Steamfitter Pipe Systems and Materials 2 — Questions and Answers
Question 1: What is the function of a reducing coupling in a piping system?
- To connect two pipes of the same diameter in a straight run
- To connect pipes of two different diameters in a straight run (Correct answer)
- To reverse the direction of flow
- To completely isolate a section of piping
Correct answer: To connect pipes of two different diameters in a straight run
A reducing coupling joins two pipes of different sizes in line, allowing a transition from a larger to a smaller (or smaller to larger) pipe diameter.
Question 2: What type of pipe thread standard is most commonly specified for threaded connections in U.S. steam and water piping systems?
- BSP (British Standard Pipe)
- NPT (National Pipe Taper) (Correct answer)
- ISO metric thread
- Whitworth thread
Correct answer: NPT (National Pipe Taper)
NPT (National Pipe Taper) is the US standard for threaded pipe connections; the tapered threads create a pressure-tight seal when engaged and assembled with thread sealant.
Question 3: A concentric reducer is different from an eccentric reducer in that a concentric reducer:
- Keeps the pipe centerlines aligned on the same axis (Correct answer)
- Keeps the bottom of both pipes at the same elevation
- Is used only for horizontal pipe runs
- Cannot be used on steam lines
Correct answer: Keeps the pipe centerlines aligned on the same axis
A concentric reducer maintains the same centerline for both pipes, while an eccentric reducer offsets one side flat, which is preferred on horizontal lines to prevent air or condensate pocketing.
Question 4: Which type of valve is best suited for throttling or regulating flow in a steam piping system?
- Gate valve
- Ball valve
- Globe valve (Correct answer)
- Check valve
Correct answer: Globe valve
Globe valves are specifically designed for throttling because their plug-and-seat design provides fine flow control; gate and ball valves are intended for full-open or full-closed service only.
Question 5: What is the primary advantage of a flanged connection compared to a threaded connection in a large-diameter steam line?
- Flanged connections cost significantly less to install
- Flanged connections can be disassembled without cutting or unthreading the pipe (Correct answer)
- Flanged connections require no gasket material
- Flanged connections have a lower pressure rating
Correct answer: Flanged connections can be disassembled without cutting or unthreading the pipe
Flanged connections allow piping to be disassembled by unbolting the flanges, making them ideal for large-diameter pipe and equipment connections that require periodic maintenance.
Question 6: What type of joint is formed when a copper fitting is heated and a filler metal (solder) is drawn into the gap by capillary action?
- Threaded joint
- Flanged joint
- Sweat (soldered) joint (Correct answer)
- Compression joint
Correct answer: Sweat (soldered) joint
A sweat joint (also called a soldered or brazed joint) uses heat and capillary action to draw solder or brazing alloy into the annular space between the pipe and fitting, forming a pressure-tight bond.
Question 7: In the metric piping system used internationally, what does the designation DN (Diameter Nominal) represent?
- The exact outer diameter of the pipe in millimeters
- The approximate nominal pipe diameter in millimeters used as a reference size (Correct answer)
- The pipe wall thickness in millimeters
- The pipe schedule number in the metric system
Correct answer: The approximate nominal pipe diameter in millimeters used as a reference size
DN (Diameter Nominal) is a dimensionless designator that approximates the nominal pipe size in millimeters and corresponds to NPS sizes — e.g., DN 25 ≈ NPS 1 inch.
Steamfitter Pipe Systems and Materials 2
What is the function of a reducing coupling in a piping system?