Lecture Notes on Valves

Introduction to Valves

• Valves are crucial in various industries (industrial engineering, manufacturing, science).
• Found in mechanical devices: HVAC systems, water systems, automotive mechanisms.
• Definition: A valve is a mechanical device that controls and regulates the flow of fluid and pressure within a system.
• Importance: Selecting the right valve can determine the success or failure of a system.

Types of Valves

Common Types of Valves

1. Gate Valve

   • Linear motion valve, used to start or stop fluid flow.
   • Does not regulate or throttle fluid flow.
   • Prone to vibration in partially open state.
   • Applications: Oil & gas, automotive, pharmaceuticals, manufacturing plants.

2. Globe Valve

   • Linear motion valve, used to stop, start, and regulate fluid flow.
   • Operates by perpendicular movement of the disk from the seat.
   • Applications: Water cooling systems, chemical feed systems, steam vents.

3. Ball Valve

   • Rotational motion valve using a ball-shaped disk.
   • Compact design, requires no lubrication, tight sealing.
   • Low maintenance costs.
   • Applications: Oil & gas, chemical storage, residential uses.

4. Plug Valve

   • Rotational motion valve resembling a plug.
   • Used for directional flow control and handling slurries.
   • Applications: Gas or liquid fuels, low-pressure systems.

5. Diaphragm Valve

   • Linear motion valve, used to start, regulate, and stop fluid flow.
   • Features a flexible disk to form a seal with the valve seat.
   • Suitable for corrosive fluids and fibrous slurries.

6. Reducing Valve

   • Automatically reduces supply pressure to a pre-selected level.
   • Operates without an external power source.
   • Applications: High-pressure steam lines.

7. Pinch Valve

   • Controls flow through rubber tubing, suitable for on/off and throttling services.
   • Ideal for slurries and fluids with suspended solids.

8. Butterfly Valve

   • Rotary motion valve for stopping or regulating flow.
   • Advantages: Lightweight, cost-effective.
   • Used for slurries and fluids with solids.

9. Needle Valve

   • Allows fine adjustments in fluid flow.
   • Features a long tapered point for gradual flow control.
   • Applications: Constant pressure pumps, automatic combustion control.

10. Swing Check Valve

    • Allows full flow, automatically closes as pressure decreases.
    • Prevents backflow, recommended for low-velocity lines.

11. Lift Check Valve

    • Used in piping systems where globe valves are flow control valves.
    • Suitable for vertical or horizontal lines with upward flow.

12. Relief Valve

    • Relieves accidental over-pressurization in fluid systems.
    • Opens as necessary to relieve pressure.
    • Typically used for incompressible fluids (water, oil).

13. Safety Valve

    • Rapidly opens fully at set pressure to prevent over-pressurization.
    • Stays open until pressure drops below a reset point.
    • Used for compressible fluids (steam, gases).

Conclusion

• Valves play a vital role in fluid systems across multiple industries.
• Importance of understanding different types of valves for effective system design and operation.

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