Piping Basics of Piping 3 — Questions and Answers
Question 1: What is the purpose of a pipe expansion loop?
- To reduce water hammer
- To accommodate thermal expansion and contraction (Correct answer)
- To increase flow velocity
- To filter sediment from the line
Correct answer: To accommodate thermal expansion and contraction
Expansion loops provide flexibility in a piping system to absorb the dimensional changes caused by temperature fluctuations without stressing the pipe or fittings.
Question 2: Which ASME standard covers pressure piping for process plants?
- ASME B31.1
- ASME B31.3 (Correct answer)
- ASME B16.5
- ASME B36.10
Correct answer: ASME B31.3
ASME B31.3 is the Process Piping code that governs design, materials, fabrication, inspection, and testing of piping in chemical and petroleum plants.
Question 3: What is the difference between a concentric and an eccentric reducer?
- Concentric reducers change flow direction; eccentric ones do not
- Concentric reducers have aligned centerlines; eccentric reducers have one flat side (Correct answer)
- Eccentric reducers are used only for gas service
- Concentric reducers are used only with flanged connections
Correct answer: Concentric reducers have aligned centerlines; eccentric reducers have one flat side
In a concentric reducer the centerlines of both ends are aligned, while an eccentric reducer has one flat side, keeping the bottom of the pipe level to prevent air pockets or liquid accumulation.
Question 4: What is 'water hammer' in a piping system?
- Erosion caused by high-velocity water
- A pressure surge from sudden change in flow velocity (Correct answer)
- Corrosion inside water lines
- Vibration from pump imbalance
Correct answer: A pressure surge from sudden change in flow velocity
Water hammer is a pressure shock wave that occurs when fluid in motion is suddenly stopped or redirected, causing a banging noise and potentially damaging pipes and fittings.
Question 5: Which fitting is used to connect three pipes at a branch point?
- Elbow
- Union
- Tee (Correct answer)
- Coupling
Correct answer: Tee
A tee fitting has three openings — one inlet and two outlets (or one run and one branch) — used to split or combine flow at a junction.
Question 6: What material property makes stainless steel preferred over carbon steel in corrosive service?
- Higher tensile strength
- Lower cost
- Chromium content that forms a passive oxide layer (Correct answer)
- Greater thermal conductivity
Correct answer: Chromium content that forms a passive oxide layer
Stainless steel contains at least 10.5% chromium, which reacts with oxygen to form a thin, stable oxide layer that resists corrosion in aggressive chemical environments.
Question 7: What is the purpose of hydrostatic testing in piping systems?
- To clean internal deposits
- To verify structural integrity and leak-tightness under pressure (Correct answer)
- To calibrate flow meters
- To flush the line before commissioning
Correct answer: To verify structural integrity and leak-tightness under pressure
Hydrostatic testing fills the system with water and pressurizes it above design pressure to confirm that welds, joints, and fittings can withstand operating conditions without leaking.
Piping Basics of Piping 3
What is the purpose of a pipe expansion loop?