Complete Technical GuideGear Pump
Everything you need to know about gear pumps: operating principle, types, industrial applications and how to specify for your process.
What is a gear pump?
A gear pump is a positive displacement pump that moves fluids through the meshing of two or more gears. Each rotation delivers a fixed volume, regardless of pressure. It is the most widely used industrial technology for viscous fluids like oils, asphalt, resins and chemicals. FB Bombas has manufactured them since 1944.
Difference between external and internal gear pumps?
External gear (FBE Series) uses two identical gears rotating in opposite directions — supports pressure up to 22 kgf/cm². Internal gear (FBEI Series) has a rotor spinning inside a ring separated by a fixed crescent — quiet operation, low pulsation, ideal for shear-sensitive fluids. FB Bombas offers both lines.
When to use a gear pump instead of a centrifugal pump?
Choose a gear pump when the fluid is viscous (above 100 cP), when you need constant flow regardless of pressure, when the fluid is shear-sensitive, or when precise dosing is required. For water and low-viscosity fluids, the centrifugal pump (FBCN Series) is more energy-efficient.
What is the flow and pressure range of FB gear pumps?
External gear FBE Series operates with flows from 0.5 to 6,500 L/min and pressures up to 22 kgf/cm². FBEI Series (internal) handles flows up to 600 m³/h at pressure up to 16 bar. Both support temperatures up to 350°C with appropriate sealing and are self-priming — simplified installation without foot valve.
What Is a Gear Pump?
Technical definition and positive displacement principle
A gear pump is a type of positive displacement pump that uses the meshing of two or more rotating gears to transport fluids. With each rotation, a fixed volume of liquid is captured between the gear teeth and casing, being transferred from suction to discharge continuously and precisely.
Being positive displacement, the delivered flow is proportional to speed and virtually independent of system pressure. This makes gear pumps ideal for applications requiring constant flow, precise dosing, or pumping viscous fluids — from lubricating oils to asphalt and chocolate.
Constant flow independent of pressure
Self-priming — no foot valve needed
Operates with fluids from 1 to 1,000,000 cP
Reversible — suction and discharge interchangeable
How Does a Gear Pump Work?
Pumping cycle through rotary gear meshing
Suction
The gears rotate in opposite directions. In the tooth disengagement zone, the volume between gears expands, creating partial vacuum that draws fluid through the suction port.
Transfer
Fluid is trapped in the spaces between teeth and casing. The gears carry the fluid along the inner chamber wall, from suction to discharge.
Discharge
In the re-meshing zone, teeth re-engage, reducing chamber volume and forcing fluid out through the discharge port with minimal pulsation.
Types of Gear Pumps
External vs. internal gear — when to use each
External Gear (FBE)
Two identical gears rotate in opposite directions. Robust design for high pressure and wide viscosity range. The most versatile and widely used in industry.
Flow up to 6,500 L/min
Pressure up to 22 kgf/cm²
Temperature up to 350°C
Viscosity up to 1,000,000 cP
Best for: oils, resins, asphalt, viscous chemicals
Explore Models
Internal Gear (FBEI)
An internal rotor spins inside an outer ring, separated by a fixed crescent. Quiet operation, very low pulsation and smooth flow — ideal for shear-sensitive products.
Flow up to 600 m³/h
Pressure up to 16 bar
Temperature up to 350°C
Minimal pulsation
Best for: chocolate, adhesives, paints, pharmaceuticals
Explore ModelsGear Pump Advantages
Why industry chooses gear pumps for viscous fluids
Constant Flow
Volume delivered per rotation is fixed and pressure-independent. Ideal for precise dosing and continuous processes.
Viscous Fluids
Efficiency increases with viscosity — unlike centrifugal pumps. Operates from 1 cP to over 1,000,000 cP.
Self-Priming
Creates sufficient vacuum to draw fluid without auxiliary devices. Simplifies installation and reduces costs.
Robust & Durable
Few moving parts, simple design. Long service life with minimal maintenance and low operating cost.
Low Pulsation
Continuous and uniform flow. Especially in internal gear, pulsation is near zero.
Reversible
Reversing rotation reverses flow direction. Flexibility for tank loading and unloading.
