STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
Q1.
A two-pipe hydronic heating system experiences excessive velocity noise near terminal units after a
retrofit pump installation. Which corrective action is MOST appropriate?
A. Increase balancing valve differential pressure
B. Reduce pump impeller diameter or install VFD control
C. Increase supply water temperature
D. Replace all circuit setters with gate valves
Answer: B
Explanation:
Velocity noise is commonly caused by excessive flow rates due to oversized pumps or increased
differential pressure. Trimming the impeller or using a variable frequency drive (VFD) reduces flow
velocity and restores hydraulic balance without sacrificing system efficiency.
Q2.
During steam main installation, a pipefitter specifies eccentric reducers with the flat side down on
horizontal condensate return piping primarily to:
A. Increase static pressure
B. Improve laminar flow
C. Prevent air pocket formation
D. Reduce galvanic corrosion
Answer: C
Explanation:
Flat-side-down eccentric reducers prevent trapped air in condensate return systems. Air pockets can
impede condensate movement and contribute to water hammer and corrosion issues.
Q3.
A refrigeration suction line installed in a vertical riser requires oil return enhancement. Which
installation method is preferred?
A. Double offset expansion loop
B. P-trap at the base of the riser
C. Dielectric union at each floor penetration
D. Concentric increaser at evaporator outlet
Answer: B
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
Explanation:
Oil entrainment in vertical risers requires adequate refrigerant velocity. Installing a P-trap at the base
promotes oil lifting during compressor operation and prevents oil logging in evaporators.
Q4.
A steam trap discharges live steam continuously. Which condition is MOST likely responsible?
A. Vacuum breaker failure
B. Undersized condensate receiver
C. Trap seat erosion or dirt accumulation
D. Thermal expansion in the return main
Answer: C
Explanation:
Continuous live steam discharge indicates the trap is failing open, commonly due to seat erosion,
debris, or worn internal components preventing proper closure.
Q5.
When interpreting P&ID drawings, a dashed pneumatic signal line between a controller and control
valve actuator indicates:
A. Gravity drainage piping
B. Electrical conduit routing
C. Instrument air communication
D. Emergency bypass piping
Answer: C
Explanation:
Dashed lines on P&IDs frequently represent signal transmission paths. Pneumatic instrument air
signals are commonly shown this way between controllers and actuators.
Q6.
In a high-pressure steam system, why are drip legs installed ahead of pressure-reducing stations?
A. To increase steam velocity
B. To collect condensate before control devices
C. To reduce thermal expansion stress
D. To improve oxygen scavenging
Answer: B
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
Explanation:
Drip legs remove condensate before steam reaches sensitive valves and regulators. Condensate
entering PRVs can cause erosion, unstable control, and water hammer.
Q7.
A fitter calculates a rolling offset requiring a 30-inch horizontal offset and 40-inch vertical offset over
a 60-inch run. What is the true travel length?
A. 50 in.
B. 60 in.
C. 70 in.
D. 78 in.
Answer: C
Explanation:
Rolling offset travel uses the Pythagorean theorem twice:
√ 302 +402 =50
Then:
√ 502 +602 ≈78
Correct answer is D, not C.
Q8.
A steamfitter performing SMAW on carbon steel observes undercut along the weld toe. Which
adjustment is MOST effective?
A. Increase travel speed further
B. Reduce amperage slightly
C. Increase electrode diameter
D. Reduce electrode angle to 0°
Answer: B
Explanation:
Undercut typically results from excessive heat input or improper manipulation. Slightly lowering
amperage reduces edge melting and improves weld profile.
Q9.
Which valve type provides the BEST throttling characteristics in hydronic balancing applications?
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
A. Swing check valve
B. Knife gate valve
C. Globe valve
D. Plug valve
Answer: C
Explanation:
Globe valves are designed for throttling and flow regulation because the linear movement of the disc
allows precise control of flow rate.
Q10.
A chilled water system repeatedly loses pressure during off cycles. No visible leaks exist. Which
component should be inspected FIRST?
A. Condensate trap
B. Expansion tank bladder
C. Steam separator
D. Balancing cock
Answer: B
Explanation:
A failed bladder in a diaphragm expansion tank can cause pressure fluctuations and system pressure
loss due to improper accommodation of thermal expansion.
Q11.
In oxy-acetylene brazing of copper refrigeration tubing, oxidation inside the tubing is minimized by:
A. Increasing acetylene pressure
B. Applying flux internally
C. Purging with nitrogen
D. Heating the joint rapidly
Answer: C
Explanation:
Nitrogen purging prevents oxidation scale formation inside copper tubing during brazing, protecting
compressors and metering devices from contamination.
Q12.
What is the PRIMARY purpose of a Hartford Loop in a low-pressure boiler system?
Exam (Updated Edition)
Q1.
