2nd Edition

Fluid Power Troubleshooting, Second Edition,

By Anton Hehn Copyright 1994

    Presents practical methods for detecting, diagnosing and correcting fluid power problems within a system. The work details the design, maintenance, and troubleshooting of pneumatic, hydraulic and electrical systems and components. This second edition stresses: developments in understanding the complex interactions of components within a fluid power system; cartridge valve systems, proportional valve and servo-systems, and compressed air drying and filtering; noise reduction and other environmental concerns; and more.;This work should be of interest to mechanical, maintenance, manufacturing, system and machine design, hydraulic, pneumatic, industrial, chemical, electrical and electronics, lubrication, plastics processing, automotive, process control, and power system engineers; manufacturers of hydraulic and pneumatic machinery; systems maintenance personnel; and upper-level undergraduate and graduate students in these disciplines.

    Foreword Z. J. Lansky


    1 Fluid Power Principles: A Review

    Hydraulic Principles

    Basic Laws of Fluids

    Pneumatic Principles

    Hydraulic System Operation

    Advantages and Disadvantages of Hydraulic System

    Comparing Hydraulic Systems

    Pneumatic System Operation


    Heat Exchangers (Aftercoolers)

    Storage Tanks

    Air Drying Equipment

    Comparison of Air Systems to Electric and Hydraulic Systems

    Air Versus Electric Systems

    Air Versus Hydraulic Systems

    2 Hydraulic Systems: Operation, Maintenance, and Troubleshooting

    Hydraulic Pumps

    Gear Pumps

    Vane Pumps

    Piston Pumps

    Hydraulic Motors

    Motor Ratings

    Vane Motors

    Gear Motors

    Piston Motors

    Rotary Motion (Fluid Motors and Rotary Actuators)

