Technical Foundation
What Is a Rotary Gear Pump Head?
A rotary gear pump head is the fluid-handling assembly of a gear pump — the housing, meshing gear set, and shaft seal — that attaches to a separate motor or drive to transfer liquid by trapping fluid between rotating gear teeth and the housing wall, then displacing it to the outlet port. Because displacement is fixed by gear geometry, flow rate scales directly with drive speed, making gear pumps well suited to metering and consistent-viscosity transfer duty.
Housing material and seal type must be matched to the pumped fluid: cast iron suits general oils and fuels, stainless steel is required for corrosive or food-grade fluids, and bronze suits moderate chemical service at lower cost than stainless. Shaft sealing is typically by mechanical seal (for continuous duty and higher pressure) or packing gland (for lower-cost, more tolerant-of-abrasives service), and the wrong seal elastomer for the fluid is a common cause of premature leakage.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| Housing Material | Cast iron, stainless steel, bronze/brass | Must be chemically compatible with the pumped fluid to avoid corrosion or contamination |
| Displacement | Fixed volume per gear revolution | Flow rate is a direct function of displacement times drive RPM, not adjustable without changing gears or speed |
| Port Size/Connection | Commonly 1/4 in to 3 in NPT/flanged | Must match piping and support the required flow velocity without excessive pressure drop |
| Seal Type | Mechanical seal, packing gland | Mechanical seals suit continuous duty and higher pressure; packing tolerates abrasives better at lower cost |
| Viscosity Range | From thin fuels to heavy oils/syrups | Gear clearances and drive torque must be sized to the fluid's viscosity to maintain rated flow |
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Applications
Where Rotary Gear Pump Heads Get Used
Rotary gear pump heads are specified anywhere consistent, metered transfer of a viscous or moderately viscous fluid is required.
Fuel & Lubricant Transfer
Cast iron gear pump heads transfer diesel, hydraulic oil and lubricants from bulk storage to equipment.
Chemical Processing
Stainless steel gear pump heads handle corrosive or high-purity chemical transfer duty.
Food & Beverage Manufacturing
Sanitary stainless gear pump heads meter viscous syrups, sauces and dairy products.
Printing & Ink Manufacturing
Precision gear pump heads meter consistent ink and coating flow in production lines.
Marine & Fuel Bunkering
Bronze gear pump heads transfer fuel and lubricants in marine engine room applications.
Industrial Lubrication Systems
Gear pump heads circulate lubricating oil in centralized machine lubrication systems.
FAQ
Rotary Gear Pump Heads Questions, Answered
How do I choose the right housing material for a gear pump head?
Match housing material to the pumped fluid's chemical compatibility: cast iron is the economical standard for oils, fuels and general non-corrosive liquids; stainless steel is required for corrosive chemicals, food-grade product, or where contamination from a ferrous housing isn't acceptable; bronze offers moderate chemical resistance at a lower cost than stainless for many industrial fluids.
What's the difference between a mechanical seal and a packing gland on a gear pump head?
A mechanical seal uses two flat, spring-loaded faces (one rotating, one stationary) to seal against the shaft, offering a tighter seal suited to continuous duty and higher pressure, but it's less tolerant of abrasive particles in the fluid. A packing gland uses compressed fiber rings around the shaft, tolerating abrasives and requiring less precision, but typically allows a small amount of weep and needs periodic re-tightening.
How does flow rate relate to displacement on a gear pump head?
A gear pump's displacement — the fixed volume of fluid moved per revolution of the gear set — is set by the gear geometry and doesn't change with pressure. Flow rate is displacement multiplied by drive shaft RPM, so the only way to change flow with a given pump head is to change the drive speed, unless a different gear set is installed.
Can a gear pump head handle high-viscosity fluids?
Gear pumps are well suited to higher-viscosity fluids like heavy oils and syrups because the tight gear-to-housing clearances that would let a thin fluid slip past provide effective sealing against a thicker fluid; however, very high viscosity increases drive torque requirements and may reduce achievable flow rate at a given RPM, so drive sizing should account for the actual fluid viscosity.
Why is my gear pump head leaking at the shaft?
Shaft leakage is most commonly caused by a worn or improperly seated mechanical seal face, an incompatible seal elastomer for the pumped fluid, or a packing gland that's loosened or worn past its adjustment range. Confirm the seal material is chemically compatible with the fluid before replacing it, since the wrong elastomer will degrade and leak again quickly.
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