Lecture 8: Valves & Fittings (Part 1 & 2)

Question 1

Purpose of Valves in Process Systems:

Answer 1

Purpose: Control the flow of fluids or gases.

Question 2

Types of Valves in Process Industries:

Answer 2

Types: Gate valves, globe valves, ball valves, butterfly valves, needle valves, check valves.

Question 3

Selecting an Appropriate Valve:

Answer 3

Factors: Type of service, allowable pressure drop, process geometry, fluid properties, cost.

Question 4

Key Factors for Valve Selection:

Answer 4

Factors: Type, size, material, flow coefficient (Cv), actuator type.

Question 5

Difference Between Globe Valve and Gate Valve:

Answer 5

Globe Valve: Regulates flow.

Gate Valve: Designed for isolation.

Question 6

Flow Coefficient (Cv) and Valve Performance:

Answer 6

Cv measures flow capacity, affecting pressure drop across the valve.

Question 7

Control Valve vs. Isolation Valve:

Answer 7

Control Valve: Regulates flow.

Isolation Valve: Completely shuts off flow.

Question 8

Calculating Pressure Drop Across a Valve:

Answer 8

Using Cv, flow rate, and fluid properties.

Question 9

Function of Valve Actuator:

Answer 9

To open and close the valve.

Question 10

Troubleshooting Common Valve Problems:

Answer 10

Identify root cause and take corrective action for issues like leakage, sticking, or failure to open/close.

Question 10

Advantages and Disadvantages of Valve Actuators:

Answer 10

Depend on factors like cost, reliability, and maintenance. Types include pneumatic, hydraulic, electric.

Question 11

Safety Considerations When Working with Valves:

Answer 11

Proper handling of hazardous materials, use of personal protective equipment, and following safety procedures.

Question 12

Valve Maintenance and Repair:

Answer 12

Tasks like cleaning, lubrication, part replacement for optimal performance and preventing failure.

Question 13

Environmental Considerations in Valve Selection:

Answer 13

Consider factors like emissions and environmental impact.

Question 14

Difference Between Rising Stem and Non-Rising Stem Valve:

Answer 14

Rising Stem: Stem moves up and down as the valve opens and closes.

Non-Rising Stem: Stem does not move.

Question 15

Difference Between Single-Seated and Double-Seated Valve:

Answer 15

Single-Seated Valve: One sealing surface.

Double-Seated Valve: Two sealing surfaces.

Question 16

Difference Between Soft-Seated and Metal-Seated Valve:

Answer 16

Soft-Seated Valve: Sealing surface made of soft material (e.g., rubber).

Metal-Seated Valve: Sealing surface made of metal.

Question 17

Difference Between Linear Valve and Rotary Valve:

Answer 17

Linear Valve: Opens and closes with linear motion.

Rotary Valve: Opens and closes with rotary motion.

Question 18

Difference Between Quarter-Turn and Multi-Turn Valve:

Answer 18

Quarter-Turn Valve: Requires a quarter turn to fully open/close.

Multi-Turn Valve: Requires multiple turns to open/close.

Question 19

Difference Between Control Valve and Shut-Off Valve:

Answer 19

Control Valve: Regulates flow.

Shut-Off Valve: Stops flow completely.

Question 20

Difference Between Globe Valve and Ball Valve:

Answer 20

Globe Valve: Linear motion to open/close.

Ball Valve: Rotary motion to open/close.

Question 21

Difference Between Gate Valve and Butterfly Valve:

Answer 21

Gate Valve: Designed for isolation.

Butterfly Valve: Designed for flow regulation.

Question 22

Difference Between Check Valve and Relief Valve:

Answer 22

Check Valve: Allows flow in one direction.

Relief Valve: Protects equipment from overpressure.

Question 23

Difference Between Diaphragm Valve and Pinch Valve:

Answer 23

Diaphragm Valve: Uses a flexible diaphragm to seal.

Pinch Valve: Uses a flexible sleeve that is pinched to close.

Question 24

Difference Between Solenoid Valve and Motorized Valve:

Answer 24

Solenoid Valve: Operated by electric current.

Motorized Valve: Operated by an electric motor.

Question 25

Types of Valve Actuators:

Answer 25

Pneumatic, hydraulic, electric, and manual.

Question 26

Purpose of Valve Actuator:

Answer 26

Provides force to open and close the valve.

Question 27

Difference Between Pneumatic Actuator and Hydraulic Actuator:

Answer 27

Pneumatic Actuator: Powered by compressed air.

Hydraulic Actuator: Powered by hydraulic fluid.

Question 28

Difference Between Linear Actuator and Rotary Actuator:

Answer 28

Linear Actuator: Provides linear motion to open/close the valve.

Rotary Actuator: Provides rotary motion to open/close the valve.

Question 29

Difference Between Single-Acting Actuator and Double-Acting Actuator:

Answer 29

Single-Acting Actuator: Moves the valve in one direction.

Double-Acting Actuator: Moves the valve in both directions.

Question 30

Difference Between Direct-Acting Actuator and Reverse-Acting Actuator:

Answer 30

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.

Question 31

Difference Between Spring-Return Actuator and Non-Spring-Return Actuator:

Answer 31

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.