Cavitating Pump Symptoms

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Questions and Answers

What is a characteristic sound of a cavitating pump?

A hissing sound

Complete silence

A sound like a can of marbles being shaken (correct)

A smooth humming noise

What are some indications of a cavitating pump that can be observed from a remote operating station?

Decreasing discharge pressure, flow rate, and pump motor current

Fluctuating discharge pressure, flow rate, and pump motor current (correct)

Increasing discharge pressure, flow rate, and pump motor current

Constant discharge pressure, flow rate, and pump motor current

What is an unusual aspect of a cavitating pump's operation?

Varying discharge pressure

Fluctuating flow rate (correct)

Stable flow rate

Constant pump motor current

What can be monitored to detect signs of a cavitating pump?

Discharge pressure, flow rate, and pump motor current Signup and view all the answers

Why is it important to monitor a pump's performance from a remote operating station?

To detect unusual behavior, such as cavitating Signup and view all the answers

What is the net positive suction head available (NPSHA) a measure of?

The difference between the pressure at the suction of the pump and the saturation pressure for the liquid being pumped Signup and view all the answers

What is the significance of the saturation pressure in the calculation of NPSHA?

It is the minimum pressure required to prevent cavitation Signup and view all the answers

What happens if the NPSHA is not sufficient for the pump?

The pump will experience cavitation Signup and view all the answers

What is the purpose of calculating NPSHA in pump design?

To prevent cavitation and ensure reliable operation Signup and view all the answers

What is the relationship between the NPSHA and the pump's suction pressure?

NPSHA is the difference between the suction pressure and the saturation pressure Signup and view all the answers

What can happen to a centrifugal pump if it is run in shutoff head conditions for a significant amount of time?

It will become damaged Signup and view all the answers

Why is pump protection necessary in certain systems?

To prevent the pump from becoming damaged Signup and view all the answers

What type of condition can cause damage to a centrifugal pump?

Shutoff head conditions Signup and view all the answers

Why is it necessary to provide some means of pump protection in certain systems?

Because the pump may be subjected to periodic shutoff head conditions Signup and view all the answers

What is the result of a centrifugal pump being subjected to periodic shutoff head conditions without proper protection?

The pump will become damaged Signup and view all the answers

What is the main component of a simple gear pump?

Spur gears Signup and view all the answers

In which direction do the spur gears revolve in a simple gear pump?

In opposite directions Signup and view all the answers

What is the purpose of the casing in a simple gear pump?

To hold the gears in place Signup and view all the answers

What type of gears are used in a simple gear pump?

Spur gears Signup and view all the answers

How many gears are there in a simple gear pump?

Two Signup and view all the answers

What is one way to reduce the power required by a pump?

Reduce the temperature of the liquid being pumped Signup and view all the answers

Which of the following can help reduce head losses in a pump system?

Reducing head losses in the pump suction piping Signup and view all the answers

What is an effect of increasing the speed of the pump impeller?

Increasing the flow rate through the pump Signup and view all the answers

What is a potential consequence of reducing the flow rate through a pump?

Decreased power required by the pump Signup and view all the answers

What is a benefit of reducing head losses in the pump suction piping?

Reduced power required by the pump Signup and view all the answers

Study Notes

Cavitating Pump

Sounds like a can of marbles being shaken due to cavitating
Indications of cavitating pump:
- Fluctuating discharge pressure
- Fluctuating flow rate
- Fluctuating pump motor current
Causes damage to the pump if run in this condition for a significant amount of time
Occurs when the net positive suction head available (NPSHA) is lower than the required level
NPSHA is the difference between the pressure at the suction of the pump and the saturation pressure for the liquid being pumped

Pump Protection

Necessary when a centrifugal pump is installed in a system with periodic shutoff head conditions
Methods to provide pump protection:
- Reduce the temperature of the liquid being pumped
- Reduce head losses in the pump suction piping
- Reduce the flow rate through the pump
- Reduce the speed of the pump impeller

Simple Gear Pump

Consists of two spur gears meshing together and revolving in opposite directions within a casing
Has several variations, with the one shown in Figure 14 being a simple example

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Description

Identify the signs of a cavitating pump, including unusual sounds, fluctuating discharge pressure, flow rate, and pump motor current. Learn to recognize these indications from a remote operating station.