    Startup, Operation, and Maintenance of Hydraulic Pumps and Motors

    General Instructions

    Pump Malfunction

    Hydraulic Motor Malfunction

    Troubleshooting Pumps and Motors

    Hydraulic Valves

    Directional Control Valves

    Check Valves

    Flow Control Valves

    Pressure Control Valves

    Solenoid Valves

    Servicing, Repairing, and Troubleshooting Hydraulic Valves

    Hydraulic and Pneumatic Cylinders

    Description and Terminology

    Cylinder Ratings

    Cylinder Cushions

    Cylinder Piston Seals

    Installation and Maintenance of Hydraulic Cylinders

    Troubleshooting Hydraulic and Pneumatic Cylinders

    Hydraulic Accumulators

    Types and Applications

    Servicing and Repairing of Accumulators

    Hydraulic System Reservoirs

    Construction and Design




    3 Pneumatic Systems: Operation, Maintenance, and Troubleshooting

    Air Compressors

    Reciprocating Piston Compressors

    Rotary Compressors

    Installation, Maintenance, and Troubleshooting

    Pneumatic Valves

    Valve Operation

    Maintenance and Troubleshooting

    Air Motors

    Types of Air Motors

    Air Motor Characteristics

    Maintaining Air Motors

    Maintenance of Air Tools

    4 Contaminants in a Hydraulic System


    Effects Control

    Filter Types

    Filter Bypass Valve

    Filter Condition Indicator

    Installation, Maintenance, and Troubleshooting of Hydraulic Filters




    5 Compressed Air Filtration, Lubrication, and Moisture Control

    Contaminants in the Air System

    Air Line Filters, Lubricators, and Pressure Regulators

    Compressed Air Filters


    Pressure Regulators

    Choosing a F-R-L

    Routine Maintenance of F-R-L Units

    Maintenance of Compressed Air Filters

    Aftercoolers and Air Driers


    Air Driers

    6 Hydrostatic Transmissions

    Principles of Operation

    Circuit Development

    Comparison of Hydrostatic Transmission Types

    Hydrostatic Transmission Controls

    Hydrostatic Transmission Start-up Procedure

    Hydrostatic Transmission Maintenance

    Troubleshooting Hydrostatic Transmissions

    Troubleshooting Guidelines

    7 Temperature Considerations

    Heat Generation

    Heat Dissipation

    Heat Exchangers: Coolers

    Heat Exchanger Types

    Adding a Second Heat Exchanger

    Miscellaneous Tips on Heat Exchangers

    Tips on Heat Dissipation by Radiation

    Maintenance and Service

    Replacement of Zinc Anodes

    Cleaning Shell-and-Tube Heat Exchangers

    Cleaning Air-Oil Heat Exchangers

    Checking for Leaks

    8 Hydraulic System Fluids: Selection and Care

    Fluid Types and Properties

    Fluid Properties

    Petroleum Oils

    Fire-Resistant Fluids


    Maintaining Fluid Performance

    9 Fluid Conductors and Connectors

    Pipe, Tubing, and Hose





    Tube Fittings

    Straight Thread O-Ring Fittings

    Hose Fittings and Couplers

    Installation Considerations

    Pipe Installation

    Tubing Installation

    Hose Installation

    Hose Fitting Installation

    Plant Air Line Piping Systems

    Use and Care of Hose and Fittings

    House Assembly Failures

    Improper Application

    Improper Assembly and Installation

    External Damage

    Faulty Equipment

    Faulty Hose

    Analyzing Hose Failures

    Modular Manifold Hydraulic Systems

    10 Seals for Fluid Power Equipment

    Seal Forms

    Dynamic Seal Application and Failure

    Radial Lip Seals

    Face Seals


    Static Seal Application and Failure



    Checking for Leaks

    Seal Materials

    Elastomeric Seal Materials

    Tips to Avoid Premature Seal Failure

    Exclusion Rings, or Wiper or Scraper Rings

    11 Fluid Power Systems: Operation, Maintenance, and Troubleshooting

    System Design Considerations

    Installation, Start-up, and Operation of Hydraulic Systems




    Knowing the System

    Maintenance of Hydraulic Systems

    Maintenance Procedures and Hints

    Hydraulic System Maintenance Accessories

    Fluid Storage and Handling

    Troubleshooting Guides

    12 Fluid Power System Malfunction Detection and Diagnosis

    Malfunction Detection

    Using a Hydraulic Tester to Troubleshoot

    Application of a Tester

    Diagnostic Instrumentation

    Bourdon Tube Pressure Gauge

    Viscosity Measurement

    Liquid-Level and Temperature Indicators


    13 Fluid Power System Noise Control

    Pump Noise

    Hydraulic System Noise Control

    Vibration Noise Control

    Fluidborne Noise Control

    Noise Measurement

    Research to Reduce Noise

    14 Electrohydraulic Servo Systems, Proportional Valve Systems, and Load-Sensing Systems


    Control System Types

    Electrohydraulic Equipment

    Properties of Feedback Control Systems


    Open-Loop Versus Closed-Loop System Characteristics

    Stability and Dynamic Response

    Electrohydraulic Proportional and Servo Valves

    Proportional Valve Construction

    Servo Valve Construction

    Servo Valve Characteristics

    Flow Control Servo Valves

    Pressure-Control Servo Valves

    Installation, Operation, Maintenance, and Troubleshooting of Servo Valves

    Installation and Start-up


    Maintenance and Troubleshooting

    Servo-system Terminology

    Appendix A. Fluid Power Symbols and Glossary

    Fluid Power Symbols

    Fluid Power Graphic Symbols

    American National Standards Institute Symbols

    Glossary of Fluid Power Terms

    Appendix B. Hydraulic Facts and Technical Data

    Hydraulic Facts

    Miscellaneous Technical Data

    Helpful Tables for Fluid Power Systems



    Anton Hehn

    ". . .provides practical explanations of component and system function, failure modes encountered in this operation of systems, and methods for locating and isolating fluid power problems."
    ---IASI Polytechnic Magazines