Hydraulics Field Manual and Training

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Hydraulics Field Manual and Training

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Hydraulics Field Manual and Training
173 Pages

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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. 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.

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 covering 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 reservoirs, 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.

TOC

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
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
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
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
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

List of Figures

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
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
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
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
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
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
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