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GFES > Pumps > Flashcards

Pumps Flashcards

1
Q

Which one of the following contains indications of cavitation in an operating centrifugal pump?

A

Low flow rate with low discharge pressure.

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2
Q

A centrifugal pump is initially operating at maximum rated flow rate in an open system. Which one of the following moderate changes will cause the pump to operate in closer proximity to cavitation?

A

Increase pump inlet temperature.

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3
Q

Pump cavitation occurs when vapor bubbles are formed at the eye of a pump impeller…

A

and enter a high pressure region of the pump where they collapse, causing damaging pressure pulsations.

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4
Q

Which one of the following contains symptoms associated with cavitation in an operating centrifugal pump?

A

Increased noise and vibration.

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5
Q

Which one of the following will promptly result in cavitation of a centrifugal pump that is initially operating at rated flow?

A

Pump suction valve is fully closed.

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6
Q

Which one of the following describes pump cavitation?

A

Vapor bubbles are formed in the eye of the pump impeller and collapse as they enter higher pressure regions of the pump.

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7
Q

Which one of the following is an indication of pump cavitation?

A

Pump motor amps are fluctuating.

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8
Q

If a centrifugal pump is started with the discharge valve fully open versus throttled, the possibility of pump runout will __________; and the possibility of pump cavitation will __________.

A

increase; increase

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9
Q

If a centrifugal pump is started with the discharge valve throttled versus fully open, the possibility of pump runout will __________; and the possibility of pump cavitation will __________.

A

decrease; decrease

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10
Q

After a motor-driven centrifugal pump is started, the following indications are observed: Oscillating flow rate Oscillating discharge pressure Oscillating motor amps These indications are symptoms that the pump is experiencing…

A

cavitation.

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11
Q

The presence of air in a pump casing may result in __________ when the pump is started.

A

gas binding.

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12
Q

Which one of the following contains three indications of a vapor-bound motor-operated centrifugal pump that is operating in a cooling water system?

A

Increased pump noise level, fluctuating pump discharge pressure, and reduced system flow rate.

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13
Q

Which one of the following is an effective method for ensuring that a centrifugal pump remains primed and does not become gas bound during operation and after shutdown?

A

Install the pump below the level of the suction supply.

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14
Q

Operating a motor-driven centrifugal pump for an extended period of time under no flow conditions will cause…

A

pump failure from overheating.

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15
Q

When a centrifugal pump is operating at shutoff head, it is pumping at __________ capacity and __________ discharge head.

A

minimum; maximum

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16
Q

Refer to the drawing of centrifugal pump and system operating curves (see figure below). Which point represents pump operation at shutoff head?

A

Point A

17
Q

Operating a centrifugal pump at shutoff head without recirculation flow can quickly result in…

A

pump overheating.

18
Q

A motor-driven centrifugal pump with no recirculation flow path must be stopped when discharge pressure reaches the pump shutoff head to prevent…

A

overheating of the pump.

19
Q

A nuclear power plant is operating at full power when a 200 gpm reactor coolant leak occurs, which results in a reactor scram and initiation of emergency coolant injection. Reactor vessel pressure stabilizes at 900 psia. All centrifugal injection pumps are operating with all pump miniflow paths isolated. The shutoff heads for the pumps are as follows: High pressure coolant injection (HPCI) pumps = 1,200 psia Low pressure coolant injection (LPCI) pumps = 200 psia If the injection pumps continue operating under these conditions, which pumps are more likely to fail, and why?

A

LPCI pumps, due to pump overheating.

20
Q

Refer to the drawing of a centrifugal pump with a recirculation line (see figure below). The flowpath through valve A is designed to…

A

provide a small flow rate through the pump during shutoff head conditions.

21
Q

Which one of the following is at a relatively high value when a centrifugal pump is operating at shutoff head?

A

Available net positive suction head

22
Q

Which one of the following describes radial-flow centrifugal pump operating parameters at shutoff head?

A

High discharge pressure, low flow, low power demand

23
Q

Which one of the following conditions applies to a centrifugal pump running at shutoff head?

A

Available net positive suction head is at a maximum value for the existing fluid conditions.

24
Q

Which one of the following would result from operating a motor-driven radial-flow centrifugal pump in a water system for an extended period with the discharge valve shut and no recirculation flow?

A

No motor damage, but the pump will overheat and may be damaged.

25
Q

hich one of the following describes the response of the pump if a complete flow blockage occurs in the discharge line just downstream of the flow transmitter?

A

The pump will overheat after a relatively long period of time, due to a loss of main flow only.

26
Q

A variable-speed centrifugal fire water pump is taking a suction on an open storage tank and discharging through a 4-inch diameter fire hose and through a nozzle located 50 feet above the pump.

A

Pump speed is decreased until pump discharge pressure is insufficient to cause flow.

27
Q

Valve A will open when pump…

A

flow rate decreases below a setpoint.

28
Q

A centrifugal fire water pump takes suction from an open storage tank and discharges through a fire hose. Which one of the following will cause the pump to operate at shutoff head?

A

The fire hose nozzle is raised to an elevation that prevents any flow.

29
Q

A centrifugal fire water pump takes suction from an open storage tank and discharges through a fire hose. Which one of the following will cause the pump to operate at shutoff head?

A

The fire hose becomes completely crimped in a fire door.

30
Q

A centrifugal fire water pump takes suction from an open storage tank and discharges through a fire hose. Which one of the following will cause the pump to operate at shutoff head?

A

A firefighter adjusts the fire hose nozzle spray pattern from DELUGE to OFF.

31
Q

Valve A will close when pump…

A

flow rate increases above a setpoint.

GFES (6 decks)

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