Aux 1 Unit 5 Pumps – Displacement, Vane, Gear

Where in a pump does cavitation typically start?

B) At the suction side or near the impeller

In a vane-type pump, what ensures that the vanes remain in contact with the casing during operation?

B) Springs or centrifugal force

How does the design of a vane-type pump contribute to its efficiency in handling low-viscosity fluids?

B) The vanes provide a smooth, continuous flow with minimal leakage or slippage

What makes vane pumps suitable for use in hydraulic systems?

B) Their good volumetric efficiency and ability to operate at high pressures

Which of the following is a type of pump commonly used in hydraulic systems?

B) Gear pump

In a double-acting piston pump, how does the fluid flow during the forward stroke of the piston?

B) Fluid is expelled from the cylinder through the discharge valve

How does the operation of a double-acting piston pump ensure continuous fluid flow?

C) By having the piston pump fluid on both strokes, eliminating idle periods

What role do the check valves (suction and discharge valves) play in a double-acting piston pump?

B) They prevent the backflow of fluid, ensuring that fluid flows only in the desired direction

How does cavitation affect the overall efficiency of a pump?

B) It decreases the pump’s efficiency by causing flow disruption and component damage

Which pump type is commonly used in hydraulic systems due to its ability to handle high pressures and variable flow rates?

A) Axial piston pump

When is a pulsation damper typically fitted to the delivery line of a positive displacement pump?

A) When the system requires a constant flow rate without pressure fluctuations

What would likely happen if the vanes in a vane-type pump did not maintain contact with the casing?

B) The pump would fail to move fluid effectively, leading to reduced flow or no flow at all

What happens when vapor bubbles formed by cavitation collapse inside a pump?

B) The collapsing bubbles generate shock waves that can cause pitting and damage to the impeller and pump casing

What is the role of the drive gear in a gear pump?

C) To transmit mechanical energy from the motor to the driven gear

What is the primary function of a relief valve in the delivery line of a positive displacement pump?

B) To protect the pump and system from overpressure conditions

Axial piston pumps are often used in hydraulic systems. What characteristic makes them especially suitable for these applications?

B) They can handle high pressures and variable flow rates efficiently

Which type of gears are typically used in a gear pump?

C) Spur gears

Which characteristic of peristaltic pumps allows them to operate without a pulsation damper?

B) The gentle, squeezing action that provides a steady flow with minimal pulsation

Which of the following is a common application for gear pumps?

A) Pumping highly viscous fluids like oils

Which of the following pumps is suitable for high-pressure hydraulic applications?

A) Vane pump

Why might operating a pump at a flow rate higher than its design capacity lead to increased cavitation?

B) The increased flow rate can cause a drop in suction pressure, leading to cavitation

How does a vane-type pump create suction to draw fluid into the pump?

B) By creating a vacuum as the rotor and vanes rotate, increasing the volume in the pumping chamber

Why is a relief valve necessary in a positive displacement pump system?

B) To prevent excessive pressure buildup that could damage the pump and system

What is the reason that screw pumps typically do not need pulsation dampers?

B) Their rotary motion delivers a smooth, non-pulsating flow

What role do the vanes play in a vane-type pump?

B) They extend from the rotor to trap and move fluid through the pump

Why is it important for a pulsation damper to be correctly sized for the pump system?

B) To absorb the correct amount of pressure fluctuation and maintain stable flow

What could happen if a gear pump is run dry (without fluid)?

B) The gears could overheat and wear out quickly, leading to pump failure

In a pulsation damper, what happens to the gas-filled bladder when a pressure spike occurs?

A) The bladder expands, absorbing the excess pressure

How does a pulsation damper typically reduce pulsations in a positive displacement pump system?

A) By absorbing the pressure spikes using a gas-filled bladder or a flexible diaphragm

Which of the following best describes the casing in a vane-type pump?

B) It provides the outer structure that contains the rotor and vanes

What happens to the fluid as the vanes rotate from the inlet to the outlet in a vane-type pump?

B) The fluid is pressurized as the volume in the pumping chamber decreases

In a double-acting piston pump, what happens during the return stroke of the piston?

A) Fluid is expelled through the discharge valve from the opposite side of the piston

Why do some positive displacement pumps, such as gear pumps, typically not require pulsation dampers?

B) They generate a smooth, continuous flow with minimal pulsation

Which of the following is a common operational cause of increased cavitation in a pump?

B) High fluid temperature, which reduces the liquid’s vapor pressure and makes cavitation more likely

What role does centrifugal force play in the operation of a vane-type pump?

B) It keeps the vanes extended and in contact with the casing to maintain a seal

What is the primary function of a pulsation damper in a positive displacement pump system?

B) To smooth out pressure fluctuations and reduce pulsations in the discharge line

What would likely happen if the clearances between the gears and the casing in a gear pump were too large?

