How Gear Pump Works

How a gear pump works is a common question for engineers, maintenance teams, students, and buyers who want a simple yet complete understanding of this widely used industrial pump. A gear pump works by trapping a fixed volume of fluid between rotating gear teeth and the pump casing, then mechanically moving that fluid from the inlet to the outlet at a controlled and continuous rate.

Because gear pumps use positive displacement, their flow remains consistent regardless of pressure variations, making them ideal for oils, chemicals, fuels, and viscous fluids.

Read More: What is Gear Pump?

How Gear Pump Works – Basic Working Principle

The basic working principle of a gear pump is the same for all designs:

1. Gears rotate inside a tightly sealed casing
   
   
2. Gear teeth separate at the inlet, creating suction
   
   
3. Fluid enters and gets trapped between gear teeth
   
   
4. Fluid is carried around the casing
   
   
5. Gears mesh at the outlet, forcing fluid out under pressure
   
   

There is no fluid flow through the center of the gears, which prevents backflow and ensures efficiency.

How External Gear Pump Works

Understanding how an external gear pump works is simple because of its symmetrical design.

Working Process:

• Two identical external gears rotate in opposite directions
  
  
• One gear is driven by a motor, the other acts as an idler
  
  
• As gears rotate, suction is created at the inlet
  
  
• Fluid fills cavities between gear teeth and casing
  
  
• Fluid is transported to the discharge side
  
  
• Meshing gears push fluid out at high pressure
  
  

Key Characteristics:

• High pressure capability
  
  
• Compact and cost-effective
  
  
• Accurate and predictable flow
  
  
• Best for low to medium viscosity fluids

How Internal Gear Pump Works

How the internal gear pump works differs slightly but follows the same positive displacement principle.

Working Process:

• A smaller external gear (rotor) rotates inside a larger internal gear (idler)
  
  
• Gears are mounted off-center
  
  
• A crescent-shaped seal separates inlet and outlet
  
  
• Fluid enters expanding cavities at the inlet
  
  
• Fluid moves smoothly along the crescent
  
  
• Meshing gears reduce volume and discharge fluid
  
  

Key Characteristics:

• Superior suction capability
  
  
• Handles very high-viscosity fluids
  
  
• Low shear and quiet operation
  
  
• Suitable for temperature-sensitive fluids

External vs Internal Gear Pump – Working Comparison

Feature	External Gear Pump	Internal Gear Pump
Gear size	Same size gears	Different size gears
Suction capability	Moderate	High
Pressure handling	High	Medium
Viscosity handling	Low–medium	Very high
Noise level	Higher	Lower
Flow smoothness	Good	Excellent

Why Gear Pumps Deliver Constant Flow

Gear pumps deliver constant flow because:

• Each rotation displaces a fixed volume
  
  
• Flow is proportional to RPM
  
  
• Pressure changes do not affect output
  
  
• Tight clearances prevent slip
  
  

This makes gear pumps ideal for metering, dosing, and blending applications.

Common Applications Based on Working Principle

Because of how gear pumps work, they are widely used in:

• Hydraulic power systems
  
  
• Lubrication circuits
  
  
• Chemical dosing units
  
  
• Oil transfer and fuel handling
  
  
• Paints, inks, resins, and polymers
  
  
• Food-grade viscous fluids

Common User Doubts Answered 

Does a gear pump work with water?

Yes, but gear pumps are better suited for viscous fluids. For water-like fluids, efficiency may reduce due to leakage.

Can a gear pump run dry?

No. Gear pumps rely on the pumped fluid for lubrication. Dry running can cause damage.

Does pressure affect how a gear pump works?

No. Flow remains constant; pressure only increases resistance.

Is gear pump flow pulsating?

No. Gear pumps provide smooth and nearly pulse-free flow.