1 / 23

TSM 363 Fluid Power Systems

TSM 363 Fluid Power Systems. Control of Power Distribution - Valve-based Controls. How to Make it Functioning as Expected?. 1. Pressure Controls. System Pressure Control Use of a line relief valve to limit the maximum allowable system pressure Other Pressure Control Functions Unloading

Download Presentation

TSM 363 Fluid Power Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. TSM 363 Fluid Power Systems Control of Power Distribution- Valve-based Controls

  2. How to Make it Functioning as Expected?

  3. 1. Pressure Controls • System Pressure Control • Use of a line relief valve to limit the maximum allowable system pressure • Other Pressure Control Functions • Unloading • Pressure reduction • Load holding • Sequential control • Others

  4. Inlet Pilot Outlet Line Relief Valve • Line relief valve is a pressure control valve. • A basic LR valve has a pilot pressure applied. • There are a few types of LR valves available.

  5. Pressure Override Characteristics

  6. Pilot Operated Relief Valves Function:protect a hydraulic system with low override characteristics. Operation:The spring loaded puppet valve opens when the pressure reaches the cracking pressure, the flow cause the back pressure drop, which leads the open of the spool valve.

  7. P P P P full full flow flow full full flow flow P P P P D D D D Improved Pressure Override Characteristics

  8. M R P H T M 800 psi 800 psi Application of Relief Valves 1,000 psi It is recommended that there is always at least 200 psi difference between two line release (pressure relief) valves in a line.

  9. Heat Generation in Pressure Relief

  10. Example Other Pressure Controls:-- Sequence Valves

  11. Functionality and Operation of a typical Sequence Valves • Controls the order of operations in branch circuits • The sequence valve is normally closed. It is set to react to a system pressure less than the setting of the pressure relief valve. • Pressure increases resulting from an actuator reaching the end of its stroke open the sequence valve.

  12. 2. Flow Controls • Uncompensated Flow Control • Example – metering-in/metering-out using needle valves • Compensated Flow Control • Example - • Proportional Flow Control • Often use of proportional directional control valve (discuss in direction control)

  13. Metering Controls of Flow • Often us of a needle valve • Simple, but energy inefficient • Commonly used in some light load, inexpensive systems for load control.

  14. Typical Metering Flow Control Approaches

  15. Flow Divider –Example of Pressure-compensated Flow Control

  16. Functionality and Operation of a Flow Divider Valve • Directs flow to two or more branches • Controls flow and also direction (e.g., priority control) • Common on off-road equipment to divide flow between circuits (e.g., power steering and front-end load or left and right crawler tracks)

  17. 3. Direction Controls • Simple direction control • On-off type direction control • Multi-direction Control • Circuits Switching-type direction control • Proportional direction control • Direction and flow integrated control

  18. P P P Pp Pp Pp QT QT PT PT PT T T T PT PT PT QP QP Qk Qk Q2 Q1 Q2 Q1 2 1 P1 P2 P2 P1 P1 P2 1 2 Simple direction Control

  19. Simple direction Control

  20. M M M M M P P P P P R R R R R M M M M M H H H H H T T T T T Multi-direction ControlCase 1: Hydraulic Cylinder Controls

  21. M M M M M M M M M M M M Multi-direction ControlCase 2: Hydraulic System Priority Controls

  22. Theoretical Base for All Valve Controls:Orifice Equation • Cd is determined experimentally • Pressure drop is proportional to flow • Valve Principles: Area is a adjusted to control pressure and flow rate • Density of petroleum-based fluids 850-950 kg/m3

  23. Lecture Summary • Discussed the basic principles of different methods of using valves to control a hydraulic system: • Pressure controls • Flow controls • Directional controls • All valved-based controls follows the same control principle

More Related