CWEA MECHANICAL TECHNOLOGIST
GRADE 9 EXAM QUESTIONS AND
VERIFIED ANSWERS
1. When calculating the Total Dynamic Head (TDH) for a pumping system, which of the
following variables must be considered to account for the energy required to overcome pipe
wall friction?
A. Static Discharge Head
B. Velocity Head
C. Static Suction Lift
D. Friction Head Loss
Answer: D
Conceptual Explanation: Friction head loss represents the energy loss due to the
resistance of the pipe walls and fittings as fluid flows through the system.
2. In a centrifugal pump, what is the primary purpose of a wear ring?
A. To balance the axial thrust of the impeller
B. To provide a mounting surface for the mechanical seal
C. To reduce internal recirculation from the discharge side to the suction side
D. To prevent the shaft from vibrating at critical speeds
,Answer: C
Conceptual Explanation: Wear rings provide a replaceable leakage joint between the
impeller and the casing, minimizing high-pressure fluid from leaking back to the low-
pressure suction side.
3. According to the Affinity Laws for centrifugal pumps, if the impeller speed is doubled, how
does the brake horsepower (BHP) requirement change?
A. It doubles
B. It increases by a factor of four
C. It increases by a factor of eight
D. It remains the same if the head is constant
Answer: C
Conceptual Explanation: Power is proportional to the cube of the speed ratio (2^3 = 8).
4. Which vibration frequency is most characteristic of a shaft misalignment condition?
A. 2x running speed in the axial direction
B. 1x running speed in the radial direction
C. 0.4x to 0.5x running speed
D. High frequency blade pass frequency
Answer: A
, Conceptual Explanation: Misalignment typically generates high axial vibration at 1x and
2x the running speed.
5. What is the primary function of a ‘lantern ring’ in a conventional packing gland setup?
A. To hold the packing in place against the gland follower
B. To act as a secondary seal in case of primary seal failure
C. To allow for the injection of lubrication or seal water into the packing
D. To dissipate heat from the shaft through conduction
Answer: C
Conceptual Explanation: The lantern ring provides a channel for seal water to lubricate
and cool the packing, and to prevent air from entering the pump under suction lift.
6. In laser alignment, what does the term ‘soft foot’ refer to?
A. The use of rubber pads under the motor feet to reduce vibration
B. A condition where the machine frame is distorted when mounting bolts are tightened
C. A shaft that is slightly bent near the coupling
D. The flexibility of the coupling material
Answer: B
Conceptual Explanation: Soft foot occurs when the feet of a machine do not rest evenly on
the baseplate, causing frame distortion and misalignment when bolted down.
GRADE 9 EXAM QUESTIONS AND
VERIFIED ANSWERS
1. When calculating the Total Dynamic Head (TDH) for a pumping system, which of the
following variables must be considered to account for the energy required to overcome pipe
wall friction?
A. Static Discharge Head
B. Velocity Head
C. Static Suction Lift
D. Friction Head Loss
Answer: D
Conceptual Explanation: Friction head loss represents the energy loss due to the
resistance of the pipe walls and fittings as fluid flows through the system.
2. In a centrifugal pump, what is the primary purpose of a wear ring?
A. To balance the axial thrust of the impeller
B. To provide a mounting surface for the mechanical seal
C. To reduce internal recirculation from the discharge side to the suction side
D. To prevent the shaft from vibrating at critical speeds
,Answer: C
Conceptual Explanation: Wear rings provide a replaceable leakage joint between the
impeller and the casing, minimizing high-pressure fluid from leaking back to the low-
pressure suction side.
3. According to the Affinity Laws for centrifugal pumps, if the impeller speed is doubled, how
does the brake horsepower (BHP) requirement change?
A. It doubles
B. It increases by a factor of four
C. It increases by a factor of eight
D. It remains the same if the head is constant
Answer: C
Conceptual Explanation: Power is proportional to the cube of the speed ratio (2^3 = 8).
4. Which vibration frequency is most characteristic of a shaft misalignment condition?
A. 2x running speed in the axial direction
B. 1x running speed in the radial direction
C. 0.4x to 0.5x running speed
D. High frequency blade pass frequency
Answer: A
, Conceptual Explanation: Misalignment typically generates high axial vibration at 1x and
2x the running speed.
5. What is the primary function of a ‘lantern ring’ in a conventional packing gland setup?
A. To hold the packing in place against the gland follower
B. To act as a secondary seal in case of primary seal failure
C. To allow for the injection of lubrication or seal water into the packing
D. To dissipate heat from the shaft through conduction
Answer: C
Conceptual Explanation: The lantern ring provides a channel for seal water to lubricate
and cool the packing, and to prevent air from entering the pump under suction lift.
6. In laser alignment, what does the term ‘soft foot’ refer to?
A. The use of rubber pads under the motor feet to reduce vibration
B. A condition where the machine frame is distorted when mounting bolts are tightened
C. A shaft that is slightly bent near the coupling
D. The flexibility of the coupling material
Answer: B
Conceptual Explanation: Soft foot occurs when the feet of a machine do not rest evenly on
the baseplate, causing frame distortion and misalignment when bolted down.
