SPED Valve & Fitting Selection 2 — Questions and Answers
Question 1: Which valve type provides the best throttling control for slurry services due to its straight-through flow path and full bore opening?
- Plug valve
- Pinch valve (Correct answer)
- Needle valve
- Globe valve
Correct answer: Pinch valve
Pinch valves use a flexible sleeve that is externally compressed, providing a straight-through, full bore flow path ideal for slurry and abrasive services.
Question 2: A piping system requires a fitting that changes pipe direction by 45° while minimizing pressure drop. Which fitting is most appropriate?
- Long-radius 45° elbow (Correct answer)
- Short-radius 45° elbow
- 45° street elbow
- Wye fitting
Correct answer: Long-radius 45° elbow
Long-radius 45° elbows have a centerline radius of 1.5× the pipe diameter, producing lower turbulence and pressure drop than short-radius alternatives.
Question 3: For cryogenic service at -200°F, which valve body material is preferred to prevent brittle fracture?
- Carbon steel (ASTM A216 WCB)
- Austenitic stainless steel (ASTM A351 CF8M) (Correct answer)
- Cast iron
- Ductile iron
Correct answer: Austenitic stainless steel (ASTM A351 CF8M)
Austenitic stainless steels retain toughness at cryogenic temperatures because their FCC crystal structure does not undergo a ductile-to-brittle transition.
Question 4: Which end connection type is preferred for high-pressure, high-temperature service above 600°F where leak-free joints are critical?
- Threaded (NPT)
- Socket weld
- Butt weld (Correct answer)
- Flanged with raised face
Correct answer: Butt weld
Butt-welded connections eliminate threaded or socket crevices and are the most leak-resistant joint for severe service conditions.
Question 5: A check valve is required in a vertical pipe with upward flow. Which type is best suited for this orientation?
- Swing check valve
- Tilting disc check valve
- Lift check valve (Correct answer)
- Dual plate wafer check valve
Correct answer: Lift check valve
Lift check valves are designed specifically for vertical pipe with upward flow, where gravity helps reseat the disc when flow stops.
Question 6: What is the primary advantage of a reducing tee over a standard tee combined with a reducer in piping system design?
- Lower material cost
- Fewer potential leak points and reduced installed length (Correct answer)
- Higher pressure rating
- Easier field modification
Correct answer: Fewer potential leak points and reduced installed length
A reducing tee combines the branch and size reduction into one fitting, eliminating an extra joint and reducing the overall piping footprint.
Question 7: Which valve is specifically designed to maintain a constant downstream pressure regardless of upstream pressure variations?
- Pressure relief valve
- Pressure reducing valve (PRV) (Correct answer)
- Back-pressure regulator
- Pressure sustaining valve
Correct answer: Pressure reducing valve (PRV)
A pressure reducing valve (PRV) automatically reduces upstream pressure to a preset lower downstream pressure, compensating for upstream fluctuations.
SPED Valve & Fitting Selection 2
Which valve type provides the best throttling control for slurry services due to its straight-through flow path and full bore opening?