the tube

is open at both ends. When it is placed in a

liquid, the liquid will rise, inside and out-

side, in proportion to the amount of liquid

1 ft

1 ft

displaced by the submerged tube wall.

0.433 psi

(2) Diagram B. In the diagram, ends of

1 ft

the tube are closed. When placed in a liquid,

the liquid level in the tube is forced down

1 cu ft

because the air in the tube must occupy a

weighs

space. Therefore, the liquid is displaced.

62.4 lb

The liquid level outside the tube rises in pro-

portion to the volume of the cylinder wall

and the volume of the trapped air below the

original liquid level. The atmospheric pres-

sure (14.7 psi) on the liquid outside the tube

is not heavy enough to force the liquid inside

10 ft

the tube upward against the pressure of the

2.165 psi

trapped air, which is more than 14.7 psi.

(3) Diagram C. In the diagram, the

upper end of the tube is closed, but some of

the air has been removed from this tube so

that the pressure within the tube is less than

14.7 psi (a partial vacuum). A perfect vac-

uum would exist if all pressure within the

tube could be eliminated, a condition that

never happens. Because the liquid outside

the tube is subject to full atmospheric pres-

sure, the liquid is forced up into the tube to

satisfy the vacuum. How far the liquid rises

Total

depends on the difference in air pressure

weight

between the trapped air and the atmosphere.

624 lb

4.33 psi

b . Force. The relationship of force, pres-

sure, and area is as follows:

F = PA

144 sq in

where

F = force, in pounds

P = pressure, in psi

Figure 1-3. Water column

A = area, in square inches

Hydraulic Basics

1-3

index-19_1.png

index-19_2.png

FM 5-499

Example:

Figure 1-6 shows a pressure of 50 psi being

applied to an area of 100 square inches. The

Area = 10 sq in

total force on the area is—

F = PA

Weight

F = 50 x 100 = 5,000 pounds

Pressure = 4.33 psi

1-2. Pascal's Law. Blaise Pascal formulated

the basic law of hydraulics in the mid 17th cen-

tury. He discovered that pressure exerted on a

fluid acts equally in all directions. His law

states that pressure in a confined fluid is trans-

mitted undiminished in every direction and acts

Pump

with equal force on equal areas and at right

angles to a container's walls.

Force = 43.3 lb

Figure 1-7 shows the apparatus that Pascal

used to develop his law. It consisted of two con-

nected cylinders of different diameters with a

liquid trapped between them. Pascal found that

Area = 10 sq in

the weight of a small piston will balance the

weight of a larger piston as long as the piston’s

Pressure = 4.33 psi

areas are in proportion to the weights. In the

small cylinder, a force of 100 pounds on a 1-square-

Figure 1-4. Pump pressure

inch piston creates a pressure of 100 psi. Accord-

ing to Pascal's Law, this pressure is transmitted

undiminished in every direction. In the larger

A

B

C

Atmospheric

Atmospheric

pressure

pressure

Figure 1-5. Interaction of hydraulic and atmospheric pressures

1-4

Hydraulic Basics

index-20_1.png

index-20_2.png

FM 5-499

cylinder, the 100 psi of pressure from the

small cylinder is transmitted to an area of 5

square inches, which results in a force of 500

pounds on the second piston. The force has

been multiplied 5 times—a mechanical advan-

tage of 5 to 1. Using the same factors, you can

determine the distance the pistons move. For

example, if the small piston moves down 10

5,000 pounds

e

inches, the larger piston will move up 2

forc

inches. Use the following to determine the

10”

distance:

F × D

1

1

D

= -----------

2

F 2

10”

100 sq in

where

F

50 psi

1 = force of the small piston, in pounds

D1 = distance the small piston moves, in

inches

D2 = distance the larger piston moves, in

inches

Figure 1-6. Force, pressure, and area

F2 = force of the larger piston, in pounds

Example: Determine D2

F × D

1

1

100 × 10

D

= ------------

D

= -------------

D

= 2 in

2

2

F

500

2

2

500 lb

100 lb

P

W

2”

