Pipefitter Core Responsibilities 5 — Questions and Answers
Question 1: When installing a pump suction line, the preferred configuration to prevent cavitation is:
- Long, straight horizontal run with an eccentric reducer flat-side up (Correct answer)
- Short vertical drop directly into the pump flange
- Concentric reducer at the pump nozzle to center the flow
- Multiple 90-degree elbows close to the pump inlet
Correct answer: Long, straight horizontal run with an eccentric reducer flat-side up
An eccentric reducer installed flat-side up prevents air pockets from collecting at the pump suction and reduces cavitation risk.
Question 2: Which type of valve is BEST suited for throttling flow control in a process line?
- Gate valve
- Globe valve (Correct answer)
- Ball valve
- Butterfly valve
Correct answer: Globe valve
Globe valves are designed for throttling because their disc moves perpendicular to flow, providing good control over partial openings.
Question 3: A pipefitter notices that a gasket is compressed beyond its recommended torque spec. What is the most likely consequence?
- Improved sealing performance due to higher compression
- Gasket blowout or extrusion leading to leakage (Correct answer)
- Reduced flange face corrosion
- Better alignment of the bolt holes
Correct answer: Gasket blowout or extrusion leading to leakage
Over-torquing a gasket causes it to crush, crack, or extrude beyond the flange face, resulting in leakage.
Question 4: What is the correct sequence for bolt tightening on a pipe flange connection?
- Start at one bolt and tighten in a clockwise circle
- Tighten opposite bolts in a cross or star pattern (Correct answer)
- Tighten the bottom bolts first, then work upward
- Tighten all bolts to half torque simultaneously with an impact gun
Correct answer: Tighten opposite bolts in a cross or star pattern
Cross-pattern tightening ensures even gasket compression and prevents flange cocking or uneven seating.
Question 5: A pipefitter must select the correct pipe hanger spacing for a 4-inch schedule 40 carbon steel line carrying water. The primary factor governing maximum span is:
- The insulation thickness on the pipe
- The allowable sag and stress in the pipe between supports (Correct answer)
- The height of the pipe above the floor
- The ambient temperature of the installation area
Correct answer: The allowable sag and stress in the pipe between supports
Hanger spacing is determined by allowable pipe deflection and bending stress, as specified in MSS SP-69 or ASME B31 codes.
Question 6: Which of the following is a pipefitter's responsibility when reviewing an isometric drawing before fabrication?
- Approving the drawing for engineering sign-off
- Verifying dimensions, material specs, and weld symbols match the design intent (Correct answer)
- Ordering all listed materials without further review
- Signing off on the hydrostatic test results
Correct answer: Verifying dimensions, material specs, and weld symbols match the design intent
Before fabrication, a pipefitter must confirm that dimensions, material callouts, and weld details on the iso match the piping specification and P&ID.
Question 7: What does PWHT stand for, and why is it performed on certain welds in pressure piping?
- Pre-Weld Heat Treatment — to preheat the base metal before welding
- Post-Weld Heat Treatment — to relieve residual stresses and restore toughness after welding (Correct answer)
- Pressurized Weld Hardness Test — to verify weld hardness after completion
- Pipe Wall Heat Test — to check for internal corrosion after welding
Correct answer: Post-Weld Heat Treatment — to relieve residual stresses and restore toughness after welding
PWHT reduces residual welding stresses and restores ductility, and is required by code for certain materials, wall thicknesses, and services.
Pipefitter Core Responsibilities 5
When installing a pump suction line, the preferred configuration to prevent cavitation is: