Ductile Iron Gear Pumps for Industrial Fluid Transfer

What Is a Ductile Iron Gear Pump?

A ductile iron gear pump is a positive displacement rotary gear pump whose housing is cast from ductile iron. Inside, two precision-machined gears mesh together; as the teeth come out of mesh on the inlet side they create a void that draws fluid in, carry it around the housing wall in the spaces between the teeth, and discharge it as the teeth come back into mesh on the outlet side. The result is smooth, pulse-free flow that stays consistent across a wide range of viscosities and pressures — exactly what industrial transfer demands.

NAPCO builds two ductile iron gear pumps: the PA200C (2-inch ports) and the PA300C (3-inch ports). Both are engineered for heavy-duty, non-corrosive service where strength and cost efficiency matter more than chemical resistance. For corrosive fluids, NAPCO offers the stainless steel PA200S and PA300S instead — see our stainless steel vs. ductile iron pump comparison for a full breakdown.

The Metallurgy: Ductile Iron vs. Gray Cast Iron

Not all cast iron is created equal. The term "cast iron" covers a family of iron-carbon alloys, and the form the carbon takes determines the strength of the finished part. In gray cast iron, carbon precipitates as flat graphite flakes. Those flakes act like internal cracks: they concentrate stress and make gray iron brittle, prone to sudden fracture under impact or shock load.

Ductile iron — also called nodular or spheroidal graphite iron — is treated during casting so the carbon forms tiny spheres instead of flakes. Those rounded nodules interrupt crack propagation rather than encouraging it. The result is an iron with dramatically higher tensile strength, meaningful ductility (it bends before it breaks), and far better impact and fatigue resistance than gray iron — while keeping the excellent abrasion resistance and machinability that make iron a great pump material.

Why It Matters in a Gear Pump

A transfer gear pump handles viscous fluids at real pressure, sometimes with entrained solids or thermal cycling from hot product. The housing has to resist the radial loads the gears impose, the abrasion of the fluid, and the occasional pressure spike from a closed valve downstream. Ductile iron's combination of high tensile strength and impact resistance lets a NAPCO ductile iron gear pump shrug off conditions that would crack a gray-iron housing — which is why ductile iron is the standard for rugged, continuous-duty industrial transfer.

Best-Fit Fluids for a Ductile Iron Gear Pump

Ductile iron excels with non-corrosive fluids. Because iron is vulnerable to acids, bases, and oxidizers, a ductile iron gear pump is matched to product streams that do not chemically attack iron. That still covers an enormous slice of industry:

• Petroleum & fuel: diesel, gasoline, kerosene, fuel oils, crude and refined petroleum, and product circulation in terminals and refineries.
• Asphalt & bitumen: hot, heavy, high-viscosity transfer where strength and thermal robustness are essential.
• Lubricants & waste oil: lube oil transfer, used-oil recovery, and oil reclamation service.
• Adhesives & sealants: hot-melt and water-based adhesives, polyurethane and silicone sealants — the PA300C is a long-standing standard in this market.
• Paints, coatings, inks & resins: viscous general-industrial fluids that are non-corrosive to iron.

For fuel and petroleum work specifically, see the petroleum & fuel transfer application page, where ductile iron is the default recommendation.

Why Choose Ductile Iron Over Stainless for Non-Corrosive Duty

When the fluid will not corrode iron, ductile iron is the more economical and, in some respects, the stronger choice. NAPCO stainless steel and ductile iron pumps of the same size share identical performance — a PA300C and a PA300S deliver the same flow, pressure, and displacement — so the decision comes down to chemistry and cost, not throughput.

• Lower initial cost: ductile iron typically runs 25–40% below the stainless equivalent, a meaningful saving across a fleet of pumps.
• Higher tensile strength: ductile iron offers excellent strength for handling dense, viscous fluids and resisting pressure spikes.
• Equal service life in benign fluids: in non-corrosive service, a ductile iron gear pump lasts 10+ years — the same as stainless, at a fraction of the cost.
• Field-rebuildable: factory-matched repair kits restore the pump on-site rather than forcing a costly replacement.

The flip side: if your fluid is corrosive, ductile iron is the wrong tool. Ammonium nitrate emulsions, strong acids, and oxidizers will pit and consume an iron housing within months. Those duties demand stainless steel. The material selection guide walks through the decision industry by industry.

PA200C vs. PA300C: Sizing Your Ductile Iron Gear Pump

NAPCO offers the ductile iron platform in two sizes. The right one depends on your required flow rate, available space, and duty cycle.

Both pumps are restored with factory-matched repair kits. The PK300C repair kit (and PK200C for the smaller pump) carry the exact gears, seals, bearings, and wear components to field-rebuild the pump rather than replace it. For tested flow curves, horsepower data, and dimensions, see the engineering & performance data page.

Not a Hydraulic Gear Pump: An Important Distinction

Search for "gear pump" and you will see two very different products that happen to share a name. It is worth being clear about which one you need, because they are not interchangeable.

Hydraulic Gear Pumps (Parker, Danfoss, Walvoil)

A hydraulic gear pump is a power-transmission component. It lives inside a machine's hydraulic circuit — on an excavator, tractor, loader, or industrial press — where its job is to pressurize hydraulic oil so that oil can actuate cylinders and drive motors. Brands like Parker, Danfoss, and Walvoil dominate this mobile and machine-hydraulics market. The fluid is always hydraulic oil, and the pump is part of the machine, not part of a piping system.

NAPCO Ductile Iron Gear Pumps (Process & Transfer)

A NAPCO ductile iron gear pump is a process and transfer pump. Its job is to move a product fluid — fuel, oil, asphalt, adhesive — from a tank, drum, or tanker through piping to wherever it needs to go, at industrial flow rates. It is plumbed into a fluid-handling system, not bolted into a hydraulic power unit. The fluid being pumped is your product, not the pump's power medium.

The short version: if you need to transfer a fluid through a pipeline, you want a NAPCO transfer gear pump like the PA300C. If you need to power a hydraulic circuit, you want a mobile-hydraulics supplier. This page — and the rest of napcopumps.com — is about transfer pumps.

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