Industrial Applications
Sectors that use gear pumps daily
Petrochemical
Oils and petroleum derivatives
Chemical
Resins, solvents and polymers
Food Industry
Chocolate, molasses, vegetable oils
Asphalt & Paving
Bitumen, asphalt emulsions, CAP
Paints & Coatings
Paints, varnishes, pigments
Oils & Lubricants
Lubricants, hydraulic, thermal
Adhesives & Sealants
Hot-melt, PVA, silicone
Thermal Oil
Heating systems up to 350°C
Gear vs. Centrifugal
When to choose each pumping technology
| Criteria | Gear | Centrifugal |
|---|---|---|
| Ideal viscosity | High (>100 cP) | Low (<100 cP) |
| Flow vs. pressure | Constant | Variable |
| Self-priming | Yes | No |
| Shear | Low | High |
| Precise dosing | Excellent | Limited |
| Ideal fluids | Oils, resins, asphalt | Water, solvents |
How to Specify
Essential data for correct sizing
Fluid Type
Fluid name, composition and chemical compatibility with pump materials.
Viscosity
Viscosity at pumping temperature (in cP or cSt). The more viscous, the better for gear pumps.
Flow & Pressure
Desired flow rate (L/min or m³/h) and system differential pressure (bar or kgf/cm²).
Temperature
Operating and maximum fluid temperature. Defines seal, packing and heating jacket materials.
Installation Conditions
Suction height, piping length, drive type (electric motor/gearbox).
Operating Regime
Continuous or intermittent, hours/day, cleaning requirements (CIP) or certifications.
Frequently Asked Questions
What is a gear pump?
A gear pump is a type of positive displacement pump that uses the meshing of two or more gears to transport fluids. Each rotation delivers a fixed volume of liquid regardless of system pressure. It is the most widely used technology in industry for pumping viscous fluids such as oils, resins, asphalt and chemicals.
What is the difference between external and internal gear pumps?
In an external gear pump, two identical gears rotate in opposite directions. In an internal gear pump, a rotor spins inside a ring, separated by a fixed crescent. Internal offers quieter operation and lower pulsation; external supports higher pressures and is more versatile.
What fluids are gear pumps suitable for?
Gear pumps are ideal for viscous fluids: lubricating oils, hydraulic oils, resins, adhesives, paints, varnishes, chocolate, molasses, bitumen, asphalt, polymers and chemicals. Viscosity range goes from 1 cP to over 1,000,000 cP.
Are gear pumps self-priming?
Yes. The meshing of the gears creates sufficient vacuum to draw fluid without the need for a foot valve or auxiliary priming device.
What is the flow and pressure range of a gear pump?
FB Bombas gear pumps operate with flow rates up to 6,500 L/min (FBE series) and pressures up to 22 kgf/cm². The FBEI series (internal) handles flows up to 600 m³/h with pressure up to 16 bar. Maximum operating temperature up to 350°C.
When to choose a gear pump over a centrifugal pump?
Choose gear when the fluid is viscous (>100 cP), when you need constant flow, when the fluid is shear-sensitive, or when precise dosing is needed. For water and low-viscosity fluids, centrifugal is more efficient.
Can I replace my current gear pump with an FB Bombas?
Yes. The FBE and FBEI series replace gear pumps from any manufacturer — Edral, Hidex, RZR, Viking, Netzsch, Maag — with connection compatibility and custom sizing. FB Bombas has been manufacturing since 1944, holds CRCC Petrobras registration and meets API 610 and API 676 requirements, with direct manufacturer technical support.
Companies that Trust FB Bombas
80+ years supplying gear pumps to industry
Need a gear pump?
Send us your fluid data and operating conditions. Our engineering team will size the ideal pump for your application.
Gear Pumps by Application
Specific technical guides by fluid type and industrial sector
For Oil
Lubricants, hydraulic, mineral and vegetable oils
For Asphalt
CAP, bitumen, emulsion and modified asphalt
For Resins
Epoxy, polyester, industrial paints and varnishes
For Food
Chocolate, honey, syrups and vegetable oils
For Fuel
Diesel, gasoline, kerosene and biodiesel
Hydraulic
HPU, presses and industrial hydraulic systems
See All
Complete FBE and FBEI portfolio
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Setores e cenários cobertos com cluster pages técnicos da FB Bombas.
Related content
Technical articles, essential definitions and products curated by FB Bombas engineering.
Technical Articles
- Gear Pump vs Centrifugal: When to Use Each
- How to Select a Gear Pump by Viscosity
- NPSH in Gear Pumps: Practical Calculation
- Installation and Startup: Manufacturer Checklist
Technical Glossary
Products & Resources
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