Pipefitter Valves, Fittings, and Supports 5 — Questions and Answers
Question 1: Which type of valve is best suited for applications requiring frequent operation and minimal pressure drop in the fully open position?
- Globe valve
- Gate valve (Correct answer)
- Needle valve
- Angle valve
Correct answer: Gate valve
Gate valves have a straight-through flow path when fully open, resulting in minimal pressure drop, and are designed for fully open or fully closed service.
Question 2: A constant-effort (constant support) hanger is used when:
- The pipe has no thermal movement
- The pipe load must remain constant throughout vertical thermal movement (Correct answer)
- The pipe requires rigid anchoring at that point
- The pipe must be isolated from vibration
Correct answer: The pipe load must remain constant throughout vertical thermal movement
Constant-effort hangers maintain a constant load on the pipe regardless of vertical displacement caused by thermal expansion or contraction.
Question 3: What does the class rating (e.g., Class 150, Class 300) on a flanged valve indicate?
- The maximum temperature rating in degrees Fahrenheit
- The pressure-temperature rating of the valve flange (Correct answer)
- The pipe schedule the valve is designed for
- The valve's flow coefficient (Cv)
Correct answer: The pressure-temperature rating of the valve flange
Flange class ratings indicate allowable pressure-temperature combinations as defined by ASME B16.5, with higher class numbers permitting higher pressures.
Question 4: A 90-degree long-radius elbow has a centerline radius equal to:
- 0.5 times the nominal pipe diameter
- 1.0 times the nominal pipe diameter
- 1.5 times the nominal pipe diameter (Correct answer)
- 2.0 times the nominal pipe diameter
Correct answer: 1.5 times the nominal pipe diameter
Long-radius elbows have a centerline radius of 1.5 times the nominal pipe diameter (1.5D), which reduces turbulence and pressure drop compared to short-radius elbows.
Question 5: Which valve type uses a quarter-turn operation and provides a straight-through bore equal to the pipe diameter when fully open?
- Globe valve
- Gate valve
- Full-port ball valve (Correct answer)
- Butterfly valve
Correct answer: Full-port ball valve
Full-port (full-bore) ball valves have a ball with a bore matching the pipe ID, providing unrestricted flow with only a 90-degree turn to open or close.
Question 6: When a pipe support must allow axial pipe movement due to thermal expansion but must prevent lateral movement, the correct support type is a:
- Rigid anchor
- Sliding support with guides (Correct answer)
- Variable spring hanger
- Riser clamp
Correct answer: Sliding support with guides
A sliding support with guides allows axial (longitudinal) movement while guiding the pipe and restraining lateral displacement.
Question 7: A pipefitter installs a Y-strainer upstream of a control valve. What is the primary reason for this arrangement?
- To reduce turbulence before the control valve
- To protect the control valve trim from debris in the fluid (Correct answer)
- To measure flow rate entering the control valve
- To allow pressure buildup before the valve
Correct answer: To protect the control valve trim from debris in the fluid
Y-strainers capture particulates and debris from the fluid, protecting sensitive control valve internals (trim) from erosion and clogging.
Pipefitter Valves, Fittings, and Supports 5
Which type of valve is best suited for applications requiring frequent operation and minimal pressure drop in the fully open position?