Introduction to Pumps

Which statement best describes a pump’s primary function?

• It creates system pressure directly by resisting flow

• It converts mechanical energy into hydraulic energy

• It stores hydraulic energy for later system use

• It regulates pressure by throttling downstream flow

A system shows low pressure despite high pump output. Which action most likely increases pressure?

• Increase pump speed to generate pressure directly

• Add a restriction downstream to create resistance

• Replace the pump with a larger displacement unit

• Vent the line to reduce hydraulic energy buildup

Which feature best distinguishes a positive displacement pump from a non‑positive displacement pump?

• No relief valve protection against overloads

• Delivery strongly affected by pressure changes

• Mechanical seal between inlet and outlet

• Smooth continuous flow without sealing

In a system experiencing rising discharge pressure, which pump type would most maintain its set output until leakage increases?

• Axial‑flow pump without casing seal

• Positive displacement pump

• Non‑positive displacement pump

• Centrifugal pump with diffuser vanes

Which statement best defines a pump’s pressure rating?

• Average pressure produced during normal operation

• Highest pressure the pump withstands safely over time

• Maximum flow the pump can deliver steadily

• Lowest pressure before cavitation begins

A pump’s flow rate is typically expressed in which units and relates to what?

• Watts per second at rated voltage, energy leaving outlet

• Kilograms per hour at any speed, mass entering the inlet

• Litres per minute at a given rpm, amount passing a point

• Metres per cycle at constant speed, distance fluid travels

You need to vary pump output without changing drive speed. Which pump type allows this and how?

• Fixed displacement, by adjusting chamber size

• Fixed displacement, by altering outlet restriction

• Variable displacement, by changing suction line length

• Variable displacement, by adjusting chamber size

Which characteristic distinguishes fixed displacement from variable displacement pumps?

• Flow is always measured in litres per minute

• Pressure rating is higher than variable types

• Drive speed increases automatically under load

• Chamber size remains constant each cycle

A technician wants more flow from a fixed displacement pump. What is the viable approach?

• Increase drive speed to raise flow

• Resize the pumping chamber on the fly

• Lower the pressure rating temporarily

• Add a bypass to reduce outlet pressure

In the diagram of an external gear pump, what does pump slip primarily refer to?

• Mechanical backlash between gear teeth

• Intended flow from inlet to outlet

• Air entrainment within the pump housing

• Leakage flow from outlet back to inlet