Basic Hydraulics

Table of Contents

Chapter 1: Principles of Hydraulics

Topics: Force, weight, mass, pressure, work, power, and energy; Incompressibility; Nondiffusion; Hydrostatic pressure; Pascal's Law; Fluid power transmission; Bernoulli's principle

Learning Objectives:

• Explain the difference between absolute and gauge pressure.
• Demonstrate how power is calculated.
• Explain Pascal's Law.
• Describe the difference between laminar and turbulent flow.
• Name the main components of a hydraulic system.

Chapter 2: Hydraulic Fluids

Topics: Viscosity; Pour point; Fluid selection; Chemical properties; System contamination; Dissolved air; Foaming; Corrosion and rusting

Learning Objectives:

• List the most important properties of hydraulic fluids.
• Explain how viscosity is measured.
• Explain the meaning of the viscosity index.
• Describe the effect of fluid temperature on viscosity.
• Name the causes of corrosion and fluid oxidation.
• Identify various types of hydraulic fluids.

Chapter 3: Strainers and Filters

Topics: Contaminant removal; Strainer performance; Types of strainers; Fibrous and nonfibrous filter media; Magnetic media; Installation

Learning Objectives:

• Name contaminants found in hydraulic systems.
• Explain the difference between a strainer and a filter, and describe the main function of each.
• Describe the two basic types of filter/strainer media.
• Draw graphic symbols for strainers and filters.

Chapter 4: Reservoirs and Accumulators

Topics: Reservoir, air separation requirements; Baffles; Reservoir cooling methods and accessories; Accumulators; Schematic symbols

Learning Objectives:

• Explain the functions of fluid reservoirs.
• Explain the purpose of reservoir baffles.
• Describe various methods of counteracting high operating temperatures.
• Identify important accessories used with reservoirs.
• Demonstrate pressure ratio calculation for a differential-piston accumulator.

Chapter 5: Hydraulic Pumps

Topics: Pump varieties, functions, and selection; Gear, screw, cycloidal, vane, axial-piston, and radial-piston pumps

Learning Objectives:

• Name the main classification of hydraulic pumps.
• List factors affecting pump selection and pump performance.
• Define volumetric efficiency and overall efficiency.
• Identify the most common types of positive-displacement pumps, and describe their operation.

Chapter 6: Piping, Tubing, and Fittings

Topics: Fluid flow and velocity; Hydraulic pressure; Pressure loss; Steel pipe and fittings; Tubing and tube bending; Hoses; Hose fittings and couplings

Learning Objectives:

• Discuss the chief considerations in hydraulic line selection.
• Demonstrate how flow velocity and pressure loss are calculated.
• Explain pipe size schedules.
• Describe various types of fittings used in hydraulic systems.
• Explain the reason for using steel pipe.
• List the main advantages of tubing.

Chapter 7: Directional Control Valves

Topics: Valve classification; Automatic, two-way, check, pilot-operated, and spool valves; Hydraulic motors; NO, NC, holding valves; Symbols; Flow ratings

Learning Objectives:

• Explain the classification of directional control valves.
• Describe how manually operated valves work.
• Explain the difference between direct-acting and pilot-operated valves.
• Describe the operation of a check valve, a spool valve, a three-way valve, a four-way valve, and a rotary valve.
• Explain the difference between normally closed and normally open valves.

Chapter 8: Pressure-Control Valves

Topics: Poppet, spool, sequence, counterbalance, holding, unloading, and pressure-reducing valves; Shock suppressors; Flow-control valves

Learning Objectives:

• Explain the functions of a pressure-control valve, a pressure-relief valve, and a pressure-reducing valve.
• Describe the operation of a spool valve, a poppet valve, and a sequence valve.
• Explain the purpose of holding valves, unloading valves, and counterbalance valves.
• Name the operations performed by flow-control valves.
• Describe how pressure compensation and temperature compensation work.

Chapter 9: Hydraulic Cylinders

Topics: Double-, single-acting cylinders; Two-piston cylinders; Positional cylinders; Cylinder construction; Rings, seals, and packing; Cylinder mounting and selection; Flow capacity; Cushioning

Learning Objectives:

• Describe the purpose of a hydraulic cylinder, and explain how a double-acting cylinder works.
• Explain the difference between "pull-type" and "push-type" single-acting cylinders.
• Describe the construction of a hydraulic cylinder.
• Explain the various methods of mounting cylinders.
• Demonstrate how to calculate the flow capacity of a hydraulic cylinder.

Chapter 10: Hydraulic Motors

Topics: Performance specifications; Starting, running, and stalling torque; Volumetric efficiency; Hydraulic motor construction; Gear, vane, and piston motors

Learning Objectives:

• Explain the classification of hydraulic motors.
• Demonstrate how the torque of a hydraulic motor is calculated.
• Calculate the horsepower output of a hydraulic motor.
• Discuss cost factors and other considerations affecting motor selection.
• Describe the construction of a hydraulic motor.
• Explain the operating principles of a gear motor, a vane motor, and a piston motor.

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