LAB # 1
FORCE, PRESSURE AND AREA

PURPOSE

This laboratory assignment will provide an opportunity  to observe the relationships between Force (F), Pressure (P) and Area (A) in two simple linear hydraulic circuits.    Pressure will be compared for two actuators under the same loading conditions.  Therefore, Force (F) will remain constant.  The purpose is to determine the effect of changing the size of cylinder in a hydraulic circuit.
 

OBJECTIVES

After completing this laboratory, you should be able to do the following:

1. Determine the purpose and function of basic components in a simple linear hydraulic circuit;

2. Identify ISO symbols and circuit components ;

3. Develop a working hydraulic schematic;

4. Conduct a computer simulation of circuit operation;

5. Observe pressure differences (extending vs. retracting);

6. Observe pressure differences between two cylinders;

7. Determine the area ratio and force ratio of two hydraulic cylinders.

This laboratory incorporates two different hydraulic cylinders in a basic linear circuit. The load will be held constant on the cylinders during extension and retractiion.  If force remains constant, then pressure should change as the effective piston area changes. This relationship is based on Pascal's Law.
 
  • Components Required:
  • Vickers Industrial Hydraulic Trainer;
  • Unidirectional, fixed displacement hydraulic pump with reservoir;
  • Relief Valve:  Set relief valve to 500 psi.
  • Directional Control Valve (4 way, 3 position, tandem center)
  • Pressure gages;
  • Linear Actuator (1.5 inch bore, 5/8 inch rod);
  • Linear Actuator (3.0 inch bore, 1.25 inch rod).
    • CIRCUIT
     

                                 CYLINDER 1                                                         CYLINDER 2

     
     

    PROCEDURE:  The following steps should be taken in carrying out the execution of laboratory one.  Take care to follow
                                  procedures as written, and always observed the safety rules.  Always assume a system is under full presure,
                                  and take measures to relieve pressure before connection or disconnecting hoses.

    ____ 1. Construct the circuits as show above on the Vickers hydraulic trainer.
     
    ____ 2. Identify the function of each component;

    ____ 3. Define the standard color codes used to represent the state of fluid in a system
                  (show legend on your schematic);

    ____ 4. Identify the name and number of each component by generating a schedule on
                  your schematic (required for written report) ;

    ____ 5. Adjust the relief valve to 500 psi;  Note: Flow rate for this circuit is 2 GPM;

    ____ 6. Complete all connections for the basic circuit using the 1.5 inch bore, .625 rod cylinder;

    ____ 7. Turn on the trainer and Shift the DCV for extension;

    ____ 8. Extend and retract 1.5 inch bore, 5/8 inch rod clyinder and record the pressure readings
                  (while the actuator is in motion);

    ____ 9. Observe and record the pressure during extension and retraction;
     
    ____10. Extend and retract the 1.5 inch bore, 1.25 inch rod cylinder;

    ____11. Observe and record the pressure during extension and retracton;

    ____12.  Record all pressure readings on the chart shown below:

    ____ 13.  Calculate the cap and annular area for each of the cylinders and record

    ____14.  Calculate the theoretical pressure ratio during extension and retraction for each cylinder;

    ____ 15. Compare observed values to theoretical pressures.

    ____ 16.  Determine experimental error;

    ____ 17. Using the format shown in the lab report guide,  submit a formal written lab report
                    by next class meeting or as requested by your lab instructor.
     

    RESULTS
     
    ACTUATOR BORE ROD DIAMETER CAP AREA ANNULAR AREA
    CYLINDER 1 1.5 INCHES .625 INCHES
    CYLINDER 2 3.0 INCHES 1.25 INCH
    CALCULATIONS:
     
     
     
     
    ACTUATOR PRESSURE EXTENDING PRESSURE RETRACTING PRESSURE IN NEUTRAL
    CYLINDER 1
    CYLINDER 2
    CALCULATIONS:
     
     
     
     
     
     
     
     

    1. What component in the system determines the maximum flow available? ___________________________________

    2. What is the maximum pressure of the system and why? ________________________________________________

        _______________________________________________________________________________________

    3. Is there any difference in pressure during extensioncompared to retraction for cylinder 1?
        ______ for cylinder 2 ? ____.

        Explain _______________________________________________________________________________

                     _______________________________________________________________________________.

    4. Is there any difference in pressure during retraction for cylinder 1 compared to cylinder 2? _______.

        Explain. _______________________________________________________________________________

                      _______________________________________________________________________________.

    5. Is there any difference in pressure during extension for cylinder 12 compared to cylinder 13? _______.

         Explain. _______________________________________________________________________________

                       _______________________________________________________________________________.

    6. Would the pressure readings you observed in the simulation be consistant with actual pressure
        readings on a  "live" system?

         Explain________________________________________________________________________

                      ________________________________________________________________________________