A gear pump is a positive displacement pump used to transfer diesel, fuel oil, lubricating oil and other viscous petroleum products under pressure. Unlike a centrifugal pump, its flow rate is almost independent of discharge pressure: whatever it delivers at 25 metres, it delivers at 100 metres. Neftgen supplies the S.p.A. (Italy) gear pump range from 5 l/min to 630 l/min, up to 100 metres of head.
Gear pump or self-priming centrifugal pump?
The two types do not do the same job. Viscosity and the required pressure decide:
- Gear pump: high pressure (50–100 m / 5–10 bar), low to medium flow, viscous liquids (oil, fuel oil, grease, varnish, food liquids). Flow stays constant as pressure rises. By-pass valve fitted as standard.
- Self-priming centrifugal pump: high flow (up to 2,300 l/min), low head (16–76 m), low-viscosity liquids — diesel, gasoline, kerosene. Tanker unloading and tank filling belong to this type.
Rule of thumb: below 600 l/min and above 3 bar, or with a liquid more viscous than 20 cSt, choose a gear pump; for high flow at low pressure, choose a centrifugal pump. If the area is classified as explosive, see our ATEX fuel pumps page — the gear range is not ATEX certified.
Gear Pump Selection Charts — Model by Flow Rate and Head
Flow rates apply to a liquid of 46 cSt / 8 °E at 40 °C. Each row gives the flow in l/min delivered at 25, 50, 75 and 100 metres of head — this is the defining characteristic of a gear pump: flow barely drops as pressure rises.
1. Monobloc gear pumps — 1400 rpm (GEAR 300 – GEAR 3600)
Pump and motor in one body. For small oil transfers, generator day-tank filling, dosing and workshop use. Cast iron body with C40 steel gears, or bronze body with AISI 316 gears.
| Model | Motor (kW) | Connection | 25 m | 50 m | 75 m | 100 m |
|---|---|---|---|---|---|---|
| GEAR 300 | 0.29 / 0.37 | ½” | 5.5 | 5.3 | 5.2 | 5.0 |
| GEAR 600 | 0.37 | ¾” | 10.3 | 10.0 | 9.8 | 9.6 |
| GEAR 1000 | 0.55 | ¾” | 16.0 | 15.0 | 14.6 | 14.2 |
| GEAR 1500 | 0.75 | ¾” | 26.0 | 25.0 | 24.1 | 23.3 |
| GEAR 2000 | 1.1 | 1″ | 36.0 | 35.0 | 34.1 | 33.3 |
| GEAR 3000 | 1.5 | 1″ | 51.0 | 50.0 | 49.1 | 48.3 |
| GEAR 3600 | 1.8 | 1¼” | 62.0 | 60.0 | 58.3 | 56.6 |
2. Base-mounted gear pumps with coupling — 1400 rpm (GEAR 4000 – GEAR 36000)
Pump and motor coupled on a common baseplate, for heavy duty and continuous service. Fuel and lubricating oil transfer, petroleum products, paint, cosmetics and food liquids. Maximum liquid temperature 140 °C.
| Model | Motor (kW) | Connection | 25 m | 50 m | 75 m | 100 m |
|---|---|---|---|---|---|---|
| GEAR 4000 | 2.2 | 1½” | 74 | 72 | 71 | 70 |
| GEAR 6000 | 3 | 2″ | 120 | 115 | 110 | 105 |
| GEAR 9000 | 4 | 2″ | 180 | 170 | 165 | 160 (80 m) |
| GEAR 12000 | 5.5 | 2½” | 215 | 212 | 208 | 205 |
| GEAR 15000 | 7.5 | 2½” | 260 | 258 | 255 | 250 |
| GEAR 18000 | 7.5 | 2½” | 310 | 300 | 295 | 290 (80 m) |
| GEAR 21000 | 11 | 2½” | 365 | 355 | 350 | 340 |
| GEAR 24000 | 11 | 2½” | 420 | 410 | 400 | 390 |
| GEAR 30000 | 15 | 3″ | 525 | 515 | 510 | 505 |
| GEAR 33000 | 15 | 3″ | 565 | 560 | 550 | 545 |
| GEAR 36000 | 15 | 3″ | 630 | 610 | 595 | 580 |
3. Base-mounted gear pumps with coupling — 720 rpm (high viscosity)
Lower speed for more viscous liquids and longer pump life. Preferred for heavy fuel oil, grease and oils that thicken in cold ambient conditions. Head up to 50 metres.
