Hydraulic Systems Maintenance

Course Number: 738

This course is the second of a pair on hydraulics, following Course 737 on Hydraulic Equipment. It deals with the system as a whole, including the use of drawings and diagrams to understand the system, the installation of equipment, maintenance, and troubleshooting. In addition to specific repairs, the course deals with planned maintenance of the system to achieve maximum performance.

Recommended Contact Hours - 15

Chapter 1: Tracing Hydraulic Systems

Topics: System components; Hydraulic fluids; Tracing the system; Schematics; Cutaway drawings; Mechanical setup

Learning Objectives:

• Name the six basic elements of a hydraulic system.
• Explain the functions of hydraulic pumps, actuators, control valves, conductors and connectors, hydraulic fluid, and fluid storage and conditioning equipment.
• Describe how to trace a system.

Chapter 2: Hydraulic Diagrams

Topics: Definition, kinds, and characteristics of schematics; Lines; Symbols; Flow patterns; Tracing a circuit; Sequence valve circuit

Learning Objectives:

• Name three basic types of hydraulic diagrams, and explain the purposes of each.
• Describe how a valve symbol is constructed.
• List the steps to follow when reading a schematic diagram.
• Identify common hydraulic symbols.

Chapter 3: Installing Hydraulic Components

Topics: Safety; Cleanliness; Pump, drive, control valves, and mechanical valve installations; Pump start-up; Valve port identification

Learning Objectives:

• Explain the importance of cleanliness in hydraulic installations.
• Describe possible consequences of neglecting safety precautions.
• Explain how motor and pump shafts are aligned before coupling.
• Explain the correct method for checking direction of pump rotation.
• List several useful hints for solenoid valve installation.

Chapter 4: Installing Piping and Tubing

Topics: General installation procedures; Tube flaring; Checking the flare; Tube bending and assembly; Hose, seal, reservoir, filter, heat exchanger, and actuator installation

Learning Objectives:

• Explain how pipe sizes are specified.
• Name the common types of pipe joints.
• List six important rules for good piping installation.
• Describe the advantages of hydraulic tubing over pipes.
• Describe the correct methods for bending and flaring tubing.
• List the key points for correctly installing hydraulic hoses, seals, reservoirs, filters, and actuators.

Chapter 5: Selecting Hydraulic Fluids

Topics: Viscosity; Resistance to chemical and physical changes; Low-temperature properties; Demulsibility; Antirust properties; Compatibility

Learning Objectives:

• List ten important properties of hydraulic fluids.
• Explain the difference between hydrodynamic and boundary lubrication.
• Explain what a fluid's viscosity index means.
• Define demulsibility and emulsibility.
• Describe how to read a viscosity-temperature chart.
• List the proper procedures for installing hydraulic fluid.

Chapter 6: Maintaining Hydraulic Systems

Topics: Inspections; Maintenance requirements; Fluid level; External leaks; Operating pressure; Fluid quality; Filter maintenance; Reconditioning

Learning Objectives:

• List the major categories of hydraulic system maintenance.
• Name and describe the six essential items in a maintenance file.
• List the steps involved in reconditioning a hydraulic component.
• Explain how to set up a maintenance plan for a typical hydraulic system.

Chapter 7: System Troubleshooting

Topics: Diagnosis and symptoms; Evaluating machine history; Determining the cause; Providing the solution; Tools and gauges; Troubleshooting charts

Learning Objectives:

• Describe the troubleshooting process.
• Explain how to evaluate recent maintenance history.
• List typical symptoms of common hydraulic system problems.
• Explain how to determine the cause of and provide a solution to a problem.
• Explain how a portable tester works.
• Describe how to keep and use troubleshooting charts.

Chapter 8: Valve Troubleshooting

Topics: Valve problems and test procedures; Disassembly, cleaning, and inspection; Repair and replacement; Solenoid problems; Reassembly and testing

Learning Objectives:

• Name five common valve problems and explain the sequence of steps to be followed in troubleshooting them.
• Describe the proper procedures for valve disassembly, cleaning, and inspection.
• Explain how to determine whether to repair or replace a malfunctioning valve.
• Describe the reasons for hydraulic "wire drawing."
• List the reasons for electrical and mechanical failures of solenoid valves.
• Explain the procedures for reassembling, reinstalling, and testing valves.

Chapter 9: Cylinder Troubleshooting

Topics: Cylinder descriptions; Troubleshooting procedures; Cylinder testing, repair, and installation; Shock absorbers

Learning Objectives:

• Name the most common types of hydraulic cylinders and identify their major parts.
• List the symptoms of internal and external cylinder misalignment.
• Explain what to do if you find internal leakage in a cylinder.
• Name the cylinder components most frequently replaced.
• Explain the purpose of a piston rod boot.
• Describe the symptoms of shock absorber failure.

Chapter 10: Pump and Motor Troubleshooting

Topics: Gear and vane pump problems; Vane motors; Axial- and radial-piston pump problems; Pump and motor repair; Pump maintenance checks

Learning Objectives:

• List the proper procedures for troubleshooting pumps and motors.
• Name some common causes of pump failure.
• Describe typical causes of cavitation.
• Discuss the major sources of problems in gear pumps and vane pumps.
• Describe the effects of contaminants in axial-piston and radial-piston pumps.
• Explain the differences between a vane motor and a vane pump.