CWEA Mechanical Technologist Grade 3
Exam Test Questions And Correct
Answers (Verified Answers) Plus
Rationales 2025/2026 Q&A | Instant
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1.
Case: A centrifugal pump is running but not delivering flow. Suction line is full of
water. What is the most likely cause?
A. Air trapped in discharge line
B. Impeller rotation in wrong direction or impeller damage
C. Excessive system pressure
D. High motor voltage
Answer: B. Impeller rotation in wrong direction or impeller damage
Rationale: Loss of flow with full suction indicates mechanical or rotational failure
at the impeller.
2.
Case: A pump is cavitating. What is the primary indicator?
A. Low noise and smooth operation
B. Loud rattling or gravel-like sound with vibration
C. High discharge pressure
D. Increased efficiency
Answer: B. Loud rattling or gravel-like sound with vibration
,Rationale: Cavitation is caused by vapor bubble collapse in low-pressure zones.
3.
What is the purpose of a mechanical seal in a pump?
A. Increase flow rate
B. Prevent leakage along the rotating shaft
C. Increase motor speed
D. Reduce electrical load
Answer: B. Prevent leakage along the rotating shaft
Rationale: Mechanical seals prevent fluid escaping around the shaft.
4.
Case: A motor is overheating but pump load is normal. Likely cause?
A. Over-lubrication or bearing failure
B. Excess flow
C. High discharge pressure
D. Low system head
Answer: A. Over-lubrication or bearing failure
Rationale: Bearing friction or lubrication issues cause overheating.
5.
What is Net Positive Suction Head (NPSH) required to prevent?
A. Electrical overload
B. Cavitation
C. Pipe corrosion
D. Valve leakage
Answer: B. Cavitation
,Rationale: Adequate NPSH prevents vapor bubble formation.
6.
Case: Pump vibration increases gradually over weeks. Most likely cause?
A. Stable operation
B. Bearing wear or misalignment
C. Increased lubrication
D. Reduced flow demand
Answer: B. Bearing wear or misalignment
Rationale: Mechanical wear increases vibration over time.
7.
What is the primary function of a check valve in wastewater systems?
A. Increase pressure
B. Prevent backflow
C. Reduce corrosion
D. Increase flow rate
Answer: B. Prevent backflow
Rationale: Check valves allow one-direction flow only.
8.
Case: Discharge pressure is high but flow is low. Likely issue?
A. Blocked discharge line or closed valve
B. Excess suction flow
C. Motor underload
D. Excess lubrication
Answer: A. Blocked discharge line or closed valve
, Rationale: Flow restriction increases pressure upstream.
9.
What does a worn impeller typically cause?
A. Increased efficiency
B. Reduced flow and efficiency
C. Increased voltage
D. Reduced vibration
Answer: B. Reduced flow and efficiency
Rationale: Damaged impellers lose hydraulic performance.
10.
Case: Pump starts but immediately trips breaker. Likely cause?
A. Excess lubrication
B. Electrical overload or seized rotor
C. Low suction pressure
D. Open discharge valve
Answer: B. Electrical overload or seized rotor
Rationale: Mechanical seizure causes high current draw.
11.
What is the function of a variable frequency drive (VFD)?
A. Increase pipe size
B. Control motor speed and flow
C. Prevent corrosion
D. Increase voltage only
Answer: B. Control motor speed and flow
Exam Test Questions And Correct
Answers (Verified Answers) Plus
Rationales 2025/2026 Q&A | Instant
Download Pdf
1.
Case: A centrifugal pump is running but not delivering flow. Suction line is full of
water. What is the most likely cause?
A. Air trapped in discharge line
B. Impeller rotation in wrong direction or impeller damage
C. Excessive system pressure
D. High motor voltage
Answer: B. Impeller rotation in wrong direction or impeller damage
Rationale: Loss of flow with full suction indicates mechanical or rotational failure
at the impeller.
2.
Case: A pump is cavitating. What is the primary indicator?
A. Low noise and smooth operation
B. Loud rattling or gravel-like sound with vibration
C. High discharge pressure
D. Increased efficiency
Answer: B. Loud rattling or gravel-like sound with vibration
,Rationale: Cavitation is caused by vapor bubble collapse in low-pressure zones.
3.
What is the purpose of a mechanical seal in a pump?
A. Increase flow rate
B. Prevent leakage along the rotating shaft
C. Increase motor speed
D. Reduce electrical load
Answer: B. Prevent leakage along the rotating shaft
Rationale: Mechanical seals prevent fluid escaping around the shaft.
4.
Case: A motor is overheating but pump load is normal. Likely cause?
A. Over-lubrication or bearing failure
B. Excess flow
C. High discharge pressure
D. Low system head
Answer: A. Over-lubrication or bearing failure
Rationale: Bearing friction or lubrication issues cause overheating.
5.
What is Net Positive Suction Head (NPSH) required to prevent?
A. Electrical overload
B. Cavitation
C. Pipe corrosion
D. Valve leakage
Answer: B. Cavitation
,Rationale: Adequate NPSH prevents vapor bubble formation.
6.
Case: Pump vibration increases gradually over weeks. Most likely cause?
A. Stable operation
B. Bearing wear or misalignment
C. Increased lubrication
D. Reduced flow demand
Answer: B. Bearing wear or misalignment
Rationale: Mechanical wear increases vibration over time.
7.
What is the primary function of a check valve in wastewater systems?
A. Increase pressure
B. Prevent backflow
C. Reduce corrosion
D. Increase flow rate
Answer: B. Prevent backflow
Rationale: Check valves allow one-direction flow only.
8.
Case: Discharge pressure is high but flow is low. Likely issue?
A. Blocked discharge line or closed valve
B. Excess suction flow
C. Motor underload
D. Excess lubrication
Answer: A. Blocked discharge line or closed valve
, Rationale: Flow restriction increases pressure upstream.
9.
What does a worn impeller typically cause?
A. Increased efficiency
B. Reduced flow and efficiency
C. Increased voltage
D. Reduced vibration
Answer: B. Reduced flow and efficiency
Rationale: Damaged impellers lose hydraulic performance.
10.
Case: Pump starts but immediately trips breaker. Likely cause?
A. Excess lubrication
B. Electrical overload or seized rotor
C. Low suction pressure
D. Open discharge valve
Answer: B. Electrical overload or seized rotor
Rationale: Mechanical seizure causes high current draw.
11.
What is the function of a variable frequency drive (VFD)?
A. Increase pipe size
B. Control motor speed and flow
C. Prevent corrosion
D. Increase voltage only
Answer: B. Control motor speed and flow
