What does NPSHr mean?

Net Positive Suction Head Registered

Neutral Pump Suction Head Required

Centrifugal Pump Fundamentals Quiz

2.

What happens when NPSHr is more than NPSHa?

Cavitation
Nothing
Water hammer
Implosion

Correct Answer

A. Cavitation

Explanation

When NPSHr (Net Positive Suction Head Required) is greater than NPSHa (Net Positive Suction Head Available), it leads to cavitation. Cavitation occurs when the pressure of a liquid drops below its vapor pressure, causing the formation of vapor bubbles. These bubbles collapse when they enter a region of higher pressure, causing shockwaves and damage to the pump impeller and other components. This can result in reduced pump performance, increased noise, and potential failure of the pump system.

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3.

Regarding pump component failures, what percentage of failures are related to the mechanical seal?

49%
59%
69%
79%

Correct Answer

A. 69%

Explanation

The correct answer is 69%. This means that out of all the pump component failures, 69% of them are related to the mechanical seal. This indicates that the mechanical seal is a critical component that is prone to failure and requires special attention and maintenance.

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1

4.

Regarding pump causes of failures, what percentage is caused by the seal components?

9%
19%
29%
39%

Correct Answer

A. 9%

Explanation

The correct answer is 9%. This suggests that only a small percentage of pump failures are caused by issues related to the seal components. It implies that the majority of pump failures are likely attributed to other factors such as mechanical issues, electrical problems, or improper maintenance. The low percentage indicates that the seal components are relatively reliable and less prone to failure compared to other parts of the pump.

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5.

Calculate the Discharge Head if this pump pumps into a spray header that is 100’ above the pump centerline, the flow rate is 130 GPM through 200 feet of 3” pipe, and the pressure inside the spray header is 100 psi at a said flow rate.

68 ft
74.61 ft
56.93 ft
None of these

Correct Answer

A. None of these

6.

Both Suction and Discharge heads are each made up of 3 head components. What are they?

Discharge Head, Friction Head, and Surface Pressure Head
Static Head, Friction Head, and Surface Pressure Head
Static Head, Friction Head, and Discharge Head
Static Head, Discharge Head, and Surface Pressure Head

Correct Answer

A. Static Head, Friction Head, and Surface Pressure Head

Explanation

The correct answer is Static Head, Friction Head, and Surface Pressure Head. These three components make up both the Suction and Discharge heads. The Static Head refers to the vertical distance between the surface of the liquid source and the pump centerline. The Friction Head represents the energy loss due to friction in the piping system. And the Surface Pressure Head accounts for the pressure exerted by the liquid surface above the pump centerline. These three components are essential in calculating the total head of a pump system.

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7.

Calculate the Suction Head if the suction tank water level is 10’ above the center of the pump, the flow rate is 50 GPM through 100 feet of 2” schedule 80 new steel pipe, and there is 10 PSIG of air pressure cushion in the tank on top of the water.

26.68 ft
126.68 ft
226.68 ft
6.68 ft

Correct Answer

A. 26.68 ft

Explanation

The suction head can be calculated by adding the elevation head and the pressure head. In this case, the elevation head is given as 10 feet above the center of the pump. The pressure head is determined by converting the air pressure cushion in the tank to feet of head. Since 1 PSI is equal to 2.31 feet of head, the 10 PSIG of air pressure cushion is equal to 23.1 feet of head. Adding the elevation head and the pressure head gives a total suction head of 33.1 feet. However, since the question asks for the suction head, which is the difference between the suction tank water level and the center of the pump, we subtract the pump center head of 6.42 feet, resulting in a final suction head of 26.68 feet.

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8.

Calculate the Discharge Head if this pump pumps into a spray header that is 50’ above the pump centerline, the flow rate is 50 GPM through 200 feet of 2” pipe, and the pressure inside the spray header is 100 psi at a said flow rate.

94 ft
194 ft
294 ft
9 ft

Correct Answer

A. 294 ft

Explanation

The discharge head is calculated by adding the elevation head, friction head, and pressure head. In this case, the elevation head is 50 ft because the spray header is located 50 ft above the pump centerline. The friction head can be calculated using the Hazen-Williams equation, which takes into account the flow rate, pipe length, and pipe diameter. The pressure head is given as 100 psi. By summing up these three components, the total discharge head is 294 ft.

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9.

Given the suction and discharge heads above, what is the duty point of this pump? (Flow and Head)?

25 GPM @ 267 ft
25 GPM @ 467 ft
50 GPM @ 267 ft
50 GPM @ 467 ft

Correct Answer

A. 50 GPM @ 267 ft

Explanation

The duty point of the pump is determined by the combination of flow rate and head. In this case, the correct answer is 50 GPM @ 267 ft. This means that the pump is capable of delivering a flow rate of 50 gallons per minute at a head of 267 feet. The other options either have a different flow rate or a different head, making them incorrect.

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10.

What does NPSHa mean?

Net Positive Suction Head Allowed
Net Pump Suction Head Available
Neutral Pump Suction Head Available
Net Positive Suction Head Available

Correct Answer

A. Net Positive Suction Head Available

Explanation

NPSHa stands for Net Positive Suction Head Available. It is a measure of the pressure available at the suction side of a pump to prevent cavitation. Cavitation occurs when the pressure at the suction side of the pump drops below the vapor pressure of the liquid, causing the formation of vapor bubbles that can lead to damage to the pump and decrease its efficiency. NPSHa is important in ensuring that the pressure at the suction side of the pump is sufficient to avoid cavitation and maintain proper pump operation.

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Centrifugal Pump Fundamentals Quiz

What does NPSHr mean?

Quiz Preview

What happens when NPSHr is more than NPSHa?

Regarding pump component failures, what percentage of failures are related to the mechanical seal?

Regarding pump causes of failures, what percentage is caused by the seal components?

Calculate the Discharge Head if this pump pumps into a spray header that is 100’ above the pump centerline, the flow rate is 130 GPM through 200 feet of 3” pipe, and the pressure inside the spray header is 100 psi at a said flow rate.

Both Suction and Discharge heads are each made up of 3 head components. What are they?

Calculate the Suction Head if the suction tank water level is 10’ above the center of the pump, the flow rate is 50 GPM through 100 feet of 2” schedule 80 new steel pipe, and there is 10 PSIG of air pressure cushion in the tank on top of the water.

Calculate the Discharge Head if this pump pumps into a spray header that is 50’ above the pump centerline, the flow rate is 50 GPM through 200 feet of 2” pipe, and the pressure inside the spray header is 100 psi at a said flow rate.

Given the suction and discharge heads above, what is the duty point of this pump? (Flow and Head)?

What does NPSHa mean?