A two-pipe hydronic heating system experiences excessive velocity noise near terminal units after a
retrofit pump installation. Which corrective action is MOST appropriate?
A. Increase balancing valve differential pressure
B. Reduce pump impeller diameter or install VFD control
C. Increase supply water temperature
D. Replace all circuit setters with gate valves
Answer: B
Explanation:
Velocity noise is commonly caused by excessive flow rates due to oversized pumps or increased
differential pressure. Trimming the impeller or using a variable frequency drive (VFD) reduces flow
velocity and restores hydraulic balance without sacrificing system efficiency.
Q2.
During steam main installation, a pipefitter specifies eccentric reducers with the flat side down on
horizontal condensate return piping primarily to:
A. Increase static pressure
B. Improve laminar flow
C. Prevent air pocket formation
D. Reduce galvanic corrosion
Answer: C
Explanation:
Flat-side-down eccentric reducers prevent trapped air in condensate return systems. Air pockets can
impede condensate movement and contribute to water hammer and corrosion issues.
Q3.
A refrigeration suction line installed in a vertical riser requires oil return enhancement. Which
installation method is preferred?
A. Double offset expansion loop
B. P-trap at the base of the riser
C. Dielectric union at each floor penetration
D. Concentric increaser at evaporator outlet
Answer: B
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
Explanation:
Oil entrainment in vertical risers requires adequate refrigerant velocity. Installing a P-trap at the base
promotes oil lifting during compressor operation and prevents oil logging in evaporators.
Q4.
A steam trap discharges live steam continuously. Which condition is MOST likely responsible?
A. Vacuum breaker failure
B. Undersized condensate receiver
C. Trap seat erosion or dirt accumulation
D. Thermal expansion in the return main
Answer: C
Explanation:
Continuous live steam discharge indicates the trap is failing open, commonly due to seat erosion,
debris, or worn internal components preventing proper closure.
Q5.
When interpreting P&ID drawings, a dashed pneumatic signal line between a controller and control
valve actuator indicates:
A. Gravity drainage piping
B. Electrical conduit routing
C. Instrument air communication
D. Emergency bypass piping
Answer: C
Explanation:
Dashed lines on P&IDs frequently represent signal transmission paths. Pneumatic instrument air
signals are commonly shown this way between controllers and actuators.
Q6.
In a high-pressure steam system, why are drip legs installed ahead of pressure-reducing stations?
A. To increase steam velocity
B. To collect condensate before control devices
C. To reduce thermal expansion stress
D. To improve oxygen scavenging
Answer: B
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
Explanation:
Drip legs remove condensate before steam reaches sensitive valves and regulators. Condensate
entering PRVs can cause erosion, unstable control, and water hammer.
Q7.
A fitter calculates a rolling offset requiring a 30-inch horizontal offset and 40-inch vertical offset over
a 60-inch run. What is the true travel length?
A. 50 in.
B. 60 in.
C. 70 in.
D. 78 in.
Answer: C
Explanation:
Rolling offset travel uses the Pythagorean theorem twice:
√ 302 +402 =50
Then:
√ 502 +602 ≈78
Correct answer is D, not C.
Q8.
A steamfitter performing SMAW on carbon steel observes undercut along the weld toe. Which
adjustment is MOST effective?
A. Increase travel speed further
B. Reduce amperage slightly
C. Increase electrode diameter
D. Reduce electrode angle to 0°
Answer: B
Explanation:
Undercut typically results from excessive heat input or improper manipulation. Slightly lowering
amperage reduces edge melting and improves weld profile.
Q9.
Which valve type provides the BEST throttling characteristics in hydronic balancing applications?
, STAR Steamfitting-Pipefitting Mastery Latest Practice
Exam (Updated Edition)
A. Swing check valve
B. Knife gate valve
C. Globe valve
D. Plug valve
Answer: C
Explanation:
Globe valves are designed for throttling and flow regulation because the linear movement of the disc
allows precise control of flow rate.
Q10.
A chilled water system repeatedly loses pressure during off cycles. No visible leaks exist. Which
component should be inspected FIRST?
A. Condensate trap
B. Expansion tank bladder
C. Steam separator
D. Balancing cock
Answer: B
Explanation:
A failed bladder in a diaphragm expansion tank can cause pressure fluctuations and system pressure
loss due to improper accommodation of thermal expansion.
Q11.
In oxy-acetylene brazing of copper refrigeration tubing, oxidation inside the tubing is minimized by:
A. Increasing acetylene pressure
B. Applying flux internally
C. Purging with nitrogen
D. Heating the joint rapidly
Answer: C
Explanation:
Nitrogen purging prevents oxidation scale formation inside copper tubing during brazing, protecting
compressors and metering devices from contamination.
Q12.
What is the PRIMARY purpose of a Hartford Loop in a low-pressure boiler system?
