Lecture 8: Valves & Fittings (Part 1 & 2) Flashcards
Purpose of Valves in Process Systems:
Purpose: Control the flow of fluids or gases.
Types of Valves in Process Industries:
Types: Gate valves, globe valves, ball valves, butterfly valves, needle valves, check valves.
Selecting an Appropriate Valve:
Factors: Type of service, allowable pressure drop, process geometry, fluid properties, cost.
Key Factors for Valve Selection:
Factors: Type, size, material, flow coefficient (Cv), actuator type.
Difference Between Globe Valve and Gate Valve:
Globe Valve: Regulates flow.
Gate Valve: Designed for isolation.
Flow Coefficient (Cv) and Valve Performance:
Cv measures flow capacity, affecting pressure drop across the valve.
Control Valve vs. Isolation Valve:
Control Valve: Regulates flow.
Isolation Valve: Completely shuts off flow.
Calculating Pressure Drop Across a Valve:
Using Cv, flow rate, and fluid properties.
Function of Valve Actuator:
To open and close the valve.
Troubleshooting Common Valve Problems:
Identify root cause and take corrective action for issues like leakage, sticking, or failure to open/close.
Advantages and Disadvantages of Valve Actuators:
Depend on factors like cost, reliability, and maintenance. Types include pneumatic, hydraulic, electric.
Safety Considerations When Working with Valves:
Proper handling of hazardous materials, use of personal protective equipment, and following safety procedures.
Valve Maintenance and Repair:
Tasks like cleaning, lubrication, part replacement for optimal performance and preventing failure.
Environmental Considerations in Valve Selection:
Consider factors like emissions and environmental impact.
Difference Between Rising Stem and Non-Rising Stem Valve:
Rising Stem: Stem moves up and down as the valve opens and closes.
Non-Rising Stem: Stem does not move.
Difference Between Single-Seated and Double-Seated Valve:
Single-Seated Valve: One sealing surface.
Double-Seated Valve: Two sealing surfaces.
Difference Between Soft-Seated and Metal-Seated Valve:
Soft-Seated Valve: Sealing surface made of soft material (e.g., rubber).
Metal-Seated Valve: Sealing surface made of metal.
Difference Between Linear Valve and Rotary Valve:
Linear Valve: Opens and closes with linear motion.
Rotary Valve: Opens and closes with rotary motion.
Difference Between Quarter-Turn and Multi-Turn Valve:
Quarter-Turn Valve: Requires a quarter turn to fully open/close.
Multi-Turn Valve: Requires multiple turns to open/close.
Difference Between Control Valve and Shut-Off Valve:
Control Valve: Regulates flow.
Shut-Off Valve: Stops flow completely.
Difference Between Globe Valve and Ball Valve:
Globe Valve: Linear motion to open/close.
Ball Valve: Rotary motion to open/close.
Difference Between Gate Valve and Butterfly Valve:
Gate Valve: Designed for isolation.
Butterfly Valve: Designed for flow regulation.
Difference Between Check Valve and Relief Valve:
Check Valve: Allows flow in one direction.
Relief Valve: Protects equipment from overpressure.
Difference Between Diaphragm Valve and Pinch Valve:
Diaphragm Valve: Uses a flexible diaphragm to seal.
Pinch Valve: Uses a flexible sleeve that is pinched to close.
Difference Between Solenoid Valve and Motorized Valve:
Solenoid Valve: Operated by electric current.
Motorized Valve: Operated by an electric motor.
Types of Valve Actuators:
Pneumatic, hydraulic, electric, and manual.
Purpose of Valve Actuator:
Provides force to open and close the valve.
Difference Between Pneumatic Actuator and Hydraulic Actuator:
Pneumatic Actuator: Powered by compressed air.
Hydraulic Actuator: Powered by hydraulic fluid.
Difference Between Linear Actuator and Rotary Actuator:
Linear Actuator: Provides linear motion to open/close the valve.
Rotary Actuator: Provides rotary motion to open/close the valve.
Difference Between Single-Acting Actuator and Double-Acting Actuator:
Single-Acting Actuator: Moves the valve in one direction.
Double-Acting Actuator: Moves the valve in both directions.
Difference Between Direct-Acting Actuator and Reverse-Acting Actuator:
Direct-Acting Actuator: Moves the valve stem in the same direction as the actuator stem.
Reverse-Acting Actuator: Moves the valve stem in the opposite direction as the actuator stem.
Difference Between Spring-Return Actuator and Non-Spring-Return Actuator:
Spring-Return Actuator: Uses a spring to return the valve to its original position when de-energized.
Non-Spring-Return Actuator: Requires power to return the valve to its original position.
