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Hydraulic Valves (PowerPoint)

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					Hydraulic Valves
        Objectives related to Valves
1.    State the function of a valve.
2.    Describe the three types of valves.
3.    List the four uses of pressure control valves.
4.    Describe two types of relief valves, and their uses.
5.    State the difference in cracking pressure and full-flow pressure.
6.    Describe the two main types of pressure reducing valves.
7.    State the function of a pressure sequencing valve.
8.    State the function of unload valves.
9.    List and describe the five types of directional control valves.
10.   Explain the difference in a valve stack and a unibody valve.
11.   List and describe two types of volume control valves.
12.   List and describe the types of flow control valves.
13.   List and describe the types of flow divider valves
14.   Describe the proper procedures to follow before and during valves disassembly.
15.   Describe the proper procedures to follow in reassembly of valves.
16.   List and describe three ways valves can be actuated/operated.
17.   Identify six common valve symbols
   Obj 1. Functions of a valve
• direct the flow of fluid
• regulate the pressure
• control volume
   Obj. 2 Three types of valves
• Pressure – adjust psi for some purpose
• Directional -- route the fluid to the desired
  actuator
• Volume Control or Flow Control -- control
  the amount of flow
     Obj 3 Uses of pressure control
                valves
•   Limit system pressure
•   Reduce pressures
•   Set pressure at which oil enters a circuit
•   Unload a pump
 Obj. 4 Types of relief valves, and
            their uses
• Direct acting -- used with low volume and
  infrequent use
• Pilot operated -- used with high volume
  with little pressure difference
    Obj 5. Difference in cracking
   pressure and full-flow pressure
• cracking -- pressure at which valve begins
  to open
• full-flow -- pressure at which valve is
  allowing max flow
 Obj 6. Two main types of pressure
          reducing valves
• Constant reduced – Set to reduce a certain amount below the
  operating system pressure.
   – Ex. 1, Set constant reduced pressure at 500 psi and the system
     pressure is 2000 pressure, the valve will keep the system pressure at
     1500
   – Ex. 2, Set at 500 psi and system pressure is 3000 pressure is reduced
     to 2500
   – Ex. 3, set at 250 psi and system pressure is 3000, the pressure is
     reduced to 2750
   – Also is ______ below the system pressure,
• Fixed amount pressure – Set to be one pressure no matter what
  the system pressure is.
   – Ex. 1, Fixed pressure is set for 1500 psi and the system pressure goes
     to 2000 psi the pressure in the circuit stays the same at 1500
   – Ex. 2, using info from Ex. 1, if the pressure goes to 3000 the pressure
     stays the same in the circuit at 1500 psi.
   – 1500 no matter what (unless total system pressure drops below 1500)
    Obj 7. Function of a pressure
          sequencing valve
• controls flow between branches/circuits
• first one then another branches/circuits
Obj 8. Function of unload valves
• Directs flow back to the reservoir
     Obj 9. Five types of directional
             control valves
1.   Check valves
2.   Rotary Valves
3.   Pilot Operated Poppet Valves
4.   Electro-hydraulic Valves
5.   Spool Valves
     1. Unibody
     2. Stack
Obj 10. Difference in a valve stack
       and a unibody valve
  Obj 11 & 12 & 13 & 14. Types of
       volume control valves
1. Flow control -- control amount of flow
  1. Restrict flow -- Usually non-compensated--
     Compensated valves do not adjust for
     pressure changes
     1. Needle (non-compensated)
     2. Gate (non-compensated)
  2. Divert flow -- usually compensated
2. Flow dividers – direct flow to two or more
   circuits
Obj 12. Types of flow control valves
Obj 13. Types of flow divider valves
Obj 14. Proper procedures to follow
before & during valves disassembly
Obj 15. Proper procedures to follow
      in reassembly of valves
 Obj 16. Three ways valves can be
          actuated/operated
• Operators for directional-control valves are
  either;
  – Mechanical or manual (many different ways to
    manually operate a valve).
  – Pilot – makes use of low volume system
    pressure
  – Electrical or Electronic
  – A combination of the above
Obj 17. Common valve symbols

				
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posted:2/23/2012
language:English
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