Piping Basics of Piping 2 — Questions and Answers
Question 1: What does the term 'nominal pipe size' (NPS) refer to?
- The exact outer diameter of the pipe
- A standardized designation that loosely correlates to pipe dimensions (Correct answer)
- The inner diameter measured in millimeters
- The wall thickness classification
Correct answer: A standardized designation that loosely correlates to pipe dimensions
NPS is a North American standard designation that does not directly equal the actual outer or inner diameter but serves as a reference for pipe and fitting compatibility.
Question 2: Which piping schedule number indicates the thickest wall for a given NPS?
- Schedule 10
- Schedule 40
- Schedule 80
- Schedule 160 (Correct answer)
Correct answer: Schedule 160
Schedule 160 has the thickest wall among common schedules, resulting in the smallest inner diameter and highest pressure rating for the same nominal size.
Question 3: What is the primary purpose of a pipe reducer in a piping system?
- To change flow direction
- To connect pipes of different diameters (Correct answer)
- To isolate a section of pipe
- To absorb thermal expansion
Correct answer: To connect pipes of different diameters
A reducer is a fitting used to connect two pipes of different sizes, transitioning the flow from a larger to a smaller diameter or vice versa.
Question 4: Which type of pipe joint uses a tapered thread to create a pressure-tight seal?
- Flanged joint
- Grooved joint
- NPT threaded joint (Correct answer)
- Butt-weld joint
Correct answer: NPT threaded joint
National Pipe Taper (NPT) threads are designed with a slight taper so that mating threads wedge together, forming a seal that tightens under pressure.
Question 5: What is the function of a check valve in a piping system?
- Regulate flow rate
- Allow flow in one direction only (Correct answer)
- Throttle pressure
- Provide isolation for maintenance
Correct answer: Allow flow in one direction only
A check valve automatically prevents backflow by allowing fluid to pass in only one direction, protecting pumps and other equipment from reverse flow.
Question 6: Which pipe material is most commonly used for natural gas distribution in residential applications in the US?
- Copper
- Cast iron
- Black steel (Correct answer)
- PVC
Correct answer: Black steel
Black steel pipe is the most common material for natural gas distribution lines because it is strong, durable, and compatible with gas service.
Question 7: What does 'pipe alignment' mean in piping installation?
- Matching pipe color codes
- Ensuring pipes are positioned correctly with no angular or lateral offset (Correct answer)
- Selecting the correct pipe schedule
- Applying the proper insulation thickness
Correct answer: Ensuring pipes are positioned correctly with no angular or lateral offset
Pipe alignment ensures that connected pipe ends are centered and parallel so joints are not stressed, preventing leaks and premature failure.
Piping Basics of Piping 2
What does the term 'nominal pipe size' (NPS) refer to?