Lecture Notes on Valves in Industry

Introduction to Valves

• Definition: A valve is a mechanical device that controls and regulates the flow of fluid and pressure within a system.
• Importance: Valves are crucial components of piping systems, and selecting the right valve is vital for system success.
• Common Applications: Used in HVAC, water systems, automobiles, and many industrial processes.

Functions of Valves in Industry

• Control Fluid Flow:
  • Stopping and starting fluid flow.
  • Varying the amount of fluid flow.
  • Controlling the direction of fluid flow.
  • Regulating downstream pressure.
  • Relieving overpressure in components or piping.

Types of Valves

1. Gate Valve

   • Function: Linear motion valve to start/stop fluid flow, does not regulate flow.
   • Usage: Oil and gas, automotive, pharmaceuticals, manufacturing.
   • Note: Prone to vibration when partially open.

2. Globe Valve

   • Function: Linear motion valve to stop, start, and regulate fluid flow.
   • Operation: Disk moves perpendicular to the seat; causes head loss due to flow path obstructions.
   • Usage: Water cooling systems, chemical feed, boiler, and steam vents.

3. Ball Valve

   • Function: Rotational motion valve using a ball-shaped disc.
   • Advantages: Compact, requires no lubrication, tight sealing, low maintenance costs.
   • Usage: Oil and natural gas industry, chemical storage, residential uses.

4. Plug Valve

   • Function: Rotational motion valve that resembles a plug.
   • Usage: Directional flow control, handling gas/liquid fuels, slurries, low pressure/temperature services.

5. Diaphragm Valve

   • Function: Linear motion valve with a flexible disc that forms a seal.
   • Usage: Handling corrosive fluids, fibrous slurries, radioactive fluids, vacuum service.

6. Reducing Valve

   • Function: Automatically reduces supply pressure to a preset level.
   • Operation: Controlled by high pressure at the valve inlet.
   • Usage: High-pressure steam lines, hydraulic presses.

7. Pinch Valve

   • Function: Controls flow through rubber tubing; suitable for on/off and throttling services.
   • Usage: Handling slurries and liquids with suspended solids.

8. Butterfly Valve

   • Function: Rotary motion valve for regulating flow.
   • Advantages: Space, weight, and cost savings compared to globe and gate valves.
   • Usage: Handling slurries and liquids with solids.

9. Needle Valve

   • Function: Allows fine adjustments in fluid flow, characterized by a tapered needle-like point.
   • Usage: Constant pressure pump governors, automatic combustion control.

10. Swing Check Valve

    • Function: Allows full flow and closes as pressure decreases.
    • Usage: Low velocity flow lines; not suitable for pulsating flow.

11. Lift Check Valve

    • Function: Used in systems with globe valves, suitable for horizontal/vertical lines.
    • Usage: Steam, air, gas, water systems.

12. Relief Valve

    • Function: Relieves overpressure to prevent equipment damage.
    • Note: Opens just enough to relieve pressure conditions.
    • Usage: Incompressible fluids (water, oil).

13. Safety Valve

    • Function: Rapidly opens fully at a set pressure to prevent equipment damage.
    • Note: Stays open until pressure drops below reset level.
    • Usage: Compressible fluids (steam, gases).

Conclusion

• Emphasis on the critical role of valves in various industries.
• Importance of selecting the appropriate type of valve for specific applications.