Centrifugal vs. Internal Gear Pumps: How to Choose
Two of the most common pump types, centrifugal pumps and internal gear pumps, dominate the market, each with its own strengths and limitations. This guide compares the two as offered by Victor Pumps, so you can match the right principle to your duty before you compare models.
Centrifugal Pumps: Kinetic Energy for High-Volume Flow
Centrifugal pumps operate on a simple, effective principle: kinetic energy transfer. As fluid enters the rotating impeller, it is flung outward by centrifugal force, generating velocity and pressure. The volute casing then converts that velocity into pressure energy, producing flow.
Pros of Centrifugal Pumps
- High flow rates: centrifugal pumps excel where volume matters, in water transfer, irrigation, and general-purpose fluid handling.
- Simple design and operation: fewer moving parts than positive displacement designs, which translates to easier operation and maintenance.
- Lower upfront cost: generally the cheaper option at the purchase order, attractive for budget-conscious, high-volume duties.
Cons of Centrifugal Pumps
- Flow varies with pressure: output falls as system head rises, so applications needing a fixed flow regardless of backpressure are a poor fit.
- Poor viscosity handling: efficiency drops sharply on viscous fluids like oils, syrups, and slurries.
- Priming requirements: most centrifugal pumps must be primed before operation, unless a self-priming design such as Victor's S-Series is specified.
Internal Gear Pumps: Positive Displacement for Consistent Flow
Internal gear pumps move a fixed volume of fluid with each rotation. As the gears rotate, expanding cavities on the suction side draw fluid in; it is carried between the gear teeth and discharged in a continuous, smooth flow.
Pros of Internal Gear Pumps
- Pulsation-free, consistent flow: ideal for metering, dosing, and shear-sensitive fluids.
- High viscosity handling: flow stays consistent as viscosity climbs, which is exactly where centrifugal designs give up.
- Self-priming: most internal gear pumps prime themselves, simplifying startup and installation.
Cons of Internal Gear Pumps
- Lower flow rates: less suited to high-volume duties than centrifugals.
- Higher upfront cost: precision manufacturing costs more at purchase, though it often returns the difference in efficiency and life.
- Some slippage at pressure: a small amount of internal slip slightly reduces efficiency at the top of the pressure range.
Making the Choice: Five Factors
- Flow rate: high volume favors centrifugal; lower, precise flows favor internal gear.
- Viscosity: thin fluids favor centrifugal; viscous fluids strongly favor internal gear.
- Pressure: both cover wide ranges, but internal gear pumps hold flow better against high discharge pressure.
- Smoothness: if pulsation-free flow matters, internal gear wins.
- Budget: centrifugal costs less up front; internal gear often costs less over the life of the duty.
If your fluid is corrosive as well as viscous, material selection may matter more than the operating principle. Start with our chemical pump selection guide for the material side of the decision.
Victor Pumps: Both Principles, One Line
Victor Pumps builds both self-priming centrifugal pumps (S-Series) and internal gear pumps (R-Series), so the selection can follow the duty rather than the catalog. Send us the flow, pressure, and fluid, and we will confirm which principle and which model fit before we quote.