| Model | Motor (kW) | Connection | 20 m | 30 m | 40 m | 50 m |
|---|---|---|---|---|---|---|
| GEAR 9000 | 1.1 | 2″ | 80 | 78 | 77 | 76 |
| GEAR 12000 | 1.5 | 2½” | 100 | 99 | 98 | 95 |
| GEAR 15000 | 2 | 2½” | 125 | 122 | 120 | 118 |
| GEAR 18000 | 2 | 2½” | 148 | 144 | 140 | 138 |
| GEAR 21000 | 3 | 2½” | 170 | 168 | 162 | 160 |
| GEAR 24000 | 3 | 2½” | 200 | 195 | 192 | 188 |
| GEAR 30000 | 4 | 3″ | 247 | 245 | 240 | 237 |
| GEAR 33000 | 5.5 | 3″ | 275 | 270 | 265 | 260 |
| GEAR 36000 | 5.5 | 3″ | 300 | 295 | 290 | 280 |
Body and Gear Materials
| Version | Body | Gears | Typical service |
|---|---|---|---|
| Cast iron (G) | Cast iron | C40 steel | Diesel, fuel oil, lubricating oil, hydraulic oil |
| Bronze (B) | Bronze | AISI 316 stainless | Marine environments, spark-sensitive service, some chemicals |
| Full AISI 316 | AISI 316 | AISI 316 | On request — food, cosmetics, corrosive liquids |
Technical Data
- Type: self-priming positive displacement gear pump, by-pass valve as standard
- Flow range: 5 – 630 l/min (0.3 – 38 m³/h)
- Head: up to 100 metres (approx. 10 bar); up to 50 metres on the 720 rpm range
- Motor power: 0.29 – 15 kW; 230 V single-phase or 230/400 V and 400/690 V three-phase, 50 Hz
- Connections: ½” – 3″ threaded
- Maximum liquid temperature: 140 °C (coupled range)
- Suction lift: 3 m without foot valve, 6 m with foot valve
- Performance reference: 46 cSt / 8 °E at 40 °C
- Speed: 1400 rpm standard, 720 rpm for high viscosity
Applications
- Diesel transfer: bulk tank to day tank, generator and boiler feed lines
- Fuel oil transfer: boiler rooms, burner feed, traced lines
- Oil transfer: lubricating oil, hydraulic oil, gear oil; oil change and filling units
- Petroleum products and chemicals: solvents, varnish, paint
- Food and cosmetics: syrup, edible oil and cream transfer with the AISI 316 version
- Dosing and blending lines: anywhere flow must stay independent of pressure
Frequently Asked Questions
Can a gear pump be used for diesel?
Yes. Diesel is the most common application, particularly on generator and boiler feed lines where more than 3 bar is needed. Because diesel has a low viscosity (approx. 3–5 cSt), the actual flow falls slightly below the 46 cSt table values and internal slip increases. Send us your duty point and we will give you the corrected flow.
What is the difference between a gear pump and a centrifugal pump?
In a centrifugal pump the flow falls rapidly as pressure rises; in a gear pump it stays almost constant. High pressure and viscous liquids therefore belong to the gear pump, high flow at low pressure to the centrifugal pump. A gear pump is also far more sensitive to dry running and to solid particles — a suction strainer is mandatory.
What does the by-pass valve do?
A positive displacement pump keeps pumping even against a closed discharge, and pressure rises to a dangerous level within seconds. The by-pass valve returns the liquid to the suction side above a set pressure, protecting the pump, the motor and the pipework. It is fitted as standard on these gear pumps.
Up to what viscosity will it work?
Catalogue performance is based on 46 cSt / 8 °E. Above 12 °E — especially with a cold liquid — the 720 rpm range is selected instead of 1400 rpm, the pipe diameter is increased and the motor is oversized. For heavy fuel oil and grease, the 720 rpm range is the standard choice.
Is the pump self-priming, or does it have to sit below the tank?
It is self-priming: up to 3 metres of suction lift without a foot valve and 6 metres with one. Underground tanks and long suction lines require a larger suction pipe and a foot valve.
Can I use a gear pump in an ATEX area?
No. This range is not ATEX certified. If the liquid is gasoline or kerosene/jet fuel, or the area is classified as explosive, the ATEX certified self-priming range must be used instead.
What about lead time and price?
Models held in stock ship quickly; the rest are supplied on the Italian factory lead time. Send us the flow rate and head through the form and we will come back the same day with a model proposal and a price.
Gear Pump Selection & Quotation Form
Flow and pressure alone are not enough to size a gear pump — we also need the liquid and its viscosity. Fill in the fields below and we will work out the model and the price.
The gear pump range is not ATEX certified. If a hazardous area is involved we will direct you to the ATEX fuel pump range.
Related Products
For flammable liquids and hazardous area (Zone 1/2) duty, see our ATEX fuel pumps and diesel transfer pumps. The gear pump range is not ATEX certified.