Piping Basics of Piping 4 — Questions and Answers
Question 1: Which type of valve provides the best flow control due to its variable orifice opening?
- Gate valve
- Ball valve
- Globe valve (Correct answer)
- Butterfly valve
Correct answer: Globe valve
Globe valves are designed for throttling because the disc and seat geometry allows precise, gradual flow regulation across a wide range of positions.
Question 2: What is the significance of pipe 'schedule' in conjunction with nominal pipe size?
- It determines the pipe material
- It defines the wall thickness relative to the pipe diameter (Correct answer)
- It sets the maximum temperature rating
- It identifies the type of end connection
Correct answer: It defines the wall thickness relative to the pipe diameter
The schedule number, combined with NPS, mathematically determines the wall thickness of the pipe, which in turn affects pressure rating and flow capacity.
Question 3: In which situation would an engineer specify a butt-weld fitting over a socket-weld fitting?
- For small-bore pipes under 2 inches
- For pipes 2 inches and larger requiring full-penetration welds (Correct answer)
- For low-pressure steam systems
- For threaded plastic connections
Correct answer: For pipes 2 inches and larger requiring full-penetration welds
Butt-weld fittings are used on larger diameter pipes (typically 2 NPS and above) where a full-penetration weld provides the strength and leak-free joint needed for high-pressure or critical service.
Question 4: What does 'MAWP' stand for in piping and pressure vessel terminology?
- Maximum Allowable Working Pressure (Correct answer)
- Mean Average Water Pressure
- Minimum Approved Wall Profile
- Maximum Ambient Weather Protection
Correct answer: Maximum Allowable Working Pressure
MAWP is the Maximum Allowable Working Pressure — the highest pressure at which a piping system or vessel may be continuously operated under normal conditions.
Question 5: Why is galvanized steel pipe NOT recommended for natural gas service?
- It is too expensive for gas applications
- Zinc flakes can clog gas appliance orifices and regulators (Correct answer)
- Galvanized pipe cannot be threaded
- It reacts chemically with methane
Correct answer: Zinc flakes can clog gas appliance orifices and regulators
The zinc coating on galvanized pipe can flake off over time, and those particles can block gas regulators, valves, and appliance orifices, creating a safety hazard.
Question 6: What is the role of pipe supports in a piping system?
- Prevent corrosion at contact points
- Carry the weight of the pipe and maintain proper alignment (Correct answer)
- Reduce flow turbulence
- Provide electrical grounding
Correct answer: Carry the weight of the pipe and maintain proper alignment
Pipe supports bear the dead weight of the pipe, fluid contents, and insulation while keeping the pipe at the correct elevation and preventing sag or deflection.
Question 7: Which document specifies the materials, sizes, ratings, and end connections for piping components on a project?
- P&ID
- Piping specification (pipe spec) (Correct answer)
- Isometric drawing
- General arrangement drawing
Correct answer: Piping specification (pipe spec)
The piping specification (pipe spec or piping class) is the engineering document that defines which pipe materials, wall thicknesses, fittings, and valves are approved for each service condition.
Piping Basics of Piping 4
Which type of valve provides the best flow control due to its variable orifice opening?