100psi

10”

1 sq in

5 sq in

Figure 1-7. Pascal’s Law apparatus

Hydraulic Basics

1-5

FM 5-499

1-3. Flow. Flow is the movement of a hydraulic fluid caused by a difference in the pressure at two points. In a hydraulic system, flow is usually produced by the action of a hydraulic

pump—a device used to continuously push on a hydraulic fluid. The two ways of measuring

flow are velocity and flow rate.

a. Velocity. Velocity is the average speed at which a fluid's particles move past a given point, measured in feet per second (fps). Velocity is an important consideration in sizing the hydraulic lines that carry a fluid between the components.

b. Flow Rate. Flow rate is the measure of how much volume of a liquid passes a point in a given time, measured in gallons per minute (GPM). Flow rate determines the speed at

which a load moves and, therefore, is important when considering power.

1-4. Energy, Work, and Power. Energy is the ability to do work and is expressed in foot-pound (ft lb). The three forms of energy are potential, kinetic, and heat. Work measures

accomplishments; it requires motion to make a force do work. Power is the rate of doing

work or the rate of energy transfer.

a. Potential Energy. Potential energy is energy due to position. An object has potential energy in proportion to its vertical distance above the earth's surface. For example, water

held back by a dam represents potential energy because until it is released, the water does

not work. In hydraulics, potential energy is a static factor. When force is applied to a confined liquid, as shown in Figure 1-4 (page 1-4), potential energy is present because of the

static pressure of the liquid. Potential energy of a moving liquid can be reduced by the heat energy released. Potential energy can also be reduced in a moving liquid when it transforms

into kinetic energy. A moving liquid can, therefore, perform work as a result of its static

pressure and its momentum.

b. Kinetic Energy. Kinetic energy is the energy a body possesses because of its motion.

The greater the speed, the greater the kinetic energy. When water is released from a dam, it rushes out at a high velocity jet, representing energy of motion—kinetic energy. The

amount of kinetic energy in a moving liquid is directly proportional to the square of its velocity. Pressure caused by kinetic energy may be called velocity pressure.

c. Heat Energy and Friction. Heat energy is the energy a body possesses because of its heat. Kinetic energy and heat energy are dynamic factors. Pascal's Law dealt with static

pressure and did not include the friction factor. Friction is the resistance to relative motion between two bodies. When liquid flows in a hydraulic circuit, friction produces heat. This

causes some of the kinetic energy to be lost in the form of heat energy.

Although friction cannot be eliminated entirely, it can be controlled to some extent. The

three main causes of excessive friction in hydraulic systems are—

• Extremely long lines.

• Numerous bends and fittings or improper bends.

• Excessive velocity from using undersized lines.

In a liquid flowing through straight piping at a low speed, the particles of the liquid

move in straight lines parallel to the flow direction. Heat loss from friction is minimal. This kind of flow is called laminar flow. Figure 1-8, diagram A, shows laminar flow. If the speed 1-6

Hydraulic Basics

index-22_1.png

index-22_2.png

FM 5-499

increases beyond a given

point, turbulent flow devel-

ops. Figure 1-8, diagram B,

shows turbulent flow.

A

Figure 1-9 shows the

difference in head because

of pressure drop due to fric-

Laminar flow

tion. Point B shows no flow

resistance (free-flow condi-

tion); the pressure at point

B is zero. The pressure at

B

point C is at its maximum

because of the head at

point A. As the liquid flows

from point C to point B,

friction causes a pressure

drop from maximum pres-

sure to zero pressure. This

is reflected in a succeed-

ingly decreased head at

points D, E, and F.

Turbulent flow

d. Relationship

Between Velocity and Pres-

sure. Figure 1-10, page 1-8,

Figure 1-8. Laminar and turbulent flow

explains Bernouilli's Prin-

ciple, which states that the

D

E