Pipefitter Valves, Fittings, and Pipe Materials 3 — Questions and Answers
Question 1: Which valve type uses a rotating disc perpendicular to flow to achieve shut-off?
- Ball valve
- Butterfly valve (Correct answer)
- Gate valve
- Globe valve
Correct answer: Butterfly valve
A butterfly valve uses a disc that rotates 90° within the pipe bore to open or close flow.
Question 2: What is the primary purpose of a swing check valve?
- Regulate flow rate
- Prevent backflow (Correct answer)
- Reduce pressure
- Throttle steam
Correct answer: Prevent backflow
A swing check valve allows flow in one direction and automatically closes to prevent reverse flow.
Question 3: Schedule 80 pipe compared to Schedule 40 pipe of the same nominal size has:
- Larger outside diameter
- Thicker wall and smaller bore (Correct answer)
- Same wall thickness
- Lower pressure rating
Correct answer: Thicker wall and smaller bore
Schedule 80 has a thicker wall than Schedule 40, resulting in a smaller inside diameter and higher pressure rating.
Question 4: A 45-degree elbow is used instead of a 90-degree elbow primarily to:
- Increase flow velocity
- Reduce friction loss and turbulence (Correct answer)
- Allow thermal expansion
- Connect different pipe sizes
Correct answer: Reduce friction loss and turbulence
A 45° elbow creates less turbulence and pressure drop than a 90° elbow by making a gradual direction change.
Question 5: Which material is most commonly used for high-pressure steam piping above 750°F?
- PVC
- Copper
- Chrome-moly alloy steel (Correct answer)
- Cast iron
Correct answer: Chrome-moly alloy steel
Chrome-moly alloy steel (such as P11 or P22) retains strength at elevated temperatures required for high-pressure steam service.
Question 6: A weld neck flange is preferred over a slip-on flange in high-pressure, high-temperature applications because:
- It is easier to install
- It provides a stronger, more fatigue-resistant connection (Correct answer)
- It costs less
- It requires no welding
Correct answer: It provides a stronger, more fatigue-resistant connection
The weld neck flange's tapered hub distributes stress and provides superior strength for demanding service conditions.
Question 7: What does the term 'CWP' stamped on a valve indicate?
- Cold Working Pressure (Correct answer)
- Certified Welding Procedure
- Controlled Water Pressure
- Cast Working Pipe
Correct answer: Cold Working Pressure
CWP stands for Cold Working Pressure, indicating the maximum allowable pressure rating at ambient temperature.
Pipefitter Valves, Fittings, and Pipe Materials 3
Which valve type uses a rotating disc perpendicular to flow to achieve shut-off?