B) The pump would experience increased leakage, reducing its efficiency

Which type of pump is characterized by its quiet operation and consistent flow, making it suitable for hydraulic systems?

B) Screw pump

Which component in a pulsation damper is responsible for isolating the gas from the liquid being pumped?

B) The diaphragm

What is the primary function of the rotor in a vane-type pump?

B) To rotate and drive the vanes within the pump

What visual signs might indicate that cavitation damage has occurred in a pump?

B) Pitting or cratering on the impeller and pump casing

What typically happens to the fluid when a relief valve opens in a positive displacement pump system?

A) It is recirculated back to the pump’s suction side or to a reservoir

What is the purpose of the outlet port in a vane-type pump?

B) To discharge the pressurized fluid from the pump

Where is the relief valve typically fitted in a positive displacement pump system?

B) On the delivery (discharge) side of the pump

How does a pulsation damper reduce pressure fluctuations in a positive displacement pump system?

B) By absorbing pressure spikes using a gas-filled bladder or flexible diaphragm

What could happen if a positive displacement pump operates without a relief valve and the discharge line becomes blocked?

B) Pressure would continue to build, potentially leading to pump or system failure

How does a gear pump ensure that fluid is moved from the inlet to the outlet without backflow?

B) The tight meshing of the gears creates a seal that prevents backflow

Why is a relief valve often installed in a system using a double-acting piston pump?

B) To protect the pump and system from excessive pressure buildup

Why might a system with multiple positive displacement pumps in parallel require a pulsation damper?

C) To smooth out combined pressure fluctuations and maintain a steady flow

What is a key component inside a pulsation damper that helps it function?

B) A gas-filled bladder or flexible diaphragm

How does operating a pump with a clogged or restricted suction line increase the risk of cavitation?

C) It decreases the pressure at the pump inlet, increasing the likelihood of vapor bubble formation

Why is cavitation particularly damaging to pump components?

C) The rapid pressure changes and collapse of bubbles result in high-velocity impacts on pump surfaces

In a gear pump, what happens to the fluid once it enters the pump through the inlet?

B) The fluid is trapped between the gear teeth and the casing and then moved around the gears towards the outlet

In a double-acting piston pump, how does the cylinder design contribute to the pump's performance?

C) The cylinder design ensures that fluid is pumped on both strokes of the piston

Why is it important for the piston seals in a double-acting piston pump to be well-maintained?

B) To prevent fluid leakage between the high-pressure and low-pressure sides of the piston

What could happen if a double-acting piston pump is operated with a blocked discharge line?

B) The pump could over-pressurize, leading to potential damage or failure

In which type of positive displacement pump system is a pulsation damper most likely to be used?

B) In a reciprocating pump system with significant pressure pulsations

What is the primary mechanism by which a gear pump moves fluid?

B) The meshing of two gears to trap and move fluid between the gear teeth and the pump casing

Why are gear pumps typically not used for pumping fluids containing large solids?

A) The solids can cause wear and damage to the gears and casing

How can inadequate Net Positive Suction Head (NPSH) available lead to cavitation in a pump?

C) It means that the available pressure at the pump suction is too low to keep the fluid from vaporizing, leading to cavitation

Which feature of axial piston pumps makes them preferable in complex hydraulic systems requiring precise control?

C) Their ability to maintain efficiency across a wide range of operating conditions

In which situation might even a positive displacement pump that usually generates low pulsation require a pulsation damper?

B) When used in a high-pressure system where even small pulsations could cause issues

What is cavitation in the context of pump operation?

A) The formation and subsequent collapse of vapor bubbles in a liquid

What is a common application for a vane-type pump?

B) Pumping gasoline or other low-viscosity liquids

In a gear pump, how is the fluid pressure generated?

B) By the reduction of the volume between the gear teeth and casing as the gears rotate

What is the defining characteristic of a double-acting piston-type positive displacement pump?

B) It pumps fluid during both the forward and return strokes of the piston

What could happen if a positive displacement pump system lacks a pulsation damper when one is needed?

B) Excessive pressure fluctuations could lead to pipe vibration, noise, and potential damage

Why are gear pumps particularly suitable for use in hydraulic systems?

B) They offer a consistent flow rate and are capable of handling high pressures

Why are screw pumps considered suitable for hydraulic systems, especially in environments where noise reduction is important?

B) They are extremely quiet and provide a smooth, consistent flow

What is the function of the inlet port in a vane-type pump?

B) To allow fluid to enter the pumping chamber

What is the advantage of using a double-acting piston pump over a single-acting piston pump?

A) It is easier to manufacture

In what way do the characteristics of vane pumps contribute to their effectiveness in hydraulic systems?

C) Vane pumps provide a steady flow and can be used for both low and high-pressure applications

1 / 72